Don’t get me wrong. I would LOVE to build a 300B SET amplifier! Everything I’ve read is how magical they sound! But for a decent pair of 300B tubes and decent output transformers I just can’t talk myself into spending $1000+ for a few watts of output per channel. I’d almost have to ration my listening time so as to not have to replace the 300B’s.
Back tracking up several posts… SET (single ended, class A) and push-pull (class AB) tube amps sound very different, like apples to watermelons.
What would you say the difference in sound between the SET and push pull is?
That’s a great question. From my personal tube amp builds:
Going after output watts and low frequency bass response, the push-pull amps win every time. But for low volume and near field the SET amps rule in my book! The midrange is just so clear.
I plan to pair the amp with a pair of Mark Audio Pluvia 7HDs or CHN110s, but not near field. I would use it for lower level listening.
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I agree with Craig - there’s just something special about an SE tube amp. Some day I’ll build another one. I built several 45 & 2a3 amps in the early 2000s but ended up selling them to raise money for Christmas when times were tight.
I have been searching through a bunch of these amps and struggling with which one to get. I agree, I think I want to try a SET am. Any thoughts on this one?
I’ve only got experience with my kit so I can’t say much about other versions.
My worry would be that they may use the same transformers as my kit. If they are already at their limit, pushing more power through them could degrade performance. Also, if the tubes are junk, how much would it cost to upgrade those?
Caveat emptor. You pays your moneys, you takes your chances.
I’d suggest looking for higher sensitivity speakers also. Pushing a lower power amp to drive lower sensitivity speakers likely kills dynamics potential by crushing the transients.
I have looked into building something from scratch with decent transformers and tubes. It looks like that would cost about $750 or so.. I need some practice, so I thought I would start with one of the ebay kits. I ordered the class AB push pull kit. I don’t have any super high efficiency speakers, so I thought I would start there. I can start a separate thread on it. I have a feeling this may start an amp building obsession.
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Which one did you buy?
I ordered this one.
I plan to do a bit of hotrodding. Maybe some updated caps, transformers, and tubes. I will build it stock first.
The price is certainly good and it looks like a nice kit. Those 6F2 and 6P1 tubes should be easy and not too pricey to upgrade.
At least the transformers must be different because I believe push-pull is wired differently? Unless I’m just thinking that vs ultralinear wiring. IDK
Looks like you can get 6p1 matched quads shipped from the states for reasonable:
6F2 I had a bit more difficulty with. It seems these may be cross compatible numbers (please verify first though): ECF82 / 6U8 / 6KD8 / 6F2
Single ended audio output transformers need to be much larger due to the need for an air gap between the core and windings. The primary is not center tapped. The air gap is needed to prevent DC saturation of the core. Push-pull transformers, however, can be much smaller because no air gap is required. The primary is centered tapped with three wires, which prevents DC core saturation.
If I were to scratch build a pull-pull type tube amp, I’d probably go with a hammond in the 1608 to 1650 series (about $185 each at Mouser for 50W/ch):
If I were scratch building a single ended amp, I’d probably go with a hammond in the 1627 to 1642 series. The 30W units are about $211 each at Mouser:
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Just my personal experience and opinion but I think Hammond iron is definitely not what I would use. Their power transformers run really hot and hum even when the load current is below their spec. There was also a big issue with one of their most popular output transformers.
I’d buy Edcor iron and paint the end bells black if you don’t like the powder coated blue color. You do have to wait a month or so for them but they sound excellent and are a much better value than the Hammonds.
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I think he was using that as more of an example of the single ended vs P-P transformers (showing higher cost for less power rating on single ended). But I get what you are saying.
I know the Hammond 200 series power transformers were prone to heating up & humming. I used one to build a 2A3 amp and that’s exactly what I experienced. The 300 series were said to be much better, but also quite a bit more expensive.
I agree on the Edcor stuff. I don’t mind the blue, but I do wish they offered multiple output taps on their standard designs.
I scratch designed and P2P built a 8 WPC SET amp that used Russian EL34 tubes, a single 6DJ8 preamp/driver tube (thanks Tom S.), and these Edcor output transformers:
Don’t be dissuade by the fact that they are sold as “guitar” amp transformers. They sound and perform excellent! The 40 - 18 kHz range is less than 1 dBu down. Unfortunately they have doubled in price since pre-covid.
These tubes… not an arm and a leg expensive:
If anyone in here can use some Genalex KT77 tubes (2) let me know. Thought I could use them in the chinese but wont work.