[Solan]

I am buying an Apogee mini-DAC while in the US this summer, and have been advised to upgrade the PSU to sigma 11. But living in Europe, I need 220V in, not 110V. What mods must I make to the original design? Or is there some other design that delivers 12 clean volts with lots of amperes to spare, for an Apogee mini-DAC?

 

[FallenAngel]

It's all in the transformer wiring. Most transformers will handle both 110V and 220V, just wire them properly. If you're building it yourself, you should know what you're doing (either by reading the transformer datasheet or you shouldn't be doing it because nobody wants you to put 220V through yourself) or if somebody else if building it for you, they should know how to wire the transformer properly for 220V. If it's somebody else building it (which I'm hoping on because it's a question you should have covered if you build it yourself, safety concerns again), just ask them to use a transformer wth 220V primaries or dual 110V/220V primaries, they're extremely common anyway.

 

[Solan]

OK, so doubling the number of windings on the transformer is all you need to do? As for safety, I will be doing the labour myself, but under supervision. I just need to know what to get, and not the least what is different from the standard sigma 11 package. If it's just the transformer, I think I should be able to cope.

 

[n_maher]

The correct wiring is typically written on the side of the transformer or at least provided in documents when you purchase it. Are you modding an existing Sigma or building a new one?

 

[Solan]

I'm primarily interested in the end result: A 220V -> 12V power supply that delivers ample and clean current into an Apogee mini-DAC.

If that is best done by modding, I'll do that. If it's best done building from scratch, I'll do that. If it's best done buying from someone who already know what they're doing ... well, then that's what I'll do. But reading the sigma 11 homepage, I got the impression it was a DYI.

 

[n_maher]

It is DIY, I just didn't know if you'd already purchased one (that someone else built) or if you were starting from scratch. Sounds like you're just starting, in which case designing for 220V operation will be no harder than 120V.

You might also consider building a STEPS power supply. It's a bit more newb friendly with the on-board fuse and trafo, less wiring to go wrong. While technically its performance isn't to the level of the sigma11 it's still head and shoulders above anything commercial you can buy.

 

[1UP]

Or not even consider a TREAD?

PSUs aren't something you should cut your DIY teeth on, and the TREAD...
1. is cheap
2. will do a fine job for DC regulation
3. allow you to use a wallwart for AC so no messing with trafos
4. let you use the Apogee straight away with wallwart whilst you're building the TREAD
5. allow you to learn the basic of PSUs so you can move on to a STEPS or Sigma.

 

[Solan]

The sigma 11 is what's been recommended to get the best out of an Apogee mini-DAC, so in the worst of cases, if I turn out to be unable to do a proper job myself, I will get someone to do it for me. Then I just need to know what to get which is different from the US version.

(A very friendly colleague of mine is a former sound engineer and teaches college electronics; I hope not to overextend favours with him, but I think he'll help if I'm in a bind.)

So, anyway, I won't step down in quality from sigma 11, but will consider stepping up. Or buy, if that's indicated.

 

[Solan]

So I built a sigma-11, and used a transformer coil that transforms down from 220 instead of 110. With the help of a colleague who is really good at this (he added a small 100k-Ohm resistor in just the right place), it ended up at not just 12V but 12.00V  

PS: My colleague strongly recommended against connecting to ground, as ground is a source of noise rather than its elimination.
 
End result: pleased as punch!

 

[Pars]

Quote:

PS: My colleague strongly recommended against connecting to ground, as ground is a source of noise rather than its elimination.>snip>  
 

I sure hope that the case is connected to safety ground of the mains. Whether you connect the PSU ground to such a grounded case I guess is optional, but the case should certainly be tied to mains ground for protection.