In-line volume control / output Impedance

Equipment / Electronics / Gear / Accessories Source Gear / Other
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Hi everyone.

This is gonna be lika a two part topic. One buyer advice and one electrical question.

I am using my headphones (mostly HD800S, Edition XS incoming) mainly on PS5 and TV but still want to be able to use a PEQ. My weapon of choice is the Qudelix 5k as it can work as an USB DAC on both sources (RME ADI 2 DAC is too expensive and has only 5 free bands. MiniDSP requires a laptop)

The Qudelix is connected to a Topping L50 via the balanced 2.5mm output. From there a 6m 3.5mm extension cable runs across the edge of my living room to the listing position.

My problem now is how to control the volume. At the moment I can only adjust by using the “headphone volume” on the PS5 or by using the volume slider in the Qudelix app. Both of them are not that convenient. Takes quite some clicks to get in the PS5 menu and unlocking the phone to use the small and unprecise slider in the Qudelix app is also not a permanent solution. I know there are some amps with a remote control. In the price range that I would like to pay the best thing would be the SMSL sh9 but this device costs more than the L50, has less power and higher distortion. Also I would like to not limit myself for an upgrade in the future. Planning to upgrade to an A30pro at some point. In generell I like those “fake balanced” amps that provide the complete power on single ended output (Smsl SP200, sh9, L50, A30pro…)

My idea now was to go with some kind of in-line volume control, like some gamer headset comes with (Coolermaster MH751). Those tiny potentiometer wheels in the cable don’t look very trustworthy though. So I was looking for something more “audiophile”. The best thing I found so far is this volume control

An even more high-quality one would be this. At least it mentions some quality Alps potentiometers. Problem is they are quite big for on the couch and the RCA connectors require more cable work and ugly adapters.

  • Does anybody know a better volume dial?
    Another idea would be a (passive, gain 0db. Probably with Relais steps) balanced preamp with remote control. Maybe somebody has a suggestion here.

Now to the technical question.
I know about the relation of the headphone Impedance to the output impedance and that it should be around 8 times higher. If not it will increase the bass on dynamic driver headphones. There are Impedance adapter available to have this effect on purpose. Those adapters are “in series” to the headphone.

The volume controls I mentioned above are wired as a voltage devider but it will still have the same effect on the frequency response because one part of the potentiometer will still be in series to the headphone. Am I right here?

If I’m correct, shouldn’t the potentiometer of the amp do the same? Or is it not located in the output of the amp but somewhere in the preamp circuit?

Text got a little longer than expected. Thanks to all who read it.

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Potentiometers that can handle >1 W are expensive (and big).

If I understood you correctly, you are looking for a Pre-Amp, which would sit between your source and amplifier.

This.
The usual order of assemblies in an amplifiers is an “input stage” so the amp presents a constant load to the devise feeding it, followed by a “pre-amp stage” where volume and tone control are located (and sometimes the input selection) followed by the “output stage” (sometimes called power stage).

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Hello MazeFrame, thank you for your answer.

My idea was not to set my amp to maximum and then adjust everything from the potentiometer. Just set the amp as loud as I ever want to listen and fine adjust via the potentiometer. Don’t think the amp will ever output more than 1W for the HD800.

This would be the more professional way to go, yes.
Would like to use the better balanced output of the qudelix 5k but that would mean the preamp needs XLR in and outs. The best thing I found so far is this one

To be honest still a little bit pricey with 260€.
Maybe I should change to the 3.5mm output from the 5K to have more choice. Like a sabaj a10h with its preamp function, remote and relay volume control.

Any other Pre-amp suggestions?

GrĂĽĂźe

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Common potentiometers can handle 200mW. 400mW still has a good selection, above 550mW is lucky, >1W is specialty stuff (and you pay for it).

My point: The HD800 is 300Ω, so to get “meaningful” attenuation, you would need a 1kΩ range poti (2.2kΩ would be preferred). And stuff like that exists Arcol Ohmite for example.

I recently grilled a poti by accident. Took all of one switched connection and disabled OCP :boom:

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