16-05-2023, 09:28 AM
Test them how Joe? I think I tested the primary L, frequency and low frequency response at full whack, apart that I used my ears. The first pair I used to build the first 807 PPP AB1 amp, my mate has it on long term loan, he's a bit of an audiophile and says him and mates said that amp and by inference your OPT's were as good as if not better than any of the high end amps they'd heard.
The other pair I built into a 807 Class A PPP mixed fixed bias/cathode bias, 807's running at 500v HT g2 300v regulated. the 807's are driven by a 6BL7 LTP and DET20 front end. I've just tweeked it, increasing the coupling cap size/lowering the LF response and also reduced the open loop gain a lot. I've not tested it on the bench but it sounds very good but i have it running with no NFB at present, needs some more work but pushed for time.
At present I'm trying to get the attached amp up and running, I'm currently running two 6BG6GA's in PP AB1, driven by a 12BH7 LTP and triode strapped 6CL6, it's ok but again needs tweeking.
This all takes time which I'm a bit short of at present as mentioned.
Andy.
The other pair I built into a 807 Class A PPP mixed fixed bias/cathode bias, 807's running at 500v HT g2 300v regulated. the 807's are driven by a 6BL7 LTP and DET20 front end. I've just tweeked it, increasing the coupling cap size/lowering the LF response and also reduced the open loop gain a lot. I've not tested it on the bench but it sounds very good but i have it running with no NFB at present, needs some more work but pushed for time.
At present I'm trying to get the attached amp up and running, I'm currently running two 6BG6GA's in PP AB1, driven by a 12BH7 LTP and triode strapped 6CL6, it's ok but again needs tweeking.
This all takes time which I'm a bit short of at present as mentioned.
Andy.
