Electronics > Beginners
Just how bad is it? Audio mixer with headphone amp.
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paulca:
How do these interface on USB?  Obviously the DAC that produces the i2s, but I mean regarding drivers and sound card emulation.
BrianHG:
HD Audio drivers for amanero & older windows https://amanero.com/

Xmos has native support HDaudio in Win10, but if you want HDaudio in older windows, you need a a driver.

Same for the CM6631a.

All the other OS, ie Mac & Linux natively support USB Class 2.0 audio.

If you don't have drivers for older windows older than Win10, the boards will run in USB Class 1.0 48KHz audio mode.

I'm  thinking of doing a DAC board with amanero and my Win7 PCs.
paulca:
So here is an LTSpice file for an example of where I'm at for two mono channels.

This is without a baxandall active volume control on the master, just a pot on the headphone amp input.  The only downside to this is that the pot interacts with the "aux out" amp (top right).

"Input Gain" (x2) and "Master Gain" show pots. Both inputs are set for slight attenuation, master is set to MIN in the up load.  Increase R19 and reduce R20 to turn it up.

C2 and C8 can be removed, I know, along with R7 and R14.
Audioguru:
What is chopping the waveform?
paulca:

--- Quote from: Audioguru on March 24, 2018, 10:17:24 pm ---What is chopping the waveform?

--- End quote ---

Is that just a Spice artefact maybe?  I'm sure it has to have a resolution it simulates at.  Maybe "minimum step size" in the simulation command might change that.

Anyway I ran through some normal cases and some worst cases.  With a quiet 0.3vpp input gained on the pre-amp I can still get 8vpp and 100mA on the headphone output.  Similarly with a loud 1.7Vpp input and slight attenuation on the pre-amp I can get sensible output levels.

Yes, if I max the input gain on a loud signal and put the master volume full I get close to 24Vpp on the output which will not impress things.  However that would be a mistake.

I don't like that the master volume pot attenuates the aux out though.  Putting another buffer before the volume pot might help.

The next thing I think I need to look at are signal and peak lights, set at sensible points roughly related to dB.  Just not sure what those levels will be, 0db and +10db?  Or the best way to do them.  Zener or voltage divider and a known Vf diode.
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