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Old 16th June 2011, 10:30 AM   #21
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Just a thought: if this is a preamp power supply, haven't you considered adding a voltage regulator of some kind?

It could bring an even greater improvement to your audio quality.
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Old 16th June 2011, 11:35 AM   #22
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I understood the idea was omitting any regulator to improve sound quality....
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Old 16th June 2011, 11:35 AM   #23
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Quote:
Originally Posted by hesener View Post
sorry wintermute for repeating this, I really should have read the thread to the end....
No Problem at all hesener!! I'd much rather someone repeat something when I've made a mistake than not say something I'm a big boy and can handle the truth

I always feel bad if I post something technically incorrect and am happy for people to point it out.

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Old 16th June 2011, 03:49 PM   #24
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Quote:
Originally Posted by QSerraTico_Tico View Post
I understood the idea was omitting any regulator to improve sound quality....
Sorry, but I thought the whole idea behind a regulator was to improve sound quality. You disagree with that?

The problem with regulators can be poor design, mostly for not taking care of dynamics. Even if that limitation sometimes is on the cicuit the regulator is feeding.
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Old 30th July 2012, 02:11 AM   #25
abetir is offline abetir  Philippines
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Hi! All,

I just build a proto of the P3A amp, it sounds fantastic but my problem was the PSU. I have a dual supply 36vac toroid rated at 500w and I have read (Elliotts site) that the maximum rail voltage for the P3A was -/+42vdc. 36vac converted to dc becomes 50vdc, it looks too much for the amp to handle. Adding outputs in parallel my do the job but I only wanted an output power of about 80-100w at 8ohms load. (sufficient enough for home use)

Anyway...anyone can suggest me a simple (no IC regulators) RCRC filter circuit for my toroid in hand? I guess it just need to drop some voltage and come up to -/+42vdc. Sorry I can't do simulations.


Thanks!

p3afront.jpg

traffof1.jpg

Last edited by abetir; 30th July 2012 at 02:14 AM.
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Old 30th July 2012, 02:43 AM   #26
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I think that the problem you will run into is that the voltage drop is dependent on current draw. As the P3A is a class AB amp it doesn't have a constant current draw.

with a regulated supply it is less of an issue provided that the maximum current possible is used to calculate the voltage drop (and that remains higher than the dropout voltage of the regulator).

With an unregulated supply you would need to go with the lowest current draw (to get the voltage down to your required 42V but then when current demands increase your voltage will sag a lot more.

Generally with Class AB amps CRC is done with very low value resistors (less than 1/2 ohm) to ensure that voltage drop is minimal, and heat dissipation is also minimal.

Someone else more experienced than I may have another suggestion, but I think your best bet is a new transformer

Tony.
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Old 30th July 2012, 02:53 AM   #27
abetir is offline abetir  Philippines
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Thanks for the feedback sir Tony,

I was reminded by one site that also built the P3A but was using an RC filter for the PSU, problem was, I forgot to bookmark the link.
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