I'm looking for recommendations for ouput transformers for an EL84 push-pull amplifier.
What high quality OPTs are currently available? Most links that I find no longer work or the product is no longer available.
- The schematic calls for 8k and I need 8 ohm output, with a 4 ohm output being nice to have but not strictly needed.
- Solid bass performance required to 20Hz. Poor/lightweight bass performance is not acceptable.
- Rated 15 watts (or more) I suppose.
- Ultra-linear is not needed.
- I cannot use toroidals. They need to be a traditional transformer with end bells and wire leads.
- I do want a very good transformer, but I don't want to spend a million dollars on a pair either. I know there are some very expensive names out there.
What high quality OPTs are currently available? Most links that I find no longer work or the product is no longer available.
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It kinda looks like the Dynakit Z-565 transformers might be available. Worth a shot: https://www.dynakitparts.com/shop/z-565-output-transformer/
Triode Electronics may still be winding the Z-565 as well.
Edcor has a similar transformer, CXPP25-8k. That's what's in my Pete Millett DCPP amp. They are ok, but I'd search for Z-565 first.
jeff
Triode Electronics may still be winding the Z-565 as well.
Edcor has a similar transformer, CXPP25-8k. That's what's in my Pete Millett DCPP amp. They are ok, but I'd search for Z-565 first.
jeff
$808 per pair plus shipping is completely out of the question.
Edcor only seems to have 10W and 25W. Does anyone know how their transformers perform? It seems that they can custom wind anything for a fee.
I don't know if having a UL output is a detriment or not. I definitely don't need it. I have read that if it's not going to be used then it is best to design the transformer without it.
Sorry you said 'Very good transformer' just 'not a million dollars' you have to remember people's budgets vary massively. The lundahls would probably be around $540 if you didn't need them to be in enclosures above the case. The Edcors are like $220 for the pair assuming 8/4 tapped secondaries. I don't know if you're going to find something that slots price-wise in-between the edcors and lundahls and offers a major step up from the Edcors? Maybe someone else will have an idea.
For the Edcors, if they say they are 1db down at 20Hz, I would personally trust them. So I think it'll meet your bass requirements in terms of having enough primary inductance. They don't use any particular fancy materials, though they claim decent quality copper/steel at least. Edcor has done very minor changes for me in the past without complaint (just like, splitting secondaries instead of center-tap, that kind of thing).
You could always contact them? But I'd guess if you ask for it without screen taps they'd probably wind it the same way anyway just without bringing the wires out.
For the Edcors, if they say they are 1db down at 20Hz, I would personally trust them. So I think it'll meet your bass requirements in terms of having enough primary inductance. They don't use any particular fancy materials, though they claim decent quality copper/steel at least. Edcor has done very minor changes for me in the past without complaint (just like, splitting secondaries instead of center-tap, that kind of thing).
You could always contact them? But I'd guess if you ask for it without screen taps they'd probably wind it the same way anyway just without bringing the wires out.
I've never used them, but for the money they might be worth a try. And they're made in the U.S. Musical Power Supplies
It looks like with your budget it might be a set of Hammonds for you. They are rated down to 30 Hz though. What are your speakers that only require 10 to 15 watts and go down to 20 Hz? There are Hammond hates in the DIY community but Shindo sees fit to use them in their entry level (~$8K!!!) amp.
S.
S.
Yes, but they are not yet quite ready to custom wind these and provide documented test results. They are moving in that direction, but not in time for my project. @Stephe mentioned them in her Monday Monologue on her YouTube channel this week.
I would have contacted Edcor already except, 1) I don't know anything about their quality, and 2) It has been a vacation week so they have been out of office.
Thermionic Labs said they can custom wind something, but I haven't yet heard a price per pair, and it will have to include shipping from Greece. I'm expecting about $400/pair from Thermionic. I don't know anything about them or their testing or quality.
I'd really like something backed up by demonstrated test results from the manufacturer. Anyone can say it will go to 20Hz -1 dB, but it's another thing to prove it.
I'm not sure I can handle more than about $350/pair, shipping and tax included.
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Not acceptable. I have Chinese transformers that are very good that can do that. These sound very good until they get below 30Hz when they fall apart above 5-6 watts: https://www.aliexpress.us/item/3256803969808190.html Above 30Hz they are great.
My own design large (roughly 4' tall and 24" wide) floorstanding 3-way speakers that I have been using since about 1996, including repowering them every 8 years or so. Approx 92-93dB efficient. Cutoff somewhere around 25Hz. Not a huge room either, so with efficient speakers that size not a whole lot of power is required for normal listening.
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If the OPT can't do it to begin with, there is no point in proceeding with a build. A manufacturer with a test bench should be able to provide test results IMHO.
The Chinese transformers are just too small. They perform and sound great down to 30Hz though.
NGO,
I suggest you stick with experienced transformer designers that have been doing it for a good long while (i.e decades). Transformer design isn’t easy. You also don’t mention at what % distortion and wattage (or voltage level) you want that 20Hz extension to be. Mind you, ALL transformers will saturate at a certain power or voltage level. And good ones get BIG and cost money. The distortion will be well over a few % even at 1/2 that max power, especially if we are talking less than 50Hz. This is a reality. So oversizing the transformer is a a good idea - but getting high end extension without compromise is also a challenge. Guess what? Your budget just got blown.
Edcor to me is good for a ”value” product. It’s decent but they do make mistakes from time to time. I had to return a pair of SE 5K transformers (Model CXSE25-5K) as the frequency extension dropped off at 11khz. This was about 1.5 years ago. There was a mistake in their interleaving but their customer service was excellent, and they even paid for return shipping. Regardless… for an 8K PP transformer, you’ve got the models CXPP25-8K and CXPP50-8K. They may have other options such as single secondaries, etc…they also have an ‘MS’ version which is designed for Pete Millett’s ‘Engineers Amplifier that he has a kit for - you can see the links on the Edcor site. Pete particularly mentioned the excellent bass response he achieved using his design and the CXPP design from Edcor. So take that for what it’s worth.
If it were me, and I liked the circuit, I would go with Lundahl and pony up the bucks. Every one of their transformers that leaves the door is tested multiple times to guarantee a certain premium level of performance. The prices vary depending on the core material, i.e. standard, amorphous core, nanocrystalline or silver. Contact Holger at Erhard Audio, he’s the US distributor.
There are even more expensive transformers, but we won’t go there.
Sadly, with many transformer manufacturers they only give you measurements under small signal or small voltages, like 1dBu for Edcor. That’s not very useful to find out the real world performance for the transformer. For the CXPP from Edcor, I would go to Pete Millet’s site and check out his measurements.
Best,
Anand.
I suggest you stick with experienced transformer designers that have been doing it for a good long while (i.e decades). Transformer design isn’t easy. You also don’t mention at what % distortion and wattage (or voltage level) you want that 20Hz extension to be. Mind you, ALL transformers will saturate at a certain power or voltage level. And good ones get BIG and cost money. The distortion will be well over a few % even at 1/2 that max power, especially if we are talking less than 50Hz. This is a reality. So oversizing the transformer is a a good idea - but getting high end extension without compromise is also a challenge. Guess what? Your budget just got blown.
Edcor to me is good for a ”value” product. It’s decent but they do make mistakes from time to time. I had to return a pair of SE 5K transformers (Model CXSE25-5K) as the frequency extension dropped off at 11khz. This was about 1.5 years ago. There was a mistake in their interleaving but their customer service was excellent, and they even paid for return shipping. Regardless… for an 8K PP transformer, you’ve got the models CXPP25-8K and CXPP50-8K. They may have other options such as single secondaries, etc…they also have an ‘MS’ version which is designed for Pete Millett’s ‘Engineers Amplifier that he has a kit for - you can see the links on the Edcor site. Pete particularly mentioned the excellent bass response he achieved using his design and the CXPP design from Edcor. So take that for what it’s worth.
If it were me, and I liked the circuit, I would go with Lundahl and pony up the bucks. Every one of their transformers that leaves the door is tested multiple times to guarantee a certain premium level of performance. The prices vary depending on the core material, i.e. standard, amorphous core, nanocrystalline or silver. Contact Holger at Erhard Audio, he’s the US distributor.
There are even more expensive transformers, but we won’t go there.
Sadly, with many transformer manufacturers they only give you measurements under small signal or small voltages, like 1dBu for Edcor. That’s not very useful to find out the real world performance for the transformer. For the CXPP from Edcor, I would go to Pete Millet’s site and check out his measurements.
Best,
Anand.
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I think I did. 15 watts would be ideal I think with 0.0000000001% distortion,
Just kidding. I wouldn't expect to use more than about 10 watts of that 15 watts.This concerns me greatly. I would think that they would test before shipping the product.
Do you actually know how much power you are using? Seriously? Any oscilloscope measurements of your amplifier ‘working’ while listening to dynamic music for example? Or are we just…guesstimating based on an estimated sensitivity of loudspeaker, sitting distance, room size, etc….? Perhaps you listen at less than 80dB levels. Dunno.
Best,
Anand.
Best,
Anand.
Yes. XrayTonyB on YouTube did a video series of this kit build where these will be used, including a lot of bench tests. I have one sitting here that I built. I want to build a second one with higher quality parts and better OPTs than the Chinese 30Hz models, which sound great but can't really do anything below 30Hz. That is where they are rated and where XrayTonyB showed them seriously dropping off in performance on his scope.
I now have three tube amps, including the little Chinese amp, a new Dynakit ST-35 that has more power than I can use, and a Dynaco ST-70 series ii (Panor Corp circa 1992) that has way more power than I can use. The ST-70 series ii has enough bass power and punch to knock every picture on the wall crooked and things inside the walls rattle. I don't need that level of power. An EL84 PP amp is fine.
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Depends mostly on how deep your pockets are!
How many threads have you started this week?
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I am supposing that there is no off-the-shelf solution other than Z-565 clones and that a custom wind will be required from someone like Edcor or Thermionic Labs. Sowter at $800+ per pair is out of the question. Lundahl doesn't seem to have traditional transformers with end bells and also costs too much. Maybe they are the best, but I guess that rules out the best.
Has anyone tried Thermionic Lab?
https://www.thermioniclab.com/en/about-us/
Has anyone tried Thermionic Lab?
https://www.thermioniclab.com/en/about-us/
