Are you a tone freak and wanting to bias your own tube amps? It’s critical to have the power tubes biased properly for the amps to sound their best, and the tubes will last for decades.
I’m a professional guitarist, a luthier, and an electrical engineer. I own several vintage guitar amplifiers that I love and maintain. I designed several BiasPro bias tool product lines that are safest and easiest, and allow anyone to perform biasing their amps.
BiasPro - purchased and
used by musicians, guitar & amp techs, amp and vintage audio hi-fi service
centers, and music stores world wide.
Hadley Hockensmith of Neil Diamond Band, Ron Freschi of Babylon A. D., Larry Rodgers of Rodgers Amplifiers, Evan
Bovee, guitar tech for 3 Doors Down/Miley Cirus,
and Paul Karoutas, guitar tech for Cheap
In order to bias correctly you’ll need to know your amp’s plate voltage value. If you don’t know it or don’t know how to measure it, I recommend purchasing with the VI Module option. It will allow both bias current and the plate voltage values to be measured.
Please email me with questions, support, and ordering. I do not accept phone calls unless we've agreed via email first. Email: firstname.lastname@example.org
• Image A: Shown - These are being phased out. BiasPro 8C-S (8-pin octal)
single stand-alone bias probe. Also available in 9-pin miniature socket BiasPro
• Image B: Shown - Quadstage BiasPro Q10 in dual
configuration with BiasPro 8C bias probes
• Image C: Shown - Quadstage BiasPro MQ13 in dual
configuration with BiasPro 8C bias probes
D: Shown - Quadstage BiasPro Q10 in dual configuration with BiasPro 8C bias
probe and BiasPro VI-8Cbias/plate
voltage combo probe (shown both the bias
current and the plate voltage value with a flip of a switch)
• Image E: Shown - Quadstage BiasPro MQ13 in dual configuration with BiasPro
8C bias probe and BiasPro VI-8C
bias/plate voltage combo probe (shown both the bias current and the plate voltage value with
a flip of a switch)
• Image F: Shown -
BiasPro 8C (octal)and BiasPro 9C (9-pin miniature) bias
probes. Also available BiasPro 7591
• Image G: Discontinued
• Image H: Shown - Bias Current / Plate Voltage Combo Probes: BiasPro
VI-8C (octal)and BiasPro VI-9C (9-pin miniature) bias/plate
voltage probes. Also available BiasPro
• 8-PIN 7591/7355 (Fisher, Scott): 7591, 7591A, 7355, etc.
VI MODULE PROBE - measuring the plate voltage
The plate voltage is typically in the 400VDC to 500VDC range (high voltage), and I don’t advise you messing with that directly unless you’re a qualified technician.
The VI module probe (in plate voltage setting) is designed with a precision resistor network to reduce the high voltage value down to mill-volts (attenuation of 1/10,000). You’re now dealing with a safe voltage value in mill-volt range rather than in hundreds of volts. For example, a readout displays 45.3 mV which corresponds to 453V actual plate voltage (ignore the decimal point).
Usually the plate voltage is the same across all power tubes, so you need only one plate voltage probe cable. They are available for all tube types listed in the “SUPPORTED TUBE TYPE” section.
• Allows you to monitor each cathode current (low
voltage side of the tube) on up to four output power tubes with a rotate
of a switch as your adjusting the bias
• Allows you to verify the newly purchased “matched” tube set. Often they’re not matched as they say
• Allows you to create your own “matched” tube sets by grouping the tubes that draws similar amount of cathode current
• Versatile open non-hardwired design – test one, two, three, or four of many different types of 8-pin and 9-pin tubes (Quadstage BiasPro Q10 and MQ13)
• Interchangeable & replaceable
probe cables - test both 8-pin octal tubes such as 6L6s and 9-pin
miniature tubes such as EL84s, and many other unique tube types
(Quadstage BiasPro Q10 and MQ13)
• Protects your investment
– start with dual and expand to quad configuration when needs arise -
replace cable if breaks - attach specifically designed cables for
unique tubes (Quadstage BiasPro Q10 and MQ13)
ELECTRICAL SAFETY DISCLAIMER
As with any electrical
equipment, amplifiers are high voltage devices.
They can cause serious injuries or even death if mishandled. Always use common sense and caution when
handling high-voltage devices. If you
are unsure of what you’re doing or are uncomfortable biasing amplifiers
yourself, let the qualified technician do the job.