Is this a good power supply for a low gain(2-3) single op-amp line stage?
Class A Parallel Regulated Power Supply Finished Board | eBay
I understand low impedance supplies are preferred over higher impedance supplies for op-amp circuits.
Thanks...
Class A Parallel Regulated Power Supply Finished Board | eBay
I understand low impedance supplies are preferred over higher impedance supplies for op-amp circuits.
Thanks...
That should do the job. It looks like an LM317 set up as a current source on each channel, feeding a shunt regulator. Each channel has to be fed with a separate transformer, or just two isolated windings on the same transformer.
You should take a look at OPC's power supply for his Wire amps here (headphone amp power supply, but it would work just fine for your purpose):
http://www.diyaudio.com/forums/vend...jects-available-here-bal-bal-se-se-lpuhp.html (third item down on the list)
It works in a similar arangement with separate transformer or winding feeds for each rail, but uses two voltage regulator chips instead of the CCS+shunt regulator. OPC is using the recently released, ultra low noise TI TPS7A3301 regulators (lower noise than the old LM317's) for each rail. Plus - the big thing! - OPC has a recent model Audio Precision THD+N tester so the low noise results have been verified and posted. Probably no test results available for that eBay PSU, at least not done with anything capable of measuring noise down to -140dB. Things can happen in the layout to make a good design have issues of course. Very important to test the results to be sure.
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Thank you for the reply.
Do you know of any photos of "The Wire" power supply?
Looking at the BOM, I saw where some resistors are SMD. While I can solder SMD devices, I'm not crazy about them.
Also, do you know of any low impedance supplies that will work with a single CT transformer? Two transformers take up twice as much space.
Do you know of any photos of "The Wire" power supply?
Looking at the BOM, I saw where some resistors are SMD. While I can solder SMD devices, I'm not crazy about them.
Also, do you know of any low impedance supplies that will work with a single CT transformer? Two transformers take up twice as much space.
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ammel68 - OPC has a photo of all the PSU pieces laid out on a table here at his build wiki (scroll down to the first photo):
"The Wire" Headphone Amp Build Wiki - diyAudio
Yeah, you are right about the surface mount, that hit me about an hour after I made that post. The SMD vs. though hole is a big difference. Also re-reading what I wrote the tone of it didn't come out quite as I intended. That eBay power supply is perfectly fine and is a good design. OPC's supply is nice and may very well be a little lower noise, but that ebay supply should also have very low noise. The LM317 is old but still pretty good with the right design.
Here is another one I forgot about in the Vendor section:
http://www.diyaudio.com/forums/vendors-bazaar/263618-tps7a4700-low-noise-ldo-regulator-pcb.html
He is using another one of those recent TI TPS7A regulator chips, that same series, but this one is a surface mount regulator (the regulator in OPCs is through hole TO-220) which has an even lower noise figure. And the best part: sounds like he is selling them as a kit, with the SMD parts already soldered on. I think that is the case anyway. I haven't been following that vendor thread and just skimmed through it. I was following the forum thread on that project before it went for sale in the vendor forum so I am up on what it does in general. In fact, for your purposes of a low current line stage this PSU may be an even better fit than opc's PSU since you don't need a lot of current. I see he has a single and a dual available, you would want the dual of course and it looks like he may still have some for sale.
That one also looks like it uses two separate transformers. But keep in mind that off the shelf transformers with just two independant secondary windings are pretty common and cheap. OPC had one specified for his PSU.
"The Wire" Headphone Amp Build Wiki - diyAudio
Yeah, you are right about the surface mount, that hit me about an hour after I made that post. The SMD vs. though hole is a big difference. Also re-reading what I wrote the tone of it didn't come out quite as I intended. That eBay power supply is perfectly fine and is a good design. OPC's supply is nice and may very well be a little lower noise, but that ebay supply should also have very low noise. The LM317 is old but still pretty good with the right design.
Here is another one I forgot about in the Vendor section:
http://www.diyaudio.com/forums/vendors-bazaar/263618-tps7a4700-low-noise-ldo-regulator-pcb.html
He is using another one of those recent TI TPS7A regulator chips, that same series, but this one is a surface mount regulator (the regulator in OPCs is through hole TO-220) which has an even lower noise figure. And the best part: sounds like he is selling them as a kit, with the SMD parts already soldered on. I think that is the case anyway. I haven't been following that vendor thread and just skimmed through it. I was following the forum thread on that project before it went for sale in the vendor forum so I am up on what it does in general. In fact, for your purposes of a low current line stage this PSU may be an even better fit than opc's PSU since you don't need a lot of current. I see he has a single and a dual available, you would want the dual of course and it looks like he may still have some for sale.
That one also looks like it uses two separate transformers. But keep in mind that off the shelf transformers with just two independant secondary windings are pretty common and cheap. OPC had one specified for his PSU.
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I'm probably showing my ignorance here, but I don't think I've ever seen a transformer with 2 independent secondary windings.
I've always used center-tapped transformers from either Rat Shack or Antek.
I assume these transformers will have 4 wires on the secondaries instead of 3?
Do you know a source for these transformers, or have a link to a 12-15V with independent secondary windings?
Thanks...
I've always used center-tapped transformers from either Rat Shack or Antek.
I assume these transformers will have 4 wires on the secondaries instead of 3?
Do you know a source for these transformers, or have a link to a 12-15V with independent secondary windings?
Thanks...
There is a good selection from Antek
AN-0212 - 25VA 12V Transformer - AnTek Products Corp
AN-0215 - 25VA 15V Transformer - AnTek Products Corp
AN-0212 - 25VA 12V Transformer - AnTek Products Corp
AN-0215 - 25VA 15V Transformer - AnTek Products Corp
ammel68 - Zoidbergslo's suggestions are the ones, but looks like something is up with Antec. Both show out of stock and the distributors don't have them. That AN-0212 is what opc recommends for the Wire.
A similar thing from Triad is the VPT24-1040, 25VA (about 1 amp per secondary) 2x12Vac secondaries and dual 120V/240 primaries. Now here is a case where Digikey is way less than Mouser:
$17.56 with 119 in stock at Digikey (#237-1325-ND)
VPT24-1040 Triad Magnetics | 237-1325-ND | DigiKey
vs. $23.46 with only 9 in stock at Mouser (#553-VPT24-1040 )
VPT24-1040 Triad Magnetics | Mouser
and for 25VA (about 830mA per secondary) dual 15Vac secondaries the Triad VPT30-830
$17.56 with 125 in stock at Digikey (#237-1326-ND)
VPT30-830 Triad Magnetics | 237-1326-ND | DigiKey
or $23.46 with 239 in stock at Mouser (#553-VPT30-830 )
VPT30-830 Triad Magnetics | Mouser
Strange that Mouser is charging so much more for the same part.
And here is one at Allied Electronics, a dual secondary 15Vac 25VA (so around 850mA per secondary) on half price "excess inventory" sale at $18 plus shipping (Allied # 62063-P2S02, an amveco)
Amveco - 62063-P2S02 - Power Products - Transformer - Allied Electronics
You are right, they will have 4 wires on the output, 2 for each of the independant secondary windings. Also possible to find two dual independant center-tapped secondaries, in which case you have 3 wires per secondary just like the Radio Shack transformers, but 6 output wires all total for the two independant secondaries. These are torroidal and come with a mounting bolt and rubber pads. Just make sure the mounting bolt doesn't also touch the top of your metal case or it acts as a "shorted turn" and fun things start happening. 🙂 The datasheets, which are linked on the Digikey and Mouser pages, tell you which wire color is what on the transformers.
Since you are not connecting the secondaries together directly in any way (they could be connected together in parallel for twice the current or series for twice the voltage) the phasing won't matter (doesn't matter which way the two secondary wires are turned going into the power supply).
A similar thing from Triad is the VPT24-1040, 25VA (about 1 amp per secondary) 2x12Vac secondaries and dual 120V/240 primaries. Now here is a case where Digikey is way less than Mouser:
$17.56 with 119 in stock at Digikey (#237-1325-ND)
VPT24-1040 Triad Magnetics | 237-1325-ND | DigiKey
vs. $23.46 with only 9 in stock at Mouser (#553-VPT24-1040 )
VPT24-1040 Triad Magnetics | Mouser
and for 25VA (about 830mA per secondary) dual 15Vac secondaries the Triad VPT30-830
$17.56 with 125 in stock at Digikey (#237-1326-ND)
VPT30-830 Triad Magnetics | 237-1326-ND | DigiKey
or $23.46 with 239 in stock at Mouser (#553-VPT30-830 )
VPT30-830 Triad Magnetics | Mouser
Strange that Mouser is charging so much more for the same part.
And here is one at Allied Electronics, a dual secondary 15Vac 25VA (so around 850mA per secondary) on half price "excess inventory" sale at $18 plus shipping (Allied # 62063-P2S02, an amveco)
Amveco - 62063-P2S02 - Power Products - Transformer - Allied Electronics
You are right, they will have 4 wires on the output, 2 for each of the independant secondary windings. Also possible to find two dual independant center-tapped secondaries, in which case you have 3 wires per secondary just like the Radio Shack transformers, but 6 output wires all total for the two independant secondaries. These are torroidal and come with a mounting bolt and rubber pads. Just make sure the mounting bolt doesn't also touch the top of your metal case or it acts as a "shorted turn" and fun things start happening. 🙂 The datasheets, which are linked on the Digikey and Mouser pages, tell you which wire color is what on the transformers.
Since you are not connecting the secondaries together directly in any way (they could be connected together in parallel for twice the current or series for twice the voltage) the phasing won't matter (doesn't matter which way the two secondary wires are turned going into the power supply).
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