What kind of music are you listening to?
If you're listening to techno or house at full volume, those have a low crest factor. So the ability to run full watts 100% of the time depends on the transformer, the heat sink, the fan, the dust balls on the heat sink. In a class AB amp full watts comes from the SOA amps rating of the multiple output transistors times the maximum rms voltage they develop. Few amps have enough heat sink/fan to run full watts very long. Most of these amps are in the PA market for beach bars and discos. Most of these have been burnt out & replaced by digital amps, which leaves an incredible opportunity for DIY audio if you can intercept the stream of class AB hardware before it reaches the scrap yard.
If you're listening to singer songwriter strumastruma, or classical music, those have a low crest factor and an undersized transformer can catch up and refill the rail capacitors while the music is lower in volume.
OTOH, if you bought a new main transformer, you can buy one with the +-15 v windings built in. Keeps all the hum source EMI over behind the steel wall/faraday cage. If your amp is professional enough to have one.
If you're listening to techno or house at full volume, those have a low crest factor. So the ability to run full watts 100% of the time depends on the transformer, the heat sink, the fan, the dust balls on the heat sink. In a class AB amp full watts comes from the SOA amps rating of the multiple output transistors times the maximum rms voltage they develop. Few amps have enough heat sink/fan to run full watts very long. Most of these amps are in the PA market for beach bars and discos. Most of these have been burnt out & replaced by digital amps, which leaves an incredible opportunity for DIY audio if you can intercept the stream of class AB hardware before it reaches the scrap yard.
If you're listening to singer songwriter strumastruma, or classical music, those have a low crest factor and an undersized transformer can catch up and refill the rail capacitors while the music is lower in volume.
OTOH, if you bought a new main transformer, you can buy one with the +-15 v windings built in. Keeps all the hum source EMI over behind the steel wall/faraday cage. If your amp is professional enough to have one.
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It depends on the PSRR of the preamp part and the quality of the regulators which currently separate the power amp ps from the preamp ps.
Generally, both psrr and the regulator's output impedance suffer at higher frequencies. Whether this is measurable in your particular amp will depend on the specific implementation. In any case it is going to lead to a very modest measurable improvement.
The subjective improvement imho is not limited to only the high frequencies, rather the opposite.
This is not something i would recommend. Transformers generally sound different but to obtain a consistent improvement due to size you would need a much bigger VA rating, definitely above 1kVA.
Having lived for a long time with a 4.5 - 6kVA transformers in the amps, it took me a while to get used to more modestly sized iron - about 1kVA at present. But a change of 20% is pretty much unnoticeable.
Btw, power amps alone stand to benefit from a separate transformer feeding the low current stages - there are many commercial examples.
Go right ahead, especially if this is not the system you depend on for listening, because odds are:
1. 50% that you will damage your sound system and have to replace it or take it to an expert for repair.
2. 80% that your modifications will compromise the system performance rather than enhance it.
That's a bit harsh😉 as I'm only going to disconnect the stock transformer's 12V output plug from the pcb and connect a separate 12V transformer instead, I'm not going to touch the transformer power amp stage outputs (40V).
Then I'll go back to stock, It's only a matter of disconneting the new transformer and put the stock transformer plug back in.
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Well, you see, you just mentioned 1 benefit, that's a positive thinking, I like you already🙂
Go ahead, try it and learn something. Go for a low noise (torroidal?) if you can find space to mount it. Then a low noise voltage regulator and associated caps etc...
Don't see the point going from 400VA to 500, 600VA. Probably get better improvement to SQ by replacing the main filters (which provide the watts we hear via the output transistors)
Don't see the point going from 400VA to 500, 600VA. Probably get better improvement to SQ by replacing the main filters (which provide the watts we hear via the output transistors)
Certainly your right. However diy audio is a hobby for me at least. I get a great deal of enjoyment tinkering, fixing and even breaking. I learn a little along the way and even try to share what little knowledge I have. The idea being that people see it's not that difficult (to do the basics) and they have fun along the way and "the movement" grows...
I've been considering doing the White Oak treatment on a Phase Linear 400.
I probably only need 25W but what a learning excercise. I'd probably give it to the nephew, a bass player, he only knows 3 notes...
If the guy puts in a separate xfmr for the pre, the best he can hope for is reduced noise and a bit of knowledge.
Couldn't find the schematic.
Indianajo posted that the pre power supply was basically dropping resistor, zener diode and smoothing cap to provide +/-16Vdc for the opamps... If you go with the small transformer you will need a bridge rectifier (ultra fast? Soft recovery? no recovery?...). 12VAC after rectification and diode Vf will give you about 16.3VDC, so you "can't" use a linear volt regulator as I earlier suggested. The zener is starting to make some sense...
The choice of main filters depends on mounting and available space. Opinion only but I like Nichicon KW for the smaller amps and United Chemicon KMH or SMH series for the larger amps.
Indianajo gave an example from Peavey amplifiers, in my Exposure amp's transformer there are two 41Vac (measured with no load)outputs and one 11.2Vac output so I don't beleive there is a dropping ressitor to lower the voltage for the preamp stage.
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Amazing that something like that amp sold for a couple thousand $$$$....
When I can slap together something that does the same thing for less than $300.
😱
You can say it on 80% of the amplifiers in the market.
BTW in the attached photos you don't see the whole amplifier, there is another PCB under the PCB that you see.
I'm familier with that amplifier already.
There is nothing spectacular about the build quality.... it's an amplifier... plain and simple.
But as things are, once you put a "name" on it that excites people, toss in some fancy features, you can price it to the moon.
Yet....... it's STILL just an amplifier.
Boring too, with only a volume and selector control.
No tone controls to "dial in" a particular sound preference.
God forbid they should spend the extra money for that - it might raise the price a few more thousand.
The already "optional phono" board is rediculously priced at $500.
McIntosh, Fisher, Bose, Hafler, Conrad-Johnson, Mark Levinson, etc etc etc...
Names..... self-made reputations, marketing hype.....compen$ated reviewers....
Dazzle the potential buyer with fancy lights and streamlined looks....
It's all rubbish to me, because I've seen them all.
I'm not one to be "swayed" by hype, only by performance and reliability.
Copper wire doesn't care what name it's got on it, it passes electricity the same as any copper wires.
Yet.... some suckers fall for the hype anyway..... it's their money after all.
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