Maintain Output Volume at Different Input Voltage? and some others

[MKreroo]

While is this is mainly targeted at the Qudelix 5K, I thought this could be beneficial in understanding some basic electronic knowledge

I don't have much knowledge in electrical so sorry for the shallow question.

On the 5K, when switching from low gain (1VRMS) to high gain (2VRMS), and the volume does not change despite the voltage change.
I can't quite understand how this is achieved, as assuming same headphone (so load), for the volume to not change, output power should be the same?
If so how does the power changes if the voltage is mostly constant, which would also mean the current is constant? (P=(V^2)/R)

As well, since headphone has "fixed" sensitivity and efficiency, how does the volume gets maintained if voltage is ~constant and power is changing?

Looked through the forum, I read that output voltage isn't really always constant as music isn't constant, could this the reason?
As in the voltage AND power are both changing when changing volume.

On a somewhat related side, I currently have the 6XX which is around 300 ohm.
To keep the volume the same, the power should be kept the same too, meaning when switching between low gain and high gain, in order to maintain the volume and voltage, only the current would be changed, unless the voltage isn't actually kept constant. If the voltage isn't kept constant/near constant, why is low gain rated at 1V and high gain at another if output voltage is depending on the load and not the mode?

Thanks

 

[NTK]

Looks like this is a feature of the Qudelix design. From the manual:

 

[DVDdoug]

On the 5K, when switching from low gain (1VRMS) to high gain (2VRMS),

So, from what NTK posted it's not a gain control but a power supply voltage adjustment.


...You could have a 10W and 100W amplifier with the same gain and there would be no difference until you push the 10W amp into clipping.

 

[MKreroo]

So, from what NTK posted it's not a gain control but a power supply voltage adjustment.


...You could have a 10W and 100W amplifier with the same gain and there would be no difference until you push the 10W amp into clipping.

so even in high gain it would be using 1V at the same volume level as normal gain?

 

[staticV3]

Low gain gives you 0-1Vrms.
High gain gives you 0-2Vrms.
Engaging high gain will automatically reduce the volume by 6dB so as to not blow your ears out.
Volume (and voltage) will stay the same, but you will now have the ability to raise the volume even further, to 2Vrms.

Edit: here's roughly how increasing the volume works:

As you switch on high gain, you get more potential/headroom to increase the volume, but the volume in percent is automatically reduced to match whatever loudness you had in low gain.
In other words: enabling high gain alone does not increase the voltage and loudness. It only gives you the ability to further increase voltage/loudness above what low gain is capable of, at the expense of noise and battery life.

 

[MKreroo]

Low gain gives you 0-1Vrms.
High gain gives you 0-2Vrms.
Engaging high gain will automatically reduce the volume by 6dB so as to not blow your ears out.
Volume (and voltage) will stay the same, but you will now have the ability to raise the volume even further, to 2Vrms.

Edit: here's roughly how increasing the volume works:
View attachment 203153
As you switch on high gain, you get more potential/headroom to increase the volume, but the volume in percent is automatically reduced to match whatever loudness you had in low gain.
In other words: enabling high gain alone does not increase the voltage and loudness. It only gives you the ability to further increase voltage/loudness above what low gain is capable of, at the expense of noise and battery life.

I see, so the amp doesn't always output 2V on high gain, that explains it then. I had the impression that amp always outputting constant voltage and was confused by how the volume can be different.

 

[staticV3]

That's not how music works.
Constant voltage = DC. Music = AC.
The signal amplitude of that AC signal is in direct relation to the loudness of your headphone.

 

[MKreroo]

That's not how music works.
Constant voltage = DC. Music = AC.
The signal amplitude of that AC signal is in direct relation to the loudness of your headphone.

Hope I'm not misunderstanding...

So loudness is related to the input signal, and that the loudness is also related to the output voltage of the amp?

So if I'm playing a quiet piece, while the amp is on high gain mode (say 2V), it isn't actually output 2V to the headphone, instead it's at whatever voltage it's needed to play the signal at a given loudness?

 

[NTK]

So if I'm playing a quiet piece, while the amp is on high gain mode (say 2V), it isn't actually output 2V to the headphone, instead it's at whatever voltage it's needed to play the signal at a given loudness?

That is correct. The "2 V" is the maximum output on the "high gain" mode. The actual output voltage is determined by the source signal (i.e. the music) and the volume setting, not exceeding the maximum output of the mode you are using.

The terms "high gain" and "low gain" are actually technically incorrect, because as the output volumes are the same when you switch modes, the gains must be the same. They should really be called "high output/volume" and "low output/volume" (or "normal output/volume") modes.