Regulated Supply Examples

Mike, K8LH · 27th December 2005, 04:05 PM

Greetings Gentlemen,

Are there examples of regulated dual-rail power supplies for '4780 amps around please? Any comments, pro or con, for regulated supplies? I'd simply like to take advantage of a spare Toriod transfo' with dual 115vac primaries and dual 38v/10.79a secondaries...

I did try a quick search of the Forums but 'no joy' so far... Some pretty lengthy threads so I might have skipped right over a good post without realizing it...

TIA... Regards, Mike

Netlist · 27th December 2005, 08:37 PM

Mike,
could this be of any help:
The (high-cap.) unregulated PSU for chipamps ?

/Hugo

jackinnj · 27th December 2005, 10:15 PM

A regulator for the LM4780, LM3875, LM3886 etc. seems to be a waste of energy -- the overhead of the regulator could go into your speakers, not heating up the room. Further, outboard regulators add a new control loop to the equation. The PSRR of the overture series chips is such that a regulator is redundant.

pinkmouse · 27th December 2005, 10:59 PM

I regulated a 3875, and it sounded exactly the same as one with about 10K uF of ordinary PSU. I'm with Jack, it's not worth the extra cost or complexity. The only advantage I can see is if you need to drop some volts from your traffo.

carlosfm · 27th December 2005, 11:04 PM

Quote:

Originally posted by jackinnj
The PSRR of the overture series chips is such that a regulator is redundant.

The LM3886 on the negative rail falls down quickly after 100hz, to lowish values of 55db at 10Khz an going down steep.
A good PSU is needed IME, regulated or unregulated.
Both snubberized, but with different values for regulated or unregulated.
Sometimes it's in these 'small' details that two amps sound a world apart, even using the same chip.
Big caps on the chips (I use 2,200uF), after the regs, throw away any preconceptions of lack of heardroom, dynamics of regulated PSUs on power amps.
Btw [subjective talk warning] a good PSU produces clean, extended and precise treble. But that should be predictable just by looking at the graphs on the datasheet.
I don't understand what's so special about these chips' PSRR, it's not bad, but also not brilliant.

But what Mike wanted to know is if he could use his trafo with a regulated PSU for an LM4780 amp.
That 38Vs trafo will produce ~53VDC, you can regulate to around 40V and the LM338s will not produce much heat, but the LM4780 chips will.

LM3886 PSRR:

27th December 2005, 04:05 PM	#1
Mike, K8LH diyAudio Member Join Date: Nov 2005	Regulated Supply Examples Greetings Gentlemen, Are there examples of regulated dual-rail power supplies for '4780 amps around please? Any comments, pro or con, for regulated supplies? I'd simply like to take advantage of a spare Toriod transfo' with dual 115vac primaries and dual 38v/10.79a secondaries... I did try a quick search of the Forums but 'no joy' so far... Some pretty lengthy threads so I might have skipped right over a good post without realizing it... TIA... Regards, Mike

27th December 2005, 10:59 PM	#4
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	I regulated a 3875, and it sounded exactly the same as one with about 10K uF of ordinary PSU. I'm with Jack, it's not worth the extra cost or complexity. The only advantage I can see is if you need to drop some volts from your traffo. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

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27th December 2005, 08:37 PM	#2
Netlist diyAudio Moderator Join Date: Jan 2003	Mike, could this be of any help: The (high-cap.) unregulated PSU for chipamps ? /Hugo

27th December 2005, 10:15 PM	#3
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	A regulator for the LM4780, LM3875, LM3886 etc. seems to be a waste of energy -- the overhead of the regulator could go into your speakers, not heating up the room. Further, outboard regulators add a new control loop to the equation. The PSRR of the overture series chips is such that a regulator is redundant.

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