nerdorama -
Transcendar did a similar thing for me with their headphone-sized transformers, back when they were still winding transformers rather than rebuilding them.
Transcendar did a similar thing for me with their headphone-sized transformers, back when they were still winding transformers rather than rebuilding them.
I got quite good results with GU50 in UnSET. up to 20w in SE. 12-15W distortions are low, mostly 2nd. Schematics is canonical from George.
Got a few measurements made this morning which I posted here:
https://hifihaven.org/index.php?threads/gu50-6p15p-se-amp-with-local-fdbk.12253/#post-279329
OK for starters on a piece of plywood. I was hoping for a little more power but 9.75W at clipping is fine. I think the parallel feed arrangement eats a bit of power compared to a series feed of an otherwise similar design. That happened as well in two versions of a 6V6 SE project. Parallel feed had more extended bass and similar HF but the series feed had a bit more power at clipping.
https://hifihaven.org/index.php?threads/gu50-6p15p-se-amp-with-local-fdbk.12253/#post-279329
OK for starters on a piece of plywood. I was hoping for a little more power but 9.75W at clipping is fine. I think the parallel feed arrangement eats a bit of power compared to a series feed of an otherwise similar design. That happened as well in two versions of a 6V6 SE project. Parallel feed had more extended bass and similar HF but the series feed had a bit more power at clipping.
I use TTG-KT88SE as OPT, TSTA 0250/001 for power. 6Ohm load on 8Ohm output. Resistors P-G1-GND 300k - 56k (47k also good). Bias around 70-80v. G2=300v (250v also good). Ip = 115ma. Vp-k=330-340V I believe. Plates are bit reddish in the dark. First stage is also UnSET with 6j49p
I reworked the power supply for a bit more voltage and re-biased and now am seeing 14.5W just before the onset of visible clipping. Took it to a friends yesterday and listened for several hours. Sounds super nice. It's dead quiet on some 105dB Altecs and with almost 15 watts it rocked the house. It is very resolving and detailed but it doesn't get harsh at all. Any glare or harshness gets aggravating with my tinintus. This may make me into a SE person. FR is -3dB at approx 20Hz and 60kHz at 1W. This changes very little at 10W.
John
John