Differences in sound: DAC vs. DAC + Pre-amplifier

[Kimo]

36 minutes ago, barrows said:

 

I would expect a manufacturer who manufactures and sells a preamp to say this.

 

 

You can find Martin Mallinson's video from RMAF on Youtube.  Be careful how you interpret it though. if you pay attention, what he is saying is that analog volume control has an advantage IF you need to use tons of attenuation.  A digital volume control is demonstrably more transparent than an analog one as long as it is not used at very high levels of attenuation.  For example, the ESS chip's volume control runs at 32 bits, so, with a 24 bit source file you have 8 bits extra for volume before you lose ANY resolution.  8 bits means that you can have attenuation up to (8*6dB) -48 dB.  The other potential drawback with digital volume control is thta it does not reduce the noise floor as the volume is lowered, again, this is a non-issue unless you use very high amounts of attenuation, and have a noisy source, both are non-issues in the vast majorities of real world systems.

 

Call Benchmark and they will describe to you in detail why they achieve better performance with a preamp.  I don't think that they will pitch their preamp.  They didn't when I spoke to them, but time is gettin harder.

 

Here is the link to the ESS paper.  It is an old one.  Maybe not as relevant these days.

 

http://www.esstech.com/files/3014/4095/4308/digital-vs-analog-volume-control.pdf

 

I have always found them to pretty much suck, but maybe I just did not hear a decent one.

 

 

 

[Kimo]

1 hour ago, Miska said:

 

Problem is that for example ESS has inherent series resistance of 600 ohm which defines the thermal noise limits. With analog volume control you are going to have hard time finding one that has equal or less inherent resistance. In addition you'll need additional analog buffer/impedance converter sections which also will have some noise and distortion.

 

 

 

 

My DAC employs a log ladder network to create a constant impedance passive attenuator, for whatever that is worth.  I can't tell the difference between fixed mode or the attentuator.   I tried but failed.

 

My amp has a pretty high SNR, so apparently it is possible to make an analog volume transparent to me at least with an ESS chip.

[barrows]

14 minutes ago, Kimo said:

Call Benchmark and they will describe to you in detail why they achieve better performance with a preamp.  I don't think that they will pitch their preamp.

 

I have no need of any convincing, I have been running amp direct for a few years now, but before I ditched the preamp, I did extensive testing, and only sold my preamp (a rather fine Ayre K5-xeMP) when I was absolutely sure that amp direct was performing better.

[motberg]

7 hours ago, Miska said:

 

Suitable range setting depends on how you use the volume control...

 

 

with a good passive pre in my system (Lightspeed LDR), I am guessing I usually use less than 25% attenuation

Speakers are very inefficient, DAC is 4 x PCM1704UK per channel, possible to 768KHz

I do not think I would damage anything if the DAC full level hit the amp

 

my question is, when using HQPlayer, how to adjust the settings to arrive at the most optimal "bit saturation".

[barrows]

@motberg,  Are you aware that LDR volume controls add lots of distortion?  

[sandyk]

6 minutes ago, barrows said:

@motberg,  Are you aware that LDR volume controls add lots of distortion?  

 

 

IIRC, some years  back, Nelson Pass posted some measurements in DIY Audio highlighting this problem .

[motberg]

8 hours ago, Miska said:

 

Suitable range setting depends on how you use the volume control...

 

Here is real world configuration:

 

Using @ericuco suggestion (thanks!) I set max vol to -10 db

my normal volume level will be a couple db less than max.

 

So - at 44.1/16 -> 176.4 K, HQPlayer vol set at -12db, what am I losing in terms of dynamic range?

Are there any settings available to optimize this (such as increasing bit depth) ?

[motberg]

57 minutes ago, sandyk said:

 

 

IIRC, some years  back, Nelson Pass posted some measurements in DIY Audio highlighting this problem .

The maker has posted also his distortion calculations and seems really low to me....

Not sure if the PS has any effect, but mine is powered by mains regenerator into LPS into 4 x LT3045 regulator

The Lightspeed has been on Stereophile Recommended Components list and gets great comparative reviews.

It certainly subjectively was much clearer to me than my Schiit Saga + in passive mode. (already sold the Saga +)

[sandyk]

1 hour ago, motberg said:

The maker has posted also his distortion calculations and seems really low to me....

Not sure if the PS has any effect, but mine is powered by mains regenerator into LPS into 4 x LT3045 regulator

The Lightspeed has been on Stereophile Recommended Components list and gets great comparative reviews.

It certainly subjectively was much clearer to me than my Schiit Saga + in passive mode. (already sold the Saga +)

 

 I would suggest that you do a Search in DIY Audio for Lightspeed and Nelson Pass to see if you can find the posted measurements  of actual LDRs

[motberg]

4 minutes ago, sandyk said:

 

 I would suggest that you do a Search in DIY Audio for Lightspeed and Nelson Pass to see if you can find the posted measurements  of actual LDRs

I already saw them... I am sure was well below audibility... remember some decimal points and zeros, etc...

[sandyk]

29 minutes ago, motberg said:

I already saw them... I am sure was well below audibility... remember some decimal points and zeros, etc...

 

 Your idea of audibility may not be the same as others who may have more revealing equipment.

 A Preamp/PA often has distortion levels well below that of most volume controls and many attenuators.

For example, both my DIY Class A Preamp and 15W/Ch. Class A Power Amplifier have distortion figures of well below .0006%

 

https://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-passive-preamp-373.html#post2386530  # 3726 

The quoted figures are far from inaudible when combined with a low distortion Preamp/P.A. 

" 0.25 % THD for -20 dB of attenuation."  

 I saw also that George HiFi also went on the defensive : 

" Get your head out of these finite distortion measurements, and listen to what your ears are telling your brain" 

[motberg]

4 hours ago, sandyk said:

 

 Your idea of audibility may not be the same as others who may have more revealing equipment.

 A Preamp/PA often has distortion levels well below that of most volume controls and many attenuators.

For example, both my DIY Class A Preamp and 15W/Ch. Class A Power Amplifier have distortion figures of well below .0006%

 

https://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-passive-preamp-373.html#post2386530  # 3726 

The quoted figures are far from inaudible when combined with a low distortion Preamp/P.A. 

" 0.25 % THD for -20 dB of attenuation."  

 I saw also that George HiFi also went on the defensive : 

" Get your head out of these finite distortion measurements, and listen to what your ears are telling your brain" 

what is the threshold of audibility ?

[sandyk]

3 minutes ago, motberg said:

what is the threshold of audibility ?

That depends on your training, experience,  and the Signal to Noise Ratio of your equipment. Naval Sonar operators can even hear things below the noise floor , as both  Miska and Paul R. can verify

[motberg]

7 minutes ago, sandyk said:

That depends on your training, experience,  and the Signal to Noise Ratio of your equipment. Naval Sonar operators can even hear things below the noise floor , as both  Miska and Paul R. can verify

Any scientific back up to the claim 0.25% THD as tested in your example is detectable by average humans?

[sandyk]

33 minutes ago, motberg said:

Any scientific back up to the claim 0.25% THD as tested in your example is detectable by average humans?

 I suggest that you do some research for yourself for a change. There is plenty of information available on the subject .

[motberg]

36 minutes ago, sandyk said:

 I suggest that you do some research for yourself for a change. There is plenty of information available on the subject .

I have not seen any valid study done where the THD was reported detected at less than .5%. That is why I was asking, since you seem to be sure 0.25% is audible.

 

In any case, it certainly is not the bottleneck in my system.

 

And now that I got HQPlayer setup direct out, I am more convinced that the Lightspeed is more representative of the direct signal than any other preamp I have heard in my system.

[motberg]

On 3/2/2020 at 3:11 AM, barrows said:

Then consider that most volume controls in software are running at 64 bits!

 

 

Thanks, can you please advise a couple software volume control options that you consider well implemented.

[sandyk]

1 hour ago, motberg said:

I have not seen any valid study done where the THD was reported detected at less than .5%. That is why I was asking, since you seem to be sure 0.25% is audible.

 To quote well respected Audio Amplifier designer Douglas Self :

Quote

Digital audio now routinely delivers the signal with less than 0.002% THD, and I can earnestly

vouch for the fact that analog console designers work furiously to keep the distortion in long

complex signal paths down to similar levels. I think it an insult to allow the very last piece of

electronics in the chain to make nonsense of these efforts.

I would like to make it clear that I do not believe that an amplifier yielding 0.001% THD is going

to sound much better than its fellow giving 0.002%. However, if there is ever a scintilla of doubt

as to what level of distortion is perceptible, then using the techniques I have presented it should be

possible to routinely reduce the THD below the level at which there can be any rational argument.

 

Audio Power Amplifier Design Handbook 5th ed. - Douglas Self p.21  Extract

 

Note that he is talking about distortion figures, not 10 , but  >100 times less than you have stated .

[DuckToller]

1 hour ago, sandyk said:

Note that he is talking about distortion figures, not 10 , but  >100 times less than you have stated .

Bonjour Alex,
please allow me to ask, if you believe these figures (0,002%THD) are audible for common audiophiles (60+ years), the majority of whom may not have been able to meet the requirements for the job as Naval Sonar operators even at young age and therefore had to forego the special training associated with it?
Stay safe and sound, DT

[bodiebill]

3 hours ago, motberg said:

And now that I got HQPlayer setup direct out, I am more convinced that the Lightspeed is more representative of the direct signal than any other preamp I have heard in my system.

 

I had the same experience with the Lightspeed Attenuator, and now with the DIY Stereo Coffee LDR preamp. Closest thing to no preamp, and I love the sound.

[motberg]

I just ran AO on the HQPlayer Win2019 GUI NAA machine...

 

Wow.... I was shocked how good this software volume control is using HQPlayer. I have tried other softwares years ago and recently the built in volume control on a Topping D70 and a Gustard A20H without major success (the Gustard was pretty good though).

 

I have not run through all my normal test tracks yet, but my preliminary observations indicate the HQPlayer vol. control has no major audible drawbacks in my system.

 

Thanks to everyone who helped get me this far.... much appreciated....

[barrows]

4 hours ago, bodiebill said:

I had the same experience with the Lightspeed Attenuator, and now with the DIY Stereo Coffee LDR preamp. Closest thing to no preamp, and I love the sound.

From a technical perspective, this is just not true.  For example, a simple passive attenuator like a Goldpoint will be much more transparent than any LDR could ever hope to be.

 

It is OK if you like the sound of an LDR, but please do not make claims about it being transparent, as this is just not the case.  LDRs add large levels of distortion, orders of magnitude greater than that of anty good preamp with simple switched resistor volume control.

 

sandyK has provided the proof.  And this has also been shown every time someone measures an LDR based preamp.

 

Here is some more info on LDR based volume controls:

 

https://neurochrome.com/pages/tortuga-audio-ldr3

 

 

[bodiebill]

5 minutes ago, barrows said:

From a technical perspective, this is just not true.  For example, a simple passive attenuator like a Goldpoint will be much more transparent than any LDR could ever hope to be.

 

It is OK if you like the sound of an LDR, but please do not make claims about it being transparent, as this is just not the case.  LDRs add large levels of distortion, orders of magnitude greater than that of anty good preamp with simple switched resistor volume control.

 

sandyK has provided the proof.  And this has also been shown every time someone measures an LDR based preamp.

 

Here is some more info on LDR based volume controls:

 

https://neurochrome.com/pages/tortuga-audio-ldr3

 

I should have written "Closest thing to no preamp to my ears". I tested with a wav file that I pre-attenuated with software so that I could play it directly from the DAC. And then compared that with the original file attenuated with a few preamps, admittedly not many. My ears (and what's between them) preferred the LDR's.

[Blake]

@barrows can correct me if I am wrong, but I don't think he has issues believing there are people who subjectively prefer the sound with a preamp inserted, he is just speaking from a technical perspective, DAC direct to power amp will be technical "more transparent" which is correct.

 

On the subjective preference, IIRC, Jim Smith has noted in the past that he has subjectively preferred the sound when a good preamp is inserted in the chain, as compared to DAC direct and he has no financial incentive for stating that belief and Jim probably has more experience listening to more systems in more environments than perhaps anyone.  I have read lots of component reviews over the years where the reviewer subjectively preferred a preamp in the chain.  So there are plenty of examples out there.  And of course there are lots of people preferring DAC direct after experimenting.  

 

Also, there is no such thing as a 100% transparent system or component.  So we are talking relative degrees of  transparency here and of course there is the question of whether the reduction in transparency resulting from the insertion of the preamp is audible, and if audible, did the other subjective sonic "improvements" from inserting a given preamp outweigh any loss of transparency.  

[Kimo]

10 minutes ago, Blake said:

@barrows can correct me if I am wrong, but I don't think he has issues believing there are people who subjectively prefer the sound with a preamp inserted, he is just speaking from a technical perspective, DAC direct to power amp will be technical "more transparent" which is correct.

 

 

 

Not according to the guys who make the most transparent electronics in the world, as I pointed out earlier.