My WiiM Pro Plus 2nd sample test

onlyoneme

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Note: due to the fact that my sample unit had significant problems with various PSUs and this was fixed with the FW update, the entire post has been corrected and updated with the most up-to-date measurements.

As you can see I finally got the second sample of the Pro Plus with promised improvements of measurements, especially in low frequencies. Time to find out what has changed.

I will use mostly the same gear as before. The biggest change is an introduction of the Cosmos Scaler, a buffer with variable gain to help get more precise results in stepped measurements. And to attenuate the impact of ESS hump for ADC Cosmos.
The second change is using Sbooster LPS as the main PSU for measurements as I believe that using such kind of power supply units is the most common path of upgrade in the "audiophiles" world.

My methodology will differ a bit. This time I'm gonna use also DeltaWave software to investigate an impact of different interconnect cables as well as power sources.

At the moment just one graph to show distortions vs frequency for -3 dBFS sweep signal:

1697447790500.png



As both units behave very similar in many aspects (for example output voltage levels) I will focus on differences only.
Both units were powered by Sbooster LPS unless otherwise noted, with the analog output level set to 2 Vrms.

I suggest to look here for details on previous measurements of the first unit:



FFT single measurements

Visible advantage in multitone measurement:
1697448057778.png



Reduced second harmonics level gives slightly better results with 1 kHz sine wave:
1697448222583.png

SINAD increases by 3 dB from 112.8 to 115.8. Dynamic range keeps the same level in range 118.9 - 119.1 dB.

As improvements are mainly for low frequencies, differences are clearly visible in the SMPTE test for IMD / low frequency distortions:
1697448428735.png

IMD reduced from -93.6 dB to -105.5 dB. TD+N reduced from -99.6 dB to -112 dB.


FFT stepped tests

The THD curve as a function of signal level has changed, below for a 40 Hz sine wave signal:

1697448825030.png

And for 1 kHz:

1697448887626.png


IMD level based on the SMPTE test:

1697449039060.png


All level tests confirm the promised improvement over the first version of Pro Plus.

One remark on plots vs level - distortion values are in dB (Y-axis) relative to the fundamental dBFS level (X-axis).


The THD curve as a function of frequency confirms what we have seen with the sweep signal. This one is for 0 dBFS signal level:

1697449225065.png







Comparisons in the time domain

As pure FFT measurements are boring already, time for something different - combining FFT analysis with time related sample matching.

Let me introduce DeltaWave Audio Null Comparator:


Using this tool I will provide delta audio files for different RCA cable / PSU combinations between both Pro Plus units. In case of cables I will include Mogami 2534 RCA-XLR cable, Mogami 2964 RCA, a stock one included with the Plus and a bit weird Douk Audio / Nobsound RCA with high 900 pF/m capacitance. As a power source I will use Sbooster LPS, Allo Nirvana SMPS, Xiaomi powerbank and the Plus' stock charger.

The reference audio file will be "this wav file evaluated by means of Audio DiffMaker":


First batch: WiiM Pro Plus "PCB-3", WiFi, Sbooster, left channel differences - cables

And second batch: WiiM Pro Plus "PCB-3", WiFi, Mogami 2534, left channel differences - power sources


In my opinion, replacing the mentioned analog interconnects or power sources does not produce any audible effect. The differences generated in the form of delta files are not large enough to affect audibility.

DeltaWave introduces PK Metric measure which is designed to be perceptually-weighted over time, kind of a synthetic metric to evaluate the audibility of captured differences. Further details are available here:

The worst measured PKEM for different cables was as below

1697463354008.png

and for PSUs

1697469762184.png

while audibility for results close to -60 dB or a bit higher is "debatable".


Finally, there is an audibility comparison between the 2 Plus revisions. The same setup - Sbooster, WiFi, Mogami 2534, 2Vrms output, no EQ, fast linear phase filter, etc.


The measured PKEM is as below

1697465376603.png

and it will be even lower when sound level matching is applied

1697465539038.png

Based on that (and previous measurements) I would stay on the position that it's unlikely to hear differences between these 2 revisions.
 
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As you can see I finally got the second sample of the Pro Plus with promised improvements of measurements, especially in low frequencies. Time to find out what has changed.

I will use mostly the same gear as before. The biggest change is an introduction of the Cosmos Scaler, a buffer with variable gain to help get more precise results in stepped measurements. And to attenuate the impact of ESS hump for ADC Cosmos.

My methodology will differ a bit. This time I'm gonna use also DeltaWave software to investigate an impact of different interconnect cables as well as power sources.

At the moment just one graph to show distortions vs frequency for -3 dBFS sweep signal:

View attachment 2644


Stay tuned.
my position is often misunderstood....
but I do not regret having insisted on what was clearly a ""serious"" problem...
maybe the wiim team can enlighten us now on what should be done? firmware? filter akm? hardware?

I await the sequel with interest ,-)
 
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my position is often misunderstood....
but I do not regret having insisted on what was clearly a "serious" problem...
maybe the wiim team can enlighten us now on what should be done? firmware? filter akm? hardware?

I await the sequel with interest ,-)
The same linear phase fast filter used above. FW of the second unit is slightly newer - 4.8.530553, but I've made a measurement also with an initial FW which was the same as of my first unit - improvement was visible also when the same FWs were used. WiiM team said already that changes affect the hardware itself.
 
Would it be possible to replicate the below measurements for wiim pro plus ? If it is no trouble for you …

I would like to be able to measure jitter in similar way, but I do not have a required equipment. The problem is called "not having enough money" ;)
As for the second measurement, I don't know exactly what the details mean. I'll try to find out.
 
I would like to be able to measure jitter in similar way, but I do not have a required equipment. The problem is called "not having enough money" ;)
As for the second measurement, I don't know exactly what the details mean. I'll try to find out.
Alright understood…!
 
Alright understood…!
Regarding the second one, I guess that the AC coupled measurement over coax with BW limited to 100 kHz would be somehow similar. Preliminary results: AC rms = 21 mV, AC peak-to-peak = 108 mV.

With additional LPF at 100 kHz results goes down to AC rms = 3 mV, AC peak-to-peak = 24 mV.
 
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Regarding the second one, I guess that the AC coupled measurement over coax with BW limited to 100 kHz would be somehow similar. Preliminary results: AC rms = 21 mV, AC peak-to-peak = 108 mV.

With additional LPF at 100 kHz results goes down to AC rms = 3 mV, AC peak-to-peak = 24 mV.
The graph in goldensound measurements spans from 20hz to 100khz . So what is the difference between bandwidth limited to 100khz and low pass at 100khz?
 
The graph in goldensound measurements spans from 20hz to 100khz . So what is the difference between bandwidth limited to 100khz and low pass at 100khz?
BW limiter is made in the hardware layer on my scope. Low pass filter is applied as an additional software function.
 
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the problem with this story because the difference is so noticeable...(there was indeed a defect),
it will have led to confusion...

particularly on the machines which have been entrusted to the "reviewers", or on the first batches marketed (already modified?)...

it's a bit stupid and not trivial
 
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Is sample of the Pro Plus with promised improvements of measurements already available for sale?
 
well no...neither of them made any reference to the differences.. at this moment they dont have the revision...
it was a posture that would mean that it would not be heard this problem of difference in thd between 1k and 50-100hz... "according to them"..
we even had wiim explaining that these distortion figures were normal and admitted not akm... for a few days later to modify and return to coherent and unrelated figures... etc.
there was a problem..it was observed..and the solution has since been found..so much the better
 
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well no...neither of them made any reference to the differences.. at this moment they dont have the revision...
it was a posture that would mean that it would not be heard this problem of difference in thd between 1k and 50-100hz... "according to them"..
They didn’t need revised hardware to state that the ”anomaly” they saw in their original test measurements didn’t have an audible impact.

I suspect that WiiM made the minor hardware change so that the Pro Plus would get a clean bill of health in the ASR measurement stakes, but that in reality and for the majority of users who buy one to listen to and not measure, it’s irrelevant.

You are free to, and no doubt will, disagree.
 
we can only use the figures when it suits us on the marketing side...
there was a DRC problem...
there was a hardware problem...
that's all (and what's more it wasn't difficult to sort out apparently )....
with your approach...neither one nor the other would have been resolved... (you made me look like a boring idiot etc in both cases...but in the end?)


frankly the color story of the wimp amp...?
 
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My statement was that it was unlikely anyone would hear the difference. And it's still valid as I'm not (yet?) convinced to change my personal opinion. I'll dive deeper into this with an analysis of DeltaWave as part of a comparison between Plus devices.
 
My statement was that it was unlikely anyone would hear the difference. And it's still valid as I'm not (yet?) convinced to change my personal opinion. I'll dive deeper into this with an analysis of DeltaWave as part of a comparison between Plus devices.
You do the most valuable thing . You present the data and devote serious work and time . Your opinion has of course substance . However the most important thing is to have correct and meaningful data which you provide … I don’t want to start an opinion debate but I don’t want any absolute positions to interfere with this .
 
My statement was that it was unlikely anyone would hear the difference. And it's still valid as I'm not (yet?) convinced to change my personal opinion. I'll dive deeper into this with an analysis of DeltaWave as part of a comparison between Plus devices.
but I respect that..a position or reality concerning you..yours..

but you have a very interesting situation..
namely being able to now listen to these two versions more and not just guess...
the mesureaments are that is clear...but subjectively?
that's funny...
;-)
(we will find some people explaining that they do not hear any difference between a mini and pro "plus"... ;-) )

your measurements will have made it possible to debug...it's already huge...
 
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