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Are pre-amps necessary

anmpr1

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The RME ADI-2 DAC has balance control.
Nice. But doesn't have the back panel flexibility I need (multiple analog inputs/outputs). It is less expensive, though. And certainly looks nice.
 

Willem

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And, as long as the digital volume control has access to the DAC's internal data path, that limitation of the noise floor is pretty meaningless (-135 dB in the ESS example). The weakness of an analogue volume control is primarily that channel balance at low volume is not very good. So as far as I am concerned the practical advantages of digital volume control outweigh those of even good analogue volume controls. There is certainly not a good argument in favour of adding a pre amplifier to the chain of you only have digital sources.
 

Willem

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The RME ADI-2 is great if you have only digital sources (RME are a pro audio company). I still only have one analogue source because my family would not let me sell the turntable. So I feed that into a Pro-Ject phono pre amp with optical output. It works a treat. I no longer have any other analogue sources, since I use the digital outputs of the disc player and the television, and I have replaced FM radio by internet radio.
 

anmpr1

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The RME ADI-2 is great if you have only digital sources (RME are a pro audio company). I still only have one analogue source because my family would not let me sell the turntable. So I feed that into a Pro-Ject phono pre amp with optical output. It works a treat.
Interesting. I didn't know you could get a phono stage with an optical output. I have a Project PhonoBox hooked to one of the HGC analog inputs, and use another of the analog RCA outputs to send a signal to a subwoofer.

I'd like a balance control. It could be done using digital sources through my PC, but not for the analog phono source, and that is where I really need it.

I tried a DBX equalizer between the DAC and amp--that gave me a subsonic filter and channel level controls. But I really didn't like it, so went back to HGC direct to AHB2.
 

rodtor

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I urge followers of this thread who want to learn more about the respective merits of digital and analog volume controls to consult the slides posted by @Willem in post #59, and also to read @Rja4000 's contributions. Very illuminating.
 

Rja4000

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as long as the digital volume control has access to the DAC's internal data path, that limitation of the noise floor is pretty meaningless (-135 dB in the ESS example)
I don't know what you mean here, but the limiting factor is more likely to be the DAC's analog output SNR, which is at best around 120dB, nowadays.
 
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rodtor

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... but the limiting factor is more likely to be the DAC's analog output SNR, which is at best around -120dB, nowadays.

Right, and you illustrated this point above very well with the graph of SNR results for different output level settings for the RME. Am I right in assuming that for most other, less expensive, DACS including those measured by Amir here to have SINAD of over 110 db or so, the output level setting is likely to be fixed? If so, is this likely to be a problem if one was to acquire a power amp that can reach, let's say, 400 watts into 8 ohms, with a balanced (normally about 4 ohm) connection from the DAC? Or would one need other information about the DAC, or the amp, before concluding that the combination is a suitable one?
 

watchnerd

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The RME ADI-2 has many virtues (such as tone and balance control, optional and adjustable dynamic loudness and some parametric filtering), but one of them is also that it has an optional auto reference level setting, for the best match between S/N and output level. And it has a very accurate digital volume control that is much better than any analogue one (and no, with modern DACs you do not lose resolution with digital volume control).

I actually find the proper reference level setting between the RME and my monitor speakers to be less clear than I would like.

Yeah, it's flexible, but there is a lot of 'gray zone' in the optimization, too.
 

watchnerd

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Nice. But doesn't have the back panel flexibility I need (multiple analog inputs/outputs). It is less expensive, though. And certainly looks nice.

The Pro version has more inputs/outputs.

I currently have 2 RTR Revoxes (analog, 4 channels), Dynaudio monitors (analog), and an iMac (digital) all hooked up at the same time on the Pro version.
 

Rja4000

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Right, and you illustrated this point above very well with the graph of SNR results for different output level settings for the RME. Am I right in assuming that for most other, less expensive, DACS including those measured by Amir here to have SINAD of over 110 db or so, the output level setting is likely to be fixed? If so, is this likely to be a problem if one was to acquire a power amp that can reach, let's say, 400 watts into 8 ohms, with a balanced (normally about 4 ohm) connection from the DAC? Or would one need other information about the DAC, or the amp, before concluding that the combination is a suitable one?
Hi
Just an opinion here:
I guess that most are fixed analog output range, indeed. (Possibly, even most of the more expensive ones are.)
Meaning that 0dBFS is always the same Vrms (with the RME, you can choose between +4dBu, +13dBu, +19dBu, +24dBu or even +28dBu with the Pro)

But with a max SINAD around 110dB, you have plenty of margin.

The main point is: depending on the use case, you may actually have a slightly better performance with a variable output device having a 112dB SINAD than with another fixed output one having a SINAD of 120dB.
So SINAD figure doesn't tell you all.

But I also own some pretty good analog preamps.
Most of them are not as good as the RME, be it at 0dB attenuation or 30-40dB attenuation.

I'll post the measurements I've made with a SPL Volume 2, a pretty good analog attenuator, and the RME outperforms it.

Bottom line: for normal use, a good, fixed analog output range DAC, with digital volume control, will probably outperform a normal, not State of the Art, analog preamp.
 
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Rja4000

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I actually find the proper reference level setting between the RME and my monitor speakers to be less clear than I would like.

Yeah, it's flexible, but there is a lot of 'gray zone' in the optimization, too.

Well, I'd do the following:
Set the output range to +24dBu
Try to find the maximum level you'll want to (usually) listen at by playing with the volume control.
When you're happy, deduct the volume attenuation from the +24dBu and set the output range to the lowest range value above (or equal to) that.
Done. Never touch it again.
Don't worry. Be happy :)
 

watchnerd

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Well, I'd do the following:
Set the output range to +24dBu
Try to find the maximum level you'll want to (usually) listen at by playing with the volume control.
When you're happy, deduct the volume attenuation from the +24dBu and set the output range to the lowest range value above (or equal to) that.
Done. Never touch it again.
Don't worry. Be happy :)

Yeah....that's not really great calibration when working across projects recorded at different reference levels.

Plus my monitors have variable dBu inputs:

  • +6dB = 0dBu /.775V max
  • 0dB = +6dBu /1.5V max
  • -6dB = +12dBu /3.1V max
So even if I did what you said, one then asks..."okay, but at which monitor input level?"
 

Rja4000

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Yeah....that's not really great calibration when working across projects recorded at different reference levels.

Plus my monitors have variable dBu inputs:

  • +6dB = 0dBu /.775V max
  • 0dB = +6dBu /1.5V max
  • -6dB = +12dBu /3.1V max
So even if I did what you said, one then asks..."okay, but at which monitor input level?"
Try at +13dBu.
If you don't use headphones, use the 2 front headphone outputs in "balanced phone mode" and at low gain.
That's how you'll get the best performance.
And the RME's analog stage is most probably better than the monitors' anyway, so it's probably better to use RME's gain as much as possible, and to leave the monitor in the lowest gain setting (-6dB)

But I don't think there is a bad choice, as long as you use a balanced connection at +4dBu or +13dBu.
 
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watchnerd

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Try at +13dBu.
If you don't use headphones, use the 2 front headphone outputs in "balanced phone mode" and at low gain.
That's how you'll get the best performance.
And the RME's analog stage is most probably better than the monitors' anyway, so it's probably better to use RME's gain as much as possible, and to leave the monitor in the lowest gain setting (-6dB)

But I don't think there is a bad choice.

-6dB is the recommendation from Dynaudio when using pro gear.

I do use headphones, too. So I'm sticking with the outputs on the back.

The RME's SNR/gain isn't the limiting factor, in my case.

It's calibrating a 0 dB reference across 2 Revox PR-99 RTR decks using test tapes, then having to adjust that for different 0 dB refs for different tape formulas made by others at the decks, then calibrating that to 0 dB at the ADC, then calibrating the monitors at the last step.

Which is a bitch when having to shift between 250 NWb/M @ 15 IPS and 370 NWb/M @ 15 IPS.
 

LTig

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Nice. But doesn't have the back panel flexibility I need (multiple analog inputs/outputs). It is less expensive, though. And certainly looks nice.
The ADI-2 PRO fs has one analog input.
 
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