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Review and Measurements of Topping TP60 and FX Audio FX502SPro Amps

RayDunzl

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#61
@amirm

Would you consider this to be a good spec for a power amp?

"Signal/noise ratio: 85dB ref. 2.83V RMS (1W at 8 ohms) "
 

amirm

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#62
@amirm

Would you consider this to be a good spec for a power amp?

"Signal/noise ratio: 85dB ref. 2.83V RMS (1W at 8 ohms) "
That is just signal to noise ratio. That is less interesting than the rest of the stuff I measure.

As to the spec, depends on whether the noise level goes up as power goes up. If it doesn't then it is good.
 

vert

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#63
Oh, not good. I happen to have the FXAudio. I use it as a TV setup with a DAC and a sub over high level outputs. I still prefer it over a class A/B amp it replaced (including in terms of convenience), and much prefer that setup to the AV receiver frankenstein I had briefly. I have been wowed by the sound sometimes, not always. Based on some reviews of it, I expected a little better maybe? Given the small cost, it's still ok. Though I'm surprised FXAudio and Topping aren't able to do better in terms of those bare-bones class D units, given their track records with other devices (FXAudio's 802 FDA and Topping's DACs).

Anyhow, that setup was going to be used to power a Stax energizer, and be replaced for TV duties, for family members' convenience, by a FDA such as the SMSL AD18. Maybe I should wait until it is tested here now.
An update to my earlier reaction to this past week's review of the FXAudio FX502S Pro, as I've had a little time today to compare it back to the amp it replaced, a Teac A-H300 mkIII from about 10 years ago. Given the review, I had to go back and compare.

Please bear with me. I know what ASR represents, but I have no experience in serious audio, or technical expertise, to speak of, and won't pretend I have, so what follows will inevitably seem unrigorous and impressionistic.

Well, there was no contest. Is the FXAudio truly high fidelity? Most likely not. But it had more details, better definition, better instrument separation, more depth and width to the soundstage. At times it really was a 3D soundscape. The Teac doesn't give me that, at least never to the same degree. Sure, there are imperfections, in timbres and the fact that the sound is somewhat thinner, but part of that may improve when I change the modest JBL Control 1s I'm still using (I've haven't gotten around to upgrade that part of my rig yet). Another thing I should mention is I don't typically listen very loud.

What this tells me, is that there has been a technological leap, regardless, with recent class D builds, as mediocre as some of them may be, and I'm not sure at all I would get a better class A/B amp in the same price range today from the likes of Teac, Denon, Cambridge, Emotiva or Atoll, as the technology hasn't changed. So I would need to spend possibly a lot more. Problem is WAF for audio gear is very low and I can't spend fortunes and experiment a lot. As bad as the FXAudio may be, a decent class A/B amp from 10 years ago simply couldn't compete. (unless of course my Teac isn't half as good as I thought it was). Sure, the FXAudio won't be the amp of a lifetime, and I'm looking forward to trying better things in the future.
 

GGroch

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#64
Fascinating stuff....but initially quite depressing, as I have coincidentally just received a FX502S Pro for my desktop system.

Like Vert, I my 1st impressions of the sound and operation for driving small JBLs nearfield has been excellent. My purchase was based on discussion of its TPA3250 chipset in the DIY site, and the IEEE Spectrum article previously referenced here. So I was surprised and depressed by the test results.

I am a bit less depressed now since reading the follow up testing of additional amplifiers, and think the release of additional amp results will provide much needed perspective on what represents acceptable and good performance in a speaker amp.

One of the primary challenges is that manufacturers play very fast and loose with amp specs. A .0025% THD+Noise spec will be quoted along side a 70 watt continuous power spec...which the eBay ads do not mention is at 10% THD.

I am old enough to remember when in 1974 the U.S. the FTC decided to solve all of this with their amp rule mandating continuous power, 20-20k, into 8 ohms, at usually 1% as the rating standard. What happened of course is that more and more amps were designed to perform only to that test....and with little reserve dynamic power or ability to handle lower resistant loads. For a lot of audiophiles the new quest became finding amps with high current and dynamic power and THD+Noise below .2% which was considered inaudible given the available sources and loudspeakers. Companies like NAD and Harman made a great business out of doing that.
So when I look at the current lack of measurement standards...I think Amir's tests will provide much needed perspective.

For my desktop use 25 wpc into 8 ohms is more than enough and if the THD at that output is below .2% I will never hear it. Except for the troubling oscillation (which I have not experienced) the FX502S Pro seems fine for that... and I am not sure spending any more would provide noticeable improvement. My guess is that the inability of the FX502S to meet published power specs for the TPA3250 chipset is its use of a 24 volt power brick (specs allow up to 33v) and other power related choices.

Anyway, very interesting and much needed stuff. My guess is that no amp will measure even close to any well designed DAC. But depending on use many may be quite good for their intended purpose...and also that there may be little correlation between price and results.
 

sergeauckland

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#65
Anyway, very interesting and much needed stuff. My guess is that no amp will measure even close to any well designed DAC. But depending on use many may be quite good for their intended purpose...and also that there may be little correlation between price and results.
That's pretty much my view, A DAC doesn't have to drive difficult loads with strange impedance characteristics at high levels, the output load for a DAC is pretty benign. Furthermore, the performance of a DAC is largely determined by the silicon and the board layout, and it's hard to get seriously poor performance, although some 'boutique' manufacturers have made heroic efforts in that direction.

Power amplifiers became transparent by the late 1970s or early 1980s, since then the emphasis has been on higher powers, lower cost and greater efficiency, not necessarily in the same product. A power amp from, say, 1985, if in decent condition, will still be as audibly competent as the best of today's equipment. Anything from Hafler, Quad, Musical Fidelity, Krell etc etc etc haven't been improved on sonically since then.
S
 

amirm

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#66
So when I look at the current lack of measurement standards...I think Amir's tests will provide much needed perspective.
Thanks for the nice perspective. I think we are all learning together. And filling a vacuum in publishing.

The problem is that home theater like magazines mostly focus on video for measurements. And audio sites either don't measure anything or only test high-end/non-home theater products. HiFi News in UK was an exception but they are a pale copy of what they used to be in this regard.
 
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#67
That's pretty much my view, A DAC doesn't have to drive difficult loads with strange impedance characteristics at high levels, the output load for a DAC is pretty benign. Furthermore, the performance of a DAC is largely determined by the silicon and the board layout, and it's hard to get seriously poor performance, although some 'boutique' manufacturers have made heroic efforts in that direction.
Well, it is possible for amps to approach the measured performance of a decent DAC if the designers decide that this is a goal. For a couple specific examples:

- The neurorchrome Modulus series have been mentioned in the 'under $500 amp' thread, and the designer presents pretty comprehensive AP measurements here: https://www.neurochrome.com/modulus-86/

- 'Jon Marsh' from HTGuide also has an AP analyzer and while he hasn't done many tests, the ones he has done are interesting. The Benchmark AHB2 measures similar to or better than the Modulus 86 (aside maybe from the IMD tests) but has substantially more power. http://www.htguide.com/forum/showthread.php?43216-Benchmarking-the-Benchmark-AHB2-Amplifier

- Even more impressive, the stupidly expensive Halcro monoblocks measure almost unbelievably well. http://www.htguide.com/forum/showthread.php?43494-Halcro-DM-68-Monoblock-Amplifiers.

- Not quite up to the level of the others, but the Cambridge 651w is supposedly a 'blameless' Douglas Self design and accounts itself well. Considering it's available for $700, it's potentially interesting as an off-the-shelf option. http://www.htguide.com/forum/showth...xpensive-Cambridge-Audio-651W-Power-Amplifier

Power amplifiers became transparent by the late 1970s or early 1980s, since then the emphasis has been on higher powers, lower cost and greater efficiency, not necessarily in the same product. A power amp from, say, 1985, if in decent condition, will still be as audibly competent as the best of today's equipment. Anything from Hafler, Quad, Musical Fidelity, Krell etc etc etc haven't been improved on sonically since then.
S
Well, I think this is the question we're all trying to answer. What measurements and what level of performance are 'good enough' to be audibly indistinguishable? This is particularly true when looking at Class D units where the switching behavior makes it more difficult to get a good picture.

I think there is broad agreement that harmonic distortion is not a great metric and is generally a 'solved problem' unless you deliberately introduce it into your design. I think the more interesting questions are around things like IMD and transient behavior which is harder to measure (but hopefully is adequately proxied by the other measurements). I personally find the multi-tone IMD test shown on the Modulus 86 page to be interesting, partly since I hadn't seen it before - the level of 'hash' below the test tones feels like it should be a pretty good indicator of overall performance.
I do agree that amps don't need to perform like the Halcro in order to be audibly indistinguishable, but the fact that we have things like the ST200 on the market and well regarded seems to be a good indication that there are still things on the market that are sub-par.

I'm still trying to figure out what my desktop system will look like and whether I'm going to bi-amp or not since that obviously impacts the budget. IMHO if you can live within the power envelope the Modulus 86 is a no-brainer - you can use the new pre-assembled modules and complete a stereo 40w/65w unit for about $700-$750. $900-950 for 65w/120w.
 

sbsj

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#68
Hi Amir, maybe one day you can measure the Emotiva A-100 speaker amp which costs $229 ;)
 

amirm

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#69
Hi Amir, maybe one day you can measure the Emotiva A-100 speaker amp which costs $229 ;)
I can but I am snake bit right now having bought a bunch of amps which I am stuck with currently. :)
 
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#70
I can but I am snake bit right now having bought a bunch of amps which I am stuck with currently. :)
I actually just ordered a BasX A-100 yesterday - a stopgap while I decide whether I'm multi-amping and how much I have to spend. I'm not sure of the protocol of sending something to you for measurement, but it's definitely possible. I also have a Dayton APA-150 which is in the same category - cheap (even cheaper than the Emotiva) AB amp with passive volume control which might make for an interesting comparison.
 
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3eaudio

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#71
FX502SPro use BTL Mode for each channel(2.0)
the Ti's measurement you enclosed is SE mode,that why it showing output power only around 30W.
below BTL mode into 8ohm can get 50W/0.1%THD+N
BTL_THDN_8ohm.JPG

the FX502SPro output is limited by the power supply(adapter),we also test it even into 8ohm,when output is higher to around 40W,it is very easy to shut down and protection(thermal think).
and we found that there is a very loud POP noise during AC Line off.
Here are some other items we tested,showing there is still opportunity to improve their design.

1. Noise
noise.jpg



2. THD+N Ratio vs Frequency-1W (one channel driven)
THD+N Ratio vs Frequency-1W.jpg



3. THD+N Ratio vs Frequency-10W (one channel driven)
THD+N Ratio vs Frequency-10W.jpg



4.THD+N Ratio vs Measured Level-4ohm (one channel driven)
THD+N Ratio vs Measured Level-4ohm.jpg



5.THD+N Ratio vs Measured Level-8ohm (one channel driven)

THD+N Ratio vs Measured Level-8ohm.jpg
 

Toku

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#72
I bought a TP60 and two FX-502SPROs. But I could not like the sound quality of those products. And I sold everything in only a month.
I was able to understand the cause of the discomfort I felt by looking at the measurement report of Amirm.
Especially I think that FX-502SPRO is completely miss design. When the volume is raised the protection circuit works and the error lamp lights up, it is an incredible operation anymore!
 
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#73
To check how much distortion YOU can hear read this article and get a copy of the Stereophile Test CD 2 tracks 21-23 (2nd, 3rd, 7th harmonic distortion @ 500hz) and the booklet if possible.
Remember even harmonics are naturally produced by most musical instruments.
https://www.stereophile.com/asweseeit/673awsi/

I used a Geek Pulse DAC/AMP driving my HiFiMan HE-560 headphones @ ~80 db since I know distortion in that setup is very low.
I personally think the test is flawed since they go 0, 10%, 3, 1, .3, .1, (.03% 7th) instead of a random sequence which is only revealed after you listen but it's the best test I've found so far.
Anyone know of a source of music with varying distortion levels?

Very interesting article about distortion, which I don't 100% agree with, but the IM part is interesting, and a "pure" amp lost in time for DIY self builders.
https://www.allaboutcircuits.com/te...stortion-class-b-audio-amplifier-audiophiles/

Interesting about Amir and hi res audio.
https://www.audiostream.com/content/abx-tests-prove-hi-res-audio-legit
 
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GGroch

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#74
To check how much distortion YOU can hear read this article and get a copy of the Stereophile Test CD 2 tracks 21-23 (2nd, 3rd, 7th harmonic distortion @ 500hz).....
Interesting about Amir and hi res audio......
Welcome....Very interesting stuff. I had not seen either of these. You may want to post this in the Psychoacoustics: Science of How We Hear section. I have not been here long either so maybe it is there...but I have not seen it.

It seems the validity of the Stereophile CD test would totally depend on you using it totally blind, like Amirm's ABX test. The Stereophile article (featuring the classic audio outlier & skeptic Bob Carver) makes the interesting point that distortion is far easier to detect in simple sources (like solo guitar strings plucked) and much harder with complex sources (symphony orchestras). Most commenters in the Psychoacoustics threads who believe they hear quite low distortion..say the opposite.
 

vert

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#75
An update to my earlier reaction to this past week's review of the FXAudio FX502S Pro, as I've had a little time today to compare it back to the amp it replaced, a Teac A-H300 mkIII from about 10 years ago. Given the review, I had to go back and compare.

Please bear with me. I know what ASR represents, but I have no experience in serious audio, or technical expertise, to speak of, and won't pretend I have, so what follows will inevitably seem unrigorous and impressionistic.

Well, there was no contest. Is the FXAudio truly high fidelity? Most likely not. But it had more details, better definition, better instrument separation, more depth and width to the soundstage. At times it really was a 3D soundscape. The Teac doesn't give me that, at least never to the same degree. Sure, there are imperfections, in timbres and the fact that the sound is somewhat thinner, but part of that may improve when I change the modest JBL Control 1s I'm still using (I've haven't gotten around to upgrade that part of my rig yet). Another thing I should mention is I don't typically listen very loud.
With a few weeks' perspective, I wish to revise my earlier post above. It was all wrong and I'm embarrassed I wrote it.

The FXAudio's sound had started to bother me on some sources and on occasion with some brittle and unnatural (distorsion?) sound, including some sibilance. On a practical level, the lack of a remote control and a headphone out, for a living room system, turned out to be another problem. Today I retried a comparison with my class AB Teac A-H300 mkIII amp. and contrary to what I wrote before, the Teac clearly is the better amp, does a fine job of amplifying the signal from the DAC, and gives nothing away to the FXAudio. With my new Paradigm Atom speakers the system is a pleasure to listen to.

My better judgement was clouded, I guess, by inflated expectations, the new toy syndrome, overall lack of experience and a probable lack of proper level matching. On the DIY Audio forum, there is a fairly long thread about the new TI 3250 chip used in the FXAudio, which is said to be "best in class". On that count alone, the FX502pro's performance is suspect, one would expect that amp to perform much better. There clearly is a problem somewhere in the design as the review said. So in retrospect the review was 100% spot on!
 
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andreasmaaan

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#76
Looking at the distortion vs power graph for the TP60, there is a big jump in distortion as the signal drops below about 10mW.

This looks to me like something resembling crossover distortion.

Can anyone more expert in this area perhaps comment on this?
 

celo

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#77
I registered to this forum after seeing this thread. Well actually I have seen it before but didn’t register back then. So, here we go:)

It is a great site/forum. Informative and show you proof with measurements. I like it!

I need to say something about the TP60 though. TP60 is one of the best amplifiers I have heard, period (the best one for me
is Pass Labs Aleph 3). Is it perfect? Of course not. The bass doesn’t have slam, little under powered for hard to drive speakers but the separation of the instruments, the soulful vocals, midrange are amazing. No joke.

I have this amp for years. I replaced it with a full Naim system with bells and whistles. Really nice sound. Then one day I thought to hook up my dust collecting TP60 with no high expectations. Sat on my sweet spot chair. Reading a magazine. Not paying too much attention to the music. No critical listening. All of a sudden, I start to hear things that I haven’t heard before. Same songs. Crazy separation. Amazing vocals. I thought I am maybe wrong. Gave the TP60 to my brother who has Pass Labs XA 30.5. He said everything I said but picked his Pass by a small margin. Not to mention his Prima Luna preamp helped Pass probably. He liked the TP60 better than his other amps, Hypex NC400.

Moral of the story is, measurements are good to have but it doesn’t mean everything. At least for me. I like to go by with what my ears here.

My Naim system is for sale.
 

Toku

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#78
I bought two TP 60. I completely agree on the sound quality of the middle range.
I think that it is the best product for those who like the atmosphere of the old analog amp.
But to me I sold it because I was dissatisfied that the range of low end and high end did not grow.
Especially weakness of bass could not bear.
Naim is a product of my yearning.
 

celo

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#79
I bought two TP 60. I completely agree on the sound quality of the middle range.
I think that it is the best product for those who like the atmosphere of the old analog amp.
But to me I sold it because I was dissatisfied that the range of low end and high end did not grow.
Especially weakness of bass could not bear.
Naim is a product of my yearning.
Yes, if you can live with weak bass and don’t mind not to have that “hi-fi” sound, there is no better amp that I have listened to for the money.
 
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