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In Reply to: RE: Which of Thorsten's schemas would you like? posted by RC Daniel on November 22, 2014 at 16:17:23
At least all of them that apply to the DIY HIFI Supply Lady Day 'Billies' 300B SET which I built WAY back when Brian Cherry first sold them as a kit.
By the way, has anyone heard from Brian Cherry lately? He is no longer available at DIY HIFI for at least the last year. Visited him in Hong Kong a couple times over the years but not since 2006 or so.
Follow Ups:
You probably already have it, but here goes. Edit: you have already linked it below. I was sure there was another, but maybe I am mistaken.
If you would also like some of Thorsten's others posts on the subjects - mostly related to his Legacy - and how these types of amps compare to other faves of his, shoot me a PM so I can send on some stuff by reply email.Cheers.
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki
Edits: 11/23/14
I have no experience with this circuit - provided for informational purposes.
"I have no experience with this circuit - provided for informational purposes."Yes that's it. I didn't remember it with an SV83/6P15P.
Does anybody have any experience with this type of tube regulated power supply? If somebody wanted to explain how this differs from using a gas voltage regulator tube, then I would greatly appreciate it. Are both useful in lowering hum?
Thanks in advance for any replys,
Jamie
Big speakers and little amps blew my mind!
Edits: 11/23/14
But I seem to recall he made some additional changes in order to flatten the frequency response in the version that DIY HIFI Supply eventually sold as a kit. I think he discusses it in the post below which no longer contains links to the schematics.
"A last trick is implemented in a pair of 1nF capacitors between the 300B Anode and 310A screengrid. This is actually positive feedback at high frequencies. This helps to overcome the HF rolloff inherent to the classic 91 Circuit, where usually 20KHz is around 3db down. In my Amp's I measure -3db somewhere at around 75KHz with this positive feedback in place, without -3db is around 20KHz as expected."
Also the 'optimized WE Cathode Bypass' which he discusses and which I suspect was likely the precursor to Jack Eliano's 'Ultrapath' circuit and which I have already implemented in my 300B amps.
I think, all and all, with his circuit description below and the circuit diagrams in page you linked to, one could pretty much duplicate the final product I heard at RMAF so many years ago.
Link below:
Hey Ivan, I did not notice that the schema had been removed from that post.Here it is:
Note, this design uses the partial WE connection: 50uF cathode bypass capacitor with 15uF B+ to cathode capacitor. Thorsten's later (DRD) amps used the full B+ to cathode connection (50uF+ using multiple capacitors in parallel) with no cathode bypass capacitor.
Cheers.
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki
Edits: 11/23/14
That's just about the same circuit that ended up in the DYI HIFI Supply WE91 SET amp.
Sure would like to take a whack at upgrading my current 300B amps but would be a LOT of work. Might try it with an octal driver with a 6V heater of some sort, like the 6J7.
Should never post before the second cup of coffee!
RCD,
I would like to second the motion for a Thorsten 91, except with a 6P15P as the driver tube, and with the JCV 6AS7 VR circuit.
Have you ever built the JCV VR circuit? Any comments about it? Does it reduce hum?
Thanks,
Jamie
Big speakers and little amps blew my mind!
Hey Steady,
No, have never built the JCV VR circuit; I am not exactly sure what it is and don't have the time to look right now.
If it is used to stabilise he driver tube screen, my guess is it would have more of an affect with the high GM pentode drivers, but I can't remember why.
Cheers.
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki
is no longer owned by Brian. I also recall there being some differences of opinion between Thorsten and the new owners regarding some of their boards... the power supply IIRC.
I will see what I can do about Thorsten's posts. I remember it taking a bit of searching to find them on AA, but I now have them saved... somewhere!
Cheers.
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki
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