Linear vs Switched mode PSU

[RothwellAudio]

I wouldn't want to get carried away with thinking that one bake off would demonstrate everything one way or another. More the start of expanding our listening experience and skills...

But, any process has to start, somewhere, and somehow. What would you suggest?

Good question. I'll have to give it some thought.

[Pharos]

A couple of years ago on the HUG forum I argued with A.S. about AB comparisons as follows.

He argued that only under controlled level conditions of 0.1 dB could we be sure to validly hear differences, but I disagreed on the grounds that substantial differences, were audible on casual listening.

I cited a 1950s farmer going to 'the smoke' and calling into a Hi-Fi shop, sitting down and listening. On return to his home farm he said to his peers; "I 'eard one of them Oi-Fois yesterday, bloomin' amazing, I want one of them."

This was in the context of his life-long listening to MW.

The point is the degree of difference between the two under consideration; if large it can be heard casually, but as it tends to zero much more rigorous testing is required, and it must take into account the type of listener, because our experiences will affect our abilities.

I also think that sometimes when we listen casually we can hear more because we are relaxed, the process of intense analytical listening can sabotage our attempts to perceive, as in the anxiety of an interview compromising our performance.

I want to add that if a bake-off is arranged between two items, which items are chosen is of great importance.
I could include a linear supply with ten stages of pi C/L s, followed by a several stage stabiliser with a massive storage cap.
Someone could also supply a cheap SMPS costing a 20th for comparison. Would that be a fair comparison of technologies/

Since SMPS were I think evolved to cut cost, this is a difficult comparison.

[Barry]

I also think that sometimes when we listen casually we can hear more because we are relaxed, the process of intense analytical listening can sabotage our attempts to perceive, as in the anxiety of an interview compromising our performance.

I never listen for differences. My modus operandi is to make a substitution and just play some music. If there is a noticable difference (and one tha tis important to me), I will hear it whether I want to or not - it will just 'leap out'. I then have to decide if the difference is an improvement or not. If it is an improvement the item stays, but I will revert back to the original item after a week or so, just to make sure the improvement was genuine. There have been a few occasions when what I though was an improvement was not; it was merely a difference.

[Arkless Electronics]

I, and many others, disagree with Jez on the subject. Many others may, perhaps, agree with Jez. Positions are clear.

We could go round in circles...but, instead, how about a bake off? Switched vs Linear. Jez is invited, of course.

It seems that everyone has missed the fact that my ENTIRE ARGUMENT is that is not whether the DC voltage comes from a SMPS or linear supply that matters but how that voltage is dealt with AFTER it has left the PSU. If it's not "dealt with" at all ie no further filtering and no linear regulator after the PSU then I would expect a linear REGULATED supply to win every time unless the circuitry being powered had exceptional PSRR. It needs to be understood that provided the post PSU circuitry to filter and smooth (plus usually regulate) the voltage is done well it matters not one jot how "bad" or "polluted" etc the voltage from the PSU is.

AFAIK some of Alans Firebottle valve phono stages use SMPS actually internally and yet they are very well thought of Likewise Chord and some Linn gear.

I am not for one second saying that any SMPS will power any piece of hi fi equipment and give the same sound quality. What I am saying is that a well implemented use of a SMPS, with suitable filtering etc, will then equal a linear supply.

To answer the obvious question here, no you can't tell which pieces of equipment have suitable post PSU circuitry to make the choice of PSU irrelevant without suitable knowledge of electronics. An in-line unit betwixt SMPS and equipment being powered could be built to act as a suitable filter and could have a linear regulator inside. Jobs a gud 'n.

SMPS are vastly more complicated than a linear supply and designing a good one is a real "black art". However, once put into mass production on a big scale the lack of large quantities of copper and iron (vastly less used) and the lack of need for huge smoothing capacitors etc means they can be much cheaper than a linear supply.

Recall what I said about the non availability of anything but SMPS as wallwarts, and often in-line PSU's nowadays and all this becomes a big issue!

Consider something like a phono stage, active line stage (DAC's etc too but I don't make them) etc. It can be powered by a 24V 1A SMPS wallwart which I can buy for about £7-10... If a customer says "no I insist on a linear regulated supply" then I would have to build it from scratch. The parts would cost me say £30-60, a nice looking case another £20-30 and labour maybe £100 -£200. If this linear regulated supply was being made in China in the thousands then it could be only £30 compared to the £7 of the SMPS.... but it's not... and to have a suitable PSU hand built as a one-off by an engineer costs as outlined above....

So far, personally, the only time I've used a SMPS for any item of hi-fi equipment was for that buffer I built for Jerry a couple of months ago. I charged him £75 for this. It sounds great and there is no background noise from it. The alternative of a Linear regulated PSU would have made this more like £250 and it is doubtful whether any audible improvement would come from this in this case.

I myself developed and tested a SMPS for use inside a budget valve phono stage (actually a switch mode DC-DC converter but it's kind of the same thing) in exactly the same way as Alan has for his kit and if I was making a < £6-700 unit this is what I would use.

How do you think all the cheaper (and mainly Chi-fi) valve equipment powered from a wallwart works? As above!

[Arkless Electronics]

A couple of years ago on the HUG forum I argued with A.S. about AB comparisons as follows.

He argued that only under controlled level conditions of 0.1 dB could we be sure to validly hear differences, but I disagreed on the grounds that substantial differences, were audible on casual listening.

I cited a 1950s farmer going to 'the smoke' and calling into a Hi-Fi shop, sitting down and listening. On return to his home farm he said to his peers; "I 'eard one of them Oi-Fois yesterday, bloomin' amazing, I want one of them."

This was in the context of his life-long listening to MW.

The point is the degree of difference between the two under consideration; if large it can be heard casually, but as it tends to zero much more rigorous testing is required, and it must take into account the type of listener, because our experiences will affect our abilities.

I also think that sometimes when we listen casually we can hear more because we are relaxed, the process of intense analytical listening can sabotage our attempts to perceive, as in the anxiety of an interview compromising our performance.

I want to add that if a bake-off is arranged between two items, which items are chosen is of great importance.
I could include a linear supply with ten stages of pi C/L s, followed by a several stage stabiliser with a massive storage cap.
Someone could also supply a cheap SMPS costing a 20th for comparison. Would that be a fair comparison of technologies/

Since SMPS were I think evolved to cut cost, this is a difficult comparison.

They were originally developed for military and aerospace use and at the time would have been vastly more expensive than a linear supply. A linear supply is typically about 60% efficient (less if regulated) whereas a SMPS can be 90%+ efficient*. Combine this with it being possible to make a SMPS around ten times lighter in weight and similarly smaller in size and you can see why the military etc wanted them!

* BTW SMPS ARE regulated by their very nature but it's very poor regulation compared to a linear regulator. A linear regulator can be used after a SMPS as well as after a "linear" PSU of course.

[PalsHuffMor]

I am not for one second saying that any SMPS will power any piece of hi fi equipment and give the same sound quality. What I am saying is that a well implemented use of a SMPS, with suitable filtering etc, will then equal a linear supply.

Thank you for clarifying, Jez. I think that is very helpful.

To answer the obvious question here, no you can't tell which pieces of equipment have suitable post PSU circuitry to make the choice of PSU irrelevant without suitable knowledge of electronics...

Or we could use our ears

[anthonyTD]

And from my own experience, and repairing kit that use SMPS over the years, equipment can sound and perform very well, As Jez has stated, what is after the raw DC element is very, very important, and where the biggest diffrences in sonics will be noticed, however; For me, my prefrence would still be with linear Supplies through out my system, and that is purely down to the aditional generation of noise Point.

It seems that everyone has missed the fact that my ENTIRE ARGUMENT is that is not whether the DC voltage comes from a SMPS or linear supply that matters but how that voltage is dealt with AFTER it has left the PSU. If it's not "dealt with" at all ie no further filtering and no linear regulator after the PSU then I would expect a linear REGULATED supply to win every time unless the circuitry being powered had exceptional PSRR. It needs to be understood that provided the post PSU circuitry to filter and smooth (plus usually regulate) the voltage is done well it matters not one jot how "bad" or "polluted" etc the voltage from the PSU is.

AFAIK some of Alans Firebottle valve phono stages use SMPS actually internally and yet they are very well thought of Likewise Chord and some Linn gear.

I am not for one second saying that any SMPS will power any piece of hi fi equipment and give the same sound quality. What I am saying is that a well implemented use of a SMPS, with suitable filtering etc, will then equal a linear supply.

To answer the obvious question here, no you can't tell which pieces of equipment have suitable post PSU circuitry to make the choice of PSU irrelevant without suitable knowledge of electronics. An in-line unit betwixt SMPS and equipment being powered could be built to act as a suitable filter and could have a linear regulator inside. Jobs a gud 'n.

SMPS are vastly more complicated than a linear supply and designing a good one is a real "black art". However, once put into mass production on a big scale the lack of large quantities of copper and iron (vastly less used) and the lack of need for huge smoothing capacitors etc means they can be much cheaper than a linear supply.

Recall what I said about the non availability of anything but SMPS as wallwarts, and often in-line PSU's nowadays and all this becomes a big issue!

Consider something like a phono stage, active line stage (DAC's etc too but I don't make them) etc. It can be powered by a 24V 1A SMPS wallwart which I can buy for about £7-10... If a customer says "no I insist on a linear regulated supply" then I would have to build it from scratch. The parts would cost me say £30-60, a nice looking case another £20-30 and labour maybe £100 -£200. If this linear regulated supply was being made in China in the thousands then it could be only £30 compared to the £7 of the SMPS.... but it's not... and to have a suitable PSU hand built as a one-off by an engineer costs as outlined above....

So far, personally, the only time I've used a SMPS for any item of hi-fi equipment was for that buffer I built for Jerry a couple of months ago. I charged him £75 for this. It sounds great and there is no background noise from it. The alternative of a Linear regulated PSU would have made this more like £250 and it is doubtful whether any audible improvement would come from this in this case.

I myself developed and tested a SMPS for use inside a budget valve phono stage (actually a switch mode DC-DC converter but it's kind of the same thing) in exactly the same way as Alan has for his kit and if I was making a < £6-700 unit this is what I would use.

How do you think all the cheaper (and mainly Chi-fi) valve equipment powered from a wallwart works? As above!

[Bonky]

Apologies for going somewhat off topic....

..The Government has just announced the banning of diesel and petrol-driven cars from 2040 and thus we will all need electric cars to replace them. It takes at present about 8 hours to charge a car 'battery' and that this will take place mainly after the rush hour...ie in the evening when most of us, I assume, listen to hi-fi. Will the charging units be SMPS? Won't there be a significant drop in mains voltage? I wonder what effect, if any, it will have on SQ---always assuming that mains noise has a negative effect on SQ (!).

BW

Richard.

[Arkless Electronics]

And from my own experience, and repairing kit that use SMPS over the years, equipment can sound and perform very well, As Jez has stated, what is after the raw DC element is very, very important, and where the biggest diffrences in sonics will be noticed, however; For me, my prefrence would still be with linear Supplies through out my system, and that is purely down to the aditional generation of noise Point.

I fully agree that it is preferable to have a linear supply. It's better to have very little noise in the first place than to have to go to all the time and trouble to filter it out. Also linear supplies are much more reliable than SMPS and vastly easier to repair if they go wrong. (SMPS generally best regarded as throw away if they go wrong unless an integral part of an expensive piece of kit)
However.... when we're talking £10 for the SMPS or £250 for the linear supply it is then quite an incentive to go to the time and trouble to filter and smooth the SMPS! And, if well implemented, the SMPS should then equal the linear supply for SQ.

The 60% efficiency of a linear (often less) V the 80-95% efficiency of a SMPS means we are increasingly finding SMPS the only choice, as the green bureaucrats increasingly get their way. Hence we will have to live with SMPS noise and get good at filtering it out well enough so it can match a linear supply.

[Edward]

And from my own experience, and repairing kit that use SMPS over the years, equipment can sound and perform very well, As Jez has stated, what is after the raw DC element is very, very important, and where the biggest diffrences in sonics will be noticed, however; For me, my prefrence would still be with linear Supplies through out my system, and that is purely down to the aditional generation of noise Point.

What does 'additional generation of noise point' mean please?

I like to think pictorially and I found the block diagram in this article very useful in understanding things (even though I imagine some here will object to some of the narrative). Are you saying that less noise is generated by the transformer in a LPSU vs. a switching PSU?

@Jez, from your explanation it would seem that an optimum audio PSU would be an SMPS but with well built smoothing and regulation most often found in LPSUs. Correct?

If so perhaps I can simply just take the output from my existing SMPS and route it via the Paul Hynes smoothing/regulators I have. thereby skipping the transformer I have. Not sure what the rectifier circuit on the board would do with a DC input. Rectify it to AC?

I'm hopeless in understanding all this but I'm trying.