Switching Power Supplies in AV Receivers

[PENG]

I'm firmly of the opinion that unregulated power supplies are the best option for power amps and I stress power amps.

I am not promoting SMPS or even the rail voltage switching/modulating methodologies at all. I also happened to dislike the regulated power supply concept for home use hifi audio amplifiers. With due respect, if I ever disagreed with you, it would almost always be when you made some sort of blanket statements. I got used to it and in fact started to enjoy reading your post since long time ago.

 

[TLS Guy]

I am not promoting SMPS or even the rail voltage switching/modulating methodologies at all. I also happened to dislike the regulated power supply concept for home use hifi audio amplifiers. With due respect, if I ever disagreed with you, it would almost always be when you made some sort of blanket statements. I got used to it and in fact started to enjoy reading your post since long time ago.

I agree we are on the same page.

There is a big problem though in that receivers have very complicated power supplies, and price is cut to the bone, so you know they are shopping in the cheapest markets for their components, which for caps is a big problem.

I plead guilty to the odd blanket statements, but these are in the nature of "Agent provocateur", to get discussion going..

 

[Johnny2Bad]

I too am suspicious of Switch Mode Power Supplies, but it has to be said that in the last year or two, designs and supporting chipsets that are oriented towards Audio have become available. Previously the typical SMPS was a model oriented toward computers, or other non-Audio applications. There has been tremendous improvements in that area recently, and the mere presence of a SMPS in an Audio application isn't necessarily a negative.

It should also be said that the design of the audio electronics themselves can mitigate many SMPS issues. If the ripple rejection and high frequency filtering is adequate, it doesn't really matter which type is utilized. As a SMPS is less expensive to implement, consumers and HiFi enthusiasts alike can benefit from lower overall costs.

That doesn't mean the SMPS gets an automatic pass, but only that careful evaluation may lead to a quality manufactured or DIY build that doesn't suffer audibly simply because a conventional power supply wasn't used.

 

[TLS Guy]

So your point was that maybe some operators of theaters/live sound/studio venues might have hearing damage and might pick a poorer amp, not necessarily the type of amp, but just in general. Can you tell the difference between a pro amp and a home consumer amp generally was what I was asking, since that's what you've implied. What are those audible clues attributed to power supply type?

Setting up DB tets of power amps is not easy. The only one I have done that with is Quad and Perreaux some years ago, with B & W speakers and also Thors. There was a definite preference for Quad especially driving the Thors which are more revealing.

I really am suspicious of receivers and Far Eastern Amp designs in general. They are far too complex with huge component counts in the power supplies and amps, as well as having a lot of internal adjustments. To me they sound woolly in the bass and not smooth in the HF with poor string sound.

I have just stayed with my brother in the UK for the second time in six months. He has NHT VT 2.4s.

He is driving then from a Yamaha receiver. I heard these some years ago at the friends house he bought them from. He was powering them form a solid amp, that I don't recall. I do remember I was impressed with them and the bass was pretty punchy. From the receiver they sound mediocre to poor. The bass is flabby and speech is not crisp.

I have a Denon at Eagan driving a pair of my JW full rangers that I know well. They are a nice speaker. I have listened to them quite a bit lately, but I seem to get listening fatigue. The top end I think is not a smooth as it should be. I will have to bring a Quad set up down and compare.

I'm pretty sure that in terms of the power amp sections of receivers, and probably a lot of amps, the sound is not top notch.

I have always enjoyed my Quad amps. They never seem to put a foot wrong, and above all are very reliable due to no internal adjustments and very low part count.

One thing I do suspect is that a lot of receivers and amps may start out OK, but diverge from new performance over time.

Peter Walker was obsessed in his designs, with not only good sound, but reliability and the ability of the design to not downgrade as the components aged. In other words, he made sure his designs were tolerant of components have a pretty wide spec range without affecting performance.

So yes, I believe that there a lot of differences between power amps. I have a suspicion that receivers in terms of their power amps, do not deliver state of the art performance. I have strong preference for separates. I also am a strong advocate of Quad amplifiers, due to superb sound which is maintained over time and high reliability over time. I have had a little over 60 years experience with Quad electronics. I admit it could be I'm used to their sound, but I doubt it. In addition I use speakers of my design exclusively and so there is the possibility that my designs optimally match Quad electronics. However I hate trouble, and the Quads are less prone to bring it to my door step than other stables. In my book they are well worth the cost.

 

[Verdinut]

I agree we are on the same page.

There is a big problem though in that receivers have very complicated power supplies, and price is cut to the bone, so you know they are shopping in the cheapest markets for their components, which for caps is a big problem.

I plead guilty to the odd blanket statements, but these are in the nature of "Agent provocateur", to get discussion going..

Since I have decided to bi-amp my 3 full range front speakers, with the Marantz SR5010, I have no option but to use an external power amp for the center channel as I am at present using 4 power amps from the SR5010 for the L & R front speakers.

From your experience, do you think the SR5010 would likely last longer if I only use it only as a preamp-processor? It is already well ventilated with AC Infinity fans.

I plan to purchase 3 new external QSC power amps to drive the front speakers. Then, I could use 4 amps from the Marantz for the surround speakers, but I will most likely use two EV 7100 power amps for these surround channels.

By the way, have you heard about the British MC2 Audio Co. that manufactures power amps which might, I believe, use a bootstrapping circuit with a Quasi Class AB configuration, but I may be wrong about this. They are publishing excellent specs but I think that the price for that kind of stuff is rather high.

 

[TLS Guy]

Since I have decided to bi-amp my 3 full range front speakers, with the Marantz SR5010, I have no option but to use an external power amp for the center channel as I am at present using 4 power amps from the SR5010 for the L & R front speakers.

From your experience, do you think the SR5010 would likely last longer if I only use it only as a preamp-processor? It is already well ventilated with AC Infinity fans.

I plan to purchase 3 new external QSC power amps to drive the front speakers. Then, I could use 4 amps from the Marantz for the surround speakers, but I will most likely use the 2 EV 7100 power amps for these surround channels.

By the way, have you heard about the British MC2 Audio Co. that manufactures power amps which might, I believe, use a bootstrapping circuit with a Quasi Class AB configuration, but I may be wrong about this. They are publishing excellent specs but I think that the price for that kind of stuff is rather high.

I suspect receivers would last longer if the amps are not used. However a pre/pro is a better solution.

I have been aware of MC2. However you can tell from the specs the power supplies are regulated.

There is this current obsession with driving 2 ohm loads, which is ridiculous. Anyone who designs a 2 ohm speaker or even a speaker that gets anywhere near 2 ohms at any point in the impedance curve is a complete ass.

There is a lot the speaker designer can do to make amp failure less likely by the way.

 

[Verdinut]

I suspect receivers would last longer if the amps are not used. However a pre/pro is a better solution.

I have been aware of MC2. However you can tell from the specs the power supplies are regulated.

There is this current obsession with driving 2 ohm loads, which is ridiculous. Anyone who designs a 2 ohm speaker or even a speaker that gets anywhere near 2 ohms at any point in the impedance curve is a complete ass.

There is a lot the speaker designer can do to make amp failure less likely by the way.

The QSC amps I am interested in purchasing are the DCA 1222 models, which use a switching power supply technology that they call "PowerLight Technology".

Usually, switching power supplied amplifiers consume appreciably less power than the ones powered by a conventional linear supply, right?

Let's compare the current consumption of the DCA 1222 amp with the conventional RMX 850a amp (These are both Class AB amps):

DCA 1222 (Power Rating: 325w/Ch @ 4 Ohm RMX 850a (Power Rating: 280w/ch @
4 OHM


IDLE 0.8A (120v) 0.5 (120v)

1/8 Power 3.8A (8 Ohm) 3.0A (8 Ohm)
(Pink Noise)
6.0A (4 Ohm) 4.5A (4 Ohm)

Well, the switching power supply that QSC use draws more AC power per output watt. Would you have an explanation? I note that it is not regulated as the rated output @ 8 Ohm is 200w/ch.

 

[TLS Guy]

The QSC amps I am interested in purchasing are the DCA 1222 models, which use a switching power supply technology that they call "PowerLight Technology".

Usually, switching power supplied amplifiers consume appreciably less power than the ones powered by a conventional linear supply, right?

Let's compare the current consumption of the DCA 1222 amp with the conventional RMX 850a amp (These are both Class AB amps):

DCA 1222 (Power Rating: 325w/Ch @ 4 Ohm RMX 850a (Power Rating: 280w/ch @
4 OHM


IDLE 0.8A (120v) 0.5 (120v)

1/8 Power 3.8A (8 Ohm) 3.0A (8 Ohm)
(Pink Noise)
6.0A (4 Ohm) 4.5A (4 Ohm)

Well, the switching power supply that QSC use draws more AC power per output watt. Would you have an explanation? I note that it is not regulated as the rated output @ 8 Ohm is 200w/ch.

It is hard to comment, as the promo copy is largely meaningless, and no circuits are published. I like to look at a circuit before purchase.

Only the DCA specifies idle current. This is important as it gives a good clue as to how the output stage is balanced class A relative to B.

The DCA has a 2 ohm rating and so the power supply is likely complex.

I suspect that the RMX has an unregualted supply, but I can't be certain.

The DCA is the more powerful amp.

The current draw is not directly a function of the power supply in a class AB amp, but a function of the output transistor biasing. The more it leans to class A the higher the draw, especially at idle and usually the better it sounds.

An unregulated supply uses very little itself. Regulated and switching power supplies will use significant power, to power the myriad of active devices, before we get to the power consumption of the actual amp itself.

As a general rule proamps like those QSC amps tend to be more biased to class B than amps for the Hi-Fi market.

One of the big reasons I like the Quads, is that the muscle is supplied by output transistors biased heavily to class B. These are the dumpers. So the amp runs cool. There is a lower powered class A amp that corrects the errors from the dumpers by a feed forward signal. This amp determines the spec of the amp. In this way you have class A performance without the disadvantage of high quiescent current with high heat output and short amp life.

This is the article from Peter Walker explaining it all in 1975.

 

[slipperybidness]

I too am suspicious of Switch Mode Power Supplies, but it has to be said that in the last year or two, designs and supporting chipsets that are oriented towards Audio have become available. Previously the typical SMPS was a model oriented toward computers, or other non-Audio applications. There has been tremendous improvements in that area recently, and the mere presence of a SMPS in an Audio application isn't necessarily a negative.

It should also be said that the design of the audio electronics themselves can mitigate many SMPS issues. If the ripple rejection and high frequency filtering is adequate, it doesn't really matter which type is utilized. As a SMPS is less expensive to implement, consumers and HiFi enthusiasts alike can benefit from lower overall costs.

That doesn't mean the SMPS gets an automatic pass, but only that careful evaluation may lead to a quality manufactured or DIY build that doesn't suffer audibly simply because a conventional power supply wasn't used.

Agreed, but you can't get around the complexity of the SMPS and the extra parts count as compared to a linear unregulated supply.

SMPS take an incredible amount of engineering to be suitable for audio. The R&D is where all the $ goes. After that, these things are spit out from automated machines for a fraction of the cost of an unregulated linear supply.

As always--SIMPLE is BETTER.

For me, it comes down to "what is your end goal?". If the advantages of SMPS fit for that goal, then go for it! For example, if you need a light amp for some reason, or perhaps for a pure HT rig where you may have a stack of amps.

If I'm talking about a purely music system, I will stick to the unregulated linear supply.

 

[highfigh]

So your point was that maybe some operators of theaters/live sound/studio venues might have hearing damage and might pick a poorer amp, not necessarily the type of amp, but just in general. Can you tell the difference between a pro amp and a home consumer amp generally was what I was asking, since that's what you've implied. What are those audible clues attributed to power supply type?

Read the post by TLS- dynamics are missing/inferior when some types of power supply are used. Someone with a serious threshold shift won't hear this as well as someone whose hearing is more intact.

When did this become a question of whether I can hear these differences?

 

[Verdinut]

It is hard to comment, as the promo copy is largely meaningless, and no circuits are published. I like to look at a circuit before purchase.

Only the DCA specifies idle current. This is important as it gives a good clue as to how the output stage is balanced class A relative to B.

The DCA has a 2 ohm rating and so the power supply is likely complex.

I suspect that the RMX has an unregualted supply, but I can't be certain.

The DCA is the more powerful amp.

The current draw is not directly a function of the power supply in a class AB amp, but a function of the output transistor biasing. The more it leans to class A the higher the draw, especially at idle and usually the better it sounds.

An unregulated supply uses very little itself. Regulated and switching power supplies will use significant power, to power the myriad of active devices, before we get to the power consumption of the actual amp itself.

As a general rule proamps like those QSC amps tend to be more biased to class B than amps for the Hi-Fi market.

One of the big reasons I like the Quads, is that the muscle is supplied by output transistors biased heavily to class B. These are the dumpers. So the amp runs cool. There is a lower powered class A amp that corrects the errors from the dumpers by a feed forward signal. This amp determines the spec of the amp. In this way you have class A performance without the disadvantage of high quiescent current with high heat output and short amp life.

This is the article from Peter Walker explaining it all in 1975.

TLS Guy,

You say:
"As a general rule proamps like those QSC amps tend to be more biased to class B than amps for the Hi-Fi market."

But an amplifier that works in Class B would have a lot of crossover distortion. Wouldn't it be more appropriate to say that, because of a higher bias to eliminate that distortion, it works in Class AB but it consumes more power than one with a lower voltage bias. Does it make it sound as neutral as the ones for the Hi-Fi market?

BTW, the idle current drawn by the RMX is 0.5A for a 120v line input according to the specs. In comparison, the DCA consumes more and wouldn't that indicate that it's the one which operates more in Class A and therefore would sound better?

If the QUAD current dumping amps were still manufactured, I would definitely put them on my list, but they are not.

The QSC RMX850a has an unregulated linear power supply, from what I can make out, using a toroidal transformer. Power rating for an 8 Ohm load of 185w/ch and 280w/ch with a 4 Ohm load. This was the amplifier which I wanted to purchase originally. But it is close to 16 inches deep which is more than the depth of my consoles and it has an objectionable noisy fan. It does have good specs though but not as good as those on the Digital Cinema Series DCA 1222. A possible solution would be to replace the fan with a quieter one, but this operation voids any warranty.

The RMX amp also can handle 2 ohm loads. It's built like a tank. One of my friends who frequently performs in gigs has used many brands of amps. The only brand which he couldn't kill is the QSC.

Would you have alternate suggestions for reasonably priced 2 channel power amps?

 

[Swerd]

I’ve read this thread, and nearly all of it is over my head. Audio by Van Alstine (AVA) sells solid state and hybrid amplifiers with 8, 12, or 16 (depending on model) active and independent regulated supplies for the mos-fet output transistors. AVA claims these designs are patented. http://www.avahifi.com/products/power-amplifiers/power-amp-compare

Few specifications are provided other than this example for the Synergy 450 amp:

The Synergy (450) produces 225 watts per channel, 20 to 20 kHz into 8 ohms at less than 0.01% THD. Eight double-die mos-fet output transistors, standard on the Synergy 450, handle difficult speaker loads (2 Ohm loads and up). Plenty of power for any rational loudspeaker.​

I am familiar with AVA amps, they are very high quality, are hand assembled in the US instead of being mass produced. They sell only by internet direct at modest prices compared to some other boutique high power amplifiers. I don't know what Verdinut's price range is, but he might consider them. I am not considering buying one, but I am curious about the regulated power supplies.

My question: Are these AVA amps with ‘active and independent regulated supplies for the output transistors’ different from those with regulated switching power supplies that have been discussed in this thread? @TLS Guy, @PENG, or others?

 

[Verdinut]

I’ve read this thread, and nearly all of it is over my head. Audio by Van Alstine (AVA) sells solid state and hybrid amplifiers with 8, 12, or 16 (depending on model) active and independent regulated supplies for the mos-fet output transistors. AVA claims these designs are patented. http://www.avahifi.com/products/power-amplifiers/power-amp-compare

Few specifications are provided other than this example for the Synergy 450 amp:

The Synergy (450) produces 225 watts per channel, 20 to 20 kHz into 8 ohms at less than 0.01% THD. Eight double-die mos-fet output transistors, standard on the Synergy 450, handle difficult speaker loads (2 Ohm loads and up). Plenty of power for any rational loudspeaker.​

I am familiar with AVA amps, they are very high quality, are hand assembled in the US instead of being mass produced. They sell only by internet direct at modest prices compared to some other boutique high power amplifiers. I don't know what Verdinut's price range is, but he might consider them. I am not considering buying one, but I am curious about the regulated power supplies.

My question: Are these AVA amps with ‘active and independent regulated supplies for the output transistors’ different from those with regulated switching power supplies that have been discussed in this thread?

Hi Swerd,

I went to the AVA site and, what I can make out is that, for the Synergy 450 amp, both the power supply and the output stages voltages are regulated. According to TLS Guy, that is not desirable in an audio amplifier.

Rail voltage for the output stages is separate from the AC line input power supply, either linear or of the switching type. They are completely different circuits.

Maybe, you could ask him for an explanation if you did not find your answer in the previous posts on this thread.

BTW, the AVA amps are outside my budget and there are good amps available at more affordable prices. Think of Emotiva, Outlaw and Monolith for instance.

 

[Swerd]

BTW, the AVA amps are outside my budget and there are good amps available at more affordable prices. Think of Emotiva, Outlaw and Monolith for instance.

That's what I thought. They certainly are not low priced amps. But I've heard them a number of times and believe they are among the best quality and lowest noise amps I've known. I've successfully pointed others who were attracted to very high priced amps, such as Classe, Bryston, McIntosh, etc. to AVA amps.

The AVA amps with regulated power circuits are a new wrinkle that I had not previously known about.

 

[TLS Guy]

TLS Guy,

You say:
"As a general rule proamps like those QSC amps tend to be more biased to class B than amps for the Hi-Fi market."

But an amplifier that works in Class B would have a lot of crossover distortion. Wouldn't it be more appropriate to say that, because of a higher bias to eliminate that distortion, it works in Class AB but it consumes more power than one with a lower voltage bias. Does it make it sound as neutral as the ones for the Hi-Fi market?

BTW, the idle current drawn by the RMX is 0.5A for a 120v line input according to the specs. In comparison, the DCA consumes more and wouldn't that indicate that it's the one which operates more in Class A and therefore would sound better?

If the QUAD current dumping amps were still manufactured, I would definitely put them on my list, but they are not.

The QSC RMX850a has an unregulated linear power supply, from what I can make out, using a toroidal transformer. Power rating for an 8 Ohm load of 185w/ch and 280w/ch with a 4 Ohm load. This was the amplifier which I wanted to purchase originally. But it is close to 16 inches deep which is more than the depth of my consoles and it has an objectionable noisy fan. It does have good specs though but not as good as those on the Digital Cinema Series DCA 1222. A possible solution would be to replace the fan with a quieter one, but this operation voids any warranty.

The RMX amp also can handle 2 ohm loads. It's built like a tank. One of my friends who frequently performs in gigs has used many brands of amps. The only brand which he couldn't kill is the QSC.

Would you have alternate suggestions for reasonably priced 2 channel power amps?

It really is not possible to compare the idle current given the amps aare of different design and power. I suspect the power supply of the DCA series significant power.

Quad current dumping amps are still available and the new QSP has restored it to deliver the same power as the 909. I think you can now take it that the current QSP is as good or better then the 909. There is an importer for both Canada and the USA.

By the way there are no fans on these amps, and they run cool.

 

[Verdinut]

It really is not possible to compare the idle current given the amps aare of different design and power. I suspect the power supply of the DCA series significant power.

Quad current dumping amps are still available and the new QSP has restored it to deliver the same power as the 909. I think you can now take it that the current QSP is as good or better then the 909. There is an importer for both Canada and the USA.

By the way there are no fans on these amps, and they run cool.

TLS GUY,

The Quad amps are a bit costly for my budget. I think I'm going to opt for the QSC DCA 1222s. QSC have been manufacturing them for several years for the cinema business and I am confident with the reliability of their products.

According to what I read on forums for the DCA line, some owners reported that they performed as well as high end audiophile amps and that they were solidly built.

I will keep you informed on my experience with them. By the way, I will start a new thread with my impressions on their performance when I have used them for a certain period. I know that several audioholics are interested in comments and info on pro audio amps.

If you like Mozart's operas, today I've just received and watched "Le Nozze di Figaro" on Blu-ray, a production from Teatro Real in Madrid. This time, the staging matches well with the period costumes and the singers holding the main roles give an excellent performance. Highly recommended.

Finally, I wish to thank you for your opinion and remarks.
Cheers,

 

[TLS Guy]

Agreed, but you can't get around the complexity of the SMPS and the extra parts count as compared to a linear unregulated supply.

SMPS take an incredible amount of engineering to be suitable for audio. The R&D is where all the $ goes. After that, these things are spit out from automated machines for a fraction of the cost of an unregulated linear supply.

As always--SIMPLE is BETTER.

For me, it comes down to "what is your end goal?". If the advantages of SMPS fit for that goal, then go for it! For example, if you need a light amp for some reason, or perhaps for a pure HT rig where you may have a stack of amps.

If I'm talking about a purely music system, I will stick to the unregulated linear supply.

I understand what you mean by a stack of amps!

However I also want my HT system to be the finest music reproducer.

 

[TLS Guy]

TLS GUY,

The Quad amps are a bit costly for my budget. I think I'm going to opt for the QSC DCA 1222s. QSC have been manufacturing them for several years for the cinema business and I am confident with the reliability of their products.

According to what I read on forums for the DCA line, some owners reported that they performed as well as high end audiophile amps and that they were solidly built.

I will keep you informed on my experience with them. By the way, I will start a new thread with my impressions on their performance when I have used them for a certain period. I know that several audioholics are interested in comments and info on pro audio amps.

If you like Mozart's operas, today I've just received and watched "Le Nozze di Figaro" on Blu-ray, a production from Teatro Real in Madrid. This time, the staging matches well with the period costumes and the singers holding the main roles give an excellent performance. Highly recommended.

Finally, I wish to thank you for your opinion and remarks.
Cheers,

You are welcome. Let us know how you get on. I have this version of the Marriage of Figaro and I love it.

 

[Johnny2Bad]

Agreed, but you can't get around the complexity of the SMPS and the extra parts count as compared to a linear unregulated supply.

SMPS take an incredible amount of engineering to be suitable for audio. The R&D is where all the $ goes. After that, these things are spit out from automated machines for a fraction of the cost of an unregulated linear supply.

As always--SIMPLE is BETTER.

For me, it comes down to "what is your end goal?". If the advantages of SMPS fit for that goal, then go for it! For example, if you need a light amp for some reason, or perhaps for a pure HT rig where you may have a stack of amps.

If I'm talking about a purely music system, I will stick to the unregulated linear supply.

It's just one example, but it is representative of what can be done with an SMPS designed for audio. Performance is illustrative of what is possible today versus the "one size fits all" supplies.

https://linearaudio.nl/silentswitcher

 

[TLS Guy]

It's just one example, but it is representative of what can be done with an SMPS designed for audio. Performance is illustrative of what is possible today versus the "one size fits all" supplies.

https://linearaudio.nl/silentswitcher

Here is the problem though.

An unregulated power supply works really well. There is a transformer, a rectifier, and two large caps. Only three points of failure, and low risk failure for all those components. If the caps ares sized properly there is gobs of peak power instantly avialble.

Now lets look at what you are promoting.

A massive increase in points of failure and a bunch of chips with a high failure risk.

I see all downsides, with no real advantage over the simpler approach.

And another thing, I have always found that elegant amps with low part counts invariably sound the best. Amps with a bunch of stuffed and cramped circuit boards, always seem wanting to me.

I think we have a bug on the site. I can see the image in my post and the edit, but it disappears on posting.