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In Reply to: RE: Dennis Had recommended it posted by ianm0 on January 26, 2015 at 15:55:45
I usually go for a Golden Ratio plate dissipations for best sound, keeping voltage high and reducing current to obtain a Golden Ratio which is 62%.
So, on a 25 Watt rated Finals plate at 62% is 15.5 Watts plate dissipation.
If P-K difference ( voltage across the output tube ) was 450 VDC and P, ( Power in Watts ) was 15.5 Watts, Current ( I ) is P over V ...or ..... I = 0.03444 A ., or.... 34.4 milliamperes.
Tubes may now last, not 10,000 hours, but 50,000 hours ... and sound better all along !!!
Have YOU documented YOUR 6SL7 pin voltages, stock amp ? If so, will you PLEASE send me yours, pins 1 through 8 ?? If not done, how do I reach Dennis Had?
Thank you. Need to know stock 6SL7 voltages ASAP.
Jeff Medwin
Follow Ups:
Jeff,
Golden ratio and high voltage/low current might get you a nice class B amplifier in push pull.
My long time question is, can SE only sound good in class A?
Some of my SE amp hv breaking sound with bias at 40% power dissipation. But pp wud not break so easily.
Cud the breaking sound be due to some kind of oscilation??
GR is about 62%, not 40%.whtz de effic of your speaker load? maybe just clipping.
Edits: 01/28/15
Its EL34 se amp with B+ at 380v. I just chk your old post about the choke, mine has a Hammond 193H with DCR at 60 ohms. For the moment I just add a 50 ohm resistor in // to the choke. The sound improved a bit.
It has 375 volts at the anode, 28.2 volts at cathode with 700 ohms of R, about 40ma and 14w dissipation. Definitely not GR.. Bypassed by 100uf of Silmic2. I adjust the bias by ear. The overall sound is the best at about 800 ohms. (I place 1k, then add variable value of R in //) but it broke from time to time just for trumpet in the mid high region. When I biased higher, the sound became dark and lazy..
The speaker is Boston acoustic A23, small and nice, for my tv.
Jeff do you think if SE only can sound good with class A? I tend to think I need to take care something else...
btw the power trf is Hammond 370hx and opt is 125ese. The amp is hand made by an 80+ yr old nanny.. here!
Tks!
William
Class A means the tube is conducting all the time. If the tube stops conducting then the wave form stops.
With single ended circuits we can't let the wave form stop, that would sound awful.
With push pull circuits one tube at a time stops but the other keeps going so the output wave form doesn't stop.
With single ended circuits there is no other tube to keep going.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Sooo.. does it mean, if we biased at 15 watts, its class A for ampli efficiency x 15 watts?
Above it, the sound broke??
Is thr any dynamic bias??
"Sooo.. does it mean, if we biased at 15 watts, its class A for ampli efficiency x 15 watts?"
Yes.
"Above it, the sound broke??"
Yes.
"Is thr any dynamic bias??"
Not with normal fixed bias or normal cathode bias. There are "sliding bias" circuits that can be used but none that I have seen used in SET amps.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Ok, my problem is solved now, i changed the output transfor output from 16 ohms to 8 ohms and the broken sound is now gone even with lower bias...
Tks!
Ok, i guess i hv to give up the nice sweet spot with the lower bias. Instead push up the bias to the golden ratio...well 50% is actually also a golden ratio.. worked out better ps n other circuitry. It has multiple groundings and old cloth cables.. haha!!
Platinum ratio = (1 + sqrt(6)) / 2 = 1.725
Golden ratio = (1 + sqrt(5)) / 2 = 1.618
I find the platinum ratio gives a brighter, cleaner sound; the golden ratio is warmer, softer, a bit too "ductile" for my taste, for lack of a better term.
BWAHAHAHAHA.
Bike photos please....
Edits: 01/26/15
Yeah, and I'm sure that thing in the picture is a GREAT amplifier.
What a load of hooey.
:-(
-Henry
Total hooey. Considering different manufacturers spec their tubes differently (some considerably more conservatively than others) the whole concept of a 'golden ratio' derived operating point is totally delusional.
Edits: 01/28/15
Does not sound very science-based to me... Modern science, that is.
That could be possible
Have you visited? It's great
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