Finished the ST-70 from Blair
Posted: Sun Jan 24, 2016 4:48 pm
Here's the, well not really, ST-70 I got from Blair. I originally made a board with 2 6AU6s as pre amps, and a 6C4 concertina, but I got a lot of oscillation with feedback. I couldn't get any more than 8db of feedback and POW. I switched to a LTP with the 6AU6s in triode mode, they seem to work pretty good.
I don't think there was any Dynaco parts left on the chassis, even the sockets say "6K6".
I don't know what the output transformers are rated for, but I'm getting 27 watts out at 1KHz. At 15KHz I'm getting a sawtooth out and that's at the most 15 watts.
It did have a voltage doubler using both 6.3 windings to make negative bias. Unfortunately it put -12 on the filaments, so I used one filament and a voltage quadrupler for bias.
Maybe in 20 years someone will get ahold of it and say "What was this guy thinking?" and rip everything out.
It does sound very good. Got to love those Russian toobs.
I don't think there was any Dynaco parts left on the chassis, even the sockets say "6K6".
I don't know what the output transformers are rated for, but I'm getting 27 watts out at 1KHz. At 15KHz I'm getting a sawtooth out and that's at the most 15 watts.
It did have a voltage doubler using both 6.3 windings to make negative bias. Unfortunately it put -12 on the filaments, so I used one filament and a voltage quadrupler for bias.
Maybe in 20 years someone will get ahold of it and say "What was this guy thinking?" and rip everything out.
It does sound very good. Got to love those Russian toobs.