Pacific Magnetics A470 OPT
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There are a couple potential problems with independent testing, even when it's available. First is the fact it usually involves only one sample. There's no way to know what the sample to sample variation might be. Second, the factory only has to change one small detail in the manufacturing process to render the earlier test results entirely void. This all raises the question as to why manufacturers aren't providing the data. They can't possibly know if the products they're offering are suitable if they haven't performed the tests. Of course, there's also the possibility they've tested the product and the results weren't good.
Jack
Jack
The Pacific Magnetics “spec sheet” says:
PRIMARY: 5.5K Ω CT
WITH +/- 30% ULTRA LINEAR TAPS SECONDARY: 4/8/16 Ω POWER: 35W
I had always accepted the Dynaco A-470 spec as 4.3K Ω CT, 33% UL. These Pacific Magnetics A-470 may be very good, but Dynaco A-470’s they are not.
PRIMARY: 5.5K Ω CT
WITH +/- 30% ULTRA LINEAR TAPS SECONDARY: 4/8/16 Ω POWER: 35W
I had always accepted the Dynaco A-470 spec as 4.3K Ω CT, 33% UL. These Pacific Magnetics A-470 may be very good, but Dynaco A-470’s they are not.
That's a nearly useless data sheet. No performance data at all.
I bought one as a "test". I saw the specs.
I retro-fitted the A470 into my HF87 replica and it does not perform as well as the Hammond 1650P. With step network & feedback somewhat optimized, the frequency response and square wave (10kHz) is not acceptable. I still have 9 days to send it back.
I retro-fitted the A470 into my HF87 replica and it does not perform as well as the Hammond 1650P. With step network & feedback somewhat optimized, the frequency response and square wave (10kHz) is not acceptable. I still have 9 days to send it back.
Yeah, the whole point of getting an A470, is that it's almost impossible to make a REAL one, behave badly. Identical frequency response from every output tap, and pretty much unconditionally stable. As Dave Gillespie put it: "it's impossible to make one squeal"...
If you're having to jump over hurdles and through hoops, to make the feedback compensation work- and it's still not giving good 10K square waves- on top of being the wrong primary impedance- then this really shouldn't be called an "A470". That's just misleading.
Regards,
Gordon.
Seems like you've answered your own question--at least as far as I'm concerned. ;-) I have found some variability in the Heyboer Peerless copies, but not enough to affect performance or the desired flat response within the audible range.
Matt's transformer project is ongoing. A lot of iterations have been tested and revised. I think he is getting close to releasing a good clone of the Z-565.
For what it's worth, I've measured a Dyna A-470. 5150 Ohms into 8 Ohms, about 4750 by ratio (subtracting winding resistance). Primary would measure about 10% lower on the 4 and 16 Ohm taps. UL ratio 36%. Leakage inductance: 12-13 mH, not super low, but near identical on all three taps.
This makes no sense at all. The Pacific Transformer website claims to have solved all the pitfalls associated with products from China. 
Keywords... claims to have.This makes no sense at all. The Pacific Transformer website claims to have solved all the pitfalls associated with products from China.
Is there a reason you didn't want to buy these from Triode Electronics? Pretty expensive, but probably worth it if the amplifier is something you really value.
Jack
Jack
Is it Triode or Dynakit parts thats perpetually out of stock? I've looked at both recently and don't remember, but the in-stock one has them for something like 350 each.
I'm perpetually cheap so I get the appeal of a less costly option if it performs the same. Thats what testing is for though, not just relying on the mfg claims.
I'm perpetually cheap so I get the appeal of a less costly option if it performs the same. Thats what testing is for though, not just relying on the mfg claims.
I think he was curious to try it. For the price I would have been curious too. ;-)
Yes, price. I don't think one transformer is worth that price. I have a limit of what I will pay for most items. $700 for a pair of OPT's for an amp project is not in my interest.
Even if I won the lottery, I would not pay $700. It's just one of those things...