SMSL M500 DAC and HP Amp Review

[Tks]

Hello.
Can't to find about volume control. Is it bitperfect or not?

John, maybe you can correct me but, the way I imagine it...

The most you should worry about this, is if your source is is capable of processing or outputting bit-perfect (which shouldn't be an issue if you run WASAPI or ASIO with no DSP in the pipeline). Volume control on-device though is pretty pointless to worry about with respect to it being "bit perfect" the moment you don't output full-scale. I wouldn't even understand how that would even work exactly speaking since all volume is essentially 'attenuated' at some point before it reaches you in practice, since you usually set volume to a certain level - unless you output full scale with no voltage gain or "unity gain" from an amp section, which sounds like a way to blow your ears away or something.

So if your device has digital-out, I suppose bit-perfect processing and handling makes sense while it's in the digital domain. Once it's out of this domain, or something besides full-scale output (whether due to volume setting, or due to DSP, or whatever else) bit-perfect ceases to exist for all intents and purposes.

At least that how it seems to be when I try to comprehend how it all works.

 

[Aporus]

John, maybe you can correct me but, the way I imagine it...

The most you should worry about this, is if your source is is capable of processing or outputting bit-perfect (which shouldn't be an issue if you run WASAPI or ASIO with no DSP in the pipeline). Volume control on-device though is pretty pointless to worry about with respect to it being "bit perfect" the moment you don't output full-scale. I wouldn't even understand how that would even work exactly speaking since all volume is essentially 'attenuated' at some point before it reaches you in practice, since you usually set volume to a certain level - unless you output full scale with no voltage gain or "unity gain" from an amp section, which sounds like a way to blow your ears away or something.

So if your device has digital-out, I suppose bit-perfect processing and handling makes sense while it's in the digital domain. Once it's out of this domain, or something besides full-scale output (whether due to volume setting, or due to DSP, or whatever else) bit-perfect ceases to exist for all intents and purposes.

At least that how it seems to be when I try to comprehend how it all works.

Sure. I'm talking about the case when my computer transmits a signal via USB via WASAPI or ALSA, that is, with high accuracy.
And my question was how does the M500 adjust the volume? If this is a digital adjustment, is it due to signal degradation and a decrease in its bit depth?

 

[Tks]

Sure. I'm talking about the case when my computer transmits a signal via USB via WASAPI or ALSA, that is, with high accuracy.
And my question was how does the M500 adjust the volume? If this is a digital adjustment, is it due to signal degradation and a decrease in its bit depth?

Well, it's tough to know for SURE, but I guess without a "bit test" like the RME has, I wouldn't know how to properly test for bit-perfect without doing a loopback or something.

As for how it adjusts volume, err, all recent AMP+DAC combo's I've seen have been basically digital volume, I don't know if this one is, but I really don't know of any off the top of my head that aren't. With that said, if it is digital, any signal output that isn't full scale, can be assumed to basically not be bit perfect as with any other digital volume controlled device (this seems true by definition with how all digital volume is controlled everywhere as far as I know). But if you're outputting with volume set to full scale output, then it should be bit perfect through and through.

 

[JohnYang1997]

Sure. I'm talking about the case when my computer transmits a signal via USB via WASAPI or ALSA, that is, with high accuracy.
And my question was how does the M500 adjust the volume? If this is a digital adjustment, is it due to signal degradation and a decrease in its bit depth?

Like I said. Just forget it. No matter how you control the volume, as long as it's not an analogue preamp or hybrid like element x /adi2dac, you will degrade SNR. You reduce 10dB volume you lose 10dB SNR. Forget about bit perfect. It's meaningless.

 

[Aporus]

Well, I wondered if ESS or SMSL had come up with some way to properly adjust the volume. As, for example, J. River's MEDIA JUKEBOX increased the bit depth to reduce losses from volume control in the player. After all, ESS also writes something about a special software approach to volume control in ESS 9038PRO:
Feature
Programmable volume control ramp-rate with +18 dB option
Benefit
Simplifies system software

 

[JohnYang1997]

Well, I wondered if ESS or SMSL had come up with some way to properly adjust the volume. As, for example, J. River's MEDIA JUKEBOX increased the bit depth to reduce losses from volume control in the player. After all, ESS also writes something about a special software approach to volume control in ESS 9038PRO:
Feature
Programmable volume control ramp-rate with +18 dB option
Benefit
Simplifies system software

There's none. And Jriver's approach won't escape the reality. The only "proper" way is to directly configure the volume of the DAC chip and use the internal volume control in the chip.
But in real world measurements these made no difference.

 

[scherbakov_al]

It is necessary to somehow come up with a way to check whether the bitness degrades or not when adjusting the volume.

 

[JohnYang1997]

It is necessary to somehow come up with a way to check whether the bitness degrades or not when adjusting the volume.

You decrease 1dB level you lose 1dB SNR. No matter what volu control is used. If you decrease 6dB in level you lose 1bit. There's no way around it. And it's not subtract from the precision of the volume control but the whole dac. Say a dac with 120dB snr which is 20bit. You get 19bit left when decrease 6dB in level.

 

[scherbakov_al]

Let's say there is 120 dB .. that's about 20 bits. The SMSL regulator has 40 positions. If I listen in the "2" position of the volume control i.e. the output will be a one-bit signal. It will just sound like digital crackle. But that doesn't happen. And I think that the music does not lose quality when adjusting the volume .. well, in any case, it does not noticeably lose.

 

[JohnYang1997]

Let's say there is 120 dB .. that's about 20 bits. The SMSL regulator has 40 positions. If I listen in the "2" position of the volume control i.e. the output will be a one-bit signal. It will just sound like digital crackle. But that doesn't happen. And I think that the music does not lose quality when adjusting the volume .. well, in any case, it does not noticeably lose.

2 position is 1/20th the level of max volume. That's not 1bit left but -26dB which is still about 16bit.

 

[Aporus]

2 position is 1/20th the level of max volume. That's not 1bit left but -26dB which is still about 16bit.

Yes, but then, as scherbakov_al said, if we lower the volume to position 2, then we will reduce volume 19x2 = 38 points, which will leave only 1 bit. It would be impossible to listen to such a signal, but we do not observe such a strong degradation.

 

[Jimbob54]

Yes, but then, as scherbakov_al said, if we lower the volume to position 2, then we will reduce volume 19x2 = 38 points, which will leave only 1 bit. It would be impossible to listen to such a signal, but we do not observe such a strong degradation.

Read what John said again. I would suggest he knows what he is talking about.

 

[Dexter_prog]

Is your amp floating or grounded? I had a hum on headphones whenever usb was connected even when the m500 was not plugged in and solved it by grounding the m500.

amp is grounded (3 pin). How did you ground the m500?

Hi, Oklei, still waiting for this reply

 

[JohnYang1997]

Yes, but then, as scherbakov_al said, if we lower the volume to position 2, then we will reduce volume 19x2 = 38 points, which will leave only 1 bit. It would be impossible to listen to such a signal, but we do not observe such a strong degradation.

You lose 1bit once you half the output level. To output a 1bit signal you need to output at 0.0002% of max output not position 2.
You get twice as much information when you add a bit not just 1 point.
20bit = 2^20 not 2*20

 

[NorthGraves]

Too bad there isn't a "DAC only" mode, to remove the volume control from the equation completely....like in Toppind D90 for example.

 

[Jimbob54]

Too bad there isn't a "DAC only" mode, to remove the volume control from the equation completely....like in Toppind D90 for example.

There is - turn it to 40 and dont touch it. Thats all the D90 DAC mode is - fixes volume at the top (or should I say disables attenuation down)- this also allows DSD.

 

[NorthGraves]

I meant completely disable/lose the preamp section.
I have no use for it anyways.

 

[Veri]

There is - turn it to 40 and dont touch it. Thats all the D90 DAC mode is - fixes volume

Eyup

 

[Jimbob54]

I meant completely disable/lose the preamp section.
I have no use for it anyways.

There is no preamp section- no extra circuits that can be bypassed- switching the D90 to DAC mode isnt taking anything out of the signal chain- just disabling the ability to reduce the volume- I'll confess to not understanding where in the signal path that happens though

Here is where @JohnYang1997 tells me I am totally wrong- but I think Im just remembering a previous post of his.

EDIT- here - he is talking about e30 but pretty sure applies to d90 too https://www.audiosciencereview.com/forum/index.php?threads/topping-e30-dac-review.12119/post-481519

 

[Oklei]

Hi, Oklei, still waiting for this reply

I grounded the M500 by grounding the raspberry pi attached to it via USB (connected the 5V ground to earth). But if you connect it to a grounded amp it should be theoretically already grounded.