MANUFACTURING NOTE: As Weber re-releases the Bias Rite units, we have upgraded some of the components. However, in order to remain sensitive enough to provide accurate reading, some parts are still very delicate. DO NOT attempt to play your guitar while the Bias Rite adapters are inserted. Doing so may very well cause the current to exceed acceptable tolerance for some of the components and damage the unit. Remember, you are only using the Bias Rite to adjust the IDLE current, which means the current level when no signal is being put through the amp.

Please Note: The locator pin in the center of the male octal plug is sensitive to breakage from twisting or lateral (sideways) force. It will break or crack and then it will be difficult to locate the proper pin orientation for re-insertion of the adapter head into the socket. An incorrect installation may damage your amp, the Bias Rite, or both. You must take great care in inserting the bias rite head in the socket. The best method is to set the head adapter on the socket and lightly turn the head until you feel it drop into the socket holes. Also keep the head straight up (perpindicular, vertical right angle) from the tube socket, and push straight down. Do not wiggle, twist, or allow it to be insterted at an angle. If you do break a locator pin, it can be repaired using thick gel super glue. For the record, I have been pushing and pulling tubes for over 40 years and was aware this could be an issue. When I designed our octal plugs, I had the factory make the wall of the locator pins twice as thick as a typical vintage vacuum tube locator pin.

We cannot warranty broken locator pins, but we will repair or replace them for $25 a head plus return shipping.
RMA Form --> Click Here

The Bias Rite Cathode Current Monitor is a self contained unit designed to allow the user to set the desired idle cathode current value with the G1 bias control. Two adapter sockets are provided so the power supply may be loaded as it would be in normal operation, an important feature since most amplifier power supplies are unregulated. One and four adapter models are also available. The Bias Rite is supplied with an integral digital readout which measures the cathode current to the tenth of a milliamp over a range of 1 to 199 milliamps. Power is supplied by an internal 9 volt battery.

The VI switch allows one to switch the digital meter between reading plate voltage and cathode current. This allows one to quickly calculate plate dissipation to ensure that the operating parameters of the output tubes are within a safe range. The VI switch is standard on all complete models. The VI option is also available on the BR-AH (head only) as a $25 upgrade.

The Bias Rite units are available with either octal or 9 pin heads, or a combination of both (BR2+2).


Insert tubes into Bias Rite Adapters, and the adapters into the ampís tube sockets.


Turn the ampís power on, and let the tubes warm up as you would if you were turning your amp on to play.


Once the tubes have warmed up, switch the 
standby off so the amp is in operating mode. Turn the power on the Bias Rite on and set the V.I. switch to Ik. This will show you the tubeís idle current (bias) in milliamps (mA).


Using the bias adjustment trim pot in your amp,
usually located inside the chassis or underneath it, adjust the tubesí bias current to the desired level.  Switching between the sockets will show each tubeís current on the meter.


Switching the V.I. switch to Vp will allow you to measure the plate voltage of each tube.

If you need help determining
the bias level that you want to
achieve, please visit this page:

Bias Calculator

Lead Time

Please be aware that most of our products, including Speakers, Attenuators, and Bias Rites, are hand-built to order, to ensure the highest quality. This means that you will need to allow at least 14 working days for us to complete your order, and then ship. Once your order has been shipped, we will email you the tracking number automatically.

We answer as many status requests as we can.
Please note that status checks within 14 working days of your original order date may be difficult to answer.

BR-2 (octal)  $120


BR-2 (nine pin) $140



BR-4 (octal) $135


BR-4 (nine pin) $175



BR-2+2 (octal and nine pin) $155



For those on a budget, the Bias Rite adapter head is available separately. The cable is terminated into standard red and black banana plugs that are inserted into your voltmeter.  With the VI Option, you can set your voltmeter to the 2 Volts DC range and the Bias Rite head does the proper scaling for reading plate voltage and cathode current.

BR-AH (octal) $40


BR-AH (nine pin) $50


BR-AH (octal) with VI option $65


BR-AH (nine pin) with VI option $75



The Right Angle Adapter allows one to bias a typical BF head without removing the chassis. The Angle Adapter is plugged into the socket, the Bias Rite head is plugged into the Angle Adapter, and then the tube is plugged into the Bias Rite head. The angle of the adapter is oriented for Fender amps where the space between pins 1 and 2 of an octal output tube socket faces the rear of the chassis. A different orientation may be specified on special order for no extra cost. Simply specify where the socket keyway is in relation to the rear of the chassis. For instance, if the keyway on the socket is facing the front of the chassis, you would specify 12 o'clock orientation. Also specify whether the tubes are mounted normal (Marshall, etc.) or upside down (Fender, etc.).

BR-RA (octal) $40


Keyway (locator pin) orientation: (i.e. 12:00, 6:00, 1:30, etc)
Using the illustration below for reference, which direction does the keyway need to point? It is your reponsibility to make sure the adapters you order will work for your purpose. Take a second to make sure you have the right direction noted.




If you purchased the Bias Rite head only (BR-AH), set your voltmeter to read the lowest volts range. Then, the meter will read directly in milliamps. For instance, when your meter reads 35 millivolts (.035 volts), it is indicating 35 milliamps of cathode current.

We feel this is adequate for the amp technician or user who is familar with tubes and their operation with regards to understanding biasing, plate dissipation, etc. However, we have had a suggestion that our instructions aren't comprehensive enough for allowing a person to use the bias rite properly. The suggestion was to include tube data, expected current readings for various amps and tubes, etc. We, of course, cannot provide that kind of data due to the wide range of applications, plate voltages, cold-to-hot bias preference, etc. Therefore, if you decide to purchase a bias rite product, please familiarize yourself with tubes, maximum power dissipation ratings, how to read plate voltage and calculate plate power dissipation, and the general operation of power output circuits. Also visit the various technical bulletin boards on the internet to get more information on the subject. Weber tests each bias rite product in an amplifier at full operating voltages and currents prior to shipping the product. Weber cannot assume liability for misuse of bias rite products nor the damage that might result from their misuse.

Content © 2000-present Weber Vintage Sound Technology

* The power dissipation calculation is plate volts times cathode current.(Vp*Ik)