Regulated Supply Examples

[Mike K8LH]

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]

Mike,
could this be of any help:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=43423&highlight= ?

/Hugo

 

[jackinnj]

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]

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]

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: