Headphone Amp - Dim Control?

[CheapSuitG]

Hola!


In the pro audio world, I’ve noticed many interfaces and monitor control sections come with a dim switch, which is really handy for quickly lowering the volume during critical listening without losing track of the original level.

I’m wondering if there’s a way to mod a headphone amp to include a similar dim switch?

My ultimate goal is to build a desktop amp station, using the Unicab and headphone amp like the “Marriage Keeper” Synchrony Pedalworks did a while back.

I plan to use it while I learn breadboarding and modding, and having repeatable volume control would be a huge benefit. For example If you change out components and the volume changes, being able to note that easily.

Any suggestions or ideas for how to implement this? Thanks!

Thanks!

 

[Brett]

The most elegant solution would be to switch gain of the amplifier, however, there's another way to do it. You can use a switched voltage divider on the output(s). If you're using a mono headphone amp, it might look something like this (you may need to adjust R1/R2):


If you're using a stereo headphone amp, it might look something like this (you may need to adjust R1/R2 and R3/R4):


In both cases, switch position as shown is full output. Switch position down is half voltage (therefore reduced dB) output.

This solution will most likely be noisier than the gain adjustment on the output amp method. If you do decide to go this route, the resistors need to be kept high enough as to not load down the output of the headphone amp(s) too much.

As far as the gain adjustment method, I'm afraid I can't be of much help without a schematic.

 

[jwin615]

The most elegant solution would be to switch gain of the amplifier, however, there's another way to do it. You can use a switched voltage divider on the output(s). If you're using a mono headphone amp, it might look something like this (you may need to adjust R1/R2):


If you're using a stereo headphone amp, it might look something like this (you may need to adjust R1/R2 and R3/R4):


In both cases, switch position as shown is full output. Switch position down is half voltage (therefore reduced dB) output.

This solution will most likely be noisier than the gain adjustment on the output amp method. If you do decide to go this route, the resistors need to be kept high enough as to not load down the output of the headphone amp(s) too much.

As far as the gain adjustment method, I'm afraid I can't be of much help without a schematic.

I don't know if that would be ideal. You still have a path to ground in the non-dim position. That will decrease max output a bit, maybe a lot with some headphones(8-300 ohm drivers). May need a 4pdt. Alternatively, a dual relay board *may* work allowing a push button to be used.

 

[Brett]

I don't know if that would be ideal. You still have a path to ground in the non-dim position. That will decrease max output a bit, maybe a lot with some headphones(8-300 ohm drivers).

I agree that it's not ideal, adjusting the gain of the output amplifier is likely the most ideal/elegant solution. Without a schematic, it's difficult to suggest alternative options.

I mentioned the path to ground in my post. Not arguing here, just trying to further my understanding on this, but is a 94kΩ path to ground really going drop output volume that much?

May need a 4pdt. Alternatively, a dual relay board *may* work allowing a push button to be used.

Can you explain this further?

 

[Robert]

I'd attenuate the signal going into the headphone amp, not the signal coming out.

 

[Brett]

I'd attenuate the signal going into the headphone amp, not the signal coming out.

That'd be a much simpler way to pad down the overall level, not sure why I'm over here trying to overcomplicate things .