Bias Master™ - TAD, tube tester, with 4 probes

Bias Master™ - TAD, tube tester, with 4 probes

Tube Amp Doctor (TAD)
Pictured: Octal
Pictured: Octal
Pictured: Noval
Pictured: Noval
Customer image:<br/>"Love my TAD Bias Master"
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Pictured: OctalPictured: Noval
Customer Images:
Customer image: "Love my TAD Bias Master"
In Stock

Bias Master™ system BM4 Measures Bias current of the vacuum tubes in your amp. Includes 4 probes and english/german operation manual.

The Bias Master™ allows you to monitor the bias current safely and easily. While adjusting the Bias control pot of your amp, the Bias Master™ shows the actual result. This lets you set and evaluate the full reasonable biasing range your amp and tubes offer to find and set your personal perfect choice.

The Bias setting has a dramatic impact on the amp's response, break-up and dynamic character.

Probe Type Measures
Octal 6L6GC, 6550, EL34, 6V6GT, 5881, KT66, KT88, KT90, KT100, KT120, 7027A
Noval EL84 types

For additional probes (for testing other types of tubes), see S-TBMA2-X

Item ID:
Tube Amp Doctor (TAD)
Part Numbers
Probe TypeOur Part NumberUPC/EAN
Product Measurements by Type
Item Height2.1 in.
Item Length5.76 in.
Item Width3.6 in.
Packaging Information
Packaging Dimensions8 in. × 5 in. × 3.75 in.
Weight (Packaging)1.048 lbs.
Product Measurements by Item
S-TBM4 - Octal versionItem Height2.1 in.
Item Length5.76 in.
Item Width3.6 in.
S-TBM4-EL84 - Noval versionItem Height2.1 in.
Item Length5.76 in.
Item Width3.6 in.
PDF: Operation ManualAll Models

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Specifications, Files, and Documents

PDF: Operation Manual Operation Manual67.08 KB

Questions and Answers

Click each question to see its answers.
Asked by Anonymous on November 3rd, 2017.
Matt H.
November 8th, 2017
Staff Member
Yes you can but the bias meter simplifies the process and does the mathematical conversions for you.
Asked by Anonymous on January 16th, 2019.
January 16th, 2019
Staff Member
No, such a list is not included with this meter, but we have provided a bias calculator that may be of assistance:

Product Reviews

5.00 out of 5 based on 1 reviews
Gary Johns - December 30th, 2021
5 out of 5

Finally got myself one of these, after wanting one for quite some time. I can now easily check and set the bias on my amps, and the TAD Bias Master makes it very enjoyable. Thanks to TAD and AES.