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

[SoundSparks]

Dear experts:

 

Many DACs have volume control function so they could serve as a DAC or as a DAC + Pre-amplifier.

 

Could you please report on the differences in the sound of your systems in both cases?

 

The latter configuration provides shorter signal path, but how does it effect the sound? What variables are in play here? I am planning my setup and would appreciate your expert advice very much indeed.

 

Please chime in!

[phusis]

@SoundSparks

 

If your only source is digital I'd put my money and effort in seeking out a proper, dedicated DAC/preamp, and disregard a separat hardware preamp altogether. Be aware to pursue items where the preamp section and volume control of the DAC are up to snuff, and this entails a thoroughly executed analogue output stage and power supply, which is especially important when connecting directly to a poweramp.

 

I don't know the limits of your budget, but above mentioned important aspects typically aren't the last word with mid priced (and down) DAC's, why I'd actually recommend you look for used, highend-ish DAC/preamps where more effort is very likely to have been invested in named areas. The claimed technological advancements of DAC chips is somehow exaggerated, I find, and shouldn't keep you from acquiring used high-end DAC/preamps (where the clock section isn't an afterthought either) with some years on their backs. I'm not saying DAC chips haven't seen notable advancement, only that with a poweramp-direct connection you want a very good analogue output stage and PSU in particular. 

 

Via my current, newly acquired BCA Roquefort DAC/preamp (a used, "older" though upgradable highend model), which I've recently compared to the very newly released, mid-priced Auralic Altair G1 DAC/streamer, it's quite obvious the former has a richer, more stable, tonally correct and well-balanced presentation. At its asking price I find the Auralic to be a very capable product (and the streamer section is blessing) with great connectivity options (i.e.: harddrive via USB), but in regards to pure sound quality and connected directly to the poweramp the BCA is simply more analogue and natural sounding. Just my $0.02. 

Compared to separate hardware preamps I've tried out, even via my former less capable DAC/preamp, the challenge to me has always been finding one that was sufficiently transparent and non-restricted (i.e.: without the sensation of it sounding like a "bottleneck" in the chain), and at the price level where this seemed to be less of an issue I've always felt it better to invest elsewhere to see actual sonic gains. 

[Blake]

This is a hotly debated topic and there have been a number of threads on this issue over the years, with some virtual blood spilt.  I've owned and and experimented with all options for volume control- several different DAC's with built-in VC, and all varieties of separate VC's (software only, and lots of different separate preamps- passive, solid state of varying designs and tube) and my experiences have been all over the map.  It is difficult or impossible to draw any absolute conclusions.    

 

Although logic says this should not be the case, I have found that in some cases, but not all, a separate preamp can improve sound quality, namely, sound staging and layering (relatively more 3-dimensional). I am a sound staging nut, so I've gone in the direction of separate preamps.  The key is, balancing the sound staging improvements with possible losses in transparency.  There are preamps I've tried though that suffer extremely little audible loss in transparency, if any at all.  However, not all preamps I've tried improve sound quality.  Some made things worse.

 

There are plenty of members here on AS with a different opinion (the best pre is no pre) and I have no problem with that, so....... you just need to try for yourself.  Right now I am playing around with a simple Schiit Sys in my office system and I'll say, it is a surprisingly good passive preamp!  Shocking even for $50....  from a sound quality perspective, I slightly prefer it to using software volume control in my desktop setup.

 

Feel free to take this video with a grain of salt as PS Audio now sells a preamp, and it is just one data point, but I've come to the same conclusion:

 

 

[fas42]

I achieved a very high standard of SQ over 3 decades ago - no longer "hifi", but rather having all the characteristics of live, natural sound - largely because of the simplicity of the system: CDP, power amplifier, speakers. A very high quality CD player for the time, with proper digital volume control, directly driving the amp - there was always enough headroom, easily enough, say, to provide dance music for a party. Just need to make sure that the output of the DAC can be dialed up to drive the amp to clipping, as a guide.

 

I am 100% certain I would never have achieved this quality, back then, with any preamp in the chain - every extra 'unnecessary' can only degrade, not enhance

[Blake]

37 minutes ago, fas42 said:

I achieved a very high standard of SQ over 3 decades ago - no longer "hifi", but rather having all the characteristics of live, natural sound -

 

Wow Frank, so you are the first person in the world that has achieved "The Absolute Sound" with your stereo system in your home! 

 

Amazeballs.  

 

 

[SoundSparks]

Thank you very kindly, dear experts!

Like many of us in this wonderful hobby, I am after the SOUND, recreating the life-like atmosphere of concert hall in my listening space...

• Would you, dear experts, consider MATRIX Audio X-SABRE PRO (MQA) DAC to represent a good choice (my budget is only up to about 2K): it is hard for me to "decipher" the manual to understand if the analogue output stage, digital volume control, PSU, and other elements employed are of acceptable quality...
• And another silly question: what separate pre-amplifier would be required in order to at least correspond to the specs of this DAC (SNR >-129dB 20Hz-20kHz A-Weighting and THD+N <0.00030% at 20Hz-20kHz A-Weighting)?
• Just found another possible contender: TOPPING D90 DAC. What do you think of this budget-friendly option, please?
• Alternatives?

Please chime in!

 

[fas42]

1 hour ago, Blake said:

 

Wow Frank, so you are the first person in the world that has achieved "The Absolute Sound" with your stereo system in your home! 

 

Amazeballs.  

 

 

 

I thought that was the point of that particular magazine ... that the publisher knew what was possible, and had a system which produced such, when the wind was blowing in the right direction ... 🙂.

[AudioLibiertarian]

On 1/23/2020 at 6:26 PM, SoundSparks said:

Thank you very kindly, dear experts!

Like many of us in this wonderful hobby, I am after the SOUND, recreating the life-like atmosphere of concert hall in my listening space...

• Would you, dear experts, consider MATRIX Audio X-SABRE PRO (MQA) DAC to represent a good choice (my budget is only up to about 2K): it is hard for me to "decipher" the manual to understand if the analogue output stage, digital volume control, PSU, and other elements employed are of acceptable quality...
• And another silly question: what separate pre-amplifier would be required in order to at least correspond to the specs of this DAC (SNR >-129dB 20Hz-20kHz A-Weighting and THD+N <0.00030% at 20Hz-20kHz A-Weighting)?
• Just found another possible contender: TOPPING D90 DAC. What do you think of this budget-friendly option, please?
• Alternatives?

Please chime in!

 

Topping D90 is an extraordinary dac!!!  I ve compared it with IFI IDSD Pro & Chord Dave  (without  a reclocker I must add) and all 3 of us ("golden ear" types) prefrered the D90. That is if your system is truly high resolution and your USB cable is really good! I bought one of the last units on the amazon from APOS,  in-stock  as-new open box, from their California warehouse. after that  all  D90 uinits have become unavailable for some reason from the amazon storefront... The Gustard A22 has been getting a good word as well, but once again not on the Amazon prime (don't wanna ship it back to China if I don't like its sound)... Whats your system may I ask ?

[Miska]

On 1/24/2020 at 1:26 AM, SoundSparks said:

• And another silly question: what separate pre-amplifier would be required in order to at least correspond to the specs of this DAC (SNR >-129dB 20Hz-20kHz A-Weighting and THD+N <0.00030% at 20Hz-20kHz A-Weighting)?

 

Benchmark LA4 would at least fit the bill, but there are likely others.

 

[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.

[Miska]

1 hour ago, bodiebill said:

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.

 

Challenge with passive ones is that they drastically modify output impedance seen by the amplifier following the passive attenuator. In addition this impedance is not constant by varies depending on volume control position. This in turn increases the impact interconnect cable has. In addition power amps typically have first order low pass filter in their input that assumes low output impedance from the source. Varying output impedance means varying frequency response of this filter.

 

This is why active buffer stage (impedance converter) is usually good idea after passive type volume control, such as potentiometer. In addition, the active buffers I've been building have an additional cable capacitance compensation circuitry.

 

Additional resistance on the path also increases noise. Higher the series resistance, higher the noise. ESS Sabre chip for example has 600 ohm worth of resistance/noise. So if you want to use analog volume control that has lower self-noise than good digital one combined with a good low impedance DAC. You need to have all series resistances below 1 kOhm.

 

[plissken]

Preamps can obviously color the sound. They can't however improve the fidelity of the inputs.

[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?

[Rexp]

The pre amp used to be THE most important component in a high-end system with solid state ones hard to find. Good ones I've had were made by ATC, Gryphon, Parasound and Simaudio. No idea whats on offer now but they wont be cheap. 

[The Computer Audiophile]

On 1/23/2020 at 5:26 PM, SoundSparks said:

Thank you very kindly, dear experts!

Like many of us in this wonderful hobby, I am after the SOUND, recreating the life-like atmosphere of concert hall in my listening space...

• Would you, dear experts, consider MATRIX Audio X-SABRE PRO (MQA) DAC to represent a good choice (my budget is only up to about 2K): it is hard for me to "decipher" the manual to understand if the analogue output stage, digital volume control, PSU, and other elements employed are of acceptable quality...
• And another silly question: what separate pre-amplifier would be required in order to at least correspond to the specs of this DAC (SNR >-129dB 20Hz-20kHz A-Weighting and THD+N <0.00030% at 20Hz-20kHz A-Weighting)?
• Just found another possible contender: TOPPING D90 DAC. What do you think of this budget-friendly option, please?
• Alternatives?

Please chime in!

 

@JoshM just reviewed the Matrix DAC you’re interested in. 
 

 

[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?

[Miska]

2 hours ago, bodiebill said:

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?

 

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

 

[craighartley]

On 2/5/2020 at 5:39 PM, Miska said:

 

Challenge with passive ones is that they drastically modify output impedance seen by the amplifier following the passive attenuator. In addition this impedance is not constant by varies depending on volume control position. This in turn increases the impact interconnect cable has. In addition power amps typically have first order low pass filter in their input that assumes low output impedance from the source. Varying output impedance means varying frequency response of this filter.

 

This is why active buffer stage (impedance converter) is usually good idea after passive type volume control, such as potentiometer. In addition, the active buffers I've been building have an additional cable capacitance compensation circuitry.

 

Additional resistance on the path also increases noise. Higher the series resistance, higher the noise. ESS Sabre chip for example has 600 ohm worth of resistance/noise. So if you want to use analog volume control that has lower self-noise than good digital one combined with a good low impedance DAC. You need to have all series resistances below 1 kOhm.

 

An alternative is a transformer based ‘passive preamp’. 

[photonman]

I have same question and thoughts.  I imagine it is all equipment and system dependent.  I have a Benchmark DAC3 L arriving on Monday so I can compare it against my Chord Qutest.  My reasoning is that I want better volume control (and balanced outs) than the software volume I am using as I am thinking I am missing out on some SQ and not having a good gain match.

[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).

[Miska]

7 minutes ago, bodiebill said:

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

 

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.

[fas42]

On 2/6/2020 at 4:16 PM, Rexp said:

The pre amp used to be THE most important component in a high-end system with solid state ones hard to find. Good ones I've had were made by ATC, Gryphon, Parasound and Simaudio. No idea whats on offer now but they wont be cheap. 

 

From my POV, pretty obvious why ...they are a basket of weaknesses, full of switches, pots, and inputs and outputs that are not terminated, plenty of loose wiring; all of these need to be handled in the best possible way to not impact SQ.

 

If one wants the highest standard of sound, absolute simplicity will always win ...otherwise, the highest quality, and therefore expensive parts are essential - either end of the cost spectrum can be winners; in the middle, not so much ... 😉.

[fas42]

On 2/9/2020 at 6:19 AM, photonman said:

I have same question and thoughts.  I imagine it is all equipment and system dependent.  I have a Benchmark DAC3 L arriving on Monday so I can compare it against my Chord Qutest.  My reasoning is that I want better volume control (and balanced outs) than the software volume I am using as I am thinking I am missing out on some SQ and not having a good gain match.

 

My experience is that the volume control, if analogue, can be THE bottleneck - if I want to assess the potential of a system, I would bypass the part altogether, with a temporary fixed resistor divider to give me a decent, non-variable gain - and see what that told me ...

[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.

[sandyk]

9 hours ago, fas42 said:

From my POV, pretty obvious why ...they are a basket of weaknesses, full of switches, pots, and inputs and outputs that are not terminated, plenty of loose wiring; all of these need to be handled in the best possible way to not impact SQ.

???

 A decent preamp these days rarely needs more than perhaps a quality multi position ceramic switch with several wafers,(or relay input control) and a decent attenuator such as a Goldmund, DACT or Khozmo 48 position. It shouldn't matter if non selected inputs are terminated or not ,when both sides of the selected input are switched through. It should also have a relatively low gain of perhaps 3 times .

 Most high quality preamps these days don't use tone or balance controls , and shouldn't need to.

 Neither should they need Tape Outputs either, which also simplifies switching, or need an RIAA  Phono stage.