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Old 17th July 2004, 11:34 PM   #1
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Default power supply: shunt or series??

I need to build a supply for 40vdc and 1.5A

It is for a SE Class A SS amp.

Hum and ripple less than 5mV.

What should I do??

I do have 4 68,000uF 50v caps... but wary to use them due to charging currents.

I am looking for a good schematic for both a shunt and a series regulator that would work for this application.

Of course looking for the best sonic way of doing it.

Thanks!!!
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Old 18th July 2004, 01:52 PM   #2
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Best system is high speed diodes, tns less than 35nS, then CLC with 68,000uF then 20mH then 68,000uF, the last bypassed with some serious film caps.

DCR of the choke should be no more than 1 ohm.

Cheers,

Hugh
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Old 18th July 2004, 02:04 PM   #3
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Default hmm...

i tried simulating that on PSUD and got a lot of ripple still.

unless I am doing something wrong..
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Old 18th July 2004, 03:09 PM   #4
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Default Re: power supply: shunt or series??

Quote:
Originally posted by AudioGeek
I need to build a supply for 40vdc and 1.5A

It is for a SE Class A SS amp.

Hum and ripple less than 5mV.

What should I do??
I don't know if any practical passive set-up will ever get to that level of ripple / hum. You can either use regulators which may not be sonically as good, or you can ask yourself if you really need that kind of ripple / hum.

I would imagine most amps have reasonably good psrr (>40db?). how much does that translate 5mv ripples on the rail into ripples on the output? does that really matter in your application?
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Old 19th July 2004, 08:47 AM   #5
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If the design is PP, then PSRR will be considerable anyway and 10-15mV of ripple is mere bagatelle.......

If the design is SE, then assuming the output is the source or emitter, then the high drain/collector impedance will ensure the ripple has little effect.

Exactly as Millwood says, active regulators tend NOT to sound marvellous, but passive power supplies do, because there is no feedback loop to synthesize intermodulation products. In any event precise regulation of voltage is not required. Impedance characteristics with frequency are far more important.

You need to build it, listen to it, figure out cause and effect, and get right away from the figures until you can prove the parameters you are measuring are a problem.

PSUD/PSpice etc are useful tools, but akin to reading about car repair in a manual, while the car sits broken in your garage. I am well aware that it is de rigeur to operate these programs with flexibility and math knowledge, but nothing can demonstrate the causal links like building and listening.

Cheers,

Hugh
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Old 19th July 2004, 09:04 AM   #6
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Why high speed diodes, Hugh ? They have sharper " knee " and give more disturbing. Amp, which need ripple 5 mV, have low PSR and is not good.
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Old 19th July 2004, 10:20 AM   #7
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What about using a capacitance multiplier? Or do these not really have the same low impedance as real caps of the same value?
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Old 19th July 2004, 02:09 PM   #8
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Hi PD,

Thank you for your post.

I did tests on the Ultra fast Soft Recovery diodes, and found them to be sonically far superior to a conventiional bridge. Others have tried Schottkys, and the Fairchild diodes, but not me. If you use a choke and a reasonable quality second cap (CLC) then the spikes are pretty small.

I know what you are saying about amps which are susceptible to high ripple, but SE amps are pretty good, Pavel, and they have low PSRR!!

Beware categoric statements, some !@#$ always proves you wrong!

I've tried capacitance multipliers. They enhance the capacitive smoothing effect by use of active devices. But the active devices do impose their own sound on the proceedings, and I seem to get better results with the real thing........

Cheers,

Hugh
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Old 19th July 2004, 03:01 PM   #9
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Hi Hugh, I know how work CLC filter, in my regulated supply I have it too. SE amps are maybe good sonicaly, but I claim, that amp should have good PSR and if haven't it, is in my look wrong. And on which parameter of amp cause high speed diodes ? I have in my amps SNR over 120 dB ( A ), respectively over 115 dB linear, with normal bridges. What can I to get better with this ? I like clear explanation .
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Old 19th July 2004, 10:53 PM   #10
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Default not emitter or source follower!!!

it is NOT emitter or source follower so I need my hum / ripple level down to nada.

so passive or active regulation???

i was thinking about the capacitance multiplier...

thoughts still the same?
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