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Bias Balance Control Kit

Product Code: BBCU-1A Categories: ,

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The Dynakit BBCU-1, Bias Balance Control Upgrade is a simple and effective circuit upgrade for equalizing the bias current between each pair of output tubes. Designed specifically for the original or new Dynakit ST-70, Mark II/III and MKIV amplifiers. The Dynakit BBCU-1 Kit includes all components, wire, hardware and a step by step by step installation & operation manual.

Easy to install via our unique bias balance pot circuit board mounting design which eliminates the need for drilled holes or chassis alterations. Simple to use and conveniently located at the front biaset octal sockets.

In operation, the bias level is first adjusted for each pair of output tubes via the original 10k bias pot, followed by the balance adjustment of the current between each pair of output tubes via the secondary balance pot. All test points are conveniently located at the front of biaset octal sockets.

The Dynakit BBCU-1 Kit is designed for installation in a working amplifier with a “good” set of vacuum tubes. Installation of this kit will not correct pre-existing tube biasing problems and/or restore the performance of weak or defective output tubes. Matched tube pairs are not required; however, refrain from mixing tube types having different electrical characteristics.

On a final note: Installation of the Dynakit BBCU-1 will defeat the use and/or connection of the Preamp Power socket to your preamplifier. Modern preamplifiers do not require this power supply connection. Accordingly, if you should have any questions please contact us at

Select the BBCU-1(A) for the MKII and MKIII Mono Amplifiers. Price is for one (1) bias kit and manual.

Select the BBCU-1(B) for the MKIV Mono Amplifier. Price is for one (1) bias kit and manual.

Select the BBCU-1(C) for the ST-70 Stereo Amplifier. Price is for one (1) dual bias kit and manual.

Note: The BBC-1 Kits (A), (B) and (C) are Different with regard to the assembly manual and provided parts. SELECT CORRECTLY FROM ABOVE SELECTION. 

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