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Edcor or Electra-Print for SSE Output Transformers (and what to ask for?)

I thought I had settled on the Edcor CXSE25-5K for my output transformers on my "I have no idea what I'm doing" SSE build. But the lead time is outrageous, and I'd read elsewhere about successful SSE builds using Electra-Print transformers. I've been emailing with the guy there about it... He's very confusing (but then again, this whole process is very confusing to me).

His prices are higher, but his lead time is much shorter: 10 days, vs the 12+ weeks from Edcor.

What specs should I ask for from him? Has anyone else here used Electra-Print transformers? What specs did you ask him to build? If it helps, I have JJ EL34 output tubes to use, I do listen to a wide variety of music, and I'll probably end up using speakers capable of significant bass extension.
 
I used the One Electron UBT-2 in my build and have been very happy with it. The specs for that transformer are primary impedance 4800 ohm, max DC current 110 mA. Maybe give this one a try, its quite affordable and readily available and sounds great with EL34 tubes.

I haven't ordered from ElectraPrint, but in looking on the website, it sounds like you need to specify primary impedance, primary current max, max power level, secondary impedance, and wire type.

For the primary impedance, around 5K ohm makes sense for the tubes used in this design (George runs simulations at 3K on his website too).

The primary current max will depend on the current across your cathode resistor (R17 and R27). That primary current will really depend on the value you choose for the resistor. George uses 560 ohms as his recommendation and I get about 57mA for this value using the recommended power transformer. Other people posting on this design have values around here and also a bit higher. So maybe you could go with 80mA here without saturating the coil.

The power level max - using the 34 tube and a 5k primary impedance, you probably will get around 5-8 watts out, so going with 10 here seems reasonable. The One Electron UBT-2 has a 13-18 max wattage output rating.

The secondary impedance would be with whatever your speakers are.

The secondary wire type, probably Copper to save money.
 
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You also need to specify the tube type and single-ended or push-pull.

Jack (Electra-Print) can be a bit ... "special" ... to deal with. You need to know exactly what you want and specify it in the (unspecified) format that he expects. Expect a pair of transformers to set you back about $600. I agree that copper is the way to go.

The James JS-6113HS might be an option for you too - if you can find a pair.

Tom
 
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I used the One Electron UBT-2 in my build and have been very happy with it. The specs for that transformer are primary impedance 4800 ohm, max DC current 110 mA. Maybe give this one a try, its quite affordable and readily available and sounds great with EL34 tubes.

I haven't ordered from ElectraPrint, but in looking on the website, it sounds like you need to specify primary impedance, primary current max, max power level, secondary impedance, and wire type.

For the primary impedance, around 5K ohm makes sense for the tubes used in this design (George runs simulations at 3K on his website too).

The primary current max will depend on the current across your cathode resistor (R17 and R27). That primary current will really depend on the value you choose for the resistor. George uses 560 ohms as his recommendation and I get about 57mA for this value using the recommended power transformer. Other people posting on this design have values around here and also a bit higher. So maybe you could go with 80mA here without saturating the coil.

The power level max - using the 34 tube and a 5k primary impedance, you probably will get around 5-8 watts out, so going with 10 here seems reasonable. The One Electron UBT-2 has a 13-18 max wattage output rating.

The secondary impedance would be with whatever your speakers are.

The secondary wire type, probably Copper to save money.

I was eager to try the One Electron UBT-2 but I can’t seem to find it in stock anywhere.
 
You also need to specify the tube type and single-ended or push-pull.

Jack (Electra-Print) can be a bit ... "special" ... to deal with. You need to know exactly what you want and specify it in the (unspecified) format that he expects. Expect a pair of transformers to set you back about $600. I agree that copper is the way to go.

The James JS-6113HS might be an option for you too - if you can find a pair.

Tom

Those James transformers do seem awfully nice. I’ll search around for a pair, though my initial googling seems to indicate that there are none readily available.
 
If you are building a SET meaning the TSE-II you do NOT want a UL tap. I think Jack makes outstanding items and is very knowledgeable. Specify total output wattage, the bigger the number the more it will cost. if building a 300b amp I usually shoot for 20w OPT and a 15w would be the lowest I would go. next is resistance, 3, 3.3, 5, etc. 3.3k or 5k is 'normal' for a 300b. 3,3 will provide a bit power but more distortion, 5k less power, less distortion - generalisation. something like this for Jack

300B SET
3,3k
DC ma 100
20W
Copper
shroud - top mount

Or just ask him, what does he recommend for a 300b SET designed by George (TubeLab) and is designed for 9w per channel and that you would like it with shrouds (top mount), and with copper. Tell him this is your first valve build.
 
If you are building a SET meaning the TSE-II you do NOT want a UL tap.

Why not? Nobody forces you to use it. If you have it, you can play with UL connection, which is not possible without it. OP mentioned that he wanted to use EL34s.

Or just ask him, what does he recommend for a 300b SET designed by George (TubeLab)

That's usually the best way to tick him off, actually. I've had several customers who came to me after requesting a transformer for my DG300B (now discontinued). I've heard of similar stories from other DIY vendors as well. That said, my experience was ~10 years ago. It's possible that he's improved his customer service since then.

I'm also 99% sure the Electra-Print transformers I received saturated below 32 Hz at 10 W (spec was 25 Hz, 15 W). The 300Bs and the transformers made some rather rude noises during that part of the sine sweep.

I'm not here to knock Jack or Electra-Print. He is knowledgable and the transformers are good (saturation issue aside). But he is particular when it comes to communication, and you can set yourself up for success if you format your request like this: "15 W, 100 mA, 5 kΩ primary impedance, 4 Ω and 8 Ω secondary taps, copper, for use with 300B". The transformers are wound to your specs. I think mine arrived in about two weeks. I was content. :)

Lundahl has some good options: Lundahl Transformers • Audio Transformers • Home

Tom
 
If you are building a SET meaning the TSE-II you do NOT want a UL tap.

I'm actually building the Tubelab SSE amp, which I gather is a bit different from the TSE-II

But he is particular when it comes to communication, and you can set yourself up for success if you format your request like this: "15 W, 100 mA, 5 kΩ primary impedance, 4 Ω and 8 Ω secondary taps, copper, for use with 300B". The transformers are wound to your specs. I think mine arrived in about two weeks. I was content. :)

Lundahl has some good options: Lundahl Transformers • Audio Transformers • Home

Tom

So Tom, what "recipe" would you give Jack at Electra-Print if you were building the SSE?

And thanks for sharing that Lundahl link. They sure look interesting. Which transformer would you recommend from them?


At this point, I'm very glad I started this thread. I was feeling stuck with two options, Edcor or Electra-Print, and Electra-Print was confusing as heck. Now I feel more confident about how to order through them, plus I feel like I have potential options with Transcendar and Lundahl as well. It's still super tough to make a decision about this, but I don't feel quite as dismayed by the 12+ week Edcor lead time. It feels like I might be able to get this amp completed sometime BEFORE July!
 
What do you guys think about these Transcendar options? The Transcendar with the specs closest to the Edcor CXSE25 would be their 20 Watt. It seems to have everything I want: 5K with 40% UL Tap to 4, 8 & 16 ohms. Max DC Bias Current 140 mA. Primary DC Resistance 215 ohms. Primary Inductance: 20 H @ 120Hz.
Very favorable frequency response of 20z to 75 kHz.

They have lower wattage options too, with the same basic configuration.

Correct me if I'm wrong, but that Transcendar transformer seems like it would be perfect for me, right? Like, I don't know what speakers I would use, so having the 3 taps would let me switch speakers as often as I like. And it has a UL tap, which means I could install that optional UL/Triode switch, right? (I don't even know what that does, but hey... I could have it!)
 
If you are building a SET meaning the TSE-II you do NOT want a UL tap.
Or just ask him, what does he recommend for a 300b SET designed by George (TubeLab) and is designed for 9w per channel and that you would like it with shrouds (top mount), and with copper. Tell him this is your first valve build.

the OP is building a Tubelab SSE, *not* the TSE, so this is not relevant.
He does want the UL option & the 5k input
 
I had a pair of Electraprint transformers. They were SE and 5k, 20 watts iirc. They looked nice from the outside. Removing the endbells revealed a scramble-wound bobbin where the windings took up around 30% of the winding window.

Take from that what you will....

I use Lundahl now, and am very satisfied.