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

[bodiebill]

Not saying that I tried very many, but the first preamps I was happy with for my Lampizator DAC were LDR (Light Dependent Resistor) passive preamps: Lightspeed Attenuator and Stereo Coffee DIY. Both really affordable. I never achieved that quality with software VC.

[bodiebill]

INPUT 1 => DAC => INPUT 2 => PREAMP => OUTPUT

 

In this case the preamp, indeed, cannot improve the fidelity of INPUT 1, but it could improve the fidelity (relative to INPUT 1) of INPUT 2, so that OUTPUT brings us closer to the fidelity of INPUT 1. Or is this too cryptic?

[bodiebill]

One practical difference between

 

(1) software VC into DAC (no preamp), versus (2) DAC + preamp

 

is that -- as DAC's often produce a slight hum -- this hum can become intolerably loud with (1) as the attenuation is before the DAC and does not affect the hum, but is mitigated with (2) as in that case there is attenuation after the DAC.

 

So (2) should be quieter. Correct?

[bodiebill]

On 2/7/2020 at 11:57 PM, Miska said:

Hum is usually due to ground currents. So one needs to check out the overall system grounding layout at that point...

 

Indeed. However I guess, even without hum, DAC into preamp will have a 'blacker background' than software VC into DAC (no preamp).

[bodiebill]

8 hours ago, Miska said:

Why would it be? For most cases, from technical perspective that shouldn't be the case.

 

When I output data to a DAC, the digital noise floor in audio band is roughly 100 dB below the analog noise floor.

 

But I don't have hum or other noises, just dead silence if I put my ear next to the speaker.

 

OK, and the analogue preamp itself could also add to the hum. So time for me to experiment rather than theorise.

[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.

[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.

[bodiebill]

10 minutes ago, barrows said:

There is not any mystery here, these things are well understood.

 

Theory is made to be well understood. Reality (read: perception), however, especially in audio, often is at odds with theory. Which for some is disturbing, for others (me included) a relief. Ratio is overrated.

[bodiebill]

deleted 🙂

[bodiebill]

Some of us believe that digital is in principle flawed and that, even at higher resolutions, some essential information is missing from the signal. Compare it to film cameras of the first decades of the 20th century.

Is it unthinkable that some coloration can correct these flaws and heighten our sense of 'being there'?

See this enhanced/distorted/smoothened/colored clip of New York in 1911:

 

 

[bodiebill]

21 minutes ago, hopkins said:

Using optical fiber and thinking it actually provides isolation is complete nonsense because you are still putting an ethernet chip inside the DAC. 

 

There are no measurements to back up the fact that this is a superior solution. 

 

I agree. And it is not absolute, but all depends on someone's requirements:

 

If one absolutely need network for whatever reason and a heavy lifting PC for HQPlayer upsampling, then the dual PC endpoint solution can bring benefits.

 

However there is a possible world in which one does not need network and does offline file upsampling, moving the hard work to outside the real time realm. There a low footprint PC (or even better: a minimalist SD transport) without network connection will bring even greater benefits.

 

Don't we all agree that network activity to some degree degrades SQ?

 

[bodiebill]

8 minutes ago, barrows said:

Do you mean other Network activity, separate from the activity of playing the music file?

...

If you mean the network activity only associated with playing the music file, I would suggest that optical fiber cable isolates the Renderer and DAC from that.

 

In my experience both have their effect, the second more than the first. But even when I played files locally, not via the network but with network attached, I got better sound when removing the network connection, alas losing my remote access of course.

[bodiebill]

3 minutes ago, barrows said:

Interesting, was this with an optical fiber Network connection?

 

Yes, with optical isolation also, using a fiber NIC in the endpoint. However in the end I changed back the last downstream part with copper ethernet as to my great surprise this clearly sounded better to my ears.

 

3 minutes ago, barrows said:

And did you ever try and verify the test with someone else removing the Network connection while you listened, without your knowledge, and were able to accurately discern the exact moment the connection was removed?

 

No, never did that so I cannot disprove placebo 🙂

However I am usually not comparing short term A/B but long term effects by living with the setups for days, being aware of the frequency of goosebumps or at least the amount of joy and involvement.

Sometimes this makes me conclude the opposite of the initial A/B assessment.

For instance if A has a higher level of detail I initially think it is better, but when I notice that I can listen to B much longer and stay involved, I choose B.

It is all very intuitive (sorry) so perhaps hard to replicate for others.

 

For years I had a complete optical network between server and endpoint, and was happy as in my mind optical was almost synonymous to noise isolation. Now I think that was an example of placebo, as when I went back to copper for the last stretch, just to try, I saw had been wrong, at least in terms of perceived SQ.

 

[bodiebill]

1 hour ago, barrows said:

I really do not want to be promoting specific products here, and have tried to avoid doing so.  But, I would suggest that actual Renderers purpose built for audio, do have a technological (not imaginary) advantage in terms of noise versus general commercial computer gear.  Built for audio products generally have much more room in the BOM to spec more expensive components (like many ultra low noise linear regulators) and more sophisticated layouts, with more isolated sections.  For just a single example of what I mean: how many commercial main boards used as a renderer have a dedicated LT 3045 regulator, just a few mms from the USB output for the USB output power leg?

i agree that long term listening is often better for really evaluating a change, although it can be very difficult.  For me, short term comparisons often lead to "ah ha!" moments, where there "might" be a "difference", but the difference in often a sideways one, and not necessarily an improvement.  We humans seem especially subject to interpreting any change as "exciting" and therefore concluding it is better; long term listening seems to even out these first impressions, especially when a wide variety of music is tssted.  I always try and verify any conclusions based on short term A/B style comparisons with long term listening.

 

Well said. And I agree about what you say about renderers built specially for audio.

Computer audiophile DIYers spend a lot of time and money to remove or mitigate the shortcomings of devices built for general use. In a top down approach, PC's have to be stripped down, network- and other connections to be made noise free, and OS'es tamed. You would expect the bottom up approach of dedicated audio products to give better results. That is not always the case though.

 

 

[bodiebill]

Just got this passive preamp and I love it:

https://www.ecdesigns.nl/en/blog/svc24

Shunt based and no need for a power supply!

 

The SVC24 sounds very similar (i.e. seems not to add its own sound signature) as the DIY Stereo Coffee LDR passive preamp it replaces, but is a tad more relaxed/quieter.