I built an amp with 6AS7 in the output. It has about 240volts as b+ and I use two bottles of 6AS7 and parallel one section of each bottle, so it's a PSE ditty. (I can squeeze more from a single section than if I use both sections in one bottle. Besides, the triode on pin 1-2-3 is never the same as the triode on pin 4-5-6, but it's easy enuff to match two triodes from seperate bottles).
I had all the components in my shack except for the proper O.T. I built the thing and since I had some Edcor 5k:16ohm O.T. laying around I used those while waiting for the OneElectrons to arrive.
The amp is pretty nice sounding, but I only get about 6Wrms out of it. These tubes really need a custom O.T. if max power is the goal, since 1600ohms is just too high for them.
I use a single 6922 as voltage gain tube, and the response is flat from about 10Hz to about 50kHz, with the One Eløectron O.T. That's without any global feedback, so I am pretty impressed.
I had the amp up for about two weeks before the One Electrons arrived, and must say I really didn't hear a lot of difference. Measurements show the One Electrons to be a lot better though.
As you can see the measurements show there is room for improvement, but they really do sound VERY good, and I intend to keep them as is. I'm building a PP 6AS7 amp and that will work on the boomers, while this SE amp will handle the tweeter.
The amp does have a little 100Hz hum, not enough that it bothers me, but it is not dead silent. Running these low impedance tubes in SE kinda makes it hard to get them 100% silent. (I'm actually planning a regulated supply for them, if I get the time. When driving the tweeters this will not be heard.
I've done some tests for fun, with tubes amps that have up to 10% 2nd orders distortion, and nobody has heard anything 'wrong' at all.
Ooh, bla bla, this got to be long...Point is to show the meaurements of the mentioned O.T.
Obviously the impedance was more 'off' with the Edcors, but I don't think that's the reason for the differences. (High impedance loads should actually give less dist.).
I had all the components in my shack except for the proper O.T. I built the thing and since I had some Edcor 5k:16ohm O.T. laying around I used those while waiting for the OneElectrons to arrive.
The amp is pretty nice sounding, but I only get about 6Wrms out of it. These tubes really need a custom O.T. if max power is the goal, since 1600ohms is just too high for them.
I use a single 6922 as voltage gain tube, and the response is flat from about 10Hz to about 50kHz, with the One Eløectron O.T. That's without any global feedback, so I am pretty impressed.
I had the amp up for about two weeks before the One Electrons arrived, and must say I really didn't hear a lot of difference. Measurements show the One Electrons to be a lot better though.
As you can see the measurements show there is room for improvement, but they really do sound VERY good, and I intend to keep them as is. I'm building a PP 6AS7 amp and that will work on the boomers, while this SE amp will handle the tweeter.
The amp does have a little 100Hz hum, not enough that it bothers me, but it is not dead silent. Running these low impedance tubes in SE kinda makes it hard to get them 100% silent. (I'm actually planning a regulated supply for them, if I get the time. When driving the tweeters this will not be heard.
I've done some tests for fun, with tubes amps that have up to 10% 2nd orders distortion, and nobody has heard anything 'wrong' at all.
Ooh, bla bla, this got to be long...Point is to show the meaurements of the mentioned O.T.
Obviously the impedance was more 'off' with the Edcors, but I don't think that's the reason for the differences. (High impedance loads should actually give less dist.).
Attachments
Nothing crappy about Edcor OPT's! Nothing crappy about one Electrons either, or John wouldn't be specifying them from Electraprint as he does. Both will be competently designed, though not cutting edge in their construction or materials. I am a designer of audio transformers, on the cutting edges of things, and I am quite glad that Edcor excellent the excellent job they do. just as I am happy with John and Jack's products, through One Electron.
Unless you build something to use with ridiculously revealing speakers, like full range ribbons, a fully sorted horn system, really good maggies, a number of electrostats or EnABL'd drivers, you don't really need to explore the edges, from Lundahl, Tribute, Intact Audio, O-Netics, Sowter and, more and more often, Magnequest. The cost to improvement ratio get's really steep beyond Edcor. And they do a fine job on music!
Bud
Unless you build something to use with ridiculously revealing speakers, like full range ribbons, a fully sorted horn system, really good maggies, a number of electrostats or EnABL'd drivers, you don't really need to explore the edges, from Lundahl, Tribute, Intact Audio, O-Netics, Sowter and, more and more often, Magnequest. The cost to improvement ratio get's really steep beyond Edcor. And they do a fine job on music!
Bud
Care to share the schematic
Semper Fi
Do you have a schematic of amp and power supply to share?
Ejam
Semper Fi
Do you have a schematic of amp and power supply to share?
Ejam
Without knowing the transformer models and specs, and the op points and load, it's impossible to say anything about the transformers themselves... There could be any number of reasons for increased odd-order distortion.
More information about the test conditions, please 🙂
Michael
Yeah, the Edcors are actually good to go, didn't mean to call them crap. The ones I used is the cheapest, XSE-MS-5k, and I used the 16ohm tap. I'm using the 16ohm tap on the OneElectrons as well since that is a more correct ratio than 8ohm. (8ohm speakers).
Soundwise I'm sure I wouldnt hear a difference if someone swapped them back without telling me😉 But I do get a better feeling just looking at the OneElectrons.
My kitchen amp is a similar design, same tubes, only smaller, a single 6922 and one 6AS7 with each channel using one triode section each. In that one I use Edcors, and it sounds killer! (Though being a kitchen amp I never expected much, and the 1.5watts is more than enough).
The higher odd harmonics with the Edcors is something to think about. Sure these little ones have smaller cores and it's perhaps b/c of too high standing currents.
???
I've no problems building amps with Edcors, and plan to use the GXSE for my next amp. For the money they can't be beat.
For guitar amps I find the cheapest XSE series to work better than 'high-end' types.
Sure I'll post schematic, just have to find the droodle in the pile of other droodles🙂
Soundwise I'm sure I wouldnt hear a difference if someone swapped them back without telling me😉 But I do get a better feeling just looking at the OneElectrons.
My kitchen amp is a similar design, same tubes, only smaller, a single 6922 and one 6AS7 with each channel using one triode section each. In that one I use Edcors, and it sounds killer! (Though being a kitchen amp I never expected much, and the 1.5watts is more than enough).
The higher odd harmonics with the Edcors is something to think about. Sure these little ones have smaller cores and it's perhaps b/c of too high standing currents.
???
I've no problems building amps with Edcors, and plan to use the GXSE for my next amp. For the money they can't be beat.
For guitar amps I find the cheapest XSE series to work better than 'high-end' types.
Sure I'll post schematic, just have to find the droodle in the pile of other droodles🙂
Off my head here, too lazy to get the notes out. The b+ is something like 230volts, give or take 10volts. The grids are at -95volts, idle is 60mA per triode. The tubes are psudo fixed biased, I have 100ohm cathode resistors to give a small autobias, which is recommended per RCA manual. Thes resistors are nonbypassed! Crazy uh, non bypassed cathode resistors on tubes with a mu of only 2! But the amp has planty gain, and my preamp is never over 1/3 before it's too loud. I have tried bypassing just to check if I get more power, but the difference was minute, so a little local feedback is exactly what I want and thats what I got😉
I'm pretty pleased that my 6922s can drive this at full power to over 50kHz. We're talking voltage swings more than +-100volts at 50kHz🙂 And they are ruler flat. Mohahahaha
Sorry folks, I had a brainfart! The Edcors were XSE25-16-7.6k and not the XSE15s.
I am positive b/c the chassis has the holes for those, besides I wouldn't run that much current thru the small XSE15. I was also surprised with the amount of bass those Edcors gave me, since their inductance is rather on the low side. Another point for the 6AS7, it'll drive anything🙂
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