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In Reply to: RE: Well, Abe... posted by AbeCollins on May 31, 2013 at 12:15:59
"Hey, why did you stop there"
Be warned, very warned: you are starting to sound like me!
An observation is not an explanation...
Rick
Follow Ups:
Before we continue this Internet battle, can we please stop and notice that Paul McGowan attributed the benefit of the larger transformer to its much lower "secondary" impedance? Could that be the crux of the issue here?
(I will admit I don't know what "secondary" impedance is.)
"Before we continue this Internet battle"
This 'taint a battle, it's but a discussion. However the actual subject may be a bit obscure.
"Paul McGowan attributed the benefit of the larger transformer to its much lower "secondary" impedance? Could that be the crux of the issue here?"
Well, it is the crux in a way, the real issue is WHY did he attribute it to that and what did he do to establish causality.
The power transformer's secondary impedance can not directly affect the signal integrity so if it matters the next step is understanding how and where the interaction is occurring.
Abe has it right, if two transformers are good how about ten of them? What this sort of thinking and exploration does is establish limits and sensitivity. If adding transformers monotonically increases the goodness then you "have a handle" on the problem: you can dial the goodness up and down. At that point you are in a good position to eyeball the various signals and busses in and out of band to see what's changing as you turn the goodness crank and hopefully will be able to sift out the root cause(s).
This is just a straight-forward, everyday engineering process, nothing unique to audio. Having not read Paul's writings I have no idea how this shook out.
Rick
The transformer destermines the Z of the circuit, larger PT with a low DCR winding, has lower Z. You dudes should think in dynamic terms.
Jeff Medwin
"The transformer destermines the Z of the circuit"
Oh? Your world is a simpler, more beautiful place than mine. Everything from the generator at the dam to the ESR of your filter capacitors are in that loop.
"You dudes should think in dynamic terms."
I do. And my thinking is that by the time you shuffle in the PSRR of the preamp stage itself along with all the other terms that the DCR of the transformer secondary is probably small potatoes. Or at least should be.
Bear in mind that this is all just a speculative argument for entertainment and fun. Without access to exactly the same gear we can't really sort it out. If I were to guess, and brother it's just that, I'd suspect that the noise profile from the power line and rectifiers were the culprits. Remember that in a low power design the rectifier conduction angle is fairly small and a lower impedance source makes it smaller yet. That reduces the window for noise to couple through which may be a good thing.
Another possibility is that the transformers differed in yet another way that wasn't quantified. Perhaps the higher current model also had less effective primary to secondary capacitance, that would be, IMHO, far more important than it's DCR. I don't know about your power lines but my power comes from pristine snowpacks melting into the mighty Columbia and rolling on through the BPA dams and into my stereo. And it looks like shit! I would be willing to post a picture of mine if we want to have an ugly power contest; time and loads have changed since Guthrie's time... Everyone want's theirs off the top, chokes cost money, weight and size.
Rick
JLH from 2009, speaking of tube amps, but it applies. "Transformer DCR sets dynamic impedance".
Cheers....BTW, Its what I hear, every time, I have changed power trannies and listened methodically.
Jeff
"JLH from 2009, speaking of tube amps, but it applies. "Transformer DCR sets dynamic impedance"."
Yea... And he had plenty of critics in the same thread adding clarification at the least. The best one you dismissed out of hand "who was that masked man (roughly)".
Usually the design approach with lower power "signal" stages, which I think this thread is about, is to try and have localized voltage sources for each critical stage. Often this amounts to a very close, low ESR capacitor but sometimes it involves local regulators.
Rick
snubbers in rectifier circuits is well known and an established audiophile tweak. Most such circuits work on the diode spike entering the component circuitry. It has been my observation that that same spike enters the power transformer secondaries and thus affects all secondary windings. I place small AC caps across the legs of the lower voltage taps (I am a tube man and B+ voltages are pretty high at times). It significantly warms up the sound and gives greater midrange and upper end detail.
Of course this is posted in regards to the reference to diode/rectifier noise. we always are careful about the noise entering the circuit, but forget the noise can be reflected back through the transformer windings.
No proof just experimental results.
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