Alberto,
10k primary impedance is pretty standard for a PP 6BQ5 (EL84) transformer.
When you connect an 8 ohm loudspeaker to the 4 ohm tap the primary impedance (seen by the tubes) will be 20k which will not suit a 2A3 PP.
When there is a 16 ohm tap you can connect the 8 ohm loudspeaker to get a 5k impedance which will be OK for a 2A3 in PP.
10k primary impedance is pretty standard for a PP 6BQ5 (EL84) transformer.
When you connect an 8 ohm loudspeaker to the 4 ohm tap the primary impedance (seen by the tubes) will be 20k which will not suit a 2A3 PP.
When there is a 16 ohm tap you can connect the 8 ohm loudspeaker to get a 5k impedance which will be OK for a 2A3 in PP.
I tried using triode-wired 6L6GC's into Dyna ST35 output transformers (8k ohms primary). I used the 8 ohm taps. I found that the bass was light and wimpy sounding for some reason. Maybe the 55mA per 6L6 was too much current for the OPT to handle properly? I know the ST35 transformers have a high primary inductance (1100 H, if I remember correctly), so that can't be it. Is it possible that any imbalance in current draw between the output tubes could have been saturating the cores of the OPT's?
FWIW, I swapped out the Dyna OPT's for a pair of OPT's salvaged (years ago) from a junked Fisher 800 receiver. Those are 7k primary but designed for 7591's instead of 6BQ5's (more current and power). Those have better bass response with the 6L6's than the Dyna trannies did.
The question is why this all happened, but heck if I could tell you. Any help out there?
FWIW, I swapped out the Dyna OPT's for a pair of OPT's salvaged (years ago) from a junked Fisher 800 receiver. Those are 7k primary but designed for 7591's instead of 6BQ5's (more current and power). Those have better bass response with the 6L6's than the Dyna trannies did.
The question is why this all happened, but heck if I could tell you. Any help out there?
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