[oneplustwo]

Can I use this toroid for my S11 to power my M3?

I'm confused about the specification about parallel and series output voltage. If I wire in parallel, 22 VAC seems a bit short as 24V is recommended on the AMB site. If I wire in series, 44 VAC seems a bit high as 40 VAC is the max recommended on the AMB site. But then the maximum power of the toroid says 25VA? I have a feeling this may be a dumb question and I just need to be edumacated in some basics so thanks for patronizing me.

 

[amb]

Use a Amveco TE-62062. Wire the two 12V secondaries in series and you get 24V. The two center positions of σ11's transformer input terminal block does the series connection for you, so all you need to do is to connect the four wires from the transformer secondaries to it (green, red, brown, blue, in that order; doesn't matter left to right or vice versa).

On the primary side, since you're in the US with 115V AC, connect the two primaries in parallel (violet and black goes to "live", yellow and red to "neutral").

The 25VA is the power rating of the transformer (VA = Volts *Amperes).

 

[oneplustwo]

Ah, that makes perfect sense. Why don't they just call is 25 Watts instead of VA?

So if I use the toroid I mentioned in the 22V configuration, will I notice a significant decrease in sound quality? My guess is that the voltage swings won't be as large as they could be so that would manifest itself in a decrease in dynamic range or slew rate? Similarly, if I use the 44V configuration, does that mean there is increase chance of damage to components (in particular the TLE2426), additional heat, and perhaps oscillation? (Besides the fact that no opamaps are rated for that high a voltage.) Just trying to increase my understanding.

Finally, is there a way to dial down the voltage of the sigma 11? I'm thinking if I wanted to build a generic power supply that I could switch around to power other things that might have different requirements, it would be nice vs. having to build a separate sigma for each one.

 

[Beefy]

Quote:

Originally Posted by oneplustwo /img/forum/go_quote.gif Ah, that makes perfect sense. Why don't they just call is 25 Watts instead of VA?

Because watts and VA are different things. This article on power factor may be appropriate.

Quote:

So if I use the toroid I mentioned...... it would be nice vs. having to build a separate sigma for each one.

You really should set up the S11 for exactly the voltage you want and leave it there. Same goes for any linear power supply. With a given transformer voltage, you can't set the voltage too high because you drop out of regulation. You can't set the voltage too low, because the output devices will get too hot burning off the excess.

I would strongly recommend you get the transformer that AMB recommends - it is recommended because it works. Don't try and make a variable supply, because you will only run into trouble.

With respect to the voltage question, I will leave that up to others. But I do know that 44V through a MMM would be BAD.

 

[oneplustwo]

Thanks Beefy, that sounds like prudent advice which I will follow. Also, thanks for the wiki article, I love a good wiki!

 

[TimmyMac]

95% chance that transformer will be fine. You just lose a couple volts of headroom (and heat). Depending on the current you're drawing you may end up getting 24V from it anyway.

 

[oneplustwo]

Hmm... maybe I'll try it and see if I can tell a difference compared to the "right" transformer. At least I know I won't fry anything. And if it works ok, maybe I'll save it for another project vs. spending the money to send it back.

So per the documentation on amveco, to parallel the secondaries, I'll connect the green and brown wires and red and blue wires together. Then on the sigma, I believe I just follow the section on "single-secondary transformers" and connect one pair to each of the outer two positions of the terminal block. Does it matter which one goes where? Doesn't sound like it based on the s11 wiring page.

 

[amb]

Quote:

Originally Posted by oneplustwo /img/forum/go_quote.gif So per the documentation on amveco, to parallel the secondaries, I'll connect the green and brown wires and red and blue wires together. Then on the sigma, I believe I just follow the section on "single-secondary transformers" and connect one pair to each of the outer two positions of the terminal block.

Yes.

Quote:

Does it matter which one goes where? Doesn't sound like it based on the s11 wiring page.

No. Because AC has no polarity.