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Power Supply Questions: Sigma 11 or 22?

post #1 of 21
10/28/09 at 1:19am
Thread Starter 
Hey guys,

I might need to build a power supply (either Sigma 11 or 22) to accommodate this:



I have to admit that I'm not well versed in DIY world so I hope you experienced DIY-ers can point me in the right direction:
  1. The builder of this amplifier suggested to get a PSU with a rating of 18V 500mA. From the Sigma 11 or 22 specification page, it seems to be possible to set the voltage to that rating. Am I good to go from here?
  2. The Sigma 22 is interesting because you can get the complete kit from Glass Jar Audio but would be it be an overkill for this amplifier? Would the Sigma 11 be enough?
  3. Would a separate enclosure be better for the PSU unit? Does putting it in a separate enclosure connected via DC cord will have any negative impact on SQ? Certainly putting it together in the same case would make it more practical.
  4. Last but not least, suppose that I have some experience in soldering CMOYs, making LODs, cables, recabling, the basic stuff. Would putting together a Sigma 11 or 22 be too difficult then?

OK, I'm looking forward to your inputs.
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post #2 of 21
10/28/09 at 3:18am
If the amp needs a dual-rail supply (+/0/- voltages), make S22
Otherwise, S11.

Probably it has a rail splitter somewhere to make hte 18V from those 2 batteries into +/-9V, in which case if you can bypass it and use a S22 it would be better.
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post #3 of 21
10/28/09 at 8:31am
Thread Starter 
Yeah, the lone op-amp near the big capacitor is used for rail splitting. It should be possible to bypass it, I need to check with the builder.
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post #4 of 21
10/28/09 at 12:34pm
Not sure of the details of this amp's design, but using a s11 would probably be keeping with the "intended" design more since that's what was specified. It would also be cheaper
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post #5 of 21
10/28/09 at 12:45pm
I'm going to say the s11 would be plenty of power, and I agree with Iniamyen that it would help to keep with the intended design while saving you money.

In terms of build difficulty it's really not too bad as long as you're confident in your soldering ability and you can take your time to study the schematic/layout/enclosure and do it right. Read through amb's entire walk-through on the build a few times before even ordering anything and make sure you're comfortable with what it entails. It's surely not as involved as many of the DIY amplifiers that exist, but you are working with AC voltage, which needs to be treated with respect.

Good luck!
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post #6 of 21
10/28/09 at 1:10pm
You could also possibly use a Tread
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post #7 of 21
10/28/09 at 2:02pm
Thread Starter 
Quote:
Originally Posted by Iniamyen View Post
Not sure of the details of this amp's design, but using a s11 would probably be keeping with the "intended" design more since that's what was specified. It would also be cheaper
Yeah, Sigma 11 was what I intended in the beginning but Sigma 22 kit is easily available so it's really tempting because getting AMB's specified parts in my country is not exactly an easy matter.

Quote:
Originally Posted by Anonanimal View Post
I'm going to say the s11 would be plenty of power, and I agree with Iniamyen that it would help to keep with the intended design while saving you money.

In terms of build difficulty it's really not too bad as long as you're confident in your soldering ability and you can take your time to study the schematic/layout/enclosure and do it right. Read through amb's entire walk-through on the build a few times before even ordering anything and make sure you're comfortable with what it entails. It's surely not as involved as many of the DIY amplifiers that exist, but you are working with AC voltage, which needs to be treated with respect.

Good luck!
OK, I guess two are in favor of the S11 now.

Quote:
Originally Posted by cobaltmute View Post
You could also possibly use a Tread
This is very interesting. How would a TREAD compare to the Sigma 11?

Additionally, it will be very helpful if you folks can help to address my other concerns such as separating the PSU in a different enclosure. I'm still not sure on this.

Here are some specifications of this amplifier if it helps:

* 3-channel active ground topology
* 3-channel buffer architecture
* Precision virtual ground reference
* Class A bias (at buffer stage)
* Jung multiloop
* Bass boost (SOUL M v2)
* DIP socket design for OPAMP rolling

I really appreciate the inputs so far. Thank you so much guys!
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post #8 of 21
10/28/09 at 2:25pm
You can definitely put the PSU in a different enclosure. Sorry for not noticing that question the first time. It's actually recommended to help keep any transformer noise from affecting your amp. Amb recommends not having your DC line running longer than 1 meter or smaller than 18AWG. You'd want to twist or braid the line at a minimum for noise rejection, also according to amb. If you read some through the s22+b22 build you should see some build recommendations that would apply similarly to your amp and a s11.

http://www.amb.org/audio/beta22/wiring.html and check out the 'Wiring and Ground' section for how he lays it out.
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post #9 of 21
10/29/09 at 8:27am
Thread Starter 
Quote:
Originally Posted by Anonanimal View Post
You can definitely put the PSU in a different enclosure. Sorry for not noticing that question the first time. It's actually recommended to help keep any transformer noise from affecting your amp. Amb recommends not having your DC line running longer than 1 meter or smaller than 18AWG. You'd want to twist or braid the line at a minimum for noise rejection, also according to amb. If you read some through the s22+b22 build you should see some build recommendations that would apply similarly to your amp and a s11.

The β22 Stereo Amplifier and check out the 'Wiring and Ground' section for how he lays it out.
Much appreciated, thanks!

For the cabling, there is no difference compared to cables used for signal right? I've never made a power cable before, just making sure.
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post #10 of 21
10/29/09 at 10:01am
K3cT, you should generally use heavier gauge wire for power. Depending on the amp, anywhere from 18-22AWG woule be good for power, but small-signal wiring can be as thin as 24 AWG or more.
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post #11 of 21
10/29/09 at 10:43am
The Tread is based on the monolithic LM317 regulator.

The sigma11 is a discrete pass transistor based regulator. Due to its output MOSFETs it can provide significantly more current (in excess of what you need).

They both will do the job in your case. the Tread can be had for $17 in kit form from Tangent and then you can add an AC wall wart (Mouser p/n 507-XT1840) for not too much more so it can be a lower cost alternative.

As for performance, I make no comments. I have only built a Tread type circuit on strip board and never worked with sigma11. However, both will provide a quality DC signal to your board.
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post #12 of 21
10/29/09 at 3:39pm
Thanks for hopping in amb, and please let me know if it sounds like I'm putting too many words in your mouth or if I'm giving poor advice!
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post #13 of 21
10/31/09 at 1:55pm
Thread Starter 
Quote:
Originally Posted by amb View Post
K3cT, you should generally use heavier gauge wire for power. Depending on the amp, anywhere from 18-22AWG woule be good for power, but small-signal wiring can be as thin as 24 AWG or more.
I happen to have a 18AWG cable in my arsenal and I'll probably use that. Thanks for the input, Ti Kan.

Quote:
Originally Posted by cobaltmute View Post
The Tread is based on the monolithic LM317 regulator.

The sigma11 is a discrete pass transistor based regulator. Due to its output MOSFETs it can provide significantly more current (in excess of what you need).

They both will do the job in your case. the Tread can be had for $17 in kit form from Tangent and then you can add an AC wall wart (Mouser p/n 507-XT1840) for not too much more so it can be a lower cost alternative.

As for performance, I make no comments. I have only built a Tread type circuit on strip board and never worked with sigma11. However, both will provide a quality DC signal to your board.
Thanks for the inputs. I think I would go for the Sigma XX now because I can commit to that.

And for the toroid, I found an ILP one which is supposed to be a popular UK brand. It has 60VA power rating and 22V AC voltage. Somehow I need a 24V DC input for the amplifier so how does one modify the Sigma 11 or 22's parts to do this?

I'm now honestly tempted to order the S22 kit instead because it's less hassle. Curse me for living in such a remote place in the world!
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post #14 of 21
10/31/09 at 6:56pm
K3cT, if your amp needs a single-polarity supply, then use σ11. If it needs a dual-polarity supply, then σ22 is the right one. σ11 is essentially one half of a σ22.

As for configuring the output voltage either of these, see their websites:
The σ11 Regulated Power Supply
The σ22 Regulated Power Supply
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post #15 of 21
11/1/09 at 5:34am
Thread Starter 
@amb
I've already discussed with the designer and the amp can accept dual-rail power supply. I just need to bypass the rail splitter to do this. Cheers!

OK, I'm rather excited to build this. Gonna spend the next couple of days to read the information available in the net then probably order a σ22 because the kit is readily accessible.
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