One situation where an SMPS is a biiig fail!

[andyr]

Seeing as how @Addicted to music is such a fanboi for SMPSs (Peter's written several times about the fact that EveAnna Manley has been using them in her amps for years) ... I decided to do an experiment, to see whether I could use a 24v Meanwell SMPS to power one of my Muse phono stages - instead of the Sbooster LPS that I've been using for a number of years.

 

The advantage would be considerable - if the experiment was successful, I would be able to make a substantial decrease in the price of my Muse!  

 

Now, Meanwell is one of the better quality mfrs of SMPSs - so I had high hopes that the experiment would be a success; unfortunately, it wasn't!    (There was a completely unacceptable 'buzz' from the spkrs - whereas, when powered by the Sbooster ... there was silence, when the music wasn't playing).

 

This is actually not surprising as phono stages involve far more gain than any pre or power amp - so their power supply needs to have a very low noise floor.

 

Incidentally, @Deepthought, given the fail with this experiment ... I suspect the iFI 12v PS that I mentioned to you will become available - as the same thing will happen when I try to power one of my head amps with it (instead of an SLA or a 12v Sbooster).

 

[playdough]

Interesting. There would almost have to be some sort of ground loop issue going on there, without a schematic, it's hard to call but the Linear PS would likely have a completely isolated output, as in the Transformer isolation.

The SMPS is likely to have a continuous Neutral through to Negative of the output, so it may well not be fit for the job, due to the design of the pre amp requiring a fully isolated supply.

There may be a need to experiment with finding out from where the buzz is coming from before canning the SMPS.

 

[andyr]

4 minutes ago, playdough said:

Interesting. There would almost have to be some sort of ground loop issue going on there, without a schematic, it's hard to call but the Linear PS would likely have a completely isolated output, as in the Transformer isolation.

The SMPS is likely to have a continuous Neutral through to Negative of the output, so it may well not be fit for the job, due to the design of the pre amp requiring a fully isolated supply.

There may be a need to experiment with finding out from where the buzz is coming from before canning the SMPS.

 

Good point, Genx - but I don't see how I can further "experiment with finding out from where the buzz is coming from" ... as:

a.  the Meanwell desktop-style 'brick' is a sealed unit, and

b.  if it is usual for an SMPS to have a continuous Neutral through to Negative of the output - any other make of SMPS is likely to be built the same way.

 

[playdough]

25 minutes ago, andyr said:

but I don't see how I can further "experiment

Personally used a generic 24v SMPS to power a Mimic circuit type of MM, DIY Phono pre amp with no problems.

If the SMPS doesn't work for your  Muse phono stage it may  be worth searching for an Isolated SMPS, or DC/DC isolated SMPS, to continue your experiment and yes they are readily available, generally for DC powered HAM Radio Operations.

 

About the only thing worth trying as the experiment stands may well be a patch lead test with or without a resistor in series from negative of the SMPS to the Ground of the system, in all essence a ground lift jumper used on a heck of a lot of pre amplifiers that are DC supplied. Has this been done ? 

Also you could try your isolation transformer connected to just the SMPS powering the Pre, to perform the Isolation.

 

Either way, there is a ground loop to be solved, welcome to the world of Pro Audio and the pain sometimes accompanying working in it.

 

 

Edited February 14, 2024 by playdough

[andyr]

16 minutes ago, playdough said:

About the only thing worth trying may well be a patch lead test with or without a resistor in series from negative of the SMPS to the Ground of the system, in all essence a ground lift jumper used on a heck of a lot of pre amplifiers that are DC supplied. Has this been done ? 

 

Easy to rig up this test - thanks.  

 

I will report back.

 

[playdough]

Hi @andyr I re edited the post with another possible solution, good luck there !!

https://www.amazon.com/NOYITO-Isolated-Power-Supply-Module/dp/B07T9PW4RL?th=1

 

Edited February 14, 2024 by playdough

[andyr]

3 hours ago, playdough said:

Personally used a generic 24v SMPS to power a Mimic circuit type of MM, DIY Phono pre amp with no problems.

If the SMPS doesn't work for your  Muse phono stage it may  be worth searching for an Isolated SMPS, or DC/DC isolated SMPS, to continue your experiment and yes they are readily available, generally for DC powered HAM Radio Operations.

 

About the only thing worth trying as the experiment stands may well be a patch lead test with or without a resistor in series from negative of the SMPS to the Ground of the system, in all essence a ground lift jumper used on a heck of a lot of pre amplifiers that are DC supplied. Has this been done ? 

 

2 hours ago, andyr said:

Easy to rig up this test - thanks.  

 

I will report back.

 

I had to whip into Jaycar to get hold of an in-line 2.1mm socket and plug but ... after making up a connection between the socket and the plug which had a 10R resistor for the link between the socket/plug ground connections - unfortunately ... there was no reduction in the awful noise from the spkrs.  

 

And in fact, I already have an isolating transformer in the mix - as I always plug the mains lead feeding any SMPS, into a small isolating transformer.

 

3 hours ago, playdough said:

https://www.amazon.com/NOYITO-Isolated-Power-Supply-Module/dp/B07T9PW4RL?th=1

 

 

Worth a try - thanks, I've ordered one.

 

[playdough]

43 minutes ago, andyr said:

I already have an isolating transformer in the mix - as I always plug the mains lead feeding any SMPS, into a small isolating transformer.

Hi @andyr It may not make any difference, but worth trying the IsoTx only for the phono Pre Amp, with no other smps powered on the secondary side.

Otherwise it's a mystery and no SMPS will fix it as the only difference in both power supplies is that "Transformer Isolation" at the end of the day,

other than the obvious circuit differences. 

I've not known SMPS to be noisy really, normally ground loop issue, in the single ended system. 

Happy to be wrong, hopefully you will solve the anomaly. 

 

Genx

 

 

 

 

[andyr]

1 hour ago, playdough said:

Hi @andyr It may not make any difference, but worth trying the IsoTx only for the phono Pre Amp, with no other smps powered on the secondary side.

 

OK - so I got out my 1KVA isotx and lugged it upstairs (it's heavy - weighing in at 14kgs!) and plugged into it only the Meanwell powering the phono stage.

 

Alas - no change to the noise level.  

 

So I'll have to make my next report when the Noyito PS arrives.

 

[playdough]

Ok, bugger.

The Linear supply might be in orders of magnitude lower in noise than the SMPS on the DC side, without measuring it, this is a mystery. Sorry to have you go through that with the isolation transformer, they are heavy awkward lifts.

 

[andyr]

27 minutes ago, playdough said:

The Linear supply might be in orders of magnitude lower in noise than the SMPS on the DC side, without measuring it, this is a mystery. Sorry to have you go through that with the isolation transformer, they are heavy awkward lifts.

 

Yes, whether an LPS has a lower noise floor than a SMPS is what I was trying to establish.  (IE. - is it acceptable to use a SMPS with such a high-gain component.)

 

But the loud buzz from the spkrs (with the Meanwell) certainly seems to be a different issue - I agree it suggests an earth loop problem.

 

So the fact that the noise isn't solved by:

• using a ground lift resistor
• or plugging the Meanwell into an isolating traffo

... both of which should kill a ground loop - is indeed a mystery.  

 

Let's see what the special 'isolating SMPS' produces!

 

[Addicted to music]

12 hours ago, andyr said:

Seeing as how @Addicted to music is such a fanboi for SMPSs (Peter's written several times about the fact that EveAnna Manley has been using them in her amps for years) ... 

 

 

 

 

EveAnna Manley,  consulted Bruno Putzey from Hypex Audio to developed the PSU for her.  the project took over 9mths with multiple failures.   The goal was to incorporate a PSU that can be adapted to all her gear so she can distribute world wide that caters for the different voltage variations.  Depending on the scope of works the SMPS can be better in providing a more consistent voltage regulation regardless of where you are in the world as power fluctuates and reduction in the noise floor compared to Linear PSU where the quality of the supply caps matter and will show up noisy as it ages,  you wont get this with SMPS.   The SMPS was not cheap to develop,  it was designed with high DC voltages to cater for her valves,  so there wasnt any cost benefits,  but the benefit was that it was less noisy and she doesn't need to used different components such as a transformer that needs to be different for where it was distribute.  Then it had to tick all the electrical and safety certifications so it complies.

Edited: yes, Im a fan of SMPS, purely for the reason they exhibit way less noise and can provided very consistent voltages regardless of the quality of mains voltage, unlike Linear supplies.   ALL the gear i work on are on SMPS are on a 30A line,  rarely are they problematic, the only ones that fail are the ones made in EU on a particular finishing gear that cost $100K.   

 

12 hours ago, andyr said:

 I decided to do an experiment, to see whether I could use a 24v Meanwell SMPS to power one of my Muse phono stages - instead of the Sbooster LPS that I've been using for a number of years.

 

 

 

I understand what you are trying to achieve, but havent you complained about the SMPS you were using saying that when you route the cables it was picking up "hum" noise.   if so why are you using the same SMPS as an experiment?

 

12 hours ago, andyr said:

 

Now, Meanwell is one of the better quality mfrs of SMPSs - so I had high hopes that the experiment would be a success; unfortunately, it wasn't!    (There was a completely unacceptable 'buzz' from the spkrs - whereas, when powered by the Sbooster ... there was silence, when the music wasn't playing).

 

This is actually not surprising as phono stages involve far more gain than any pre or power amp - so their power supply needs to have a very low noise floor.

 

 

 

Did you check the specs provided or even asked via email whether that particular SMPS was suitable for a phono stage voltages?  If not you are going about it the wrong way.    Not all SMPS are made equal,  remember,  the SMPS that Bruno developed for Manley Audio took well over 9mths, and months of testing after to get there.  

6 hours ago, andyr said:

 

OK - so I got out my 1KVA isotx and lugged it upstairs (it's heavy - weighing in at 14kgs!) and plugged into it only the Meanwell powering the phono stage.

 

 

 

 

Would not suprise me.....why bother,  but you had to tick that off!   if its going to be noisy connected to 230V mains, its going to noisy regardless.  it could be and most likely that the SMPS you are using isnt suited for you phono, or vise versa. 

 

But FYI, all the cheap SMPS that ive tried on DACs I never had a problem, none were noisy! And some of these are cheap power bricks that were phone charges, and to be really silly i tested a 5VDC SMPS that was used to charge my hair clipper.....all good, dead quite through the speakers via Sanders Pre/power amplifers.  All quieter than a Linear power brick that was old and "hum" straight of the bat.   The DAC is a Topping D50,  it could also be that the Topping has better PSRR (power supply rejection ratio)  as it has circuits designed to cater for  inconsistent supply and added noise rejection compared to your phono.

 

 

 

Edited February 14, 2024 by Addicted to music

[andyr]

On 14/02/2024 at 10:24 PM, Addicted to music said:

But FYI, all the cheap SMPS that ive tried on DACs I never had a problem, none were noisy! 

 

The 6x Meanwell SMPSs (which are not regarded as "cheap cr@p") which I have powering:

• 3x Topping E30 DACs
• my Beis A2D converter
• the nanoDIGI
• and a 4-way digital source selector

 

... all work perfectly (in particular, do not cause any horrible noises through the spkrs).

 

Only trying an SMPS on:

a.  my phono stage, and

b.  the 'Paris' head amp that I build

 

... have problems arisen.

 

On 14/02/2024 at 5:43 PM, andyr said:

 

Let's see what the special 'isolating SMPS ' produces!

 

 

Alas - having just tried that ... it was no better than the Meanwell.  

 

So it would seem that linear PSs - or SLAs - are required for these devices.  Possibly because of the large amount of gain they have?

 

[POV]

Unlikely that it's related to gain.  More likely there is some kind of ground loop happening. 

[andyr]

True, Drew - but I have NFI why a ground loop should be happening ... when it doesn't with the other 6 SMPSs.

 

[Addicted to music]

 

4 hours ago, andyr said:

 

Alas - having just tried that ... it was no better than the Meanwell.  

 

So it would seem that linear PSs - or SLAs - are required for these devices.  Possibly because of the large amount of gain they have?

 

 

Maybe just stick with your traditional linear PSU nor SLA.   High Gain and fast circuits are unstable at audio frequencies.   im only speculating but Many DIY designers who have open free to the public circuits  are usually designed with minimum component count.   One design you are already using in which I would never use, but he uses it to his advantage marketing "better sound".   This may not be compatible with certain circuits.   Unlike say something from Silicon Chip etc where they provide text book solutions chasing the best numerics.

If you played with opamps,  usually ones that are specific for audio will have low gain and are usually unity gain capable, are heavily compensated, so there are circuits built in to prevent oscillation that can run into self destruction,  limited slew rate and high PSRR.    if you have a scope, you can analyse the traces and be able to identify whats happening so you can compensate for it, all part of the fun.

[andyr]

Thanks, Peter.  Not interested in using opamps.

 

[PicoWattson]

My BMC MCCI Phono stage uses an SMPS and is dead quiet.  Recently the 24v Linear PS to my SOTA TT developed a hum possibly due to aging components. That was replaced with a so called low noise no name brand of SMPS I found on ebay, and sure enough back to total silence.