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Old 9th Apr 2021, 8:05 am   #10
snowman_al's Avatar
Join Date: Dec 2018
Location: Llandeilo, West Wales, UK.
Posts: 825
Default Re: Mullard 3-3 voltages query

Sorry to go against the grain, but I do not like the 3-3 design.
For every one you have working in spec, there are 2 failures...
They are so dependant, amongst several factors, on the EF86 and EL84 characteristics being the same as the originals used in the 'model' amp. First step would be try several other EL84s first, then other EF86s.
You do not say what value cathode resistor you have at the moment?
Also a random output transformer might need feedback changes from the Mullard values. Have you tried it with the feedback disconnected?

If all else fails, do what the BBC did, and AC couple the EF86 to the EL84 as in their AM8/2A circuit...
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