Learning towards MINI DAC

[chchyong89]

Thanks a lot for the help ^nightanole.



So this go like this right?
I think i will go for AD1896 because it's definitely cheaper compare with SRC4192.

[mace1337]

If it needs to be cheap, why not use just the PCM2707? Why go for the SRC and extra dac?

[chchyong89]

it's no longer challenging

One more question, any possible to make the windows
volume control functionable if i construct like this:

PCM2707(IIS)->WM8501


And i have one question that i doubt for a very long
time, I have tried

PCM2707(IIS)->TDA1543 : the volume control in (OS)windows is not working
PCM2704(DAC) : Volume controllable in windows.

Is it mean that if i use PCM2704(IIS)->(Any DAC), then the
volume control in windows is functionable? Or..?

Thanks

[nightanole]

Uh you do realize that if you use the windows volume control you just lost all your resolution right?

Think about it. right now with volume disabled in windows, and no pot, the amp would be running full volume. Now you turn down the windows volume to normal listen levels. You just reduced your bit resolution from 16 bit down to 8 or even 4 bit.


PS: schematic looks good so far.

[TzeYang]

chchyong,

software attenuation before DAC is bad because for each 6dB decrease in attenuation you lose 1 bit of resolution.

[chchyong89]

I added a pot at the output stage, which i might want to drive Headphone/earphone. Do i need to increase the value of the capacitors?
Do this see ok?

[nightanole]

Now we are going for a wolf 8501...

Pots in the right place. it doesnt have to be 10k, but it can be since your using 22uf caps, so id stick with the 10-25k mark. You will now have to buffer the output of the pot with a opamp to run headphones. You cant have a pot and run headphones directly at the same time.

i dont have much experience with running an opamp without an negative supply. You would need something that works at low voltage (5v rails) and runs at or below unity gain. Again you could run the opamp directly from usb via a ferrite bead and run it in unity gain. Amb used a AD8656 for the headphone version.

Yes your output would need to be cap coupled and be big like your original design.

This might help but its from 2000 so im not sure if you can get any of the chips.

http://courses.cit.cornell.edu/bionb...ngleSupply.pdf

[mace1337]

Originally Posted by nightanole

i dont have much experience with running an opamp without an negative supply. You would need something that works at low voltage (5v rails) and runs at or below unity gain. Again you could run the opamp directly from usb via a ferrite bead and run it in unity gain. Amb used a AD8656 for the headphone version.

Actually in the Gamma 1 the headphone output is from the WM8051 directly so no opamps. The 8051 is capable of driving headphones directly and it runs off of a 5v supply. It's a pretty handy chip.

Then again, the PCM2707 does this too, it just sounds worse.

[nightanole]

8051 can run headphones directly or used with a pot, but not both. Thats a given with any dac. Ya gotta have an opamp right before the cans, or have the dac drive them directly with big caps.