Regarding bias of ST70 with DIYTUBE driver board

knowledge base for the classic Dynaco ST70

Regarding bias of ST70 with DIYTUBE driver board

Postby kevco » Sun Jun 28, 2009 11:33 am

I'm a bit of an amateur, so please be kind to me! When biasing the ST70 with DIY board installed as per the instructions, I reach a bit of a problem... After dialing in 400mV on both sides with no trouble, and balancing the outputs using the balance pots on the driver board to 0 volts, flat, I reach item "5" on the instructions, stating "adjust to 500mV...using the Dynaco wire-wound pots". My problem is here- when turning the left pot up, I run out of turn at about <>480mV. No more pot to turn...The right dials in 500mV without trouble. Any ideas? I know I'm dealing with pretty small differences here, but there's nothing wrong with perfection in my book! ;) Any help would be greatly appreciated. I should note that this amplifier works perfectly and sounds awesome.
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Postby TomMcNally » Sun Jun 28, 2009 1:10 pm

A couple of simple resistor changes will give you more range ...
see this thread:

http://www.diytube.com/phpBB2/viewtopic.php?t=3163&highlight=bias
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