Balanced power and switch mode power supplies

[skatbelt]

In one of his videos on YouTube, PS Audio's Paul McGowan states that switch mode power supplies are happier with single ended power as opposed to balanced power. He does not really explain why. The reason I am interested is this matter is because I use an isolation transformer (in a 230V country), wired for balanced output, to power all my audio components of which two use switch mode power supplies. One of them is a Chord DAVE.

 

Is Paul's statement true? And if so, can anybody explain it technically (in terms that I as a generalist can understand.... 😉)?

 

I already asked this question over at the isolation transformer thread but didn't get a reaction.

[The Computer Audiophile]

I bet @barrows has some knowledge in this area. 

[mansr]

By balanced, do you mean the secondary side of your isolation transformer has a grounded centre tap?

 

As for Paul's claim, bear in mind that US electrical wiring differs in some ways from typical European wiring (and British is different again). Some things that are true in one place might not be in another. The claim also strikes me as overly generalising. It's not too far-fetched to imagine a power supply design that is affected by these aspects of the AC side. At the same time, nothing says all power supplies must be designed this way.

[barrows]

@skatbelt,  This is an interesting question.  I think it is likely true that not all power supplies will "like" balanced power at their input.

Back in the old days, of the earlier generation PS Audio Regenerators (the P-300, P-600, P-500, & P-1000), SMPS would often make trouble for those PS audio regenerators.  This trouble was actually caused by the high amount of capacitance that SMPS had across the AC line a their input.  This large amount of capacitance was often a problem for these older Regenerator designs to power (being essentially power amplifier circuits the Regenerators did not like a lot of capacitive loading).  I do not know if the current PS Audio regenerators (which are considerably different in design) have the same issue with SMPS loading. This may be the reason for Paul's posting RE balanced power and SMPS, or it may not be.

 

As to your situation, I would contact Chord technical support directly, and ask them point blank if there is any detriment to powering the DAVE via balanced power as you are.  There are so many factors involved in power supply design, that it would probably be assuming a lot to make a general recommendation.  Of course, balanced power is not "standard", so if in doubt, one is a bit "safer" to not use balanced power.  I would be interested to hear what Chord has to say about this in reference to DAVE.

[Foggie]

5 hours ago, skatbelt said:

In one of his videos on YouTube, PS Audio's Paul McGowan states that switch mode power supplies are happier with single ended power as opposed to balanced power. He does not really explain why. The reason I am interested is this matter is because I use an isolation transformer (in a 230V country), wired for balanced output, to power all my audio components of which two use switch mode power supplies. One of them is a Chord DAVE.

 

Is Paul's statement true? And if so, can anybody explain it technically (in terms that I as a generalist can understand.... 😉)?

 

I already asked this question over at the isolation transformer thread but didn't get a reaction.

Not sure if this directly applies, but recall somewhere recently that the Chord (designer/eng) recommends the SMPS shipped with Dave  is all that is needed

[The Computer Audiophile]

16 minutes ago, Foggie said:

Not sure if this directly applies, but recall somewhere recently that the Chord (designer/eng) recommends the SMPS shipped with Dave  is all that is needed

Almost all manufacturers say this. Otherwise they’d admit they shipped a lesser product than they could’ve. 

[skatbelt]

53 minutes ago, Foggie said:

Not sure if this directly applies, but recall somewhere recently that the Chord (designer/eng) recommends the SMPS shipped with Dave  is all that is needed

 

There is no separate SMPS shipped with DAVE. It is build in so it cannot easily be bypassed. Although there are some reports on DAVE even performing better when modified and powered by a high quality LPS, the SMPS in DAVE is state of the art in its category.

 

My personal experience is that DAVE profits from: better power cords, a dedicated power line and an isolation transformer and it all sums up.

 

@The Computer Audiophile thanks for the redirection and @barrows thank you for your reaction. I will ask Chord and report back. My subjective observation is that DAVE certainly performs better with the isolation transformer in place but I cannot say if this is because of the IT blocking noise from the power line or because of the power being balanced (or a combination of both or may be even the positive effect of the first aspect overcompensating the negative of the second).

 

The other component I use with a SMPS is a Lyngdorf TDAI-3400. With this unit I am not sure. It sounds more detailed, crisp and real with the IT in the chain but also a bit lean, edgy and less musical. So here is a clear trade-off. When I saw Paul's video, it got me thinking... Before the TDAI-3400 I owned it's predecessor, the TDAI-2200. This unit has a LPS and profited from the IT in all aspects.

 

The underlying problem for me is that I cannot exclude one component from the IT's signal because this introduces other issues. It is all or nothing.

[skatbelt]

5 hours ago, mansr said:

By balanced, do you mean the secondary side of your isolation transformer has a grounded centre tap?

 

Yes.

 

5 hours ago, mansr said:

Some things that are true in one place might not be in another. The claim also strikes me as overly generalising. It's not too far-fetched to imagine a power supply design that is affected by these aspects of the AC side.

 

I agree and actually experienced it. See my comments one post back.

 

[Foggie]

3 hours ago, The Computer Audiophile said:

Almost all manufacturers say this. Otherwise they’d admit they shipped a lesser product than they could’ve. 

Yes but in this case I recall (could be wrong) him going into a fair amount of detail about how good the Dave pwr supply was and stating no benefit from an external LPS etc... this just seemed more than usual.  

 

Again I could have misinterpreted it, and certainly people are free to experiment.

 

 

[skatbelt]

22 hours ago, barrows said:

Back in the old days, of the earlier generation PS Audio Regenerators (the P-300, P-600, P-500, & P-1000), SMPS would often make trouble for those PS audio regenerators.  This trouble was actually caused by the high amount of capacitance that SMPS had across the AC line a their input.  This large amount of capacitance was often a problem for these older Regenerator designs to power (being essentially power amplifier circuits the Regenerators did not like a lot of capacitive loading).

 

Barrows, one more question, in your opinion, is it more likely that Paul's statement is more related to the other design principles of the older PS Audio regenerators than them having balanced power output?

[skatbelt]

18 hours ago, Foggie said:

Yes but in this case I recall (could be wrong) him going into a fair amount of detail about how good the Dave pwr supply was and stating no benefit from an external LPS etc... this just seemed more than usual.  

 

Again I could have misinterpreted it, and certainly people are free to experiment.

 

 

 

Just to make sure you understand correctly, I am not debating the power supply of the Chord DAVE. My questions are about the power fed to DAVE.

 

I live in a large city in the Netherlands and the steps from (1) normal mains power to (2) a dedicated 10 AWG power line with a special circuit breaker for audio and (3) including an isolation transformer in series with it makes a substantial positive difference in the performance of DAVE. Power cords do also make a difference with DAVE but very marginally.

[barrows]

1 hour ago, skatbelt said:

Barrows, one more question, in your opinion, is it more likely that Paul's statement is more related to the other design principles of the older PS Audio regenerators than them having balanced power output?

I should probably not try and read into what Paul has said further, and I would just be speculating.  As to whether balanced power is "good" for SMPS, or not, I think it would be a big generalisation to suggest either way.  The first step (after the input filter) in a SMPS is to rectify the AC to DC, and once that happens certainly the rest of the circuitry could care less if the incoming AC was balanced before rectification.  I am no expert on SMPS though...  Maybe someone reading here might know more about SMPS design and how balanced power might affect it?  From the level of understanding I do have, I do not see how having balanced power coming in would be a "problem" for a SMPS. 

[greenleo]

On 3/18/2019 at 12:20 AM, Foggie said:

Not sure if this directly applies, but recall somewhere recently that the Chord (designer/eng) recommends the SMPS shipped with Dave  is all that is needed

DAVE does not use ext SMPS.

[Foggie]

8 hours ago, greenleo said:

DAVE does not use ext SMPS.

yes, wasn't worded very well and was referring to the quality of its own power.  May bad and should have been more thorough

[Speedskater]

Henry Ott writes about SMPS instability when receiving power from sources like UPS's and regenerator's.

Basically it's a problem of the SMPS adjusting to the UPS, while at the same time the UPS is adjusting to the SMPS.

[barrows]

1 hour ago, Speedskater said:

Henry Ott writes about SMPS instability when receiving power from sources like UPS's and regenerator's.

Basically it's a problem of the SMPS adjusting to the UPS, while at the same time the UPS is adjusting to the SMPS.

Any references to share for further for further investigation of the subject?  I am finding it hard to conceive how this instability might be caused?