First off I want say this is a well made, American product. The plate voltage switch makes it easier and safer, and the duel probes allow you to bias to the highest value of all the tubes. It is essentially the best in it's class, and at a decent price too!
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I got my Bias Pro a few days ago now ( speedy postage BTW ) & I have just used it for the first time and i must say the quality & ease of use is second to none . Such a well built bit of kit . I have been putting buying this off for a while now but i'm so glad i got it . Now i can Bias all my amps with ease . cheers . Dave from Australia
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Got my BiasPro!!! I have no experience biasing an amp but this made it very easy! Everything was just as I ordered and just as you said it would be. Thanks for a great way for me to save money by not having to use an amp tech for such a simple task. Thanks, Kevin
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Hello Ken. The bias tool arrived safely Yesterday, and no customs fees Thank you for lowering the value for me. I must say I am very impressed with the quality of your work and your great attention to detail. The label over the battery was very nice to see. My TAD Bias master looks like a toy compared to yours. Thank you again for a fantastic product and great service! Have a nice day
Regards, Tony Packer Music Repair Services Wales
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Hi Ken I’ve just finished refurbishing my Marshall JMP800 50W Master Volume amp, and the BiasPro tool has been a godsend in helping me do this. Firstly, it highlighted that my bias and plate voltage were WAY off what they should have been, and probably why the EL34’s were glowing brightly all the time Replacing the bias capacitors (and the filter caps for good measure) got me to bias currents and a plate voltage on the BiasPro that now made sense. I then had an oscillation problem at high gain/low volume that took me a while to sort out but that’s done now as well. The BiasPro allowed me to check the bias currents and plate voltage extremely easily and SAFELY, and meant I could use one meter for all readings by selecting what one I wanted rather than having multiple meters. All in all this is a great product, and I wouldn’t be without it now that I’ve got it!
Many thanks! Steve
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The BiasPro is really a easy to use tool for the bias adjustment without touching the circuit inside my amp, especially I like the plate voltage and bias current switch that help me a lot when tuning the bias with carefully monitoring the plate voltage. This is the first time I do the bias check, lucky I was able to discover my amp has some problem on the bias current and I need to take the amp to a amp-tech before damaging my new NOS power tube. I will surely recommend my friend to get one of these for the amp maintenance. Best regards,
Hei
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Hi Ken, Just wanted to drop you a line to express how happy I am with my new BiasPro. Opening the package, I was greeted with what looked like really great craftsmanship. The probe looks like it was assembled with care and attention to detail. The heat resistant sleeves near the sockets are a nice touch. The sockets inserted nice and firmly, but not too firmly, and felt solid. The probes worked perfectly and were very accurate when compared to a manual bias with 1ohm resistors. The Plate Voltage/Current switch worked flawlessly and really makes getting an amp biased-up a breeze. All in all, I couldn’t be happier! Thanks for a great product! Will shop with you again! Jerry McDougal Satyrnine Amplification
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Just wanted to let you know received unit and am very pleased. I have already biased two amps with it. Got my blackface Bassman sounding incredible with power tubes matched within .5ma and biased at 50%. Volume is more than adequate, tone exquisite. Found my old 71 Champ ( all original ) was biased at 110%. Biased it down to 70% with some other mods cleaned up the tone nice. Great products easy to use.
Thanks a bunch
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Hi Ken, My BiasPro came in and have used it to bias my Marshall 1987x. Once I understood the math behind the process and got my amp tuned properly, it hit me how clever your BiasPro is. This thing is fantastic and my amp is useable again! I’m more empowered as a musician to get the most out of my amps now, and I’m really really glad to give my business to a guy like you instead of some giant corporation. Also I really appreciate that you bothered to email with me on a holiday. That is uncommonly great service, brother. Cheers!
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Ken, I received my QuadStage BiasPro MQ13 w/VI MODULE and was very pleased with it. It was straight forward and easy to use. I was able to bias my 6a20 (Deluxe Reverb Clone). Your tool allowed me sort through a lot of vintage 6v6gt tubes and find ones that really did having matching Cathode current. Since that amp doesn’t have individual bias adjustment for each tube this is very important. Found a set of old Magnavox tubes .. they sound great. It’s nice knowing that my bias is set right and not just assuming it is. I also like having the VI/Module so I can read the Plate Voltage and the Cathode current. Another feature that I didn’t appreciated at first is having the Plate voltage switch on the probe separate from the meter (just in case you ever need to use the probes separate from supplied meter). For amps that have external bias adjustments it’s so cool not even having to open up the chassis to set your bias. It’s a great tool Thanks Ken! Brad Mathis Tucson, AZ
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Hi Ken, Your Bias Pro was perfect for adjusting the individual power tube bias pots on my Rocknroll Amps 50 watt clone of Robben Ford's Dumble #102 amp. Talk about singing! It is so much easier to use, the nuisance of removing the chassis front the cab in many cases is avoided by using this product. Thanks, Gary "Wheaties" Allen
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Hi Ken, I recently received my BiasPro and companion plate voltage probe via post and just wanted to let you know how well the device worked. Out of the packaging I read through the instructions and proceeded to re-valve and re-bias an Orange Rockerverb 50 MkII with JJ tubes. The Bias Pro worked a treat to initially determine the plate voltage and bias values, which I could easily adjust to my preferred settings. Excellent product. I am an experienced guitar technician with a few years experience doing basic work on amplifiers. This product has reduced my work time significantly and improved my safety factor ten fold, well done. I am very happy. Regards, Nathan Sydney, Australia.
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Ken, I finally got a chance to use my Biaspro to rebias a new set of EL34's in my Bogner Shiva head this weekend and wanted to drop you a line. I worked like a charm! Everything was very well-built and the instructions were VERY easy to follow. I'd recommend this bias meter to absolutely anyone! I've got the Quadstage BiasPro Q10 with two (2) BiasPro 8C bias probes and one (1) BiasPro PV8C plate voltage probe. If I ever get an amp with four (4) octal tubes or an EL84 amp I'll DEFINITELY be ordering more probes!
Also, if I ever get around to it, I've still got a couple of guitars that could use nut adjustments and/or replacements and some possible fretwork. Just tough to find the time to get ANYTHING done lately!
Thanks a ton, Matt Thompson
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Hi Ken, I ordered the Q10 with 4 current reading probes and 1 voltage probe for el 84 type tubes. The product is really outstanding in quality and so very accurate.
When I received the kit, I measured the tubes in my guitar amp as a reference and then I installed a matched quad of JJ el 84's and began to take measurements. Plate voltage came in at 530 V and current readings of 13 ma, 16 ma, 16 ma and 19 ma (without biasing the circuit (original tube quartet read 13 ma for each tube) so you guessed it, the discrepancy was way too large so I had to order another matched quad to at least get in the ballpark figures.
I got the new set yesterday and this afternoon I proceeded to install and bias the amp. I had 8 tubes to play with as my thinking was that what dealers sell as matched sets may well be in a tube tester but in an amplifier, they may not be so well matched.
I spent 3 hours inserting tubes and trying different permutations before I finally got a quad of tubes to read close enough to call it a successful mission. The amp is a Seymour Duncan 84-40, the diagram is readily available on the internet.
All I can say is that your product was a charm to work with, trust me the probes came in and out of the sockets too many times to count because of the tube permutations that I tried out. The pins on your probes are dead straight after that torture test, I had to straighten the pins on the tubes too many times lol. You offer an outstanding product that is so easy to use and the probes can withstand some abuse, mind you I handle tubes and probes gently but still the probes got in and out of the sockets so many times that I am amazed that they are of such a high quality.
So if this can help any of your customers, even though the differences are beyond 10% (ideally it should be within 5%), try switching your tubes to different sockets, bias below nominal value (60%) and bring it up gently toward the current draw you are aiming at. Large discrepancies at higher current draw may be closely matched at lower (but usable like 60% of max current) current readings.
Still as a buyer, don't believe the matched set that you just bought is actually matched, you may need more tubes to find the closest match.
Thanks again Ken for a fantastic product, I love its accuracy. Regards, Yvon Loiseau
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Hey Ken, Well, where do I start? I tried out the MQ13 with the voltage probe and then the two bias probes on my 7591-driven Ampeg GS-12 Rocket-2 this evening.
First off, let me say that both your instructions/write up on how to use the MQ13 with the bias probes and the supplement for the voltage probe are written really well and everything was explained clearly. I had no problem understanding the process and, after reading it through very carefully, the process was quite intuitive. That was this afternoon. Then this evening I tried it out on the little Ampeg (cathode-biased push-pull 7591s) just to check it out. The whole process took maybe 25-30 minutes tops, but that included removing/replacing the back and I was really taking my time and lettng things cool down a bit between probe swaps. It also included running some calculations at the end to determine at what percentage of max plate dissipation this little cathode-biased amp was running at.
And I'm so glad I did! I've had this amp since a few months after it was manufactured in 1965 and all the tubes are still original! I had recently tested all the tubes on my Hickok TV-3 and they all tested string to various degrees. The two push-pull 7591As were fairly closely matched for transconductance coming in at 9200 and 8750 micromhos, where 4250 is minimum good on the TV-3 -- incredible after 49 years even though it hasn't been used much in the last few decades.
Anyhow, after testing with the MQ13 it became clear the tube bias was quite mismatched (see below), and that probably suggests some components in this old calthode-biased amp have drifted substantially out of spec, not surprisingly.
Results were as follows: #1-7591A showed 351 plate volts and #2-7591 showed 350v (I checked both just for the heck of it). Bias current on #1-7591 was 43.3mA and on #2-7591 was 52.1mA! Doing the calculation to see what percentage of the 7591's 19-watt maximum plate dissipation it was running at showed 80% on #1-7591 and 96% on #2-7591 -- seems very high even for a cathode-biased amp? And that may explain why #2-7591's transconductance has aged more rapidly than #1's. So, I will likely send this amp to my tech for a thorough going-over wen I can afford it -- it is a little noisy (randomly) so might well need a cap job and probably some out-of-spec resistors replaced as well.
In summary, I'm glad I tried your products! They worked flawlessly and demonstrably confirmed what I has suspected -- that this little Ampeg needs some professional TLC -- I suspected such but I just didn't realize how far out of spec it really had gotten since it was still working acceptable well overall for occasional practice.
I also have a 1963 Ampeg Super Echo Twin (ET-2A) which I love and am in the process of refurbing and it will likely need a cap job too but now I'm anxious to see how it tets too!. And the Fender Super 60 210 I want to try using the probes on to adjust the bias once I have time to retrieve it from storage at my friend's house and finish refurbing it -- probably by spring.
Ken, feel free to use whatever pieces of above you would like as a testimonial on your website. I am very pleased with it all!! All I'd ask is that you don't use my last name -- maybe just say "Dan from Saugerties, NY" or something like that.
Thanks again for such a nice set of products -- so nicely designed and that work so well -- and for all your help with the weirdness we encountered with ebay not working right -- glad I bought them!
Best regards, Dan
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Ken, Thanks for sending through the meter and probes. They took only about a week to get to me here in Australia and were packed very carefully. Testing has been easy and straightforward. Firstly, I was able to establish the plate voltage of my amp using the plate voltage probe. Having the shunt resistor close to the socket meant I could trust the reading - and conduct the test safely. Testing the cathode current was also very easy with the twin 8-pin probes. In the end, within about an hour I had fully biased my amp for two new EL34s. I saved money on the tech - but best of all had the satisfaction of doing the job myself. Thanks again for an excellent product I’ll use each time I change output tubes. Matt - Australia
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I used the BiasPro Q10 to find 2 matching vintage Mullard el34's from my random stock. Then I used it to set the bias on my 1985 50w Marshall JCM 800 with those 2 tubes installed. I followed the very easy to read and understand instructions that were included with the BiasPro and was very suprised at how simple the procedure was. The optional Plate Voltage Probe made things even easier by allowing me to read the amps plate voltage without having to poke around in the chasis. The BiasPro Q10 and its bias probes are build very well and should last a long time. Im very happy with my purchase and my Marshall has never sounded better. Thank you!
Anthony M.
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Hi Ken, So I just got done biasing 3 different amps and the BiasPro worked like a charm. Hooked it up to my multimeter and tested it on EL34's/KT77's and 6L6GC's -- super easy to operate, very accurate readings, and way safer than poking around in the chassis. The youtube link you have in your ebay listing was really helpful too (for showing how to do biasing calculations, etc.). All in all, I couldn't be happier with the BiasPro. For anyone who's serious about maintaining their tube amps, this is going to save them a lot of money in the long run. Thanks again for building such a quality product. Robert Brown
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The Tube Bias Probe Tester Tool Socket is at home. Extraordinary build quality and superb precision! I am very satisfied with the purchase, and it has been a pleasure to do business with you. Of course, I leave positive feedback in ebay.
Best regards.
Jose
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Ken, I've really enjoyed using the BiasPro Q10 that I purchased from your company via eBay. It works great and is well worth the $$ for a professionally made product, I have a vintage amp restoration business and was getting really tired of installing cathode resistors in the amps for biasing. This product is simple to use and makes the job fast and accurate! Tom Schupbach
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I used your tester it worked great, simple and easy to use, your instructions on biasing were very helpful
thanks rex
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Ken, Thank you so much for a very pleasing and transaction. I am very satisfied with the items. I got my bias probe right real fast and was really surprised when it includes biasing informations to which I did not expect. It's nice doing business with you Ken and fully satisfied with the outcome. Your #1 on my lists! sam
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I received my Bias Pro unit this morning, and have already used it to bias three of my prize amps - it works exactly as advertised, and makes the job so much easier and accurate! I now have total confidence that my power tubes are running right in the center of the 'sweet tone' zone... Thanks, Hadley Hockensmith (Neil Diamond Band/LA Studio Musician)
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Hi Ken, Finally had the opportunity to try out the Bias Pro and it didn’t disappoint. Easy to use, clear instructions made the job simple. For your information I had purchased an AXL AKITA AT30 amplifier, made in China with stock Shuguang 6L6GC tubes. I was lucky in that I had purchased matched sets of RFT ECC83 pre-amp tubes and a matched pair of Tung Sol 6L6GC STR tubes which I planned to put in the amp. I tested the stock Shuguang tubes (remember the amp was brand new with less than 3 hours playing) prior to doing any changes. Results below
Tube 1 Shuguang 6L6GC = 41.6mA
Tube 2 Shuguang 6L6GC = 46.3mA
Not exactly matched were they? Before tweaking any bias I decided to test the brand new Tung Sol 6L6GC STR’s, results below
Tube 1 Tung Sol 6L6GC STR = 34.2mA
Tube 2 Tung Sol 6L6GC STR = 34.3mA
I’m happy I did this before messing around with the bias on the amp. No biasing was necessary, if anything I could hot them up a bit but for my preferences and playing they are spot on.
Again, I can’t recommend the Bias Pro highly enough.
Regards
Richard Fearon
Saharri Park T'breds WA
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Hello Ken, I bought the Quadstage Bias Probe Q10 from you back in February and now that I've had some time to use it with a few different tube changes and amp bias's, I wanted to let you know that product thing is amazing!!!! Actuate and flawless. I love it!!! Thank you, -Carl
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I wanted to thank you for the bias probe - I do a lot of amp repair & tube amp setup - this is the 3rd Bias probe I have owned - The first one was a Groove Tubes Bias Tool which lasted over 9 years - the second probe was purchased from SRS webstore off of ebay - this lasted maybe 5-6 months & was only used around 15 times before the wires snapped right off from being thin & having no strain relief. I also broke a couple of EL34 Guide pins in the SRS Probe because the socket was low quality - you get what you pay for!! Your Bias Pro is top notch - Down to the wires, strain relief & socket - I could tell right away that this was well built & will last many years as well as providing accurate readings. I had an orange Thunderverb 50 that had an electronic problem & the SRS Probe broke in the middle of biasing the amp - I had to shut the amp off until it was Biased so I appreciate your instant shipping - I rarely leave feedback & never feel the need to email an ebay seller - Thanx Again
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Helped me find a bias issue I have with a Mojotone JMP 45 amp kit my dad made for me. The adjustable bias pot ranged between 54-87 mV! Way above optimal 45mV to spec it to 70% max. Troubleshooting issue now. thanks for potentially preventing some damage. FB.
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It was the first time i ever biased tube amps, i have 2 for stereo, yea i know im spoiled, but im happy so thats good! Anyway what a difference, both heads were off and too hot, they're el34 quads, albion tct100's i followed your instructions, plus some advice from albion and in about 45minutes, warm up time and cool down time included, i was done! the sound was improved 10 fold and im sure my tubes will last alot longer. P.S. the guy who used to bias my heads is permanently fired, he was purposely burning up my powertubes for job security, he lost alot of other customers too. knowledge is a powerful tool, i now know how to change new parameters, VERY important ones, and have the ability to play mad scientist, Thats my favorite job right there, Oh yea, don't be stupid with high current, thats the true killer! there now noone can sue me for the mad scientist bit! If you guitarist out there do not get this product and learn to use it, you are pissing away money and multiple available tones in your amp, seriously......try it! S Thom
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yes sir, the bias pro worked very good. I am a pro. musician and have been for over 35 years. all I use are fender tube amps and this worked very well easy to use, and will keep your amp performing gig after gig. thanks, scott walker
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I have already saved so much money and have been able to bias most of my amps....a side benefit has been calling out tube suppliers that have sent me "matched sets" that have varied significantly more than what is acceptable. Your tool will help keep them honest. Thank you. - felirick
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Mr. Koga takes his products and customer service seriously. My QuadStage BiasPro Q10 just arrived yesterday. Shipping was extremely fast. Customer service was above and beyond. As for the product. It seems well made. It comes with two bias probes of your choice plus extra RCA bias jacks to add more probes. I haven’t had too use it much since it arrived yesterday. But it seems to work just fine. Very easy too use. Comes with nstructions and cathode current range chart. Keep up the good work Ken! Thanks, Andy
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Hi Ken, just wanted to say that I am more than satisfied with the MQ10. Shipping was faster than I (and USPS) expected, arriving two days earlier than what they told me. Out of the box, it was super simple to set up and the instructions make it virtually impossible to mess anything up. I play out of a modded 6505+ running on two EL34's, and found out that the bias setting on my amp was only allowing the EL34's to run at 14-15 mA. After using your product, I biased the amp so the tubes are running at 35 mA and it made a world of difference. I'll never have to waste my time and money giving my amp to a technician to replace the tubes ever again! Great product and customer service. Keep up the good work! - Joel T
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So I finally got to use this yesterday and man am I happy I bought it. Super great tool. Helped greatly. Also, because I bought the 4 probes I found that one of my "matched" pairs was about 10 ma apart. Thanks for such an awesome product. - contentsunknown
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Ken, One was a Q 10 and the last one is a MQ 10. I purchased both since I have 3 benches and sometimes need a meter that can be moved around, hence the MQ 10. As far as your products go, I think you are selling as good of a product as any of the other guys and probably better than most, Allesandro, Weber. I have had their stuff and am constantly repairing it. You seem like a good guy and know what you are doing, so why not give yours a try. BTW, I did order a Compu-Bias for 259.00 and have never received the meter or got my money back. I much rather deal with an individual than some company that just takes your money. - rodgersamps
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Ken, I think it's a great product. Hooked it up to my multimeter and biased Hot Rod and my Deluxe Reverb. Thanks much. - Rich
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Hi Ken , well here's my review and yes i can give your bias meter the thumbs up .. all went well apart from finding out my new "matched" quad of Winged C are actually 13ma apart , though this is really another benefit of doing it yourself in a way as if i took it to a tech unless i was lucky enough for them to have a match for my dud tube i would probably have to pay anyway and take it back to get redone once another tube in range could be sourced , i can match one closer with my old spares to use till a replacement arrives now ..i have also had to wait 2 weeks just to get my amp baised at times so am happy to be doing it myself , was all straight forward and very easy to use and another reason i went with yours even though a cheaper one is available was because im picky about the amp (1995 VHT/ Fryette classic 2x12 combo ) and tone and wanted a precise plate voltage reading so the the optional probe was a no brainer ... i recommened this to anyone with basic electrical knowledge , specifically caps discharge and how amps hold a lethal charge even when unplugged ..if you understand this and are careful where you poke around then biasing / matching your own tubes with this unit is very easy and you'll get your money back in no time ... not to mention no longer having the hassle of drop off / pick up / no amp to use periods .. good stuff , all looks well made and i get the impression you stand behind your product should any probs arise . All good , cheers , Cam .
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Hi,I,m very pleased with your Bias Pro it works a treat,I wish to purchase 2 BiasPro 9C leads as my new laney amp runs EL84's, would you send an ivoice. cheers Graham
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Hi there, In 1994, I bought one of the first Fender '65 Deluxe Reverb reissues. While it's always sounded very good, it's never been "great". With the recent introduction of better quality 6V6GT tubes, I've been itching to see what I could do with this underappreciated workhorse.
Biasing with the sturdy MQ10 and accessory probes couldn't have been easier. Armed with a cotton cloth to handle the tubes and a small screwdriver to tweak the Fender bias pot, I biased the TungSols in 15 minutes flat. Five minutes of that time was spent reading the included clear instructions on how to successfully bias your output tubes. It's like having a new amp!
If you know how to pull a tube out of your amp, you're halfway there. Even better, it also let me compare the TungSol 6V6GTs to some JJ 6V6S tubes I had laying around. The MQ10 let me tweak my amp in a few minutes. More time playing, less time chasing tone!
Thanks for this great tool. bc
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Hi Ken, I received the the bias pro for my fender dual showman red knob head which runs 6l6GC power tubes.
It also has a port to check the bias in the back but its just a single port which checks the overall bias of all four tubes not individuals. So using the bias pro with the 8c plugs I followed the directions that you provide with the unit and found that one of my so called matched tubes isn't so matched. Thanks for the help and a Great product. Lee Faria
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I recently purchased the quadstage bias pro and I love it. As a novice and a long time tube amp collector the bias pro lets me know exactly what my current is going across my power tubes relating to the overall health of my amps.I currently have 13 point to point fender,vox and marshall amps which translates into a lot of power tubes. I find the tool safe and accurate and wish I would have gotten one sooner. I would recomend this tool to every tube amp owner. Paul Christman Green Bay WI
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Hi Ken, I recently purchased your BiasPro 9C-S and I love it! Its built very well and makes biasing an amp so much easier. Before I purchased it I was poking around the amp's circuitry with my multimeter leads to bias the amp. It can get quite difficult only having two hands trying to hold and adjust everything. The BiasPro is really convenient and also much more safe. The instructions that come with it are great, very detailed. It definitely shows the time and quality you put in to making such great products. Thank you, Thomas Maxwell
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Ken, I love this thing. It works great. It can be a money maker matching tubes & doing the bias adjustment. It made a big difference in sound but i followed your instructions specifically. I love the PV8C for checking the actual plate voltage, takes the guess work out of it & don't have to read schematics. i'd recommend this tool to anyone who works with tube amps. Thank you very much for such a good easy to use product. Respectfully, Steve
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Ken, I received your bias meter today and just finished bias my amp ! It was just too good to be true ! It was so easy to do and seems so accurate,the reason why I'm saying this is I already have similar biasing meter which was way off compare to your meter ! And another reason why I ordered yours was ,my cayin amp. Anybody who owns this amp knows how ridiculously difficult and dangerously designed for biasing ,especially who doesn't have much experience to begin with ,but it was so easy and fearlessly done I don't feel stupid anymore! I don't know how to thank you for your wonderful product and your first rate service ,I wish everyone who owns Cayin A88t integrated amp finds out about your meter . Once again thank you for your truly great product!
Sincerely, Jae
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I recently ordered a Quadstate BiasPro Q10 with two BiasPro 8C bias cables and one BiasPro PV8C plate voltage cable from Ken Koga and A-Sharp Fretworks. First off I must say that Ken was very helpful and informative helping me with my order and the shipment was very prompt. When the package came and I opened it the first thing I noticed was the great craftsmanship of the products. Handmade in the USA by Ken the quality of these biasing tools stand out. I had never tubed my own amp before and with the easy to understand instructions it couldn't have been easier. Overall I cannot stress enough the quality and ease of use of these products. I would recommend them to everyone from the novice to the professional. Thanks Aaron
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To Ken Koga @ asharpfretworks, Your Quadstage BiasPro Q10 is a terrific, simple and easy to use bias tool. Both the parts quality and build are excellent. Quality probe sockets that are smooth and easy to insert even in tight sockets. The ability to check four tubes at the same time is a wonderful time and effort saver. Great for checking quads for matching, without the need to power off the amp and move probes. I have been using the Q10 for nearly a year now and it is excellent, and is as accurate as any other method that I have tried.
I liked the Q10 so much, I also bought the MQ10 metered version, and it is also a quality piece of equipment. The MQ10 is even better and easier to use. Great equipment, and a must have for amp techs, or anyone that wants to do their own amp biasing. I really appreciate what you have done at Asharpfretworks, and your awesome customer service. Thank you very much, Shimmilou
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Hi Ken, I purchased one of your 8-pin BiasPro products a couple of weeks ago and finally got around to using it. Just wanted to let you know that the instructions were nice and clear, and it took me no time at all to bias a pair of Sovtek 5881 output tubes in my Engl amp head. Great product, easy to use! Cheers from Australia!
Philip
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Hi Ken, The Bias Pro saved my Marshall Handwired Plexi. I put new Mullard EL34s in her and played it for about a month, and it was sounding a bit edgy on the top end. When I tested the plate voltage and the bias with the MQ10, it turned out I was running those tubes at 95%of its maximum cathode current. Yikes!!! Using the Bias Pro I turned it down to about 70%, and probably saved my tubes, and my tranny. Now it sounds more rounded on the top and the bottom ends, with just the right amount of power tube distortion! Best regards
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Mr. Ken,
the silverface AB763 amps had a 1000k resistor installed on the bias board
the blackface AB763 amps had a 470k resistor installed on the bias board
I removed the 1000k and installed the 470k and the bias adjusts as it should
your tool is great, allows me to easily swap out tubes and read on my FLUKE meter
I am new to the Fender amp electronics including bias adjust
I had the reissue amp and thought to purchase a vintage amp
With a recap and bias adjust this vintage amp is really a joy
great tone and plenty of power
all the best to you Anson Alexander
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Hello Ken, I received my BiasPro Meter Yesterday and put it straight to work. Using the instructions included with the meter I determined that the plate voltage of my amp was 400 volts...Wow that was quick and easy! so on to setting the bias. The bias setting on my amp was more than double than recommended { I am suprised that nothing had melted all this time! } So, I set the correct bias for my amp using the BiasPro Meter and it has never sounded better! Just want to say thank you! The BiasPro Meter is easy to use and works as advertised...Money well spent!!! Cheers! Mark Estes
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Hi Ken, I received the quadstage biaspro a couple weeks back and tried it out today. Having no previous experience at biasing amplifiers everything went smoothly, and I am very satisfied with how my amp responded. The included instructions were clear and summarized the process in a way that was easy to understand. It's good to see someone who takes pride in their work, and I would recommend this product to anyone looking for a high quality biasing tool. Thanks for the good product support. Take care, Justin
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Hi Ken, Just wanted to let you know I received the Quadstage BiasPro MQ10 and was able to bias up my amp for the first time by myself without having to send it off to the amp tech. Very nice tool and so easy to use. The instructions are easy to follow and the info you provide is very helpful. Thanks for making a great bias tool at an affordable price!
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Ken, I recently received a Quadstage BiasPro MQ10 with the full quad setup (4) 8C probes and a PV8C probe. The integrated design of the MQ10 is easy to use and a great value. The quick response to my order email was great and the PayPal invoice made payment a breeze. I had my order in 3 days, thanks for getting that right out to me.
The included documentation is easy to follow and informative. I had no trouble setting the bias on my Peavey JSX head. It was set fairly cold, sounded good but after biasing the tubes a bit hotter it really kicks butt now. Getting the full quad configuration made the process quicker and easier.
I then checked my Peavey 6505+ combo and after some searching on the internet found that i will have to get a mod done on that amp to be able to adjust the bias. The tubes are running rather cold on that one as well. While Peavey might set the tubes on the cold side they do ship their amps with decent tubes (not cheap ones that need to be replaced immediately).
Thanks Ken for making a great product! The modular design is fantastic. If I need a couple of 9C probes down the line it will be an easy addition. Sincerely, Joe Roth
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hi ken, just to let you know that your bias pro arrived on fri 24th feb, i am new to valve amps so have never biased vales before, within about 1/2 an hour of opening the box i had read the instructions and biased 2 shanling el34 power amps, this would have been quicker if i hadnt needed to leave the valves to cool between amps,
this looks a great piece of equipment that you provide and has given me confidence that my amps are running correctly and efficiently. many thanks keith
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Ken,Your meter probably saved me from frying out a couple of amps. Those Crates, were way to hot, I adjusted them with your meter and they run great. The Venus, never did Bias out for me no mateer what we tried and I sent it back to factory. It needed repair, it was a sick amp. Even thouhg it played it was way out of wack. Bias Pro is one great tool. Thank You Mike
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Hi Ken, Tyson Fiddler here. Just wanted to let you know I recieved my bias probe last week and finally got around biasing my amp. Couldn't be happier with your product. This was my first biasing job so I was a little hesitant but after much research online, I finally decided to give it a try. Everything worked out fine. The amp was actually running quite hot so I backed it off a bit and got a much better sound out of it. I'll be sure to recommend your BiasPro to anyone I come across looking to bias thier amps as well. Positive feedback will be left for you. Thanks. Tyson
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Hi Ken, I finally got around to biasing my SuperReverb Reissue with the Bias Pro MQ10. Following your clear and precise instructions the job was easy and fast. I was very impressed with the quality of the product. The amp has come alive now. Thanks for making such a great product. Steve
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Works great. Easy to use. Just plugged it in to my digital multi-meter, hooked up the amp and the tubes. Piece of cake. After the amp warmed up, the actual biasing took less than 30 seconds. Nice workmanship. I had years of experience repairing tube based electronics in a former career. David
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The tester came yesterday, but no one was home, so I had to pick it up from the P.O. today. Just removed the chassis plugged the tubes into the tester probes and then plugged those into the amp. They each read around 41.7. I have a Germino Club 40 50 watt head. If you've never heard of this brand, Greg Germino builds "Plexi" style amps that are as close to the originals as can possibly be built with todays components. He even sources items that are still manufactured from vendors from that time period. At any rate, the Club 40 is his take on the original JTM-50 and JMP-50. An absolutely wonderful amp.
I'm not sure what his ideal is for biasing tubes for this amp, but I have a call into him. I biased each tube (for now) at 35 ma. I'm going to try this for awhile and make minor adjustments and see what sounds best to my ear.
Your tester is so easy to use. I love the fact that I now don't have to pay to bias tubes. Before, I had to wait 2 to 3 weeks to get it back. - joeelliso3
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Hi Ken, The MQ10 is great, I checked my JVM I just received,a factory restock and it wasn't even close. The tubes do not come close to matching. I did some tube switching to put the range as close as I could. It sounds so much better. Remember this amp is a new restock amp. I have ordered a new tube set for it. The on line store I got it from wants me to send it back so they can check it out. My MQ10 helped me make my amp usable while waiting for the tubes to make it great. thanks ps please send me 4-BIASPRO 9Cs and 1-BIASPRO PV9C. I want to check a peavey 50-50 thanks again
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Hi Ken, Just wanted to let you know that your meter worked flawlessly! I recently purchased an integrated stereo tube amplifier. This is my first foray into tube amplification and based upon my limited knowledge (of electricity) and research (your site and others) it became apparent that proper bias setting of the tubes is critical to performance. The amp is equipped with what the manufacturer calls Easy Bias, which is an LED light for each tube, but that really only gets you close (+/- 5mV) to the recommended bias level. The BiasPro MQ10 allowed me to tweak all 4 KT-88's at the same time with ease and has really sweetened up the sound of this beast! With your meter I was able to dial them in so they are now all running within less than 1mV of each other. I think that's fantastic and I am really happy that I found you and your gear! Joe
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Ken: Recieved my MQ10 Tube Bias Tester with two eight pin probes and the optional plate voltage probe. Upon inspecting the the contents of the shipped items I was immediately impressed by the overall quality. I was even more impressed by the usage instructions and supporting documentation!
I followed the easy and clear instructions and took the plate voltage measurement on my Fender Hot Rod Deluxe lll amp in a matter of minutes. I plugged this number into the included formula and found the appropriate bias range for my amp and power tubes. I inserted the power tubes into the included probe sockets, measured the bias, and made the simple bias adjustment - which set it to the desired range. I could not believe how far off the bias was from the factory!! The amp sounds great now! The whole process of reading the instructions, getting the actual (instead of the schematic) plate voltage, and reading and adjusting the power tube bias took less than an hour! To say I am a happy purchaser is an understatement. Especially for the price you charge. I was looking at comparable products that cost 3 times as much! Thanks for the Great Communication and answer to my questions and for Setting me free of the terrible repair shop cost and experience every time I need to change power tubes! I will highly recommend your products to everyone I know! Mike Morrison
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The bias probe is a very nice tool to have and I am pleased with the ultra high quality build of this device. Biasing a 4 tube amp, such as my Fender Twin and Music Man amps is a quick and painless job now. You can be proud of this tool and know that being "Made in the USA" can be a good thing. Randy
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I recently ordered the Biaspro tool and even though I haven't received it yet I am already impressed with the customer service I have received. My special request for shipping was accommodated and he was willing to work with me to help me get my tool in the mail quickly to help me get my amp running again for a rapidly approaching gig date. Also, he was quick to respond to any questions or requests via email. Great communication, a great product concept at a great price. I'll let you know if it does not work, but I don't see why it wouldn't; its a brilliantly simple design. Worth every penny for any tube amp owner. Justin Riege
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Hello, Ken! I've recently purchased your tube amp biasing tool from ebay and here is my feedback regarding re-biasing my power amp, which is the VHT 2/50/2 with EL34 power tubes.
First of all i would like to express my regrets (no worries, not about the tool!).It was foolish from my side to choose to buy only 2 probes instead of having 4 probes, which makes re-biasing job WAY more easy to accomplish. I've spent numerous dozens of minutes for inserting and pulling out the probes back and forth before having the job done.
My first task was to check whether the old tubes were still good or not, so first i measured them (in 2 attempts because i had only 2 probes). The probe inserting procedure required to partly dismantle the tube support bracket, because the tubes are placed horizontally and there's just not enough space in the chassis for a tube together with the probe. But that was just a technical issue of the amp itself.
Then i read the biasing tool manual and measured each power tube pair bias currents for each of the channels of my stereo amp. What i came across was that the tube bias currents were a bit different for each tube, and this difference was out of the 2-3 mA range stated in the tool manual. My readings were showing about 6 mA difference between the tubes in channel A and about 10 in channel B.
Besides that i was unable to re-bias the tubes of channel B to keep the currents within the range stated in the manual for the EL34 tubes (as per manual should be 30-40 mA), bacause the biasing potentiometer of the amp was already set to the maximum current. So the tubes were supposed to be replaced anyway.
The next step was to measure the new tubes i got from the web superstore thomann.de
These were 2 matched pairs of SOVTEK tubes, but when i installed them and measured, it appeared that the bias current difference between the tubes was even greater than with the old tubes. However the re-biasing was possible with the potentiometer of the amp.
I marked the tubes and then tried to swap them with ones from the other channel, but the difference became even greater.
Well, here are my final re-biasing results:
for channel A one tube was reading 38.6 mA, the other one 25.9 mA I choose to leave it this way, because if i tried to increase the lower value, the higher value would go out of the upper permissible value (beyong 40 mA) which is kinda more dangerous than just if it was lower than the lower value.
for channel B one tube was reading 36.2 mA, the other one 30.5 mA That's basically how it is set now with the new tubes in.
My conclusion is that even the matched tubes in sets are sometimes not that well matched as they are meant to be. I really don't know if it can be rectified somehow, maybe you can suggest some method?
Regarding the tool itself i have to admit, that it is easy to use, the manual is full of all the important info regarding the use of the tool and the recommended settings for different tube types. Very important aspect is that there are safety measures in it. Fit for dummies and newbies like me. :D
The only thing i really regret (it is mentioned above) that i haven't ordered immediately another 2 probes, and maybe also a couple of 9 hole probes, just in case if some of my friends ask me to help them to re-bias their amps too. Unfortunately the shipping fee is quite high and those bastards in the customs add the shipping fee to the total taxed value of the unit and now it is more expensive to order them compared if it was done with my first order.
Yeah, the selfish people always pay twice! Well, that's it. If you have some questions don't hesitate to contact me. Best regards and have a nice day! Nikita Oravs
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Just a quick note to say that the bias probe kit arrived last Saturday, within the time you suggested. I got back from a business trip yesterday and have been rebiasing a couple of 6L6-based amps with the probes today. The experience has been revelatory:
1. One amp has been biassed very hot (probably too hot for the valves they used) and the pair of 6L6 valves recently installed were not matched - over 10mA difference. This was done by a "professional" amp tech.
2. The other amp was biassed too cool (only 20mA) , which I suspected, and rebiassing has really opened the tone of the amp up.
I now have the freedom to bias these amps the way I want for my playing, rather than relying on a tech's choice. In short, an excellent piece of kit. Thank you. I should have bought one of these from you a long time ago. Paul
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Ken..... I have been using the nine pin Bias Probe for tube matching for my Vox amps. When you buy a matched set they are some times a little off or can drift with use. With the Bias Probe it makes it possible to check and keep an eye on the performance of the amp. I can then swap out tubes and make my own matched set as they change or if they were unmatched in the beginning......
Thanks!!!!! Carl
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Ken, I had read good reviews about your BiasPro tube biasing tool on ebay and Google so when I got a new amp and wanted to put in some NOS power tubes I thought I would try your product instead of taking my amp down to the local tech and having it disappear for weeks and be out 80.00 dollars. With your excellent detailed instructions, my Fluke multi-meter, and your sturdy well built unit I was able to set my tubes up in 20-30 minutes. The BiasPro worked exactly as you said it would, was not some flimsy piece of foreign made junk, and paid for itself 3 times over the first time I used it. With out a doubt this is one of the best ebay or any other kind of purchases I have made in years. Thanks for the great designed product, the super fast ship, and the easy to follow step by step instructions. Chris in Denver.
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Hello Ken! Your gadget arrived today. I purchased a voltmeter from Autozone and in less than an hour I biased 2 amps with no problems. One was a 65 Fender Deluxe Reverb Reissue with 6V6s and the other was an original 66 Vibrolux Reverb with 6L6s. The local big-name tech here in town, while well-respected, was charging almost $55 for biasing service. Well, upon hearing that I decided to teach myself to fish. I'm glad I did. Not only did I bias my power tubes in both amps in less than an hour, but also found out how closely they were matched, as well as finding out that the tubes in my original 65 Vibrolux were biased to 50mA! I imagine that with a bias that hot, it could have damaged something in my prized amp. Luckily I had your gadget around to get it back down to where it should be. I don't know anything about electronics and I'm definitely not a technical person, but this made the project dummy-proof.
Your product also allows me to experiment a bit. I've read on the popular online message boards that a lot of folks like to try running 6L6s in their Deluxe Reverb Reissues. This requires adjusting the bias. Well, now that I have your product I can put the 6L6s from my Vibrolux into the Deluxe Reverb Reissue, bias them accordingly, and see if I like the change. If I don't, no sweat. I can just put them right back in the Vibrolux and re-bias within minutes. All of these things I learned tonight would have taken weeks of going back and forth to the local amp tech and could have cost me a lot of $$$ on top of that! I'm not patting you on the back. I'm patting myself on the back for making such a smart decision to purchase your product.
Now let me qualify this positive feedback by saying that the operation was very quick and easy because I've spent a lot of time over the past few weeks reading the online message boards and trying to familiarize myself with the jargon. I learned a lot from folks much more experienced with this kind of thing than me. Therefore, I did not have to spend time doing calculations with plate voltages and dissipation when I received your product. Every expert out there has a different opinion as to what is too "hot" and what is too "cold" for whatever tubes in whatever amp. I took the time to absorb as much information in as I could and decided for myself. Once I did that, using your product was the easiest part of the operation. Doing the reasearch, putting in the time required to learn about what it actually means to bias an amp, gives confidence to the layperson that what they're doing is for a correct, logical purpose.
Best Regards, Ben Johnson
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Hey, Thanks so much for the BiasPro. I've been playing guitar professionally for several years, and just needed something so I could get my amps dialed in when working from home. The BiasPro works great. Biasing products can get pricey, but this was a great deal and will be used often. Got it super fast and couldn't be happier with it. Had it up and running within minutes of opening it. Thanks again!
Clint Milburn
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great tool....29.00 bucks...tuned up 4 amps....found out what was wrong with a 65 super reverb i got cheap..a guy put "new" tubes in and it sounded bad....tubes were not in range...retubed, played it 3 showess so far with no issues. thanks, will be getting more from you. send me that page again and i will post my findings if you would like....BIGGIN
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Hi, Ken..
I purchased a MQ10 from you last week on ebay..I absolutely love it..I would like to order the companion plate voltage cable(EL34,6L6,etc)please send me an invoice and I will pay as soon as I receive it...My email is xxxx@xgmail.com
Thanks Jeff
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Hi Ken, It's Jarrad from Australia here how are you? I have just received the bias probe and got stuck into a couple of my amps with it, what a fantastic little tool you have made! It made biasing my amps very safe and easy and has instantly won a spot in my tool kit. The instructions included were very concise, and though I have been a professional electrician for 14 years and playing with music gear for longer, I feel that even a complete newbie to amps and multi meters etc. would have absolutely no problem biasing an amp with your probe, a decent meter, and your detailed instruction sheet. Thankyou for providing me with this excellent little helper, I wish you much success and I will definately spread the word around my local scene too, Kind regards and thanks again,
Jarrad Daniel, Adelaide, South Australia
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“BiasPro made it a breeze to match-up a quad of 6L6s for my B15 fliptop since I didn’t have to dismount the chassis to take readings.” And even though the B15 is nominally a non-adjustable fixed-bias amp, the (easily obtained) readings have me thinking about testing some other types of tubes or tweaking its bias circuit components for a bit more headroom. Next up is my buddy’s Marshall…
Thanks!
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Ken I found problem. Some one modified bias circuits and had V7 and V10 with no bias voltage. I corrected wiring and used bias box and was able to balance out ok. I should of started with more basic trouble shooting and I would of found sooner. But guy I purchased from was not truthful and he did not tell me that amp had been modified so I was going off deep end of things.Thanks for your time and bias box tool makes great troubleshooting tool. GOD BLESS ! jerry Rodriguez
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Ken. Last time I had my hands on tubes it was Raytheon Hawk equipment. (slightly newer than clay tablets). I am awash in Triple xxx Heads. A good problem.
So, To bias. Head one: Checked the Plate V and then the bias's. The OEM Sovtek 6l6's Ranged 43ma to 24 at 489pv. Amp sounded hollow on the cleans, top was piercing and bottom was good. I took out the 24 ma tube and put in one that ran at 35. Bias adjust put the 43 to 38, paired with the 35 that went to 36.5 as part of the pair. The other two, were running at 37.5 and 36, and moved down to 32 and 34. This resulted in a better more musical clean, the top was still real dingy..for lack of a better descriptive. OverDrives Had the same issues out of control upper range, hollow in the mids. I played with EQ, between steps, all night long, so scale wise the description stands. Changes: JJ12ax7 in V1 and a new balanced JJax7 in V4..I let the Soviet EH's stay in v2 and v3..This amp turned into a very manageable critter. I get Super cleans now, the jangly top is now just searing...PRS; low rent, G&LStrat; hi rent, and Ibenez Artcore with a mini bucker are the inputs I have. The amp loves the buckers now, but sounded bad with the G&L. The V1 and V4 change made the G&L responsive and As I discovered the more widely adjustable of my guitars. Channeling Jimi and Buckethead at will now.
Amp 2 - 484 Plate volts. Soviet tubes out for full JJ Change to 6Ca7's. All four new tubes bias ranged at 32.3 to 33.1. I did notice the Amps really did not settle down for at least a half hour. (they had not been in service for a long time) With the bias wobbling 1-2.5 ma around the settle point.
This amp is now a crusher. Bottom big and articulate, mids... you can now waltz to a shred fest. The treble has never sounded better...The Vol knob is your friend with this rig. A bit of tired old midiverb in the back and the sustain is forever.. could stadium...this...yes I could...
The changes in the sound quality with just a balanced bias are startling. A couple of less harmonic preamp tubes make a difference - together a huge difference.
Oh yes... your Bias tools...People, they are worth the price of admission! Have fun, be safe, (remember plate volts). Yes, It is ok to be biased.
Thanks . John
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Hey Kenny, Firstly let me say that the item arrived perfectly. Its a long long trip to North Queensland Australia. Secondly, I am very impressed at the standard, quality of the item. Congratulations on manufacturing, supplying a top notch product that fills a void in what is a growing industry - Valve amps.
I will now train my son how to use this time saving valuable tool.
I will do a video of our experience with your Biaspro and send you the link (it will be on youtube) Hopefully this will help with more sales for you, even if only to Australia.
Oh yeah Kenny, have you sold any of these to Aus before ? Anyway mate, take care, smile, and one day if your really really lucky you can come visit and I'll take ya fishing - REAL fishing mate !
Regards, Greg Ashby
Ken- Received the order today (that must be a record for USPS). I have already measured the plate voltage for my Metropoulos GPM45 and am in the process of measuring the cathode current. Having the MQ10 makes this an exceptionally easy procedure. Being a replica of a Marshall JTM45, the most time consuming portion of the measurement procedure has been removing the chassis from the head cabinet!
The amp is decidedly running cool which explains it's present sonic character (the plate voltage is a bit lower than the spec). I confirmed what my ears were telling me about the amps sound. Can't wait to play through it now that it's biased in the correct operating range. Ran the cathode current up to just below 70% plate dissipation for the KT66. The tone test will begin after a cool down and buttoning the amp back up.
Thanks for a terrific package. The BiasPro could not have been simpler to use, the directions were concise and effective, and your customer service has been excellent (I know I asked a lot of questions before I purchased but you always replied in short order). On top of that I placed the order late Friday and it arrived Monday!
A lot of people avoid biasing their own amps and I can't blame them because of the nature of the operating voltages used in tube amps. However, I would guess that those people are potentially leaving a lot of tone on the table. Your MQ10 system is so easy and accurate that anyone thinking about biasing their own amp should consider it an essential tool in optimizing the tone of their tube rig.
Best regards- Matt Kozink
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Hi This is the third one-These are great, I now need the 7591 version. Thanks Tim
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Excellent service and prompt delivery. The device worked perfectly and easy to understand biasing instructions were provided. Makes biasing simple and safe. I highly recommend this device.
- hellmwc
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Just received your BiasPro and went at it with my new DRRI. FINALLY, I am able to evaluate how well my tube vendor does (or does'nt) match my 6V6's. Additionally, I now know which hardness of tubes I should purchase (given the DRRI's bias limitations). Setting the bias was the EASY part. Gaining knowledge from the BiasPro's use was the FUN part.
Cameron
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Hello Ken, thank you for the fine product and most especially for the detailed instructions. I had purchased the bias rite as the do it yourself kit from Tube Depot. The instructions for assembly were incomplete and there was nothing on how to properly use it. It was a bit of a pain for newbie to put together but I ended up crushing it by accident pulling out of the amp( a little too strong for my own good at times). Yours looks a lot better! At least I get how and why it works now.
Thanks again. - joeyp_2718
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I don't think I justified your product in my feedback. I can not express enough how neato it is to have my new tube meter. Now a days it is hard to find something that is more than a gimick to make me sound better. Thanks and I am a bi rube roller and this is the mast accurate and most inexpensive tool for a guy like me. A guy named James Hysong turned me on to this too. Best regards Joe Z.
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Hi, The BiasPro is great! Physically the unit is much better than any bias tool i've used before. One big improvement with your model is the probe tube sockets. I wrestled with probe testers previously with the tube sockets being too tight and extremely difficult to use.. the BiasPro model is designed just right. Made checking my various amps much more easy and I wasn't afraid of snapping off guide pins. Very happy with the product. One question .. has any of your other customers identified a nice small hard case for the BiasPro QuadStage ? thanks, DAn.
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