.... make sure the DC common returns (the 0 V... or the negative rails 🙂 ) are not connected to the mains IEC ground...
None of the Meanwells I've used do that. Actually no power supply I've seen does that any more, not even the cheap $5 power supplies available locally. The latter do blow up regularly, but the earth is not connected to either output node.
The one sold in diyaudiostore has a common 0 volts return (24V DC negative) connection to IEC ground.
https://diyaudiostore.com/collectio.../products/meanwell-24v-5a-psu-with-power-cord
https://diyaudiostore.com/collectio.../products/meanwell-24v-5a-psu-with-power-cord
Metal case is connected to output gnd , the same metal case at other side connected to mains input earth. If you try to connect in series two such power supplies, one will get shorted through earth terminal.
Take 2 power supplies & wire them up like so:
PSU 1 -> pos. rail as +V
PSU 1 -> GND as GND
PSU 2 -> pos. rail to PSU 1 GND
PSU 2 -> GND as -V
**per google search
PSU 1 -> pos. rail as +V
PSU 1 -> GND as GND
PSU 2 -> pos. rail to PSU 1 GND
PSU 2 -> GND as -V
**per google search
I do not see why you want to use such a circuit for a first build.
Build one with a linear supply, or a single ended one.
It won't affect the sound at all.
Build one with a linear supply, or a single ended one.
It won't affect the sound at all.
Please expand on this comment. Have you measured this or have other experience of this phenomenon?
I read about it long back when I was trying to repair a PLC supply, it had two TL494 in it, but master slave configuration.
In this case, two independent controllers in two supplies will control the switching transistors to maintain the voltage, and it is quite possible they will not have the exact same frequencies, leading to 'beat frequencies', an old RF term.
The other issue is that the rails may have slightly unequal voltages, that will also cause fluctuations, as the controller responds and tries to correct the voltage (mostly they are voltage reference, I believe).
The load is not constant, fluctuating with the music, another possible issue.
This may not be fully filtered out, leading to noisy or unstable operation.
Unless the OP has supplies in hand, it is better to use a single supply, preferably linear.
Or somehow use two supplies with the same controller, IIRC the 494 has a 5V reference on chip, and the 494 + 339 was a very common configuration in PC SMPS, the 339 was to compare the voltages on different rails, it was quite a reliable circuit.
So that means modifying a SMPS, not everybody can do that.
Or getting a bipolar one, as shown above.
That is my opinion, I will be happy to be corrected if it is my mistake.
It also depends on how the signal is fed back, some use a signal from the output transformer, some an opto-coupler, and some use a separate dedicated winding on the output transformer, which may give frequency feed back as well.
If you think the information is wrong, please delete this post.
In this case, two independent controllers in two supplies will control the switching transistors to maintain the voltage, and it is quite possible they will not have the exact same frequencies, leading to 'beat frequencies', an old RF term.
The other issue is that the rails may have slightly unequal voltages, that will also cause fluctuations, as the controller responds and tries to correct the voltage (mostly they are voltage reference, I believe).
The load is not constant, fluctuating with the music, another possible issue.
This may not be fully filtered out, leading to noisy or unstable operation.
Unless the OP has supplies in hand, it is better to use a single supply, preferably linear.
Or somehow use two supplies with the same controller, IIRC the 494 has a 5V reference on chip, and the 494 + 339 was a very common configuration in PC SMPS, the 339 was to compare the voltages on different rails, it was quite a reliable circuit.
So that means modifying a SMPS, not everybody can do that.
Or getting a bipolar one, as shown above.
That is my opinion, I will be happy to be corrected if it is my mistake.
It also depends on how the signal is fed back, some use a signal from the output transformer, some an opto-coupler, and some use a separate dedicated winding on the output transformer, which may give frequency feed back as well.
If you think the information is wrong, please delete this post.
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I have built multiple amplifiers with different kinds of switching supplies, and have had no issues. No issues with linear supplies either. Both have their own parameters for use and amplifiers designed for one kind of supply are usually best with that kind of supply. Simple low-feedback designs like the ACA work much better with SMPS, the low-ish PSRR means a lot of filtering is required to run them with linear supplies. They also are typically single-ended, and do not need the burst power that linear supplies can deliver (and are better suited to).
What you desribe is not an issue anymore. The filtering requirments for these supplies in audio applications take care of almost every nasty output and because the switching frequency is so high, you can use very simple filter and and small capacitors. Many high end devices now use switching supplies (not just in audio) because it's possible to get noise very low, well below what a conventional linear suply can deliver.
What you desribe is not an issue anymore. The filtering requirments for these supplies in audio applications take care of almost every nasty output and because the switching frequency is so high, you can use very simple filter and and small capacitors. Many high end devices now use switching supplies (not just in audio) because it's possible to get noise very low, well below what a conventional linear suply can deliver.
What I meant was that two controllers can interfere, a single supply is no longer an issue, here the recommendation was tying two supplies at a common point, hence my opinion.
One controller is say running 384.200 kHz, the other 384.600 kHz,to the switching transformers, a 200 Hz difference, may come through on the DC side.
If you have actually got good results in such a configuration without any problems, please delete my posts.
One controller is say running 384.200 kHz, the other 384.600 kHz,to the switching transformers, a 200 Hz difference, may come through on the DC side.
If you have actually got good results in such a configuration without any problems, please delete my posts.
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We don't delete technical posts Naresh - unless they're dangerous and obviously misleading. That's not how any of this works.
A minor correction, I intended to say 'switching transistors', rather than 'switching transformers' in Post #37 above.
It is actually 400 Hz difference, I must have been distracted. But you get the idea.
Apologies to all.
It is actually 400 Hz difference, I must have been distracted. But you get the idea.
Apologies to all.