Where to adjust volume - Roon, DAC, or Amp?

TLDR: My normal listening volume has my amp volume at around ~10%, is there any potential for better sound from a system by lowering the digital volume (either in Roon or the DAC) and increasing amp volume?

Longer version:
My main setup has two digital sources, a RoPieee via USB and Puffin Phono Stage via SPDIF, into a Topping DX3 Pro DAC, feeding a Sugden A21 amp (Class A - if that’s important here).

So for both vinyl and Roon, there’s multiple places I can adjust volume - at the source (both digital volume), at the DAC (also digital), or obviously via the amp volume (aka “the normal way to change the volume”).

At normal listening volumes, the amp volume is only around 10%. Sources and DAC are all essentially at 0dB (“essentially” because I do have some headroom in Roon for DSP to avoid clipping).

I have often wondered though if the amp is not “doing enough work” (scientific, I know!). So over the weekend tried adjusting the DAC volume down to -12dB, and turning the amp up to ~40-50%. It felt like there was a difference, as if the amp was just a little more in control of the speakers. I played a variety of things, and the most marked was guitar-heavy rock (Smashing Pumpkins - Soma) and quite detailed techno (real techno: Julian Miller - Leaving Earth). In both cases things felt more powerful, but zero distortion or loss of detail/imaging.

I tend more towards science over snake oil, and this is almost impossible to A/B test. So I’m hoping people more learned than I around amplification might have some insight. Is there something around impedance going on? Something unique to Class A amplification? Or is it just a zero-dollar placebo upgrade? :wink:

I prefer adjusting volume in the analog domain so I use my tube-based line stage to adjust volume before the signal heads into my tube-based amplifier.

I never attenuate the signal fed to the line stage.

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Looks like the Sugden A21 has a traditional analog potentiometer volume control? Such controls tend to sound worse and have channel imbalances at lower volumes. Also, the specs for the A21 indicate a low input sensitivity of 170mV, which can be overloaded by your DX3’s max output of 2V. It is not surprising that you set the A21’s volume control to a low 10% :slight_smile:, indicating too much gain upstream.

I think you are on the right track by decreasing upstream gain (not surprised you are hearing better SQ).

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I adjust volume at the preamp.

Roon is configured with constant volume, my DAC has no control volument at all and even it would had, I guess I wouldn’t use it. My preamp has remote but I would use even without it.

I never use digital volume it’s not lossless. It’s what amps where made for after all. If the amp has low sensitivity and the line level coming in is too high from your source then you might get some distortion and clipping so you could drop it a little to get to a level where it sounds better but use the amp for normal volume adjustments.

Thanks so much for the logic, it does make sense. One thing to note is that my amp is the A21SE - so 110mV, not 170mV (and 30W vs. 23W). I assume this even greater difference is more reason to lower the level upstream?

Regarding the rated output of the DAC (2Vrms) compared to the sensitivity of the amp (110mV) - is there a ratio that one would normally be looking for?

Also happy to hear my ears may be working well! :slight_smile:

It’s not obvious from the manual of the DX3 Pro DAC how the volume control is implemented. If it’s a 32-bit digital volume control, you might experiment with a -12 dB setting in Roon’s Headroom Management DSP with the DAC’s output set back to “fixed” to see how that compares to -12 dB via the DAC’s volume control. Good luck!

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Use an attenuator.

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Any reason why the bit depth is important?

Is there any advantage to using an attenuator vs. lowering the signal while it’s still in the digital path?
(I am tempted to try the Rothwell attenuators - just to add another option to the mix. :grimacing:)

Sure. It has to do with quantization noise (sounds like tape hiss). There’s less with the 64-bit math that Roon uses than you’ll find in DACs with a 32-bit digital volume control. Is there enough to hear a difference? Probably not…especially when attenuating only 12 dB, but it it costs you nothing (but time) to experiment. :slight_smile:

Keep us posted.

What hacker19 said about potentiometer and what CrystalGipsy said about digital volume are true. Attenuator is simpler and therefore can sound better than both.

(Our product line offers what we believe to be an even better digital volume algorithm, but that is not the appropriate solution for you.)

Both - levelling in Roon, analog control on the amp.

Once into 24 bit, the levelling at even the typical fixed point precision of DSP chips (never mind the 64bit float in a computer) isnt really the problem. The problem tends to be the re-dithering back down to whatever integer bit depth the DAC needs (depending on the dither algorithm used - some are good, some are awful). Roon with a 32 bit DAC seems to use 32 bit when it can, so precision TBH ceases to be an issue however you look at it - if you have a 32 bit DAC. The noise floor is typically well above the representation that 32 bit can handle and likely even above the 24bit lsb value - and that is just the DAC, never mind the rest of the chain.

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Is there a way to get Roon to use its own digital volume control with a Linn streamer when its DVC is set to disabled? Occasionally I compare the Linn’s DVC vs my Vitus analogue, and this discussion has got me curious as to whether Roon could bring something to the DVC party that’s better than what the Linn can do (a Katalyst KDS).

But with the Linn streamer set to fixed volume, I find that Roon is just telling me that the Linn’s volume is fixed (I guess there is some handshaking going on), and I can’t see how to enable Roon DVC in that case. It may be that this would cause other artifacts that would not be desirable, but just curious.

Peter Lie has the solution to your problem. Amazon has a selection of line input attenuators that will allow your amp to operate in more of its sweet spot.

Try the Schiit Sys, about $100 and works very well to attenuate the signal.

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Same issue for me with a Sugden pre and power amp combination. The 2.1V RMS (4.2V with the balanced outputs) output from my Leema Dac is too ‘hot’ for sensible volume control on my HA-4 Pre amp at modest volume levels. I use a combination of headroom management in Roon and attenuators on the output from the Dac. This works well for me to give better volume control at modest listening levels and I am more than happy with the sound quality. But there is always the nagging doubt that the attenuators could be harmful or that there may be a better way to do this, or a better combination of Dac and amplifiers ?

I ordered some -15dB Rothwell attenuators and they arrived yesterday. While I haven’t had a “serious” listen, on first try I think they’re the best solution. (@EricJ I had the same nagging doubt, but after doing some reading (and based on @wklie having a lot of experience in hifi) I understand why they’re a transparent (and probably the most transparent) solution)

So while un-scientific, here’s what I found:

  • Roon @ zero, DAC @ zero: comfortable listening volume was ~7 o’clock on the Sugden. Hard to adjust, and by ~10 o’clock it was loud
  • Roon @ -15dB, DAC @ zero: comfortable listening at a little over ~9 o’clock. A bit more definition and overall feeling of control in the speakers.
  • Roon @ zero, DAC @ -15dB: Honestly the same as above - if there’s a different I couldn’t pick it. I used this setting for a week as the DAC also has my TV and Phono as inputs.
  • Roon @ zero, DAC @ zero, -15dB attenuators: comfortable listening at ~10 o’clock. Similar definition improvement, possibly a little more of the “control” side of things than either digital solution. With my ear right up to the speakers, there was also definitely a lower noise floor.

So I’m happy with the attenuators, and will be sticking with them - particularly given it means I can use any input on the DAC.

Thanks for all the help above - plenty of learning for me and I’m happy with the outcome. :slight_smile:

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The Sugdens do seem to be sensitive. I was wondering what their DAC put out, figuring they must match components fairly well. However it’s spec’d at 2.15V! So even with a full Sugden system it seems things would be very loud.

I would say adjust volum on your pre/processor. I’m lucky enough to have direct access to the volume control on all my setups (Matrix Audio Element X, Moon MiND2 Network Player connected to Moon 430 HAD and Trinnov Altitude32).

What you should avoid is to control volume in Roon unless it is able to control the volume directly on your device (via Roon RAAT).

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