Graham Slee Headphone Amps - Optimum input signal level for Solo?

Optimum input signal level for Solo?

Printed From: Graham Slee Hifi System Components
Category: Headphone Audio
Forum Name: Graham Slee Headphone Amps
Forum Description: Questions, answers and product information zone for Graham Slee Headphone Amplifiers
URL: https://www.hifisystemcomponents.com/forum/forum_posts.asp?TID=5719
Printed Date: 27 Mar 2026 at 2:27am
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Topic: Optimum input signal level for Solo?

Posted By: Davywhizz
Subject: Optimum input signal level for Solo?
Date Posted: 27 May 2024 at 11:40am

Hi all

I couldn't be any happier (or more impressed) with my Solo SRG, especially since adding the PSU 1 power supply.

I'm currently feeding it from a Topping EX5 DAC. The line out/preamp output is variable, the maximum available being 2.1 volts RMS with the unbalanced outputs. I'm using some decent quality Chord RCA cables.

It suits me to control the listening volume using the DAC remote control, just for minor adjustments between the recording levels of different tracks.

So far I have been keeping the DAC output at around 75%, but am wondering if there is an optimum input level for the Solo, or if others have found settings they prefer? I don't hear any differences moving the DAC output volume anywhere between 70 and 80.

Replies:

Posted By: Fatmangolf
Date Posted: 27 May 2024 at 10:37pm

That is good news. I think the Solo is designed to allow for different headphones impedances and sensitivities so you can use the volume setting works best in your system. Yours will be fine if it sounds good.

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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.

Posted By: Lucabeer
Date Posted: 30 Oct 2024 at 6:30pm

It's widely proven that ON PAPER all DACs perform best when the DIGITAL volume control (the one that goes in steps) is left at 100%. At 100%, you exploit the full resolution of the output stage of the DAC, you don't introduce any digital tinkering, and you get the best S/N ratio that the chip can offer.

And that's what I do on my DAC, which outputs a very similar (high!) RMS output level. And the Solo does not clip, even with such a hot input, because it's well designed and its volume pot actually acts as an attenuator at the INPUT stage (before the op amp) so it prevents any amp clipping at the root.

100% on the DAC, then, and I exclusively use the volume knob of the Solo between 9 and 12 o' clock to fine tweak variations in recording level between albums. Been doing that for 15 years, no issues at all.

But... if you prefer to let it at 75% because it's handier to use the remote from the sofa instead of turning the knob on the solo... go on like you are already used to! I actually doubt that anyone can hear a difference in sound quality (that's why I wrote "on paper"), on a modern high-bit DAC with a decently designed output stage! Measurements might say it's slightly worse, but we are in the realm of differences which no human ear can hear.

Posted By: Davywhizz
Date Posted: 30 Oct 2024 at 10:06pm

Thanks Lucabeer.

I'm sure you're right; it's best to use a fixed output DAC and control the final volume further on in the chain. It was just so convenient to use the remote control on the preamp, within a narrow range, to adjust for different recording levels.

As it happens, things move on and last week I replaced the Topping DAC with a NJC Audio reference DAC. So now I need to get up to adjust the volume. But it sounds even better and pairs well with the Solo.