One Transformer Per Channel? Or One Total?

[asgorath]

I am going to build a 3 channel gainclone on mariposas's reference design and am wondering how many transformers I should use. I am told that one transformer per channel is optimal, but is it really much of a difference? I am trying to build a solid 60W/ch amplifier that sounds excellent and want to know if this is worth the extra bucks.

On that note, should I get:

1x ~400 VA transformer
or
3x 220 VA transformers?

[tlmadsen]

One transformer is just fine.

Thomas

[asgorath]

For mariposa's design, there seems to be no advantage to a split 24+24 supply. It seems a center tapped transformer would work just fine. Or is this just to help with a better star ground?

[carlmart]

Which is mariposa's design?

[asgorath]

My "audiophile" LM3886 approach

[asgorath]

What do you think about one of these per channel?

http://www.partsexpress.com/pe/showd...number=129-084

[Tekko]

Waaay too small. That transformer is max 50VA. For 3x60 (180 watt amp total) watt amp you need atleast a 400VA transformer as you have maximum 40% efficienty in the amps otherwise it will drain the ps caps very fast and the ps voltage will sink so low that the amp may start to act like beeing turned on and off.

[jaudio]

Are you sure? The 129-084 is big in size and weighs more the PE 120-210 and it weighs more than PE 120-220.

[Tekko]

4.8 lbs is not mutch for a power transformer, equals about 100-120VA transformer which is nor enough for a 3x60w amp. a 400VA transformer weights like 11 lbs and even that is too small, a 3x60 watt amp needs 180 watts of power and if we count in the efficienty of max 40% you will need a 450VA transformer to power all three channels to 60 watts.

Do the math: 450VA x 0.4 (40%) = 180VA / 3 = 60VA. VA and watts are close to each other but not the same, from 400VA you can use around 380 watts if i remember right.

[asgorath]

Originally posted by Tekko
4.8 lbs is not mutch for a power transformer, equals about 100-120VA transformer which is nor enough for a 3x60w amp. a 400VA transformer weights like 11 lbs and even that is too small, a 3x60 watt amp needs 180 watts of power and if we count in the efficienty of max 40% you will need a 450VA transformer to power all three channels to 60 watts.

Do the math: 450VA x 0.4 (40%) = 180VA / 3 = 60VA. VA and watts are close to each other but not the same, from 400VA you can use around 380 watts if i remember right.

Don't forget that I said one of these per channel. So for a 60W amp @ 40% efficiency we need 150W per channel. So you don't think one of these transformers will put out 150W? Also, I have been reading about CarlosFM's Regulated snubber power supply and he said it doesn't take nearly as much

Originally posted by CarlosFM
Well I shall say that with 1,000~1,500uf capacitance you need a big trafo, and it's never enough.

Go regulated and 150~200VA is enough for two LM3886 chips.
Bass is TIGHT, voltage doesn't sag and the "juice" is always available.

For $5 a transformer this would save me about $35 in parts cost and according to Carlos would not create any difference in performance. What do you guys think of this?