That's +/- 1dB. Have a look at the graphs on the datasheet, they go way below 30Hz.
My daily driver uses the 1650HA, and when I originallt built it I measured full power output (27W) at 20Hz, it was virtually the same as at 1Khz.
I also compared with my Onkyo SS amplifier, bass in both cases very good, at least to my ears. My speakers are Monitor Audio BX5, entry level stuff, they are rated at 37hz anyway.
https://www.hammfg.com/electronics/transformers/classic/1608a-1650a.pdf "Frequency response 30 Hz. to 30 Khz. at full rated power (+/- 1 db max.)."
I'm looking for something genuinely rated 20 Hz. to 18 or 20 Khz. at full rated power (+/- 1 db max.). I don't think it's unreasonable. If something is already down 1 dB at 30Hz, then we have more serious problems at 20Hz.
The question now I guess is how much does it cost and who can be trusted to do it with proof? I didn't expect a custom wind to be required, but maybe so.
I'm looking for something genuinely rated 20 Hz. to 18 or 20 Khz. at full rated power (+/- 1 db max.). I don't think it's unreasonable. If something is already down 1 dB at 30Hz, then we have more serious problems at 20Hz.
The question now I guess is how much does it cost and who can be trusted to do it with proof? I didn't expect a custom wind to be required, but maybe so.
I have not done any standing wave calculations for a couple of decades.
But if you have a small room, it will not have standing waves at 20, 25, or even 30Hz that are needed for your loudspeakers.
The best amplifier in the world is not going to overcome a small room, without some low frequency boost.
But if you have a small room, it will not have standing waves at 20, 25, or even 30Hz that are needed for your loudspeakers.
The best amplifier in the world is not going to overcome a small room, without some low frequency boost.
I doubt any transformer manufacturer has a test amp that they connect every piece to and then run a full suite of tests on before shipping. That time would retail cost as much as these budget transformers sell for.
YES, I have adjusted the speakers over the years since 1996 (about) when I built them with a very well calculated, measured, and auditioned slightly enhanced bass response, and they also were designed to enhance the very bottom end. Listen to this system in my room and you get a live performance with a live recording, or the same result as a massively expensive system in a special showroom. A pipe organ sounds like a pipe organ should, as evidenced by the pipe organ player who spent years helping me tweak them. I don't live in a warehouse and never will so they were designed and refined in a "normal" room. They don't sit 1/3 of the way out into the room either.
That isn't why we are here. There is no point in blaming the speakers or the room before we even get started. If you have poor performance from 20Hz to 30Hz before you even get started then there is no point in starting to begin with, assuming the rest of your system can reach below 30 Hz. If I were using a small bookshelf speaker, or the Klipsch Heresy ii's that I onced owned, then there would be no concern. I got rid of the Heresy ii's for just this reason along with a very expensive pair of KEF reference speakers that couldn't do it.
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You could overrate the OPT, using one with higher design power, it will perform better at lower power output.
Guaranteed performance at 18~20hz is going to cost a lot.
Guaranteed performance at 18~20hz is going to cost a lot.
20 watts has been suggested. I just didn't think I was headed in the direction of a custom wind for this seemingly simple application unless I want another Z-565 clone. I'll ask Thermionic and Edcor I guess. I am supposing that people who want this use Lindahl or Sowter. Lindahl won't work, and for the $800+ price of Sowter, I'll abandon the project and go back to my overhauled and upgraded ST-70 series ii, paying for the air conditioning bill in summer. I would need a new entertainment center and cooling fans blowing on it, but it always has sounded great all the way down to the bottom. 🙄
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Option here from Poland ... PP Ogonowski
These guys in the UK have a good reputation Majestic Transformers
I have had good success just keeping an eye on auctions. Found Lundahl, Sowter and these Partridge OPTs that way.
These guys in the UK have a good reputation Majestic Transformers
I have had good success just keeping an eye on auctions. Found Lundahl, Sowter and these Partridge OPTs that way.
Attachments
Did Sowter go out of business?
Did they get acquired by another company?
I thought Sowter made good transformers.
Did they get acquired by another company?
I thought Sowter made good transformers.
Sowter
They do but I objected to the $800+ per pair cost. For that price I'll abandon the project and use the amplifiers I already have. Lundahl won't work, and for the $800+ price of Sowter, I'll abandon the project.
They do but I objected to the $800+ per pair cost. For that price I'll abandon the project and use the amplifiers I already have. Lundahl won't work, and for the $800+ price of Sowter, I'll abandon the project.
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$800 + per pair. Think what it would cost me Landed in the US.
Cheap is not Good; Good is not Cheap - Frank Reps writing in "Sound Practices". Frank built the Baby Ongaku that was designed by Gordon Rankin, owner of Wavelength Audio.
The old saying went more like this: You get what you pay for.
We still live in the same universe.
Cheap is not Good; Good is not Cheap - Frank Reps writing in "Sound Practices". Frank built the Baby Ongaku that was designed by Gordon Rankin, owner of Wavelength Audio.
The old saying went more like this: You get what you pay for.
We still live in the same universe.
In that case, I'll abandon this and get what I already paid for, which is the proven amplifiers I already have. I refuse to believe that there isn't a 20Hz-20kHz (-1dB) option below $800+ for an EL84 PP transformer of roughly 15W.
@OldHector I'll look at your links when I have a chance. Thanks.
Thermionic says as of 10 minutes ago that they can do it and they will provide test results. We will see what Edcor says.
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Push pull, using global negative feedback, you can easily get a clean 1 Watt sine wave output at 20Hz;
and with a frequency response at 20Hz that is only -1 dB less than at 1kHz.
The same amplifier performance at 5 Watts out, is more difficult.
You need more lamination and more copper wire.
and with a frequency response at 20Hz that is only -1 dB less than at 1kHz.
The same amplifier performance at 5 Watts out, is more difficult.
You need more lamination and more copper wire.
https://primarywindings.com/product/25w-8000-ohms-ultra-linear-push-pull-output-transformer/
Interesting, they quote 20 to 30Khz +/- 1db. But it does not state whether that is at full power.
Interesting, they quote 20 to 30Khz +/- 1db. But it does not state whether that is at full power.
An EL84 PP is an extremely easy transformer in terms of HF response vs output power vs primary inductance. If one needs that kind of bass response, just has to increase core size\turns a bit.
Perhaps you can share with us your experience with the Thermionic output Transformer set you had used for your KT120SE design. I wasn’t aware of Thermionic labs until I saw your design. I realize it’s SE and the OP wants push/pull recommendations but your input (or a link to your subjective review + measurements if available) would be great to read. I perused your video series but you said very little about them.
Best,
Anand.
Beggars can't be choosers. You really need 20Hz? A 5-string bass lowest note (assuming normal tuning) is 31Hz. If you're using a tube amp for your home theater you're doing it wrong. With your budget and FR spec, you may want to consider a subwoofer for your lowest octave. Then you may be able to find a transformer you can afford.
Given your budget, and if there are no size constraints, and you don't want to wait for custom, maybe the way forward is to pick a stock transformer but up-rated in power to 30 or more watts. Assuming you'll only get about 15 watts max out of a pair of EL84s, you stand a good chance of getting the bass extension you desire with an oversized tranny. Just a thought. (I have had experience with Lundahls in a EL34 amp and they were awesome, once they had broken in. I know, out of your budget.)
S.
S.
Even in the vintage market a pair of output transformers with those specs, like the Triad HSM-81 for example, would cost close to $1,000 USD or more unless you're lucky. They're potted and have no end-bells so they're out.
