multi-secondary toroids ?

Hi,

I'm considering a multi-channel amp and one approach I like requires me to have an independent single rail power supply for each channel. I could use a separate off-the-shelf power trafo for each channel. I could also use a single large (say, 600VA to 1kVA) toroid with multiple secondaries.

Anybody got any experience / recommendations sourcing toroids with, say, 5 independent secondaries ?
 
You might be into custom order territory there, although if you could get your hands on a 1kVA core, you might consider it DIY windable since the turns per volt will be fairly low. 5 200kVA transformers isn't a total mess but for the same weight in materials the single transformer will have less loss at full load. You also get the benefit of a very large core and heavy primary winding to serve secondary windings that might be fully loaded while other are not.
 
Big transformers generally have lower regulation. This lower regulation is an advantage when it comes to delivering current to the speaker.
The PSU average voltage stays higher when peak demand comes along with a low regulation transformer.

Using separate windings on a big transformer allows all these windings to give that low regulation benefit to each of the PSUs.
That can sometimes be an advantage compared to a dual mono amplifier which uses two smaller transformers.
A four winding secondary will probably perform better than two dual secondaries in a dual mono amplifier.

If any of the PSUs are regulated, then transformer regulation for that PSU becomes irrelevant.

Finally,
the total secondary winding VAs can be different from the Primary VA.
One could ADD extra secondary windings to fixed primary+secondary and the secondary VA will now be higher than before. If the average current drawn from the multiple secondaries is the same as the average before adding, then the regulation of the transformer per winding will be lower. This comes about because one has increased the copper volume.
 
Plitron currently has a 2400 VA monster with five 60-0-60 secondaries in their surplus listings:
Surplus Transformer

wow, that's a beast alright - no worries about a low Zout supply. I will think about this.

I've taken my research a step further - I can buy an Emotiva 5 channel amp with 1.2kW toroid and case, soft start, heatsinks, amplifiers - it's all there for less than I can buy the parts. Even if I upgrade the capacitors to higher quality devices I'd be hard pressed to spend more than it would cost me to buy the parts to build it myself and it would take me many weeks. Would a design of my own sound better - well of course it would ! but the economics and time investment are no longer looking favourable....