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Dynaco Stereo 35 replacement output transformers

I have a set of Edcors in a not-quite Z565 clone. Mine are 40% UL taps, but they offer a 23% now. Maybe a bad assumption, but I'd think they are essentially the same as mine, just with the tap points moved.

If thats the case, based on my results vs Dave's results using them on otherwise identical Magnavox 9300 builds, I can say the HF response is not identical. With some tuning I'm it can be worked out but I wouldn't expect to plunk an Edcor into a design perfectly tuned for the Dyna iron and expect it to be identical. I'm not using the UL taps either, its possible putting them in use changes things slightly.
 
I have used the original Z565 with cloth leads in UL, pentode and triode; great sound...never any issue. They make a very detailed and sweet sounding pp 245 or 6L6/EL34s in triode amps. They always sound great with EL84s
But, for the sake of this thread, the newly offered opts deserve some testing. The large core originals have over 40H on their primary, with less than 20 mH leakage on each secondary, which is not an easy task...
 
I bought several things from Magnequest in years past. I miss him as a source for good transformers and interesting lamination choices sometimes.
 
guitargrump said:
I'm now definitely reassured that MPS isn't a just fly by night operation...Dynakit seems like their always out of stock... Hammond has transformers. Edcor is always pay and wait...

I haven't looked at triode electronics yet... And magnequest is another new company name to me... I will be checking them out...I think that mostly covers what is readily available transformer wise outside of china
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zackthedog said:
Toi my knowledge Magnequest no longer sells OPTs retail. To be honest, I don't know what Mike LaFevre is up to these days, does anyone know?

Sourcing quality OPTs is becoming a big problem. I have a large order in to Heyboer for a batch of their Peerless copies, but man they are slow, I need to call them. My next step would ElectraPrint. Not cheap but I think the quality is assured.
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Yeah, based on what I've read on other forums, Magnequest has been out of business for a while now.

Here's a couple more options:

There's a manufacturer in Greece called Thermionic Lab that seems to have some nice stuff. They've been selling on eBay for a while now. I've been meaning to ask if anyone here has used their OTs.



And just a few days ago I came across another US manufacturer selling on eBay. His brand is Little Titan Transformers and, according to the description, he worked at "one of the oldest transformer manufacturers before they closed the doors". Looks like he only makes PP OTs. Most of his previous eBay sales have been related to model trains.
 
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one can easily access the listing, the buyers and ask their opinions...do it all the time. seller may have money back if not satisfied. what's the spec sheet look like?
 
crispycircuit said:
They HAVE TO BE TESTED! You can't trust their specs or comments. Mediocre is not what were looking for. I'm all for new transformer companies. If we could get some samples? They could be selling in volume. Somebody get the word out...
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Amen. Unfortunately "volume" seems to be a discouragement these days. I wish it were otherwise.
 
Squidward said:
I thought Magnequest used Peerless designs? I think Heyboer winds those too.
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Mike claimed that to have bought all the old Peerless blueprints. There was some contension back in the day (1990's) about who actually "owned" the designs, or if that was even possible, given copyright law, and he got very testy about Heyboer duplicating some teardowns (our good friend Douglas can attest to this). Regardless, his Peerless 20-20 copies were VERY good. I foolishly gave a pair to a friend years ago, wish I hadn't. But they were challenging to work with and you had to know what you were doing, which I decidedly did not in those days. His SE designs were his own and are still very hard to beat, if you can find any. The FS-030 and FS-010 are landmarks in SE transformer performance, IMO.
 
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raycarr00 said:
one can easily access the listing, the buyers and ask their opinions...do it all the time. seller may have money back if not satisfied. what's the spec sheet look like?
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Unless eBay has changed their policies, it's not possible to contact other buyers. Even if you could, how many of them are likely to have the means to test response, distortion, resonance, phase shift, balance, etc. at various output levels? The transformers really would need to be sent to a transformer manufacturer willing to test his competitors' products for free. Good luck with that. Honestly, I tend to think that if these suppliers had a high quality product and could produce it in any reasonable quantity, they would be working with AES or Triode Electronics, not eBay. We like to think that the reason they're on the the auction site has to do with economics and investment capital. Unfortunately, its a pig in a poke unless these otherwise unknown sellers at least provide real technical data and some means of assuring that they know how to do this properly.

Jack
 
zackthedog said:
To my knowledge Magnequest no longer sells OPTs retail. To be honest, I don't know what Mike LaFevre is up to these days, does anyone know?

Sourcing quality OPTs is becoming a big problem. I have a large order in to Heyboer for a batch of their Peerless copies, but man they are slow, I need to call them. My next step would ElectraPrint. Not cheap but I think the quality is assured.
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My last order from Mike was in 2017 for a pair of Brooklyn B18 output transformers. I was looking for a pair of his nickel pin striped MQ-565 Dynaco clones, but he recommended his nickel striped M4 B18 transformers with screen grid taps.

I do have a really great alternative output trans. Our Brooklyn B-18. It has a 8K primary with screen taps. And has a 16,8,and 4 ohm secondary which is configured by series or paralleling the three separate secondary windings (hookup provided). The advantage being that as you go down in impedance your also increasing the copper (via paralleling) cross sectional area. It is much more efficient than the SCA-35 output in this respect.

It has the same height and width as the original Dyna outputs but one quarter of an inch less stack. Still plenty of iron for a 15-20 watt amp. I can build it (it would be one of the last pairs, almost out of the nickel) with nickel pinstripes.
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For single ended, Electra-Print is excellent. My 2A3 (EML mesh plate, octal socket) amp uses his 3k ohm output transformers. I have the Heyboer Peerless S-265-Q, but haven't had a chance to build an amp for them yet.

magnequest-brooklyn B18.gif Magnequest B18.jpg


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I'm intrigued by @trainbuftony 's offer to measure some output transformers. I might even be willing to buy a pair to offer for the examination.

It also causes me to wonder what a complete set of measurements might be and how to execute them. Maybe I have the tools already. I have sig gen, scope, picoscope, DATS unit, big power resistors, etc. Just wondering. Maybe there is already a thread describing this. Or maybe a new thread needs to be started.
All the best,
John
 
I'd build another st35 clone with EFB and run it up to 17 watts.
At 1000 hz I'd check the distortion then I'd run it up and down the frequency generator until I found the 3db rolloff points.
That should be sufficient to BS test their claims.
I could probably post a square wave photo but I don't have a lot of time to try and tune the square wave into what a given person might find "right"
My MO would be more "observe and report"
That's what I'd be willing to do.
It's not a paying gig so it gets done in my limited free time..

Capice?
 
nerdorama said:
I'm intrigued by @trainbuftony 's offer to measure some output transformers. I might even be willing to buy a pair to offer for the examination.

It also causes me to wonder what a complete set of measurements might be and how to execute them. Maybe I have the tools already. I have sig gen, scope, picoscope, DATS unit, big power resistors, etc. Just wondering. Maybe there is already a thread describing this. Or maybe a new thread needs to be started.
All the best,
John
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One way of doing this is to replace one of the transformers in a ST35 / SCA35 with a test subject and examine
square response at low and high power. In short test both sides and look for differences.
 
I sold my ST35 to a friend and I guess I could ask for it back.
Since I kind of want it back I think I'll probably let him keep it and get to work building myself a replacement.
But where to source the trannies?
That's why the task of "testing a pair" is capable of fitting into my busy schedule...
 
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