WiiM Amp Pro Streaming Stereo Amplifier Review

[keiron99]

So, i have a pair of kefs q150 and wiim amp would i notice an improvement with the wiim amp “pro”? Or my speakers are bottlenecking?

Would be keen to hear views on this. I’m deciding whether to hold out for the Pro or get the original for about £120 less.

Are the measurable improvements really audible in the real world?

 

[JeremyFife]

It makes sense to measure all amplifiers in the same way so that they can be compared. It makes sense to add new measurements (FTC) over time. Obviously, those new measurements can't be applied retrospectively.

It doesn't make sense to blindly rate all amplifiers based on those measurements without taking context into account.

If I had a large room and a pair of Salon 2s, the WiiM amp would be pitifully under specified.
If have a smaller room, a TV as the main source and a family as the main audience (and let's say Kef Q350s) then the WiiM is pretty bloody perfect.
A 'proper' amplifier would be woefully wasted in that second scenario, and would need several more boxes around it.

Based on measurements, the WiiM is good except for the edge cases. Based on features and price it's feckin amazing.

I do agree that we need a brutally objective assessment where all amps are compared strictly. Happy to consider the WiiM Amp Pro as 'fine' in that case.
We then need to temper that assessment based on context and our considered membership view. We all need to accept the measurements, noone needs to accept my opinion.

 

[Haskil]

I accept your opinion!
This is a perfect summary from a reasonable, informed and pragmatic point of view.
Well done !

 

[morillon]

This is precisely the problem... a case by case in terms of speaker+amp behavior... difficult to understand... the pffb is good news... will help...
(historically we were worried about the very low impedances in the bass, the big "greedy" speakers etc etc "we could understand it quite easily... but here I find it more delicate to understand...d as much as can concern simple "libraries" etc to which This is quite naturally intended for this little "all in one"...)

 

[Laagman]

Are you planning on testing the phono stage of the ultra too? Have only seen subjective reviews of the phono functionality.

 

[AdrianG]

Would be keen to hear views on this. I’m deciding whether to hold out for the Pro or get the original for about £120 less.

Are the measurable improvements really audible in the real world?

Ok I ordered the pro version from amazon, as soon as it arrives I will do subjective a/b comparison and update here, If i don’t hear an improvement right away the pro is going back

 

[Dennis_FL]

Why would you want that with a streamer/dac/amp already? The external dac won't be any better.

You wouldn't

 

[Burnside]

Why would you want that with a streamer/dac/amp already? The external dac won't be any better.

You could be feeding an external headphone amp, perhaps?

 

[Brian Hall]

You could be feeding an external headphone amp, perhaps?

In that case I would not pick the wiim amp or amp pro (and I haven't). Big fail by Wiim not including a headphone amp or line out option.

I listen with headphones a lot so the Wiim amps are not a good choice for me. The Ultra is much better.

 

[ryanmh1]

So yes, I'd prefer, as I wrote, even better performance, but I'm still going to buy one to put under my TV. And I agree with those who have spoken here that these distortion rates are in frequency zones and at levels where they won't be audible when listening to music or watching a film or program.
This is undoubtedly why ASR readers voted as they did, why Amir commented on his test in the way he did, and why so many others followed his example.

This is where I'll beg to differ. They voted how they did because they are technically ignorant about power amplifier design, by and large. To be clear, that's not a criticism. Most of those who understand anything about amplifier design tuned out long ago and stopped commenting because they just get made fun of and get blasted with the old canard that "you can't even hear the harmonics of 10kHz, so who cares."

Consider this: Why is it that any number of people can build a DAC which is below .001% THD from 20Hz to 20kHz but almost no one can achieve this in a power amplifier? In power amplifiers, they can't do it because it is hard. As it turns out, it matters. Bob Cordell, who literally wrote the book on designing and measuring power amplifiers, explains this much better than I can. So, here you go: https://www.diyaudio.com/community/...stortion-analyser.154260/page-12#post-2810564. Bruno Putzey's feedback article is a good follow-on which is much more technical and explains the underlying science: https://linearaudio.net/sites/linearaudio.net/files/volume1bp.pdf.

Ironically, the FTC 20Hz to 20kHz test which some are deriding (although I cannot tell if those comments are sarcastic or not) happens to significantly capture what Bob Cordell says is important. I, for one, will take an amp with -78dB 1kHz THD+N that stays under .02% from 20Hz to 20kHz from 250mW to 400W over an amp with -100dB 1kHz THD+N and -54dB at 15 or 20kHz any day of the week. There are a dozen of the former for sale on eBay right now for under $200 used. [It's a friggin' 20 year old PA amp that was a real moonshot for those who care, and takes a lot of work to the fan to use it at home -- I just finished one up that had been on my shelf for years and can't wait to give it a work out]. For the former, just buy this thing. After all, it's RaNkeD HiGh On tEh sINaD chART!!?! AmiRitE!?!

Ah well, the last few weeks have been a fun little second attempt to try to drag a little science back into understanding of amplifier measurements and audibility. Hopefully some of it rubbed off somewhere. I've said my piece on this again, for now. [I lied! See edits.]

EDIT: That's not to say HF distortions are the end-all measurement. They're not. The real challenge is teasing out IMD and nasty potentially audible problems in all of their forms. 1kHz SINAD just doesn't do that, and its shortcomings simply become quite obvious in reviews of products like this. Same complaint I had in a review of a prior Cambridge product which was worlds superior to this (sidebands a full 10dB lower) but got a bad review based largely on SINAD. Perhaps a course correction is finally in order, and perhaps at least enough was captured in the old measurements to extrapolate from them, and integrate them into a better list and ranking which relies on a better figure of merit. This important work was done well with speakers, and perhaps it's time to attempt the same for arguably the second most important and distortion-prone component in most signal chains. Just a thought.

SECOND EDIT: This is a helpful paper from Audio Precision: https://www.diyaudio.com/community/attachments/non-lineardistortion-pdf.640471/. They built intentionally broken circuits specifically to test various forms of distortion and nonlinearities. The most sensitive test for close to every last thing? 20kHz THD. 'Nuf said. It's possibly an end-all for "doesn't suck" but won't tell you what's wrong.

THIRD EDIT: Why not a "clean" multitone? Because two "-100db noise floors" are not necessarily equal. The "noise floor" in a multitone potentially consists of both correlated distortion and uncorrelated noise. The former is a potential issue, the latter is not unless the noise floor is an inappropriate match to the speakers (i.e. audible at primary listening position). Too easy to fail an amp that is actually good (a la Cambridge CXA81). A pretty much "guaranteed" "problem free" amp is one with low THD20 and an appropriately low SNR. And it's so easy to test for and interpret! It's just one number and a power sweep!

 

[JoetheLion]

If I had a large room and a pair of Salon 2s, the WiiM amp would be pitifully under specified.

For what? For listening at 60db? 70db? 80db?

 

[JeremyFife]

For what? For listening at 60db? 70db? 80db?

Fair comment, I was being a bit glib. The wee WiiM Amp Pro would sound pretty good in most circumstances (I think)

Let's say; filling a large room with bass-heavy, highly dynamic orchestral music listening at 80/85dB SPL at 4m ...

I was really just trying to make a general point, perhaps it doesn't hold up anyway?

 

[Haskil]

This is where I'll beg to differ. They voted how they did because they are technically ignorant about power amplifier design, by and large. To be clear, that's not a criticism. Most of those who understand anything about amplifier design tuned out long ago and stopped commenting because they just get made fun of and get blasted with the old canard that "you can't even hear the harmonics of 10kHz, so who cares."

Consider this: Why is it that any number of people can build a DAC which is below .001% THD from 20Hz to 20kHz but almost no one can achieve this in a power amplifier? In power amplifiers, they can't do it because it is hard. As it turns out, it matters. Bob Cordell, who literally wrote the book on designing and measuring power amplifiers, explains this much better than I can. So, here you go: https://www.diyaudio.com/community/...stortion-analyser.154260/page-12#post-2810564. Bruno Putzey's feedback article is a good follow-on which is much more technical and explains the underlying science: https://linearaudio.net/sites/linearaudio.net/files/volume1bp.pdf.

Ironically, the FTC 20Hz to 20kHz test which some are deriding (although I cannot tell if those comments are sarcastic or not) happens to significantly capture what Bob Cordell says is important. I, for one, will take an amp with -78dB 1kHz THD+N that stays under .02% from 20Hz to 20kHz from 250mW to 400W over an amp with -100dB 1kHz THD+N and -54dB at 15 or 20kHz any day of the week. There are a dozen of the former for sale on eBay right now for under $200 used. For the former, just buy this thing. After all, it's RaNkeD HiGh On tEh sINaD chART!!?! AmiRitE!?!

Ah well, the last few weeks have been a fun little second attempt to try to drag a little science back into understanding of amplifier measurements and audibility. Hopefully some of it rubbed off somewhere. I've said my piece on this again for now.

I wrote the following, which you ignored in your reply:


“Of course, we would have preferred even better distortion values, which do not vary with amplified frequencies, as well as lower intermodulation distortion, although again the values are all below -68 dB...”

- 68 dB is 0, 039 %

- 54 dB at 15 Khz : 0,2 %
- 62 dB at 10 Khz - 0,08 %
- 68 dB at 5 Khz : 0,04 %

[URL scroll down=“true”]https://sengpielaudio.com/calculatrice-thd.htm[/URL]


And also:
“Most of yesterday's reputable integrated amplifiers and amplifier blocks, both transistor and tube, don't do any better. But they're a lot more expensive.

And finally this:
“If you look at what this Wiim Amp Pro gives to the market today, at the price it's sold for, and if you take a time machine and see what you could get as an integrated amplifier for the same price in 1982, the year the CD was launched.... You can't find much choice for a hundred dollar-euros...”

And the problem with measured defects is knowing, when you take your eyes off your computer to check whether a device is in the blue, green, orange or red, and start listening to music, whether or not these undisputed objective defects are audible, under what conditions and in what proportion. This is important in real life. And it's no mean feat. I'm a convinced objectivist, attached to the quality of engineering put into products, but like many ASR readers I'm also a music lover, a pragmatist. And I've noticed that many of us own one of those little Class D amps with perfectible performance. We knew it when we bought them, and we don't suffer when we listen to music with them. We know we're not talking about a Purifi, a Nilai, an NC 500 from Hypex or any of those excellent Class D amps whose engineering is far more advanced than the amplification part of the little Wiim Amp Pro we sometimes own.

So yes, I'd prefer, as I wrote, even better performance, but I'm still going to buy one to put under my TV. And I agree with those who have spoken here that these distortion rates are in frequency zones and at levels where they won't be audible when listening to music or watching a film or program.
This is undoubtedly why ASR readers voted as they did, why Amir commented on his test in the way he did, and why so many others followed his example.

-----------------------
You definitely have the art of quoting only what interests you for your demonstration.

So here is what I responded to, but note in passing that the distortions you announced were erroneous and that they were missing a 0 after the decimal point.

I understand your new answer, but in truth it hardly interests me in the context of this discussion which follows the measurements of a small economic amplifier-streamer which will make people happy wherever it will be used and for what for it is done. Just like these small amplifiers from Fossi, Ayiama and co which have no claim to be Sota in their field but just to do their job in a small footprint and with a quality that seems to satisfy many users. Several ASR participants explained this, as did I.

The voters voted in a relevant way, as relevant as the most learned electronics engineer who would consider things in a pragmatic and practical way... staying away from discussions on the sex of angels and they considered that this device deserved its happy panther .

 

[JoetheLion]

I was really just trying to make a general point, perhaps it doesn't hold up anyway?

You can calculate it using simple formulas. The result is that in the vast majority of cases, for most speakers, for example at a listening position of 3 meters from the speakers, 20 watts is completely sufficient, even if peak levels in dynamic passages are taken into account. This is about, say, 85 dB, a volume that is damaging to the hearing in the long term. Ask your ear doctor.

We are always fascinated here by the insane measurement results of amplifiers with Purifi or Hypex modules that have 250 watts or more “power”. For practical everyday use, this is of no significance whatsoever.

 

[JeremyFife]

You can calculate it using simple formulas. The result is that in the vast majority of cases, for most speakers, for example at a listening position of 3 meters from the speakers, 20 watts is completely sufficient, even if peak levels in dynamic passages are taken into account. This is about, say, 85 dB, a volume that is damaging to the hearing in the long term. Ask your ear doctor.

We are always fascinated here by the insane measurement results of amplifiers with Purifi or Hypex modules that have 250 watts or more “power”. For practical everyday use, this is of no significance whatsoever.

I agree, and I often use the Crown calculator. What's interesting is two separate things: the headroom power needed for dynamic peaks in some music and real edge cases of difficult loads.
It's the (possibly irrational) worry about sufficient headroom that would push me to wanting more power for an 'ideal' amp. I just don't think I would buy a 'difficult' speaker.
There's another point too, not one I'm so interested in but relevant to some people: that of wanting engineering excellence. I get that.

We're drifting off topic now I think.

 

[shuppatsu]

Consider this: Why is it that any number of people can build a DAC which is below .001% THD from 20Hz to 20kHz but almost no one can achieve this in a power amplifier? In power amplifiers, they can't do it because it is hard. As it turns out, it matters

Does it matter? You haven’t established why it would matter. I think for this reason you and your interlocutors have been going around in circles. I’m still unsure of your position.

.20%, .08%, and .04%. Audible or not, that translates right into "not good" by any reasonable metric. It also suggests it is prone to IMD, which in fact it does exhibit. Audible? I'll leave that for someone else to judge. But as an amplifier it's not impressive.

I already responded to this, but I suspect a disagreement about this underlies the other disagreements, so I'll try again.

Some people prize exceptionally engineered products for their own sake, like a fine swiss watch. For pride of ownership or for the unavoidable psychological benefit of listening to something from SOTA components. By this rubric, all other things being equal, a 130 SINAD amp is necessarily better than a 120 SINAD amp, because, audible or not, it's more impressive.

Another perspective incorporates value engineering. We have extensive literature (example, another) showing that the bar for amp transparency at a given volume is pretty low. Once that bar has been cleared, further improvements are unnecessary from the perspective of a hifi enthusiast who is not a measurements fetishist. You can't be more transparent than transparent.

Most of us fall somewhere between these two perspectives. I identify much more strongly with the second camp, but I still paid a (very small) premium to buy an L30 II headphone amp because I liked owning something with SOTA measurements, even though I could buy an equally transparent amp for less money. But I would not claim that those measurements make it a better amp than say, the Topping DX1.

You also seem to split the difference. In the above quote, you say that it doesn't matter whether these perceived defects are audible. But here you address audibility:

We also know it can cause IMD which is much more obnoxious to the ear than low order harmonics since there is no masking by the music. We see the bad 19+20 sidebands confirming IMD. There's a sea of trash in the multitone, unlike say, a NCx500. Noise is good, but we know noise isn't a major audibility issue in any event, in terms of being objectionable. We also know 1kHz results don't say all that much about audible problems. So what we see is an amp that is maybe mass market receiver level, but scores high on the SINAD chart.

I'm not sure I agree with this. Generally speaking, noise is a much more significant audibility issue than distortion, at least with sensitive headphones. Maybe less so with typical speakers. Regardless, the main point is that you suggest that the IMD problem is audible. To bolster this point, you link to a forum post by Bob Cordell. He says this about audibility:

But one can argue that distortion we hear, especially that from high-frequency signals, is IM rather than harmonics. The spit on a cymbal that we hear due to poor amplifier HF performance is not due to harmonics that are above the audio band, but rather IM that is reflected down into the more audible portions of the audio band.

This seems sensible, and I think Cordell makes the case for why, as an amp designer, one should care about this. But this means nothing to me in the context of this amp. The missing piece is whether the IMD exhibited by this amp meets the threshold for audibility. And nothing you or Cordell says sheds any light on that question.

Ah well, the last few weeks have been a fun little second attempt to try to drag a little science back into understanding of amplifier measurements and audibility.

Is this science, saying something is bad because it suffers from bad measurements, without establishing that the measurements meet the audibility threshold? Aren’t you committing the same error that you inveigh against when you accuse people of rAnKiNg AmPs By SiNaD? Can you point to a study showing that this level of IMD has ever been distinguished in a blind test?

 

[Dougey_Jones]

Truly awesome product, probably worth 3x what they're charging.

 

[ryanmh1]

Is this science, saying something is bad because it suffers from bad measurements, without establishing that the measurements meet the audibility threshold? Aren’t you committing the same error that you inveigh against when you accuse people of rAnKiNg AmPs By SiNaD? Can you point to a study showing that this level of IMD has ever been distinguished in a blind test?

Again, bad 15kHz THD is just an indicator of a potential problem. Maybe it's fine, maybe not. Your money, your gamble. Buy this for whatever the feature set is, not for the "great" technical performance of the amplifier, which does not exist.

 

[amirm]

Are you planning on testing the phono stage of the ultra too? Have only seen subjective reviews of the phono functionality.

Sure.

 

[audioje]

Could have been better but came out even better than my initial expectation. This will be an excellent gift to many "old" audio fans who are holding on to their beloved passive speakers. Will get one for the reason!