WiiM Ultra Streamer Preamp Review

[Joffy1780]

Thanks for that, and you are right, I did partially misunderstand your post. I appreciate your explanation.

I also don't really understand it ( ) and I'm hoping that some members will comment from a technical point of view. Is this something that applies to all digital volume control, or just to the WiiM implementation? I find it very strange (not impossible) that this wasn't called out in measurements.

I do, however, stand by my original view that if there is a difference it has to be demonstrated by measurements or by controlled listening.

I really appreciate your reply - that's interesting. I'm off to read more!

https://forum.wiimhome.com/threads/...mprove-digital-volume-control.3063/post-47075
Here is Wiim's, albeit simple, explanation as to how their digital volume control is implemented.

 

[Miguelón]

Is this something that applies to all digital volume control, or just to the WiiM implementation?

All digital volume controls.

In digital domain, the highest volume is 111…..1 and the lowest is 000….0

The times of 0 and 1 are the bit depth: 16 numbers to CD and 24 to DVD or studio recordings.

When you attenuate volume on the digital domain, each number you cancel corresponds to half the “height” of your signal because binary system. This results in approximately 6 dB less volume.

Classical DAC (fixed) to preamp (variable analogue) combination gives theoretically the most transparent results in signal fidelity.

In practice there are systems like oversampling all digital files to max resolution, which is 24/192 in WiiM DSP, to mitigate this loose of information but I don’t know how it works and solve the problem in practice.

If its as I think, even at -60 dBFS you’ll loose 10 bits and keep with 14 effective bit depth.

In my own, and absolutely subjective and maybe wrong experience, as a classical interpreter of piano and chamber music the best enjoyment I hear is by XLR balanced and fix volume through an external DAC which receives data by usb output of the WiiM.

The difference between XLR and RCA maybe due to poor implementation of RCA section on my DAC as was suggested.

The other part I believe is audible and to complex tracks very evident, because in my Ifi Dac I can bypass the preamp section and regulate volume on the digital side.

As the signal is quite strong, 4,2 Vrms, I should attenuate a lot the digital volume and sound as a AAC bad bluetooth… not super bad, but why do it like so if I can do it in my taste.

You can consult “digital volume” and “dBFS” in any audio trustable website library, they are things I ignore.

In studios they always work with the “highest information as possible” principe, because they will perform a lot of treatment to the signal and should preserve room to that

 

[Abdo]

All digital volume controls.

In digital domain, the highest volume is 111…..1 and the lowest is 000….0

The times of 0 and 1 are the bit depth: 16 numbers to CD and 24 to DVD or studio recordings.

When you attenuate volume on the digital domain, each number you cancel corresponds to half the “height” of your signal because binary system. This results in approximately 6 dB less volume.

Classical DAC (fixed) to preamp (variable analogue) combination gives theoretically the most transparent results in signal fidelity.

In practice there are systems like oversampling all digital files to max resolution, which is 24/192 in WiiM DSP, to mitigate this loose of information but I don’t know how it works and solve the problem in practice.

If its as I think, even at -60 dBFS you’ll loose 10 bits and keep with 14 effective bit depth.

In my own, and absolutely subjective and maybe wrong experience, as a classical interpreter of piano and chamber music the best enjoyment I hear is by XLR balanced and fix volume through an external DAC which receives data by usb output of the WiiM.

The difference between XLR and RCA maybe due to poor implementation of RCA section on my DAC as was suggested.

The other part I believe is audible and to complex tracks very evident, because in my Ifi Dac I can bypass the preamp section and regulate volume on the digital side.

As the signal is quite strong, 4,2 Vrms, I should attenuate a lot the digital volume and sound as a AAC bad bluetooth… not super bad, but why do it like so if I can do it in my taste.

You can consult “digital volume” and “dBFS” in any audio trustable website library, they are things I ignore.

In studios they always work with the “highest information as possible” principe, because they will perform a lot of treatment to the signal and should preserve room to that

and using the fixed output on the Wiim Ultra doesn't solve this?

 

[Mort]

and using the fixed output on the Wiim Ultra doesn't solve this?

Not if we need the Wiim for volume control

 

[Joffy1780]

From Wiim - Our volume table is 8-bit, and considering the maximum bit-depth is 24-bit, we employ 32-bit processing for volume control to avoid any loss in precision.

 

[Abdo]

Not if we need the Wiim for volume control

Yes, I understand, this is my biggest problem, because I use the Wiim exactly to control the volume that goes to the 30-year-old MA6800, which is completely analog, it even has a remote control, but it works very badly, most of the time I'm in the office, kitchen and I want to increase or decrease the volume, and then I have to go to the McIntosh to do it. And from what they're saying, this loss occurs even if I return with my CXN V2... or would there be some DAC that I could control the volume from the iPhone without this loss?

 

[somebodyelse]

Not offended at all, but think there’s a little miss understanding on my post.

Each 6 dB you go down on the WiiM remote or the WiiM knob, or the WiiM app you will loose 1 bit of information.

This is a fact, not an opinion. And is true to every DAC, no matter the construction. You can in someway attenuate this by over sampling all to 24 bit/192 kHz which all modern DACs do.

But you still retouch and loose information as down as you low the volume, and increase the noise.

With a bit perfect (or close to bit perfect if you equalize some modes by lowering gain at the desired frequencies) you will send the most of the original digital data as possible.

The difference is not a game changer, many tracks have enough data at 12-13 bits to be totally satisfactory, but complex recordings (I mean many instrumentals playing at same time, tiny dynamic mattering, high dynamic range between sections) maybe desirable to have a true preamp (voltage analogue attenuator in this case) to preserve the most of the original. As an extreme, a 16 bit CD played at -60 dBFS sounds like a bad bluetooth.

I find simplicity very attractive, but WiiM lack a good preamp section: only works at 2, 1, 0.8, 0.5, and 0.2 mV and that’s all.

At best, in my setup I can choose the 0.5 V rms signal output and keep the digital volume at 85% or more, still I don’t exactly how much this is in terms of dBFS

POST EDITING: It would cost barely nothing to WiiM team to put an analogue volume knob on the front of the hub, and let the remote or the amp to work digitally. I was quite deceived when I learned my 400€ all-in-one was only a streamer-DAC. I don’t think they can consider that is a DAC-preamp because lacks of analogue section. One can always choose its best preference to treat signal with the 3 block DAC, preamp, amp…

There are other threads on digital volume control where it is explained why this is a non-issue in reality, with perhaps a few corner-case exceptions. Essentially if you can't hear the noise from the DAC then anything that is lost in theory is inaudible in practice. In your CD example 48dB of the attenuation comes without loss as the output would be 24 bit. Anything that is 'lost' is below -144dBFS, well below the noise floor of the DAC. If you can't hear the DAC's noise you certainly can't hear what's been lost.

 

[Miguelón]

As WiiM specifies 32 bits is wide enough to don’t subtract any audible influence even at -50 or -60 dBFS digital volume.

This invalidates my argument, since no meaningful information is lost on the process.

I will repeat tests at home with my girlfriend changing connections and me looking oposite side. Is not very scientific but should be enough to loose references one matching volumes.

In this case only the bad implementation of the RCA at the Ifi DAC, or maybe psychological effect knowing the basic process of attenuating volume digitally.

 

[Miguelón]

There are other threads on digital volume control where it is explained why this is a non-issue in reality, with perhaps a few corner-case exceptions. Essentially if you can't hear the noise from the DAC then anything that is lost in theory is inaudible in practice. In your CD example 48dB of the attenuation comes without loss as the output would be 24 bit. Anything that is 'lost' is below -144dBFS, well below the noise floor of the DAC. If you can't hear the DAC's noise you certainly can't hear what's been lost.

Yes, seem I’m still on formation on basic digital signal, and yet not study oversampling techniques. I just calculated 16 bit at the only information can be treated.

But no matter the rational argument I try to cancel my conviction that direct WiiM RCA => Active monitors should sound perfectly transparent I cannot avoid feeling my best perception with the external DAC and bit perfect

 

[Soniclife]

https://forum.wiimhome.com/threads/...mprove-digital-volume-control.3063/post-47075
Here is Wiim's, albeit simple, explanation as to how their digital volume control is implemented.

I read that as what they are doing when you use the digital out, not what happens when you use the analogue out. The volume control for the analogue out should be handled by the dac chip these days, they have extra tricks available to them beyond changing the numbers.

 

[Soniclife]

Yes, seem I’m still on formation on basic digital signal, and yet not study oversampling techniques. I just calculated 16 bit at the only information can be treated.

You haven't factored in dither, which should always be used when reducing volume or bits digitally.

What Is Dithering in Audio?

In this piece you’ll learn what dithering is, why you need to dither, how it improves dynamic range, and why dithering isn’t masking anything.

www.izotope.com

24/192 Music Downloads are Very Silly Indeed

people.xiph.org

With dither this is beyond a non issue.

 

[Miguelón]

I read that as what they are doing when you use the digital out, not what happens when you use the analogue out. The volume control for the analogue out should be handled by the dac chip these days, they have extra tricks available to them beyond changing the numbers.

No. From this I’m quite sure that only algorithms are used in the digital signal to vary volume, whatever the output is used.

I suppose that they exist some way to change strength of a signal with transistors without moving parts, and not altering digital but there are not implemented on audio gear.

WiiM has voltage discrete values from 2 to 0,2 Vrms in 5 steps. Mine is adjusted on 0,8 Vrms to better match the Genelec G Three and use high digital volume.

The problem of loss on quality signal with digital attenuation and introducing new distortions is not totally solved.

As far as I know, the most clean path possible today is DAC => preamp (or monitor control) => amp.

Is what is used on professional facilities, and to unify voltages they align -20 dBFS with +4 dBU to keep maximal digital information and 24 dBFS of headroom to avoid clipping (maximum signal accepted is 24 dBu by pro gear)

 

[Joffy1780]

I read that as what they are doing when you use the digital out, not what happens when you use the analogue out. The volume control for the analogue out should be handled by the dac chip these days, they have extra tricks available to them beyond changing the numbers.

It is the same for both analogue and digital outputs.

 

[mlsstl]

I turned in my "audiophile card" a long time ago, but I'm perfectly happy with the WiiM volume control (other than I wish they'd reduce the number of rotations it takes to go from 0 to 100.)

First, in my room, if I check the sound level with nothing playing or making any noise, my sound level meters (have both a phone app and an old Radio Shack analog meter) show the background level is between 30 and 40 dB. My average listening level is rarely more than 85 dB or so, with a few peaks a bit above that thrown in. So, my need for a zillion dB of dynamic range isn't a big priority. It's very easy for anything at the low end of the dynamic range of a recording to end up lost in the background noise.

For me, the accuracy of the volume knob tracking the left and right channels together is more important than losing a few bits at lower volume that are already swamped by the background noise. Digital volume control is much better on this point than ordinary potentiometers, especially at the bottom of the range, and the equal of more expensive stepped resistor pots.

 

[Soniclife]

It is the same for both analogue and digital outputs.

Where do they say that?

 

[Joffy1780]

Where do they say that?

I can't seem to find that, but where do they say otherwise?

 

[Soniclife]

I can't seem to find that, but where do they say otherwise?

It would be against the normal way of doing things, DAC chip manufacturers have this covered, there is little for the designer to do. The digital output isn't part of the dac so would need to be designed by them, unless some SOC they used did it for them. Didn't they change the volume steps for the digital output at some stage with firmware?

 

[Joffy1780]

It would be against the normal way of doing things, DAC chip manufacturers have this covered, there is little for the designer to do. The digital output isn't part of the dac so would need to be designed by them, unless some SOC they used did it for them. Didn't they change the volume steps for the digital output at some stage with firmware?

@WiiM Team could you perhaps clarify?

 

[antcollinet]

but the problem is the “preamp”.

Really?

What problem is that? Have anything to back. your statement up?

 

[antcollinet]

All digital volume controls.

In digital domain, the highest volume is 111…..1 and the lowest is 000….0

The times of 0 and 1 are the bit depth: 16 numbers to CD and 24 to DVD or studio recordings.

When you attenuate volume on the digital domain, each number you cancel corresponds to half the “height” of your signal because binary system. This results in approximately 6 dB less volume.

Classical DAC (fixed) to preamp (variable analogue) combination gives theoretically the most transparent results in signal fidelity.

In practice there are systems like oversampling all digital files to max resolution, which is 24/192 in WiiM DSP, to mitigate this loose of information but I don’t know how it works and solve the problem in practice.

If its as I think, even at -60 dBFS you’ll loose 10 bits and keep with 14 effective bit depth.

In my own, and absolutely subjective and maybe wrong experience, as a classical interpreter of piano and chamber music the best enjoyment I hear is by XLR balanced and fix volume through an external DAC which receives data by usb output of the WiiM.

The difference between XLR and RCA maybe due to poor implementation of RCA section on my DAC as was suggested.

The other part I believe is audible and to complex tracks very evident, because in my Ifi Dac I can bypass the preamp section and regulate volume on the digital side.

As the signal is quite strong, 4,2 Vrms, I should attenuate a lot the digital volume and sound as a AAC bad bluetooth… not super bad, but why do it like so if I can do it in my taste.

You can consult “digital volume” and “dBFS” in any audio trustable website library, they are things I ignore.

In studios they always work with the “highest information as possible” principe, because they will perform a lot of treatment to the signal and should preserve room to that

And here is why non of that matters.

Dac chips are doing the volume control in either 24 bit or 32 bit DSP. All the bit depth gives you is low noise floor. 16 bit audio has a (digital) noise floor around -96dB. 24 bit around -144dB. 32 bit processing results in a noise floor around -192dB.

In reality though those numbers are not the important ones. Because the analogue electronics in the output stage of even the best measured DACS is not achieving dynamic range of better than about -130dB. Let's say -115dB is typical for a good DAC - eg the Topping D10s at $100. So even the lower spec DACS with a 24bit DSP pipeline - have lower digital noise floor than the analogue noise floor of the output stage.

But even this analogue noise floor is still lower than the level of audibility, assuming your maximum volume level is below that 115dB. In reality you could go 30dB above that, and any DAC noise will still be lower than your room noise floor.

And here is the important thing. Turning down the volume digitally doesn't increase the noise floor, it just reduces the signal. Just like listening to a quiet part of the music.

So If you can't hear the noise at 0dbFS, then you can't hear the noise also at -100dBFS or -150dBFS - the noise is inaudible.


So it doesn't matter that you are "losing resolution" by turning down the volume digitally, because the noise remains inaudible.