Stupid 5w SET Amp
- Thread starter bsujeep
- Start date
Mike Stehr
Poverty Audio
Here's the 71A circuit I'm going to attempt to breadboard.
http://www2u.biglobe.ne.jp/~tossie/71ASE-E.html#circuit-fig
One reason is I have some 6SL7's, though I do have some 76's. Or was it 27's....or both 76 and 27.
I have these little 4-5 volt DC power supplies that will heat the 71A's. 5 volts AC is too much too tame for my limited brain.
http://www2u.biglobe.ne.jp/~tossie/71ASE-E.html#circuit-fig
One reason is I have some 6SL7's, though I do have some 76's. Or was it 27's....or both 76 and 27.
I have these little 4-5 volt DC power supplies that will heat the 71A's. 5 volts AC is too much too tame for my limited brain.
bsujeep
Go Boise State!!!
Before I started this thread I dreamed about SS amps. Now I dream of tube amps and have no clue what I am dreaming about. I hate weird dreams like that.
Divotdog
"I can fix it Grampa"
Just returned from bsujeep’s and got to listen to Dolly, very nice little amp Nate, very well done, we did a little vinyl and then spun some CD’s that was the best I had heard a CD sound in a long time, the little amp certainly lit up Bill’s Fortes, the only problem I had with it was the base, but never fear by the time she goes back to Cableguy she will be wearing some new Mahogany clothes. :thmbsp:
Redboy
a few good watts
Awesome, Mel! That base sucks and it's because I built it. My woodworking skills make a drunken beaver look like a skilled artisan! :sigh:
I've been kicking around the idea of building a Super Dolly, with better iron (though the Edcor is no slouch!) and some choice parts. That particular amp has some decent coupling caps, but I'd like to hear what some nice oils in that position would do, as well as some better stuff in the power supply.
A project for another day, I suppose.
I've been kicking around the idea of building a Super Dolly, with better iron (though the Edcor is no slouch!) and some choice parts. That particular amp has some decent coupling caps, but I'd like to hear what some nice oils in that position would do, as well as some better stuff in the power supply.
A project for another day, I suppose.
Hemingray
Vintage Geek
Well, These are my two SETs. One is Mono, the other is true Stereo. Please excuse the gloriously craptastic wiring on these. These were the first two SETs I'd ever made, using mostly scrounged components.
Mono: Started off as just a two tube job using a 6P5GT and a 12FX5 with attached speaker from parts radio. Speaker is now external, and has a 35W4, 6L5G, and the same 12FX5.
Stereo: 2x 25C5, 12AX7, and 25CK3 as the rectifier.
Both work pretty well, although likely not even a third as good as everyone else's SETs. I'd done these in my spare time for pure fun and do like the sound these guys produce. Pretty good use for plain-jane, not-so-popular tubes.
Mono: Started off as just a two tube job using a 6P5GT and a 12FX5 with attached speaker from parts radio. Speaker is now external, and has a 35W4, 6L5G, and the same 12FX5.
Stereo: 2x 25C5, 12AX7, and 25CK3 as the rectifier.
Both work pretty well, although likely not even a third as good as everyone else's SETs. I'd done these in my spare time for pure fun and do like the sound these guys produce. Pretty good use for plain-jane, not-so-popular tubes.
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currituckco
Super Member
Can't resist...here's my SET 46 amp, convertible to 45...
dnewma04
The Healer
Can't resist...here's my SET 46 amp, convertible to 45...
Love it. That's my favorite amp posted so far. Well, maybe next to Kegger's electrocution device.
eratosthenes
Active Member
I have a nice pair to come home to. My Bottlehead SET...
and a Zenith console pull, an EL84 SEP, turned into a standalone...
and a Zenith console pull, an EL84 SEP, turned into a standalone...
currituckco
Super Member
Thanks. The little silver box to the right is a bucking transformer I wired up to bring my 125v line down to the ~110-115 that monster old PT expects.
jaymanaa
RIP 1961-2018
Can't resist...here's my SET 46 amp, convertible to 45...
Are you running those strapped? If so is there any appreciable gain in power?:scratch2:
mhardy6647
Lunatic Member
what OPTs did you use in your 'ragtop'?
roberts67
Volts Vinyl Tubes
Hello!
Ok, that is a funny comment. I knew exactly which amp you were referring to. I am sure it sounds wonderful. Peace. Robert
Ok, that is a funny comment. I knew exactly which amp you were referring to. I am sure it sounds wonderful. Peace. Robert
currituckco
Super Member
Yes, strapped. I don't know about any gain in power - I've only run them this way. I know when I strapped EL34s for triode there was a loss of power by about half. 46s are supposed to be slightly lower power than 45s...where would the gain in power you're anticipating come from?
Anyway, this 1.25wpc sounds great on altec duplex speakers. That's for sure!
And mhardy - I used magnequest Rh40 "robin hood" transformers. Seem great to me, but I have nothing to compare them to.
Mike Stehr
Poverty Audio
Here's a 71A stereo breadboard circuit, with DC heating for the 71A's.
Mike Stehr
Poverty Audio
Thanks. It still came out grainy....wore out ol' dinosaur camera.....
Those James universal OPT's are hidin' behind those oil caps, BTW.
This circuit sounds like god on my LaScalas, I was really suprised how good it sounds.
Of course all the usual rules for low watt triodes apply....thrash metal and congested sorts of music won't fly....and at 750 millivolts isn't gonna rattle rafters, either.
But in my small place, it gets up to and a bit above moderate listen levels. Plenty loud enough for me.....the tone is what it's all about to me. Buttery smooth midrange and top end. Bass is strong, clean and natural sounding.
I'm using this circuit with a few differences:
http://www2u.biglobe.ne.jp/~tossie/71ASE-E.html#circuit-fig
The 71A's are heated with these little DC supplies my retired EE audio buddy gave me. Xentec inc. Model XE15-3.
The have 120 volts AC in, or 240 @ 60Hz, + or - 10%.
DC output is 2-4 volts @ 3 amps. I use one each for each 71A, and they seem to pull 5 volts running a 71A without breaking a sweat.
I remember bridging two together to try to swing the filaments of two (7.5 volt?) 801A's.....they couldn't do it, and kept tripping the protect mode.
But I got four now....two bridged might swing one 801A...hmmm..
These things eliminate filament growl/line noise with the 71A's. Which is a 5 volt filament.
I'm not used to listening to triodes without a little bit of growl. It's quite interesting and nice.
Some complain of using SS devices to heat with DC on triodes, which is more glare or dullness.
I don't notice this, or don't know really what to listen for, or need to do some comparisions with AC heating.
The 71A's 2K cathodes resistors are bypassed with a 22uF Solen 400 volt metal polys across NOS Sprague 600 volt "Chlorinol" oil caps.
The cathode bypass cap, to the resistor for the first half of 6SL7, is a 470uF 100volt Nichicon Muse.
Instead of 22uF for decoupling for 6SL7, I'm using 100uF 450 volt Nichicons.
I'm using my James universal OPT's. The supposed spec primary load for 71A is 5K. I've been swapping between the 3.5K primary, and 5K primary. I seem to prefer the 3.5K tap, with the B+ at around 150 volts......strange that....
But it seems to sounds less stressed at lower voltage, and more full and open with the lower primary tap.
I may need to tweak with the dropping resistor for the 6SL7 for a lower value, but for a first take this things sounds damn good.
I was visiting some friends last night, (never visit a video junkie who throws in a 6 hour movie, argh...) but I told them I was listening to a amplifier circuit that used 75 year old tubes. That usually raises some eyebrows.