Linear Vs Switching Supplies In Audio Equipment

[Krankshaft]

My other post got me thinking about why I see so many linear supplies in audio equipment instead of switchers.

By audio equipment I mean home theater systems, home speaker systems, and the like.

I already know what the audiophools think about the subject but I want a rational explanation .

They could drop the weight of these products drastically (and the cost) by using switchers.

Not only that switchers won't throw out as much heat as the sun itself when the equipment was off .

The drawing of their maximum rated current and wasting it as heat when plugged in irregardless of load really is wasteful.

For example take my Labtec 2.0 speaker system with a 1 amp 15 volt linear adapter that thing was probably more expensive then the unit was to manufacture. Why did Labtec choose that over a cheaper switcher?

Take a look at the comparison pics the respective switcher is next to it and I'm not even going to get into the weight difference.

The only downside I can think of is high frequency noise but most switchers operate out of the range of human hearing anyways.

So what's the big deal?

Even if the high frequency noise got into the amps output you couldn't hear it anyways. Plus most of the high frequency noise is filtered out in a well built switcher.

I must admit though those toroidal power transformers in the pricier home theater units are cool looking .

[PCBONEZ]

Re: Linear Vs Switching Supplies In Audio Equipment

Yeah, the sound you hear is out of range of the switchers but the modulation frequencies that sound rides on to get through tuners and amps is not.

If you add more noise to the modulated signal there is going to be more noise in the sound after the demodulator strips out the carrier signal.

.

[starfury1]

Re: Linear Vs Switching Supplies In Audio Equipment

was wondering when this might pop up....I was a bit surprised over at that other forum awhile back how many were playing with switchers....

Well I guess years ago switchers then are not what they are now, is one side
The use of IC power Amps might lend its self to a switcher.
Since we are are talking regulated supplies I think for these things.

With BIG power Amps Non regulated (soft) supplies were used for the current delivery and Dynamics.
Regulated supplies were No No's

That was may understanding of it in the 80's...these days I don't really have a clue whats being used and going beyond stereo I suppose is another ball game.

Sound is (to me anyway) a subjective thing
its up to what the individual person find enjoyment with.

Technical aspect would be to produce as close as possible to the original without adding to or subtracting from it in anyway
but even the room you are listening to it in,
is in some way going to alter the sound.
(not to mention the actual state of your hearing)

A lot of technical problems that came with the first transistor amps, the sigma hang on even thought they had been solved with later designs.
(cross over distortion hard clipping etc)

To some people Valve is it and there is no changing there minds, if they are happy with it why not
(if they like the distortions characteristics of a valve so be it)

So to me if a switcher works for you (generally speaking you) then why not.
(so long as you can keep it quite RF wise as above)

Audio is a very complex subject and no matter were you stand you wont be in someones good books on the subject.

you can throw in a few black cats, black magic and witches covens too to get the sound you want

So anybody seen any projects or pages on say a BIG power amp driven by a Quality beefy switcher?
I suppose the design (and barring effects of fixed voltage) it would have to be build like the VRM of a computer MB...very Big current very short time.

It is an interesting Topic (controversial I suppose) and I guess one were people will just have to "agree to disagree" on some points just except that thats the other persons opinion and be done with it.

Id be interested in what the present views are on using switchers in audio.

Just my thoughts on it....and yeah I can see the merits Krankshaft, but what are the real technical down sides (as you say)

I guess with audio there are a lot of myths that were based in some aspect of fact that just hang around and continue to be perpetuated

Cheers

[999999999]

Re: Linear Vs Switching Supplies In Audio Equipment

PSRR is the ratio of the change in supply voltage to the change in output voltage of the (amp) caused by the change in the power supply.

The PSRR of a typical integrated chipamp (let alone discrete designs) is much worse at increasing power (noise) frequency. If you are lucky you can see this as it specifically relates to the chip in your speaker set, if that chip datasheet graphs this.

The frequency of the switcher doesn't have to be down in the audible range, rather the dirty power effects the *accuracy* of the amplification.

With typical at-home audio gear the size and weight differences aren't that much, and a switcher is a less reliable PSU (the basis for this website is failing switching power supply caps?), particularly when seen over decades rather than the short expected lifespan of a computer or especially other lower cost consumer electronics.

Plus most of the high frequency noise is filtered out in a well built switcher

Relatively speaking, a switcher still has very noisey output (you can add more complex output filters of course but then they start growing in size, cost, weight, till the former held advantages are just about gone), they are typically used in digital circuits instead of analog where the precise voltage isn't as important as that it just be within a certain threshold(s).

That particular Labtec amp and speakers may not be the greatest, the difference in sound from an unregulated, linear, or switching PSU may not be as great in this situation as some - and you can listen yourself to hear if the result meets with your approval.

Here's an example of a (LM3886) chipamp PSRR graph, notice what a big difference there is between the AC line frequency range and up around 50KHz which might be roughly the frequency of a switching supply.

[starfury1]

Re: Linear Vs Switching Supplies In Audio Equipment

Thanks 9's for the tec stuff on it
so basically switchers and audio is still not a good idea.

I was wondering more so on the designs these days with higher switching and possibly better filtering (as you said more complex)

although achievable with probably degraded performance audio wise on an IC amp, probably not a good idea at all with a discrete built Power Amp
(which is really were you want to reduce the size)


seems not really, OK thanks

Cheers

[999999999]

Re: Linear Vs Switching Supplies In Audio Equipment

Class D amps are more immune and more often used with switching supplies, like in some low to mid home theater speaker, amp + DVD player sets. Whether a class D amp is today worthwhile for more than driving a sub (if even that)is a whole different can of worms, you can never get all audiophiles to agree on anything, especially when marrying two controversial topics together.

Otherwise, yes some newer chipamp chips or integrated driver chips allow for higher PSRR, but IMO, if the expectation isn't higher quality audio output, is there really a need to switch? Maybe in today's greener world it would be the power savings but then you also face topics like biasing the amp further into class A for improved sound which also uses more power.

[starfury1]

Re: Linear Vs Switching Supplies In Audio Equipment

possibly thats were they are playing with the switchers, with class D...my day it was stereo and class A/B amps mostly discrete build.

I am really these days way out of touch with it all.

did find a pdf on basics of class D and outline of others here Definitely going to have to have a read of this page Here

Seems from the quick read on class D,
that due to the way they work it does involve quite complex design and layout. akin to a switchmode psu
(but thats not necessarily how they operate.)

these seem to have come a long way, I sort of lost interest at about the time these were starting to be used as an audio amp
(and of course were bagged out)

Yeah like I said I do have to agree when it comes to Audio sometimes "never the twain shall meet" some people just have there perceptions and there's no changing their minds
So I know what you mean about that can of worms

Thanks 9's

Cheers

Oh and just on wall warts as in linear...there is a push to ban them in Oz and use switchers...yeah its the green thing carbon emissions etc.

[Krankshaft]

Re: Linear Vs Switching Supplies In Audio Equipment

Thanks for all the input.

[starfury1]

Re: Linear Vs Switching Supplies In Audio Equipment

Keep us posted on how you go Krankshaft on the other thread with the psu

cheers

[inspiron18]

Re: Linear Vs Switching Supplies In Audio Equipment

Some Technics and Sony amplifiers from the late 70's and early 80's used switching power supplies and they got some pretty good reviews!

http://www.vintagetechnics.info/controlpower/sec01.htm
http://www.thevintageknob.org/sony-TA-P7F.html
http://www.thevintageknob.org/sony-TA-N86B.html

i happen to own the technics one SE-C01 & it sounds amazing!

[mxslick]

Re: Linear Vs Switching Supplies In Audio Equipment

QSC Audio has had a few lines of high-powered, high quality audio amplifiers using switching power supplies.

Here's a LINK to the cinema products line I use. Great amps, super reliable, nice price point and light in weight.

[cadiman]

Re: Linear Vs Switching Supplies In Audio Equipment

all car audio amps use switching power supplies. with class A/B or B. When I was building systems we didn`t have class D amps.

It has been my expierence that car amps always had better sound. and no wonder,
you had unlimited current available (700 amp car battery).

I can`t say much about todays amps. They are not built the same (home and car)

The type of power supply is the result of cost, space, and what kind of input power is available and little to do with audio.

audio amps are current amplifiers and work better with alot of available power

[japlytic]

Re: Linear Vs Switching Supplies In Audio Equipment

all car audio amps use switching power supplies.

This is true for most of the higher powered (I estimate over 50W per channel) units.

There are pitfalls with switching power supplies in audio (and audiovisual) equipment, but provided that good design principles are followed, there should be no major problems.

[Trinite]

Re: Linear Vs Switching Supplies In Audio Equipment

I think another thing is that linear power supplies would be more tolerant of heavy loads, as a massive toroidal transformer can store quite a bit more energy and is able to handle the sudden spikes in power consumption better than the smaller transformer of a switcher. This would be less of an issue in an automotive system, as you have a huge reservoir of power already via the battery. Automotive systems would have to use switchers anyway, since they perform DC-DC conversion.

[Th3_uN1Qu3]

Re: Linear Vs Switching Supplies In Audio Equipment

It's true that a big toroid is generally more rugged, but in a switcher it's not the transformer which has to handle the spikes, it's the transistors. Besides, a switching power supply has a faster transient response than an unregulated linear which has the mains frequency as maximum response time. In a SMPS the transient response is dictated by the output filter.

Also a switcher doesn't need those big bulky unreliable soft start schemes that big transformers need. Unfortunately, where switchers are implemented, this tends to be done as a cost-cutting measure, and most likely outsourcing the production. You'll be surprised how many "audio" engineers don't have a darn clue on how their design actually behaves in power terms and order an underrated power supply. Hence we see more and more gear advertised with "peak power" ratings.

Switching power supplies are an awesome technology if done right.

[PCBONEZ]

Re: Linear Vs Switching Supplies In Audio Equipment

Switching power supplies are an awesome technology if done right.

And they go way beyond our little world of IT gear and consumer electronics.

In the 80's I worked on some gear that relied on what amounted to a Proprietary SMPS that used SCR's vice transistors.
Efficiency wasn't a concern. Reliability was.
Input was 440 vac 3 Phase and OP per SMPS was up around 50 kW.
These were set up as redundant in that the OP from a pair was auctioneered.
There were six auctioneered OP's that each controlled 2 phases [by way of + & - DC on the two phases they controlled] of an array of LARGE 12 phase DC stepper motors.
They used SMPS because as the motors turned the load on any given motor's phase might sit at zero for many hours then jump to 100% for a fraction of a second then back to zero. Another reason for SMPS was that at any given time the total of all OPs [12x50kW= 600kW total capacity] was only 1/4 of the total capacity and linears would have required burning off 450 kW somewhere as heat.
[1/4 of power beacuse. - taking a time snap-shot.]
Phase pair 1 @100% = 50kW
Phase pair 2 @66% = 33.3kW
Phase pair 3 @33% = 16.7kW
Phase pair 4 @0% = 0kW
Phase pair 5 @33% = 16.7kW
Phase pair 6 @66% = 33.3kW
[If moving, the phase pair at 100% power cycles 1 thru 6 then back to 1 for a complete rotation.]
-- Remember 6x50kW= 300kW of capacity [50%] is not used due to the auctioneers sharing load.
-- Then only 50% of the remaining 300kW is used at any given time by the sum of the motors.
~~


I met a guy locally that did the same job I did back then but he went of to work for someone else and ended up on the design testing team for an SMPS for a laser used in the Star Wars program.
- Wouldn't tell me much about it but he did say it's switching frequency was 1Ghz.
~ Pretty cool!
.

[Trinite]

Re: Linear Vs Switching Supplies In Audio Equipment

It's true that a big toroid is generally more rugged, but in a switcher it's not the transformer which has to handle the spikes, it's the transistors.

True. Depends on the control logic, I guess. I've seen some cheaper switchers that will sag quite a bit under sudden load before the PWM controller finally increases the duty cycle on the power FETs, but good units seem to stay pretty solid, regardless. I would have to say for a lower-end unit, you are probably better off with a linear supply vs a cheap switcher, and with a higher-end, a good switcher may do very well.

[Th3_uN1Qu3]

Re: Linear Vs Switching Supplies In Audio Equipment

It depends on how they are configured. In some cases reaction of the PWM controller is delayed or even prohibited to go to full output under a heavy load because the output transistors can't take it.

Tests on a so-called high end unit of a reputable manufacturer of PA amplifiers (advertised as 2kW power) showed that it sustained it for some milliseconds... then in 1 second it fell down to 300 watts. I don't remember which unit it was but if i recall the link to that test i'll post it here.

[Krankshaft]

Re: Linear Vs Switching Supplies In Audio Equipment

Lets not forget about noise which is what I think the real issue is especially in audio equipment.

The noise can be suppressed but never fully eliminated. All of my variable bench supplies are linear can't beat the simplicity, reliability, and clean output.

The only advantage for switchers I see in audio equipment would be reduced weight, copper content, and better efficiency since linear transformers waste power as heat. I'm sure manufacturers would have already moved to switchers if they could to cut costs.

There has to be a serious engineering issue in the way.

[Pyr0Beast]

Re: Linear Vs Switching Supplies In Audio Equipment

Not really. More likely an ideology issue.

Laptop amplifiers have all switched power supplies. So do LCD TVs and other consumer junk and I see no one complaining.

Linear regulators are simple but can also be garbage as SMPS can be. If done properly there shouldn't be any or very small difference.