with triodes have not yet tried, but with pentodes the results are excellent. CFB 14-16% allows you to completely abandon the general feedback. The sound is much better.These NFB OPT windings have what effect in sound quality?
Great news, thanks for inform.with triodes have not yet tried, but with pentodes the results are excellent. CFB 14-16% allows you to completely abandon the general feedback. The sound is much better.
Wonder what tech info I need to order an OPT with CFB 16% to 6C33 SE??
Wonder what tech info I need to order an OPT with CFB 16% to 6C33 SE??
That's typically a tube that will not benefit so much from CFB.
I have something similar
6E5P ccs-300b- IT - gm70
1075v 90ma
It sounds really nive, like a 300B on steroids
Similar to mine. 3A5 -> 4P1L -> IT -> GM70. 1050V 93mA.
Next mod is higher B+, 1200VDC 80mA. I have gathered all the necessary components but lack of free time is a problem.
Next mod is higher B+, 1200VDC 80mA. I have gathered all the necessary components but lack of free time is a problem.
I had mine at 1200v to begin with and changed it to 1075 which seems to be a sweet spot with my OPT (Monolith Magnetics)
I had mine at 1200v to begin with and changed it to 1075 which seems to be a sweet spot with my OPT (Monolith Magnetics)
You never know if you don't try
You have better sound at 1075V B+ or? Lower B+ higher current. For OPT is better lower current because DC pre magnetization will be lower. Looking at the graph, GM-70 has even lower THD on 1200V 80mA operating point.
But, at the end, sound is what makes the magic and I'll see what's better for my ears. Good to share the experience.
Regards
It is an interesting design, and quite valid. I designed and built a much simpler GM70 amp that I completed about 7 years ago, class A1 fixed bias with interstage driven by a triode connected D3A, and all solid state supply with SiC rectifiers for the 1kV supply and CLCLC filtering with the chokes in the negative lead to minimize stress on the insulation.. I can get almost 20W in A1 with 7K primary 100mA/1kV. It remains in service to this point in time.
Hello, can you share your shematic?
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