The JE Labs/ Angela SE 2A3 amp done my way
- Thread starter Redboy
- Start date
I am noticing a little less power. That just means I'm turning the volume to 11 o'clock rather than 9 o'clock, though. That won't bother me, since I never listen at really loud levels and I do seem to have enough reserve - I don't know for sure at the moment because the kid's in bed and I can't test that. Before I rewired, I did hear a little more sibilance than I was comfortable with - that seems to be gone now. Tamed the highs a tad, and brought out the lows more to my liking.
I don't know about the feedback thing, Jay... I just put this thing together according to the schematic. I didn't actually understand why I was doing what I was doing, and still don't for the most part - but it's coming.
I don't know about the feedback thing, Jay... I just put this thing together according to the schematic. I didn't actually understand why I was doing what I was doing, and still don't for the most part - but it's coming.
jaymanaa
RIP 1961-2018
Without using any fancy lingo (because I don't know any), feedback is where you take some of the amplified signal (usually from the output of the output TX) and inject it back into the small signal tube (in this case the 6SL7). Somehow this reduces distortion and sacrifices some power (maybe someone could explain it to both of us
). I was thinking with your higher Z you could do away with it, or reduce it, but I don't see any on the schematic. Have you checked your plate disapation on the 2A3s (just curious as to what it is). I think you may be at the dreaded "buy some NOS 2A3s" stage of the game. :drool: I started out with Sovteks in my monos, and they are very nice, but the old RCAs really do have something special going on. I was listening to mine last night and paying special attention to the bass response. Sometimes I think we get conditioned (by other types of amps and speakers) to expect our pants legs to move with the bass notes, but when you really listen to a well mastered recording on SET, I think the fidelity is definately there. There is a "texture" or maybe "resonance" to the bass notes, instead of just a "boom". 
). I was thinking with your higher Z you could do away with it, or reduce it, but I don't see any on the schematic. Have you checked your plate disapation on the 2A3s (just curious as to what it is). I think you may be at the dreaded "buy some NOS 2A3s" stage of the game. :drool: I started out with Sovteks in my monos, and they are very nice, but the old RCAs really do have something special going on. I was listening to mine last night and paying special attention to the bass response. Sometimes I think we get conditioned (by other types of amps and speakers) to expect our pants legs to move with the bass notes, but when you really listen to a well mastered recording on SET, I think the fidelity is definately there. There is a "texture" or maybe "resonance" to the bass notes, instead of just a "boom". 
PakProtector
AK member
hey-Hey!!!,
NFB doesn't cost any power. It reduces the gain though. The gain reduction noted with the 5k load is not just a power drop, but also due to an increased step down ratio in the output TX.
cheers,
Douglas
NFB doesn't cost any power. It reduces the gain though. The gain reduction noted with the 5k load is not just a power drop, but also due to an increased step down ratio in the output TX.
cheers,
Douglas
jaymanaa
RIP 1961-2018
Thanks for the clarification Douglas. Something didn't feel just right when I used the word power, and now I understand it better. :thmbsp:
If I'm understanding feedback correctly, then I believe the answer is "no, I don't have any feedback in this circuit." But Jay, you already pointed that out.
Could be. I've had a couple of people offer to look through their stashes, but nothing's come of it yet. I'm definitely willing to try it. This exercise has been well worth it for me. I've got a nice looking finished product that will be really special once ejfud finishes his magic, and I've got lots of stuff in the garage that I need to part with anyway. Might as well make it work for me.jaymanaa said:
jaymanaa
RIP 1961-2018
mhardy6647
Lunatic Member
Zombie thread alert.
interestingly, this thread's titular amplifier now finds itself somewhat incongruously sitting in a suburban living room not too far from Boston, hooked to a motley agglomeration of sources (with no preamp) on one end and a really nice pair of Altec 604E duplexes (in "Billfort's" cabinet design and with Mastering Labs XOs) and Fostex T90A 'supertweeters' hooked to the other end. It seems to like it there, too.
Suddenly, there is a lot of Redboy in my living room...
interestingly, this thread's titular amplifier now finds itself somewhat incongruously sitting in a suburban living room not too far from Boston, hooked to a motley agglomeration of sources (with no preamp) on one end and a really nice pair of Altec 604E duplexes (in "Billfort's" cabinet design and with Mastering Labs XOs) and Fostex T90A 'supertweeters' hooked to the other end. It seems to like it there, too.
Suddenly, there is a lot of Redboy in my living room...
mhardy6647
Lunatic Member
Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaagh!!
Not at all. The CD player and DAC have that newfangled remote-control volume thingy. The tuner and reel to reel decks have variable output levels... and the SUT/phono preamp has a Martin Luther "signature" model passive preamp (attenuator) on its output. The sources are all connected to Mr. Amp via a state of the art 4-in/1-out switch box from the world-renowned audio boutique, Chez Radio Shaq.
mhardy6647
Lunatic Member
I think that the kittehs are increasingly terrified to even set foot in the living room
Also, it may be recalled that Harpo the Kitteh from Heck who spent two years in exile at our household was re-united with his mistress when she matriculated into law school last fall and now lives in Virginia... Harpo had a tendency to show up during gear photography sessions at my house during his tenure there.
Also, it may be recalled that Harpo the Kitteh from Heck who spent two years in exile at our household was re-united with his mistress when she matriculated into law school last fall and now lives in Virginia... Harpo had a tendency to show up during gear photography sessions at my house during his tenure there.
Not surprising but that link's bustedHere's my schematic. It's the project from Angela Instruments: http://www.angela.com/catalog/how-to/SE.2A3.html, and I'm building it by the book for my first attempt. I'm not savvy enough to start making it my own yet.
Thanks for your help.
I think if I dug a hole straight down, I'd show up somewhere in your neighborhood.
Yes, but thanks to the internet wayback machine, it's still out there somewhere!
http://web.archive.org/web/20060618122016/http://www.angela.com/catalog/how-to/SE.2A3.html
