solderdude
Grand Contributor
For that you can use something like a passive attenuator.
I recommend something like that because such amplifiers have way too much power for sensitive heaphones (the sensitivity is the culprtit here)
It is quite easy to build such amplifiers. All one needs is stereo potmeters with a reverse log taper or stepped attenuators (relay or switch) and could make the lowest position so that the signal is muted.
In fact my own headphone amplifier design uses an inverting amplifier (for other reasons).
Manufacturers of headphones like to sell more devices so headphones tend to have a high sensitivity and low impedance.
That doesn't mean amplifier manufacturers should not focus on this only and not make amplifiers for higher sensitivity headphones.
There are workarounds to remove the noise issue where it counts.
When you take a look at the Meier Corda Jazz, O.K. maybe not the best example, that uses that topology you can see that noise wise at 50mV the Atom has it beat.
The reason is the topology (non inverting) amp before the volpot, low gain setting and buffer after the volpot.
The only downside is you can clip the input easily on high gain setting but one would not be using this for sensitive headphones.
Also consider that at 80 dB SPL average (which is moderately loud) you can't hear any noise 70dB down let alone 90dB down.
But I do agree that those designing headphone amps and are using stepped or relay volume control could just as easily design it inverting and get slightly better 50mV noise numbers.
I recommend something like that because such amplifiers have way too much power for sensitive heaphones (the sensitivity is the culprtit here)
It is quite easy to build such amplifiers. All one needs is stereo potmeters with a reverse log taper or stepped attenuators (relay or switch) and could make the lowest position so that the signal is muted.
In fact my own headphone amplifier design uses an inverting amplifier (for other reasons).
Manufacturers of headphones like to sell more devices so headphones tend to have a high sensitivity and low impedance.
That doesn't mean amplifier manufacturers should not focus on this only and not make amplifiers for higher sensitivity headphones.
There are workarounds to remove the noise issue where it counts.
When you take a look at the Meier Corda Jazz, O.K. maybe not the best example, that uses that topology you can see that noise wise at 50mV the Atom has it beat.
The reason is the topology (non inverting) amp before the volpot, low gain setting and buffer after the volpot.
The only downside is you can clip the input easily on high gain setting but one would not be using this for sensitive headphones.
Also consider that at 80 dB SPL average (which is moderately loud) you can't hear any noise 70dB down let alone 90dB down.
But I do agree that those designing headphone amps and are using stepped or relay volume control could just as easily design it inverting and get slightly better 50mV noise numbers.