What recommendations for new output transformers for a el34 push pull ultra linear amp? The first, and only, pair I’ve ever bought are lundahl ll1679pp. Im very pleased with them. But also wondering if there is a better option to try on my next build? Any help is appreciated, thank you.
I have limited experience with Lundahls but the EL34/KT77 amp I heard improved a lot when the stock transformers were replaced with Lundahls (I think it was a LL2769). I'm sure there are better but at what cost?
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Serious question, what do you get when you get a "better" transformer? What is it that makes them better and how does that manifest itself? Does a higher quality transformer have any impact on the circuit that can be used?
for a more concrete question, if we compare a transformer from Hammond and Monolithic Magnetic for this PP el34 amp, what would be the measured difference and what would we hear? Sorry for the questions, thanks for any thoughts.
for a more concrete question, if we compare a transformer from Hammond and Monolithic Magnetic for this PP el34 amp, what would be the measured difference and what would we hear? Sorry for the questions, thanks for any thoughts.
One good performer is A-470 from former dynaco. They are still reproduced and available at several
sources. See https://www.dynakitparts.com/shop/a-470-output-transformer/ for one.
( i think they are out-of-stock but ask them for delivery date )
Given the same turns ratio, output transformers may differ in the core cross sectional area and the primary inductance, which both affect it's power capability in the low end, it's stray inductance and winding capacities which compromise it's high end, and the windings' DC resistance. The bigger the bandwidth, the easier the circuit can be designed and the better sonic properties can be expected. The lower the resistance, the higher the efficiency.
Best regards!
Within reasonable limits, you pay for what you get, +/- about 50% (if you leave all the scammers out of the equation).
Of course, as you go up the price per performance scale, the other rule takes over: 90% of the performance for 30% of the maximum price, and 99% of the performance for 99% of the maximum price.
Just my opinion and experience.
Of course, as you go up the price per performance scale, the other rule takes over: 90% of the performance for 30% of the maximum price, and 99% of the performance for 99% of the maximum price.
Just my opinion and experience.
How would you possibly beat Lundahls? Tangos? Pulls from an old McIntosh? Speaking of which, too bad you didnt say EL84, as I've recently noted in an old Hammond AO-33 chassis. there's two 8 Ohm OPTs that happen to have the "McIntosh" cathode winding...
Not that such would guarantee better SQ than a famous brand, but if you're hunting around for something unusual, different or maybe-maybe-maybe - that might be a fun tack. It's a reasonably sized chunk of iron too.
Not that such would guarantee better SQ than a famous brand, but if you're hunting around for something unusual, different or maybe-maybe-maybe - that might be a fun tack. It's a reasonably sized chunk of iron too.
Mac had 1:1 ratio plate to cathode. Those Hammonds (and many recordplayers and tape machines) don't... 10:1 more typical. i.e. just enough to barely get a little NFB, not enough to straitjacket the tube into compliance.
And yet: those eBay Hammond carcasses are still sonic gems, because old man Hammond had a really good ear, and tweaked for his approval not for meter readings.
I did a quick look across some other Hammond AO-XX chassis; none of them have the feedback scheme shown above. That particular unit (which caused me to research the schematic) went for $80 BIN with shipping. I note there arent any more AO-33s on ebay at the moment.
AO-33 is the amplifier pack of the PR-40 tone cabinet and the D-1xx series of organs. But I'd never (!!!) advocate to scrap such a beautifully sounding instrument just for some amp components.
Anyway, there are even more Hammond amps with CT'ed OT secondaries, e. g. AO-68 from a K-100, AO-41 or AO-47 from L-100 organs, tone cabinets liekJR-20, JR-40, PR-20 etc. All these OT's feature really big and heavy cores wrt. their nominal output power.
Best regards!
Anyway, there are even more Hammond amps with CT'ed OT secondaries, e. g. AO-68 from a K-100, AO-41 or AO-47 from L-100 organs, tone cabinets liekJR-20, JR-40, PR-20 etc. All these OT's feature really big and heavy cores wrt. their nominal output power.
Best regards!
I was actually asking! I am prone to believe that better transformers do indeed improve performance but I don't know enough about design to understand what is being improved.
So they will have better bandwidth. If I'm not mistaken that means that you might not need as much negative feedback to stabilize circuits right? Do "better" PP transformers handle unbalanced signals better? In other words can you get by with less well match tubes with a "better" transformer? What does a more efficient transformer get you?
I will commission a PP amp sometime this year and I;'m trying to figure out if it makes sense to specify a particular transformer. Reading through this forum I see sentiments like Monolithic Magnetics makes first class transformers, Lundhal makes some really good ones and some so so, Hashimoto is either amazing or totally over priced depending on who you talk to, maybe Soweter can no longer be trusted now that they have moved and lost some staff, and Edcor is decent for the money but doesn't compete with the best.
Should I just say screw it, use a MM transformer and be done with it? Would using a different transformer change the design process? Other than cost is there any downside to "drinking by label" and buying on reputation? So many questions...
It would be hard to go wrong with MM, I've been using them in my more ambitious designs for about 6 years and have used about 25 of them so far in projects for me and friends. I have also used a fair number of Lundahl's smaller SUTs and line to line transformers.
If the builder usually uses Soweter would he have to change anything in order to use a MM transformer instead?
I've read several threads in which @tubelab has gotten great performance out of cheap transformers by futzing with the circuit. Would he get even better with a more expensive transformer? I assume that different circuits would be (could be?) needed with higher bandwidth, lower resistance transformers.
Yes, better bandwidth. But have a very close look at the datasheets.
Better bandwidth OT's allow for more global NFB, hence lower THD, lower output impedance and even better bandwidth, without massive compensation. Anyway, NFB reduces THD just by it's feedback ratio, but doesn't eliminate it completely. So tube matching has it's benefits even with bigger NFB. More efficiency means more power at the secondary windings at a given power at the primary (= less thermal loss).
Best regards!