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What SMPS to replace my linear power supply?

Gorgonzola

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A bit over a decade ago I constructed a power amp based on an SDS-258 modules from Class D Audio. The kit I purchased included a linear power supply. Presently I'm contemplating replacing that PS with a switching-mode one. The current linear supply puts out +/- 62 VDC.

I would like advice on a proper SMPS to replace the linear.

Incidentally the SDS module is/was Class D Audio's audiophile offering whereas the CDC model testing by Amir is not considered by them to be a good.

My reasons for this swap are essentially two:
  • This amp is a backup amp for my main amp, (Purifi), and others so gets move around fairly often; it's excessively heavy thanks to the large transformer; hence I would like a much lighter SMPS supply,
  • Secondly, more on principle more than practical consideration, I would like a efficient, less power-hungry supply
Of course I don't want the sound of the amp to be adversely affected, though again of course, if the SMPS is appropriate and functioning properly I won't hear a difference.

Here's a pic of my DIY amp -- restrain your laughter regarding the crudeness of my case and assembly;

gi.mpl
 

Wes

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any hospital grade pS should have low ripple

what's wrong with the LPS?
 
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Gorgonzola

Gorgonzola

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any hospital grade pS should have low ripple

what's wrong with the LPS?
Thanks for the medical/hospital grade suggestion.

There is nothing wrong with that linear supply that I'm aware of. Less weight and lower power consumption are what I'm looking for.
 

Hogh

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Less weight will surely be possible with a SMPS. Im however not sure you gain much efficiency. The toroidal transformer have around 10% (?) loss and then a bit of voltage drop over the bridge rectifier. Hard to beat that even with a good SMPS.
 

Exprymer

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Look for Ressonant LLC topology SMPS. The efficiency is almost 98%, doesn't have EMI transmissions due to ZVS and offers a shitload of power.
 

audio2design

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Look for Ressonant LLC topology SMPS. The efficiency is almost 98%, doesn't have EMI transmissions due to ZVS and offers a shitload of power.

Gee, if only I could completely ignore EMI when I make LLC power supplies .... They are lower EMI, but they are not 0. Usually you have a boost front end, but I have seen fixed voltage versions, i.e. 120 only or 277 only with simple diode/bulk cap for audio. Unlikely to find anything at 98% without paying an absolutely fortune. You lose almost 1.5% just on the front end bridge, not to mention the output diodes, never mind FETs, etc. Still one of the best architectures for high power though.
 

Exprymer

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Gee, if only I could completely ignore EMI when I make LLC power supplies .... They are lower EMI, but they are not 0. Usually you have a boost front end, but I have seen fixed voltage versions, i.e. 120 only or 277 only with simple diode/bulk cap for audio. Unlikely to find anything at 98% without paying an absolutely fortune. You lose almost 1.5% just on the front end bridge, not to mention the output diodes, never mind FETs, etc. Still one of the best architectures for high power though.


hmm, Yeah, as you said they have pretty low EMI, which in my opinion has very little to do with audio, as Amir has already showed us, it's a totally different Realm in terms of frequency and it's isolated from the audio input signal. Ressonant topologies also are never fixed voltage AFAIK, because it's inherent design is with a feedback control, modulating the frequency. This topology alters the gain by lowering and raising the Switching Freq. For 1000W< applications the cost won't be high, the form factor way lower and certainly above 90% efficiency, which we won't never have with a linear PSU.
 
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audio2design

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hmm, Yeah, as you said they have pretty low EMI, which in my opinion has very little to do with audio, as Amir has already showed us, it's a totally different Realm in terms of frequency and it's isolated from the audio input signal. Ressonant topologies also are never fixed voltage AFAIK, because it's inherent design is with a feedback control, modulating the frequency. This topology alters the gain by lowering and raising the Switching Freq. For 1000W< applications the cost won't be high, the form factor way lower and certainly above 90% efficiency, which we won't never have with a linear PSU.

The other benefit for audio is LLC converters operate over a narrow high frequency band, typically 100-200KHz, which is nice for audio. Sorry I was assuming more prior knowledge. I said front end, i.e. pre-LLC stage. The vast majority of LLC supplies will have a boost converter front end. However, for audio, since it seems to ignore PF/THD in most cases, a simple bridge/bulk capacitor has been used.
 

tomchr

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As stated above: If it ain't broken, don't fix it. It looks like a pretty nice build overall.

That said, if you really get the itch, I believe the Hypex SMPS1200A400 puts out roughly the voltage you need. Do check their min/max specs to make sure it'll work for you.
There's also Connex Electronic. https://connexelectronic.com

Tom
 
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Gorgonzola

Gorgonzola

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As stated above: If it ain't broken, don't fix it. It looks like a pretty nice build overall.

That said, if you really get the itch, I believe the Hypex SMPS1200A400 puts out roughly the voltage you need. Do check their min/max specs to make sure it'll work for you.
There's also Connex Electronic. https://connexelectronic.com

Tom
I have looked a Connexelectronic even before you mention. In fact my LPS is one of theirs connected driven by an Antek transformer..

I have a serious problem of not really knowing what the heck I'm trying to do :confused: since I have no real electronics training. I bought a cheap Mean Well knock-off SMPS to experiment with, +/- 48 volts. Here's what I figured out:
  • My amp had +, - , and ground connections
  • My connecting my linear supply, (also with +, - , and ground); measuring across the outputs I get :
    • 60 volts across + to ground
    • -60 volts across - to ground
  • The SMPS has +, -, and a ground connections; measuring across the its outputs I get:
    • 115 volts across + to ground
    • -115 volts across - to ground
    • 48 volts across + to -
I guess this wasn't what I was expecting, but apart from the 45 volts vs. 60 volts from the linear, this isn't going to work.

What am I misunderstanding? What should I be looking for?

I wonder if Connexelectronics SMPS500QRv3 +/- 60 volt version would work? I note that this supply, like most of their supplies, is unregulated.
 

DVDdoug

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Those measurements are weird... Do you have a link to the specs?

Often the "ground" is just a chassis ground and floating relative to everything else. Sometimes a dual power supply will actually have two separate power supplies, so 4 terminals plus maybe a ground terminal. In that case you'd ground the - terminal for the positive supply and ground the + terminal for the negative supply.

I don't know about the 115V. Maybe it's just "leakage" and it goes away with a load.
 

tomchr

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Which Mean Well switcher do you have? I don't ever recall seeing a Mean Well that'll deliver a bipolar/split supply.

For the Connex, I'd probably go with the SMPS800RE (±60 V) or SMPS600RxE (±60 V). Both are regulated.

Tom
 

restorer-john

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You say this:
  • Secondly, more on principle more than practical consideration, I would like a efficient, less power-hungry supply
How is replacing a perfectly functional toroid and bank of capacitors with another, costly, resource intense, newly constructed SMPS, an exercise in "efficiency"? It's the complete opposite.

What are you going to do with the toroid and filter caps? Throw them in the trash or in a box in the garage? Recycle them? I see no 'efficiency' gains to be had at all.

Of course I don't want the sound of the amp to be adversely affected, though again of course, if the SMPS is appropriate and functioning properly I won't hear a difference.

How do you know that for sure? You likely don't. The toroid and existing PSU may outperform what you replace it with, or the new PSU may be better. The transient capability may suffer with an SMPS or the continuous output may be more or less. Audible changes are likely for sure.

Measure the amplifier as it stands with as many parameters as your test setup allows first. How much power does the amp consume anyway, when idling, or when playing music?
 
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tomchr

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John, I agree with you from an engineering perspective. But part of DIY is the ability to try different things and see what you like or don't like - or just to try something different. It's a hobby. And it's OP's time and money...

Now back to engineering: I doubt there'll be a significant difference in efficiency between an SMPS and a 'linear', unregulated power supply, especially at low output power. The SMPS mostly saves weight and provides regulation (in most cases anyway).
If you compare an SMPS to a regulated linear supply, the SMPS wins on efficiency 99.9% of the time. At high output current the SMPS wins hands-down.

Tom
 
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Gorgonzola

Gorgonzola

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Which Mean Well switcher do you have? I don't ever recall seeing a Mean Well that'll deliver a bipolar/split supply.

For the Connex, I'd probably go with the SMPS800RE (±60 V) or SMPS600RxE (±60 V). Both are regulated.

Tom
Thanks a lot. One of those models like the ticket.
 
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Gorgonzola

Gorgonzola

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You say this:

How is replacing a perfectly functional toroid and bank of capacitors with another, costly, resource intense, newly constructed SMPS, an exercise in "efficiency"? It's the complete opposite.

What are you going to do with the toroid and filter caps? Throw them in the trash or in a box in the garage? Recycle them? I see no 'efficiency' gains to be had at all.
...

How do you know that for sure? You likely don't. The toroid and existing PSU may outperform what you replace it with, or the new PSU may be better. The transient capability may suffer with an SMPS or the continuous output may be more or less. Audible changes are likely for sure.

Measure the amplifier as it stands with as many parameters as your test setup allows first. How much power does the amp consume anyway, when idling, or when playing music?
Mainly I'm looking for a reduction in weight since, as it happens, I have to tote this amp from place to place fairly often. I you had my arthritis you'd understand.
 

restorer-john

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you had my arthritis you'd understand.

I understand for sure. :) My right hand/forearm at the moment (last month and a half) has some absolutely hideous nerve pain that makes even operating a mouse or opening a door/turning a tap impossible. No idea what caused it. My partner has to even cut up my food.

Sure made me realize what I take for granted. Luckily, I am mostly left handed, although it's obvious how much the right arm did most of the heavy lifting.

No moving HiFi for me either...
 

forlau

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I had a Connex SMPS300RE with the LJM 12-2, but there was a lot of noise overlapping the signal output. One could see a lot of small ripples overlaying the sine signal. On top, compared to a linear power supply with the same amp, it sounded dull. Sure, the SMPS was lighter and much easier to build the amp (because soft start and aux voltage for speaker protection are already included) but I would not use it again, at least not for hifi.
 
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