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Just how bad is it? Audio mixer with headphone amp.
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paulca:
So keeping with the flat gain structure idea, where all baxandalls could potentially be at 0db unity gain, would it not make sense to set the headphone amp up to be at "moderately" full volume at that input level?

So that would be an input of normal line level 500mV-1V peak to peak.

Not sure if that idea has legs, but after choosing the active gain stages to prevent attenuate, gain, attenuate, gain all over the place, it would be a shame to stop it there.
BrianHG:

--- Quote from: paulca on March 01, 2018, 06:56:35 pm ---So keeping with the flat gain structure idea, where all baxandalls could potentially be at 0db unity gain, would it not make sense to set the headphone amp up to be at "moderately" full volume at that input level?

So that would be an input of normal line level 500mV-1V peak to peak.

Not sure if that idea has legs, but after choosing the active gain stages to prevent attenuate, gain, attenuate, gain all over the place, it would be a shame to stop it there.

--- End quote ---
Full input line level is 1V rms.  Just above 2.5vp-p.
This is also a good level for your headphones max volume, but, be careful.  If you are using the series 32 ohm resistor instead of direct drive, you will need to double the output at the op-amp pin, ie just above 5Vp-p.  This should match a high end consumer DAC unit.


--- Quote ---What voltage is line level?
While the nominal levels themselves vary, only two reference voltages are common: decibel volts (dBV) for consumer applications, and decibels unloaded (dBu) for professional applications. The decibel volt reference voltage is 1 VRMS = 0 dBV.
--- End quote ---
https://en.wikipedia.org/wiki/Line_level
Bassman59:

--- Quote from: paulca on March 01, 2018, 06:56:35 pm ---So keeping with the flat gain structure idea, where all baxandalls could potentially be at 0db unity gain, would it not make sense to set the headphone amp up to be at "moderately" full volume at that input level?

So that would be an input of normal line level 500mV-1V peak to peak.
--- End quote ---

Line level for professional audio is defined as +4 dBu, which is 1.23 Vrms or 3.4 Vpk-pk. Depending on the headphones, that might be uncomfortably loud. But just because there's a "nominal" +4 dBu doesn't mean signals coming in are actually at that level. That's why there are input gain trims and output levels on a mixer. I've seen plenty of mixer headphone amp circuits with a gain of ten on the driver amplifier.

Audioguru:
Is the maximum level for your incoming audio already squashed with a limiter or are faint sounds already boosted with automatic-gain-control? Is so then you do not need much level adjustment.
But for live sounds you should have enough up and down adjustment range of probably plus 20dB down to zero. A logarithmic volume control will cut -20dB when set to halfway. Then what will protect your hearing and headphones if the headphones amplifier has enough power to blow your head off?
BrianHG:

--- Quote from: Audioguru on March 01, 2018, 09:03:34 pm ---Is the maximum level for your incoming audio already squashed with a limiter or are faint sounds already boosted with automatic-gain-control? Is so then you do not need much level adjustment.
But for live sounds you should have enough up and down adjustment range of probably plus 20dB down to zero. A logarithmic volume control will cut -20dB when set to halfway. Then what will protect your hearing and headphones if the headphones amplifier has enough power to blow your head off?

--- End quote ---
He could use my green led clip trick in his pre-amp.  In fact, to protect the next device in even with his line level output, I would strongly recommend it.  Feeding a 30vp-p into an audio amp can also destroy the audio amp as well.

Actually, depending on where it is in his design, he may have to go with 2 red LEDs for the lower voltage.
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