the answer is yes. in CD resolution while the volume is controlled by the WiiM into level 1, while you are connected to an external DAC (doesnt matters how (USB,Toslink, Coax)) the issue is audible. but as I said before, I just bought a pre-amp and currently set the WiiM to fixed volume, and just controlling the volume with the pre-amp. this was solved the issue for me.
Issue with Distortion at Very Low Volume When Using WiiM Ultra with External DAC
- Thread starter AssafAviv
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slartibartfast
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I realise that now. It doesn't half get confusing when someone replies to a post meant for someone elseNo, @AssafAviv is the OP.
In particular when "I have exactly the same issue" turns out as "this is a completely different issue".I realise that now. It doesn't half get confusing when someone replies to a post meant for someone else
No personal offense intended, of course. It's just not helpful in the end.
I definitely heard the difference,that's why I then went and done a Google search about it and found this thread,I thought I heard some distortion when I had the wiim connected to my main stereo speaker system so I connected the wiim to my headphone setup and I heard a difference right away when switching between the wiim vs the zen stream connected to a gustard dac,if bits are bits then I shouldn't have heard any difference playing the same track on both streamers,but I did,
I can also confirm that the OP problem described matches 100% my own. I did A/B tests with other gear to confirm. Wiim Support is on my case, happy to share any developments. I hope this issue will get resolved, otherwise I will have to look for another streamer as the experience significantly suffers. 
As soon as digital volume control is applied bits are not bits anymore, naturally. They must be manipulated in one way or the other to change the volume.
There is nothing abnormal here, it's simply a result of digital volume attenuation.
This is probably more obvious on a 16 bits source than a 24 bits one.
The WiiM gets 16 bits amplitude data. Let's say you reduce the volume to 25% of max. This means you are sending to your DAC a 16 bit digital signal where all samples amplitude have been reduced by 4, ie, 2 bits are lost, this is now effectively a 14 bits signal.
The poster says very low volume. Divide by 128 and it's 7 bits you now lost. You now have a 9 bits signal. It *will* distort especially if it's only 44kHz.
If you use the WiiM internal DAC then it's worked around by scaling the samples to 32 bits before attenuation. But that doesn't work if you are sending to the digital output the same bit depth as the source. I'm that case the WiiM can only lost resolution.
The only ways I can think around it are:
* For USB, to use the USB volume control messages to control the DAC own volume (if it supports it) instead of scaling down the bitstream. I don't believe WiiM supports this today.
* To use the option to force the output resolution and aet it to the max (24 bits) which should limit the effects of the loss, but that will only work if WiiM implement the output forced resolution scaling *before* the volume attenuation (I sincerely hope so but I can imagine engineering shortcuts that would make them do it the wrong way around). Sadly scaling frequency is tricky and not great, you really only want to scale bit depth in that case. I don't know if WiiM supports it (travelling away from my device right now so I cant check)
This is probably more obvious on a 16 bits source than a 24 bits one.
The WiiM gets 16 bits amplitude data. Let's say you reduce the volume to 25% of max. This means you are sending to your DAC a 16 bit digital signal where all samples amplitude have been reduced by 4, ie, 2 bits are lost, this is now effectively a 14 bits signal.
The poster says very low volume. Divide by 128 and it's 7 bits you now lost. You now have a 9 bits signal. It *will* distort especially if it's only 44kHz.
If you use the WiiM internal DAC then it's worked around by scaling the samples to 32 bits before attenuation. But that doesn't work if you are sending to the digital output the same bit depth as the source. I'm that case the WiiM can only lost resolution.
The only ways I can think around it are:
* For USB, to use the USB volume control messages to control the DAC own volume (if it supports it) instead of scaling down the bitstream. I don't believe WiiM supports this today.
* To use the option to force the output resolution and aet it to the max (24 bits) which should limit the effects of the loss, but that will only work if WiiM implement the output forced resolution scaling *before* the volume attenuation (I sincerely hope so but I can imagine engineering shortcuts that would make them do it the wrong way around). Sadly scaling frequency is tricky and not great, you really only want to scale bit depth in that case. I don't know if WiiM supports it (travelling away from my device right now so I cant check)
slartibartfast
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Is that true, that digital volume control acts directly on the original 16 bits when using an external DAC? I find it hard to believe. Like you say it would sound awful.
hgo58
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We still don't know how the volume control on the USB output is done. @WiiM Support has not replied.
Anyway, no matter where it's done, a 1% volume level will have a low dynamic range (few bits).
I did try to set my WiiM Ultra to 1% and by turning the amp full up I got fine sound. No distortion but of course not much dynamic. I don't have DAC with USB, so using optical to the DAC.
slartibartfast
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Yup, using 1% volume just seems like system gain is far too high.
It’s your external dac that may be faulty - replace it .
Or your power amp has crazy high gain
This is WAY to low . You must lower the gain in your power amp 20 dB
Optimal sound quality is to have the volume at 40-50 when playing at medium level .
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What else could it do ? Since unless you use fixed resolution, the external DAC shows that it's getting a bitstream with the same resolution as the source.
So you get 16 bits of data, reduce the volume, then send 16 bits of data to the DAC, the only way this can work is by reducing the resolution, ie dropping bits.
Only if you use fixed resolution can you potentially scale to something higher such as 24 bits, then apply volume, and send those 24 bits out.
The only possible saving grace with external DACs would be via USB where it's possible to remotely control the DAC volume instead but we don't know if WiiM uses that capability.
With coax and optical there is no such possibility.
This is why I reduce the gain on my power amp (I could do it via reducing the volume on the DAC too) as to avoid using too low volumes on the WiiM itself
slartibartfast
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Good point
Hi, I suggest you guys to read the following presentation of ESS:
ESS-Digital-vs-Analog Volume control presentation
ESS-Digital-vs-Analog Volume control presentation
That’s 14 years old, and Wiim have already said they work at 32 bit resolution to minimise the impact of volume changes on their 24bit stream. Plus major vendors like Linn (not WiiM
) use digital volume control on their entry level £3k systems all the way up to their £35k flagship digital streamer/amps, so it’s not all bad. Like all things, it depends…
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That Scottish WiiM with one "I" and two "N"s?
slartibartfast
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How does it work when external DACs are used though?
Oops… Linn of courseThat Scottish WiiM with one "I" and two "N"s?
As I've explained in another thread.... it can't
