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Home BR-4 Bias Rite
Item Code: BR-4
BR-4 Bias Rite Item Code: BR-4

BR-4 Bias Rite

  • Bias Rite (Four Octal Heads)

Can be used to bias amps with as many as 4 tubes (but can also be used for just 2).

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. Four 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. 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.

This item is hand-built to order, to ensure the best attention to detail is paid to its construction.  We build them one at a time, on a table - not hundreds at a time on an assembly line.  This allows us to reduce the margin for error and produce an overall higher-quality product.  Please allow at least 7-10 business days for your order to be built and then shipped.

Warranty: 1 year coverage. We will most certainly repair anything beyond that, but we cannot cover it under warranty. (Standard bench charge starts around $35)

Technical Details


In order to remain sensitive enough to provide accurate reading, some parts are 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 (perpendicular, vertical right angle) from the tube socket, and push straight down. Do not wiggle, twist, or allow it to be inserted 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." -Ted

We cannot warranty broken locator pins, but we will repair or replace them for $25 a head plus return shipping. See RMA form here.


Click Here to see Instructions for Use

We feel this is adequate for the amp technician or user who is familiar 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.

Customer Reviews of BR-4 Bias Rite

Just get one


September 12,2018
Just get one

Just received my Weber Bias rite BR-4 after a bit of a wait and immediately put it to use on my Marshall slp to check just how matched (amp tech’s words) the tubes where and happy to say they where pretty close. The BR-4 is definently worth it and if you plan on getting more hands on with your amp then this will make the job that much easier. I bought a few items and they were all packaged well and were delivered to my home in Australia in 10 days so i’m Very happy with service provided and I will definently be making more purchases from Weber. Do your self a favour and check them out