Topping PA5 Review (Amplifier)

[Lambda]

Ok. measured. For my 70dB average listening point, I am running 2.4 volts at the amp speaker terminals. Full power is 23.42 volts. This is into 8 ohm speakers.

1 kHZ tone at 0 dB.

How exactly did you do this?

You would need to play music and turn the amp up to your listening level.
then without changing the volume play from the same DAC a 0dB sine wave and measure the output voltage.

(you can also play -10dB sine wave to be save and later add +10dB)

Is your Meter true RMS? Can it measure 1khz

 

[Gio]

My PA5 just arrived. The first thing I want to say is the surprise of how small it is. I knew it was but I didn't expect it to be held with one hand! The second thing, I did not expect, is to hear sounds that I did not hear with my previous amplifier (NAD 302). This is something I would have expected more when changing the DAC than the amplifier. The third thing is the soundstage. Very detailed and defined. At the moment, listening is really enjoyable.

 

[MarkWinston]

This is something I would have expected more when changing the DAC than the amplifier.

You just done called out the whole 'All competant DACs sound the same when volume matched' tribe with just one sentence.

 

[IPunchCholla]

If you're average listening level is 0.7W then the peaks/crescendos will be higher. Probably as much as 10x higher. Possibly as much as 20x for classical.

.7 isn’t average it is a 1 kHz tone at 0 db. It should represent the peak? If I measure at the speaker actual signal using my equipment I don’t normally even get that. I get closer to .3 as peaks. Probably because I’m not running at 0 dB but have my parametric eq set down -6 db to account for any peaks that might occur.

Anyway, I don’t hear any clipping, noise, or distortion in my listening case. And the numbers I am getting would seem to support that, as would Amir’s.

 

[IPunchCholla]

Nice to hear you hear good stuff. I'm not a classical guy but I do delve in it from time to time if it is busy and interesting.

I’m not really a classical guy either. But I love that piece. Spent most of the day listening to Radiohead. I tend to genre dive cyclically.

 

[IPunchCholla]

How exactly did you do this?

You would need to play music and turn the amp up to your listening level.
then without changing the volume play from the same DAC a 0dB sine wave and measure the output voltage.

(you can also play -10dB sine wave to be save and later add +10dB)

Is your Meter true RMS? Can it measure 1khz

Like you said. I turned the amp up to normal listening volume. Marked the location of the knob (it has a handy black dot on the dial). I disconnected the speakers and attached my meter and output a 1khz tone from Audition. I metered ( meter measuring rms and reporting 999.9 HZ). I verified that nothing in the audio chain was attenuating the signal and metered again with the same result. I double double checked connections and the metered with the volume knob all the way up to get the max. Then confirmed the measurement. I then put everything back together, returned my amp to the normal setting and went back to my listening position (a bit less than two meters from the speakers) put on music to confirm listening levels and verified them by ear and metering.

All of this leads me to conclude that my peaks are around 85 dB @ 2.4 volts/2 meters with plenty of power in reserve before the signal is adversely effected.

 

[Lambda]

Sounds like a good test to me!

I’m just confuses with the result.

About sinsu 2.4V RMS at 0dBFS gives you about 0.7W RMS Max.

"Normal music" is most of the time not an continuous sine wave so its RMS is usually at least 6-12dB lower. ("average" below 0dBFS)
saying with normal music the RMS voltage shuld be on average more like ~1V rms (if it is 2.4V with a 0dBFS sine)

This means 0.125W or 1/4W for to speakers to get 70dB SPL at 2m
according to this https://mehlau.net/audio/spl/
This is possible if your speakers have over 83dB sensitivity

Your absolute peak power would be
((2.4V * square root of 2)²/(8Ohm))*2 = so around 2.8W

This sounds to low but after doing the quick and ruff calculations it actually seams to check out.

 

[ryanmh1]

There isn't any. @J-Sine is completely misinterpreting the THD+N curves (I'm not sure if there is an agenda going on here or not). It is already known that the PA5 is a very LOW noise amplifer - as stated on the chart he is quoting, as well as generally in the review.

He may be misinterpreting it, but it would be better if it were noise. It may be worse than that. It was mentioned once off the bat by @pma months ago and then promptly forgotten or ignored (although I gave up after page 35). This is nowhere close to state of the art--it's not even very good. This "normal distortion rise with frequency" (see comment on chart) was normal two or three decades ago. While many amplifiers still do that, the good ones don't. Good amplifiers that use proper feedback schemes and/or don't run out of open loop gain so they can apply enough feedback do not. This rise is only "normal" only for old amplifier and badly designed newer ones. Follow the 15kHz line out to, say, 10W. The amplifier is creating distortion of .02%. Now go out to clipping, which we'll just call 80W. THD+N has risen to about .08%. It's impossible to tell whether that is THD or N, since if there is distortion which is not harmonic, it would show up as N.

A simple CCIF IMD test would help reveal what is what, but that's a test Amir rarely does. The multitone helps, but because it is a multitone, it can also serve to mask distortions with another one of the tones. This is why Audio Precision counsels against (or at least, does not advocate for) using this as a distortion test or a test of an amplifier's linearity. The high frequency sweeps, though, at least give you *some* inkling that all is not rainbows and unicorns. There's a problem here, and this ain't no Benchmark or a Purifi. I have measurements sitting on my desk with a sweep for a 20+ year old lowly PA amplifier. At 20kHz (which would be a *slightly* worse case than 15kHz), THD+N is under .005%. A two decades old amp that can be had for a few hundred bucks is more linear that this chip amp by an order of magnitude. (To be fair, I bought this specifically because it does this and used a unique feedback topology that allows it to do this--it may well be the only PA amp capable of this.)

Taking some modern, available examples, the AHB2 at 5W is at .002% at 15kHz, rising to a worst-case of .003%. A NC500, .005% at 5W. The latter is Class D done right. A McIntosh MC462 will give you .0035% at 100W. See https://www.stereophile.com/content/mcintosh-laboratory-mc462-power-amplifier-measurements. To be fair, the Behringer A500 measurements were at .13% at 15kHz, while this is at .02%, so at least it's better than that... Again, we don't really know how linear the amplifier is and how much trash it's *potentially* throwing into the audible spectrum because we don't have a CCIF 2-tone. But, amps that do well at 20kHz *ALSO* tend to do well on the 2-tone, and vice-versa. The inverse is also true. Bad 20kHz THD, bad 2-tone.

If we were ranking things in term of the amplifiers ability to stay linear at high frequencies, this is about on par with the lowly Onkyo M282 tested awhile back (graph cuts off at 10kHz, so it's not clear). But that will crank out 150W if you need it. It also costs about $300. Anyone that thinks there's some sort of Purifi or Hypex grade performance here at a cut-rate price is just wrong. It's a one trick SINAD pony, whereas those better amplifiers appear to offer the whole package. Topping did a nice job of gaming the SINAD (THD+N) at 1kHz (as noted in the review itself with re: the gain structure). That was a nice trick. If they can manage to cure the inherent high frequency linearity issues of the Texas Instruments chip, it would be an amazing if not impossible trick. But they haven't done that and probably can't, so what they've done here just isn't terribly impressive at all, in my book. Ain't no such thing as a free lunch.

If I wanted to be sure I bought a highly linear and technologically superior amplifier without the potential for audible defects? I wouldn't buy this when its high frequency performance is mediocre, at best. In fact, that's why I didn't buy this and bothered posting this. In short, the charts aren't showing noise rising at high frequencies. They are showing worse, and probably showing that this amp does what these TI chips tend to do that Hypex or nCore do not: Get nonlinear and start spraying off distortion that is not harmonic at higher frequencies. Audible problem? Who knows, but I would prefer to have something that does not exhibit this problem. .08% THD at 15kHz at only 80W is just plain bad. Sorry for the book and the diatribe, but someone needed to set the record straight, and since I spent way too long reading this thread, I thought I might as well do something slightly productive with the investment of time..

Edit: Rate the amp using FTC specifications and it would be this: Less than .08% THD+N from 1/4W to 80W into 4 ohms, 20Hz to 20kHz (whcih is probably generous, since the cut-off was at 15kHz). That's not exactly impressive. That's plain terrible. I have 40 year old amplifiers that blow that out of the water. The merits of the specification might be debatable, but it is what it is.

 

[mctron]

Have we all forgotten this amp costs $350?

 

[IPunchCholla]

He may be misinterpreting it, but it would be better if it were noise. It may be worse than that. It was mentioned once off the bat by @pma months ago and then promptly forgotten or ignored (although I gave up after page 35). This is nowhere close to state of the art--it's not even very good. This "normal distortion rise with frequency" (see comment on chart) was normal two or three decades ago. While many amplifiers still do that, the good ones don't. Good amplifiers that use proper feedback schemes and/or don't run out of open loop gain so they can apply enough feedback do not. This rise is only "normal" only for old amplifier and badly designed newer ones. Follow the 15kHz line out to, say, 10W. The amplifier is creating distortion of .02%. Now go out to clipping, which we'll just call 80W. THD+N has risen to about .08%. It's impossible to tell whether that is THD or N, since if there is distortion which is not harmonic, it would show up as N.

A simple CCIF IMD test would help reveal what is what, but that's a test Amir rarely does. The multitone helps, but because it is a multitone, it can also serve to mask distortions with another one of the tones. This is why Audio Precision counsels against (or at least, does not advocate for) using this as a distortion test or a test of an amplifier's linearity. The high frequency sweeps, though, at least give you *some* inkling that all is not rainbows and unicorns. There's a problem here, and this ain't no Benchmark or a Purifi. I have measurements sitting on my desk with a sweep for a 20+ year old lowly PA amplifier. At 20kHz (which would be a *slightly* worse case than 15kHz), THD+N is under .005%. A two decades old amp that can be had for a few hundred bucks is more linear that this chip amp by an order of magnitude. (To be fair, I bought this specifically because it does this and used a unique feedback topology that allows it to do this--it may well be the only PA amp capable of this.)

Taking some modern, available examples, the AHB2 at 5W is at .002% at 15kHz, rising to a worst-case of .003%. A NC500, .005% at 5W. That's Class D done right. A McIntosh MC462 will give you .0035% at 100W. See https://www.stereophile.com/content/mcintosh-laboratory-mc462-power-amplifier-measurements. To be fair, the Behringer A500 measurements were at .13% at 15kHz, while this is at .02%, so at least it's better than that... Again, we don't really know how linear the amplifier is and how much trash it's *potentially* throwing into the audible spectrum because we don't have a CCIF 2-tone. But, amps that do well at 20kHz *ALSO* tend to do well on the 2-tone, and vice-versa. The inverse is also true. Bad 20kHz THD, bad 2-tone.

If we were ranking things in term of the amplifiers ability to stay linear at high frequencies, this is about on par with the lowly Onkyo M282 tested awhile back (graph cuts off at 10kHz, so it's not clear). But that will crank out 150W if you need it. It also costs about $300. Anyone that thing there's some sort of Purifi or Hypex grade performance here at a cut-rate price is just wrong. It's a one trick SINAD pony, whereas those better amplifiers appear to offer the whole package. Topping did a nice job of gaming the SINAD (THD+D) at 1kHz (as noted in the review itself with re: the gain structure). That was a nice trick. If they can manage to cure the inherent high frequency linearity issues of the Texas Instruments chip, it would be an amazing if not impossible trick. But they haven't done that and probably can't, so what they've done here just isn't terribly impressive at all, in my book. Ain't no such thing as a free lunch.

If I wanted to be sure I bought a highly linear and technologically superior amplifier without the potential for audible defects? I wouldn't buy this when its high frequency performance is mediocre, at best. In fact, that's why I didn't buy this and bothered posting this. In short, the charts aren't showing noise rising at high frequencies. They are showing worse, and probably showing that this amp does what these TI chips tend to do that Hypex or nCore do not: Get nonlinear and start spraying off distortion that is not harmonic at higher frequencies. Audible problem? Who knows, but I would prefer to have something that does not exhibit this problem. .08% THD at 15kHz at only 80W is just plain bad. Sorry for the book and the diatribe, but someone needed to set the record straight, and since I spent way too long reading this thread, I thought I might as well do something slightly productive with the investment of time..

Edit: Rate the amp using FTC specifications and it would be this: Less than .08% THD+N from 1/4W to 80W into 4 ohms, 20Hz to 20kHz. That's not exactly impressive. That's plain terrible. I have 40 year old amplifiers that blow that out of the water. The merits of the specification might be debatable, but it is what it is.

FYI, this entire statement is a classic example of the informal logical fallacy "argument from ignorance". In case you're unfamiliar, the formulation is no information is known about X which proves X is true. For example, "The ranger didn't say what she was wearing when she was accidentally shot by a hunter in the woods, therefore we know she wasn't wearing blaze orange, because the ranger would have noted that".

If we don't know wether it is noise or distortion, we don't know. We can't say it is probably one or the other. If we can say it is probably one or the other we have to know that from something, not nothing.

So far a number of people have jumped into this thread saying that the PA5 is creating harmonics in non-audible frequencies that loopback into the hearable range. That at reasonable listening levels for which it was designed, you have to play it at power that is causing clipping, that the high-frequency THD+N into power is such that there will be distortions and noise, probably audible. What none of those people have provided is any sort of evidence for any of these claims. Just speculation and hypothesis that have been repeatedly show to be based on false assumptions.

It's fine for you to doubt the quality of the amp. but at a certain point it kinda feels like put up or shut-up.

I am very, very happy with this amp. I don't hear any of these supposed issues. I have seen no proof that these supposed issues exist. So I am going to tune this thread out, and move on to solving the next link in my music stack, speakers. What FR response are mine doing? Am I hearing what I think I am hearing? and is there an equivalent of the PA5 in the speaker realm?

 

[MarkWinston]

Have we all forgotten this amp costs $350?

Some are expecting it to be in the 200 range, some are scrutinizing it like its a 35000 dollar amp. You cant please everyone, even with great measurements. SMFH.

 

[BoredErica]

pma's going to post the same thing over and over and over again about thd at high frequencies and any time people challenge him on his claim he'll just stop responding. It wasn't ignored, in fact pma brought it up twice in this thread alone and when challenged both times stopped responding. I even specifically pinged pma to get a response out of him and no dice.

All there is on pa5 is being unable to be 100% sure if FR will change under complex loads. What little we can see, there is basically no difference in Amir's simple test so there isn't a reason to think it has problems in the first place. Amir has also tested multiple amps with complex loads and found no problems out of very budget amps.

I think pa5 is transparent just like how purifi is transparent just like how benchmark is transparent. But you can't say aiyimia is transparent 100% of the time.

I do not see any good evidence that thd of pa5 would be audible in *music* and every person so far who has tried to argue otherwise have no idea what they're talking about or are the same 1-2 usual people and we run the same conversation on loop. Maybe people will actually have a discussion this time instead of giving me another round of deja vu.

 

[AudioArchitech]

I fully changed my setup, moved my speakers around while comparing amp to amp, for science ; )

For you guys who find the centre image is shifted, how are your speakers set up within the room and where is your seating position relative to them?

Mine are as symmetrically placed as I can get them (they're in the lounge), about 1m clear of the rear walls, equally toed in towards the listening position (centre of the sofa), angled identically and at the same distance +/- 2mm. My Mrs. is relatively forgiving of my speaker placement obsession

Of course, speakers never moved, all the same, symmetrical.

 

[antcollinet]

in fact pma brought it up twice in this thread alone and when challenged both times stopped responding. I even specifically pinged pma to get a response out of him and no dice.

My challenge was likewise ignored.

 

[gfinlays]

FYI, this entire statement is a classic example of the informal logical fallacy "argument from ignorance". In case you're unfamiliar, the formulation is no information is known about X which proves X is true. For example, "The ranger didn't say what she was wearing when she was accidentally shot by a hunter in the woods, therefore we know she wasn't wearing blaze orange, because the ranger would have noted that".

If we don't know wether it is noise or distortion, we don't know. We can't say it is probably one or the other. If we can say it is probably one or the other we have to know that from something, not nothing.

So far a number of people have jumped into this thread saying that the PA5 is creating harmonics in non-audible frequencies that loopback into the hearable range. That at reasonable listening levels for which it was designed, you have to play it at power that is causing clipping, that the high-frequency THD+N into power is such that there will be distortions and noise, probably audible. What none of those people have provided is any sort of evidence for any of these claims. Just speculation and hypothesis that have been repeatedly show to be based on false assumptions.

It's fine for you to doubt the quality of the amp. but at a certain point it kinda feels like put up or shut-up.

I am very, very happy with this amp. I don't hear any of these supposed issues. I have seen no proof that these supposed issues exist. So I am going to tune this thread out, and move on to solving the next link in my music stack, speakers. What the effort are mine doing? Am I hearing what I think I am hearing, and is there an equivalent of the PA5 in the speaker realm.

Just from subjective impressions, the PA5 is more neutral and reveling than my £5500 DK Design VS.1 Signature MK.III (a bargain price given its build) The AHB2 is also more revealing (not surprising really, given its measurements) than the DK. As for PA5 vs AHB2, I will delve a little deeper at the weekend. I also think whether differences are audible will also depend on speaker design and drive units. I have a bit of an advantage here - My ZRTs incorporate a couple of the lowest distortion drivers available and I didn't cheap out on crossover components, especially with respect to tolerance values. CSD plots are exceptionally clean and John Krutke's driver integration and crossover design are simply superb. Yes, as a big standmount 2-way, power response and directivity aren't spectacular, but sitting in the 'sweet spot', the sound is sublime. I wish 'audiophile' speaker companies (with teams of engineers on staff) would put as much effort into achieving low distortion speakers with good frequency response, minimum phase, benign impedance, exemplary driver integration and great listenability as guys like John Krutke and Troels Gravesen put into their designs.

If I were the CEO of a top tier speaker company, I'd be offering these guys six-figure plus salaries and a shit-load of benefits to get them on my staff.

 

[gfinlays]

I fully changed my setup, moved my speakers around while comparing amp to amp, for science ; )

Of course, speakers never moved, all the same, symmetrical.

No need to be facetious!

What I was getting at is whether the PA5 was showing up any stereo image imbalance that you had perhaps become accustomed to with your previous kit.

 

[AudioArchitech]

True, my bad

I'll do some more testing, will flip the speaker outs...

 

[ryanmh1]

If we don't know wether it is noise or distortion, we don't know. We can't say it is probably one or the other. If we can say it is probably one or the other we have to know that from something, not nothing.

So far a number of people have jumped into this thread saying that the PA5 is creating harmonics in non-audible frequencies that loopback into the hearable range. That at reasonable listening levels for which it was designed, you have to play it at power that is causing clipping, that the high-frequency THD+N into power is such that there will be distortions and noise, probably audible. What none of those people have provided is any sort of evidence for any of these claims. Just speculation and hypothesis that have been repeatedly show to be based on false assumptions.

There's no speculation here. Distortion rises at high frequencies. We know the 20kHz THD is terrible. And we know it is not "noise" since there is a noise measurement. What we know (from what we know about amplifier design and measuring or reading lots of amp measurements) means we know with a high degree of certainty that if someone wants an amplifier that does not exhibit nonlinear distortion substantially higher than a Hypex (which is measureably an order of magnitude better), they should probably buy something else. This is no "guess" from ignorance. It's a logical deduction. What would need to be proven is the inverse: That this amplifier does not behave like virtually every single other amplifier exhibiting high THD20, particularly TI chip amps.

And, yeah. It costs $350. But it's being touted as some sort of Hypex competitor or "second only to Benchmark." It ain't. It's an amp with a downright bad FTC spec, if you spec'd it the way we spec'd amps for years. Is any of this audible? Who knows. It probably sounds fine. But since the goal of many seems to be to find products which are somehow technically superior and free of any potential defect, the awful 20kHz THD number is fair game, and it's largely been ignored in favor of this nearly useless 1kHZ THD+N spec.

If we want to talk price, well... You could buy a TPA3251 based amp off ebay for about $60. Does this amp sound $290 better? Probably not. No doubt this is a very fine implementation of some or another TI chip amp, but if we're talking audibility, does any of that make a difference if the fundamental flaw of bad THD20 cannot be fixed? Valid question, and one that cannot definitely be answered without more thorough measurements.

 

[gfinlays]

There's no speculation here. Distortion rises at high frequencies. We know the 20kHz THD is terrible. And we know it is not "noise" since there is a noise measurement. What we know (from what we know about amplifier design and measuring or reading lots of amp measurements) means we know with a high degree of certainty that if someone wants an amplifier that does not exhibit nonlinear distortion substantially higher than a Hypex (which is measureably an order of magnitude better), they should probably buy something else. This is no "guess" from ignorance. It's a logical deduction. What would need to be proven is the inverse: That this amplifier does not behave like virtually every single other amplifier exhibiting high THD20, particularly TI chip amps.

And, yeah. It costs $350. But it's being touted as some sort of Hypex competitor or "second only to Benchmark." It ain't. It's an amp with a downright bad FTC spec, if you spec'd it the way we spec'd amps for years. Is any of this audible? Who knows. It probably sounds fine. But since the goal of many seems to be to find products which are somehow technically superior and free of any potential defect, the awful 20kHz THD number is fair game, and it's largely been ignored in favor of this nearly useless 1kHZ THD+N spec.

If we want to talk price, well... You could buy a TPA3251 based amp off ebay for about $60. Does this amp sound $290 better? Probably not. No doubt this is a very fine implementation of some or another TI chip amp, but if we're talking audibility, does any of that make a difference if the fundamental flaw of bad THD20 cannot be fixed? Valid question, and one that cannot definitely be answered without more thorough measurements.

I'm 52 years old and my hearing tops out at 16kHz. THD at 20kHz is meaningless.

 

[antcollinet]

I'm 52 years old and my hearing tops out at 16kHz. THD at 20kHz is meaningless.

THD at 20kHz is meaningless for everyone, as it is above 10kHz. Then take the spectral power density of music - I'm not remotely worried by those charts.