|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
76.90.39.24
In Reply to: RE: Here is the schematic for one channel ..... posted by Triode_Kingdom on June 04, 2017 at 08:43:02
"That's an unusual treatment of the suppressor grid"
I think vinnie just left out the cathodes. G3 connects to the cathode.
Also I'm guessing the G2 of the output tube connects to the plate.
While I'm at it, using a 47uf cathode bypass cap instead of a 470uf cathode bypass cap was probably ill advised if the amp was being used full range.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Follow Ups:
Why do you say ill advised? I used it because that was what I had on hand, but it sounds just fine. What are you expecting to have happen?
Yes, each G3 should also have a k by it.
Edits: 06/04/17 06/04/17
"What are you expecting to have happen?"A loss of amplifier bass response and a loss of damping factor.
When the cathode is not bypassed to the lowest frequency of interest it allows current feedback to happen at the low frequencies (amplifier bass response loss).
That current feedback will increase the plate resistance of the output tube and that will lower the damping factor (and, depending on the speaker being used, cause the speaker's bass output to increase).
The two in combination can cause bloated, slow sounding bass on most true full range speakers.
On the other hand, some speakers need just that kind of thing to produce low bass.
On the third hand, if the speakers have no output at the lowest of frequencies then the effect might not be heard at all.
I was just saying that technically cathodes should be bypassed all the way down to the lowest frequency that the amplifier is meant to be used at.
For instance, (speaking of just the filter created by the total cathode impedance and the cap) if the -3db point was calculated at 4Hz with a 470uf cap in place (leaving 40Hz completely un-attenuated and phase shift free) then a 47uf cap would give a -3db point of 40Hz (meaning that the amplitude would be down at least some all the way up to 400Hz and the phase would be shifted all the way up to 400Hz)
If it sounded "good" to you, I can't/won't argue with that. But it's just not technically correct.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 06/04/17 06/04/17
Well, just for the hell of it I will have to try it with a 470 uf cap (if I can find one in my parts bins somewhere) just to see what it sounds like by comparison.
In addition to speaker response, whatever it might be, I'm pretty sure Vinnie isn't using full range OPTs.
--------------------------
Buy Chinese. Bury freedom.
There are many factors that can play into this.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Isn't the 125ese considered a full range opt?
From the data sheet,"Designed for general purpose or replacement use (not Hi-Fi) in single ended tube output circuits.
Frequency response: 100 Hz. - 15 Khz (+/- 1db max. ref. 1 Khz).""For full frequency response (20 Hz. to 20 Khz.) single ended output transformers - see our 1627-1642 Series"
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 06/04/17
Yes, I know what the blurb says, but many people have been very impressed with the performance of them, myself included. Don Garber also offered them as a cost saving option in his 2A3 amp and said he was impressed with the bang for the buck you get with them.
Besides, how many of us are really running opts that go 20 to 20? Not very many I will bet, considering the extra cost. It's that last 5% again that can cost you big bucks.
Very few gapped SE transformers will go flat to 20Hz because it's hard to get the necessary inductance without introducing a lot of capacitance that causes losses of the high frequencies.
Having said that, the "big buck" transformers get very close to 20Hz and extend well beyond 20kHz.
There are a lot of things that factor into what a system ultimately sounds like but I have always believed that the best output transformers, together with circuits that are built as broad band and distortion free as possible results in really good sound.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Can't argue with that, but it leaves one thing out. How close to perfect do you want to get, and how much are willing to spend to get there?
I suppose for some people money is no object, but for the rest of us there will always be trade offs. Each of us has to determine for themselves what those will be.
It's not a philosophical issue. The Hammond transformers you're using fall short of hi-fi performance. Reasonable cost alternatives are available from Hammond, Edcor and Triode Electronics. Used transformers by HK, Scott and Fisher also show up occasionally on eBay. Full range OPTs will make a significant contribution to the sound of your amps.
--------------------------
Buy Chinese. Bury freedom.
It is a philosophical issue in that we all have our own opinion of what "reasonable" is and what sounds good to us and how much we want to spend.
There is no such thing as perfection with audio electronics.
Even with the best parts it's always a series of compromises, as is life.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: