PC mixer

[Analog_Fan]

hi there,
For experimenting i wanna build a PC powered audio mixer and sourcing the 12V power from the ATX psu in from the pc.

What's your thoughs about this schematic?
I have done in the past for CV mixing in the modular synthesizer and worked perfect, but AC coupling was not needed.

 

[Tubetec]

Powering audio devices from a desktop PC isnt a good idea at all , you'll almost certain have noise issues in the analog signal path .
A small standalone mixer with USB connection to the PC will do exactly what you want .

 

[Analog_Fan]

Powering audio devices from a desktop PC isnt a good idea at all , you'll almost certain have noise issues in the analog signal path .
A small standalone mixer with USB connection to the PC will do exactly what you want .

Well Thnx, i was thinking about adding a USB B connector, but i though the ATX psu would do the same job.
Should i opt for the USB B type connector?

 

[Analog_Fan]

OPA1642 or OPA1678?
For witch should i decide?

OPA1642 seems to be very power efficient.

 

[ruffrecords]

I would advise you to change all the 1K pots and resistors to 10K.


Cheers

Ian

 

[Piedwagtail]

Check ebay for '

5V TO 12V -12V +12V Mini DC-DC converter board'​

for your experiment.
Agree with Tubetec - noise issues will need to be solved.

R

 

[Analog_Fan]

I would advise you to change all the 1K pots and resistors to 10K.


Cheers

Ian

the values where Falstad standard, the actual values of the resistor in the circuit is 10K, i only have 100K(A) dual gang pots.

 

[Analog_Fan]

Check ebay for '

5V TO 12V -12V +12V Mini DC-DC converter board'​

for your experiment.
Agree with Tubetec - noise issues will need to be solved.

R

5V should be enough, splitting them, results in +2.5V/-2.5V witch leaves me about 1V headroom over line audio.
It works in phones, co players, etc.

 

[Piedwagtail]

?
USB 5V > tacked on converter board gives you +12 and -12 for your opamps.

The one I use has all the ins/outs in a row such that you can solder in a pin array and have it as a plug in on your pcb.


R

 

[ccaudle]

results in +2.5V/-2.5V witch leaves me about 1V headroom over line audio.
It works in phones, co players, etc.

CD standard is 2V RMS maximum output, which is just a little more than +2.8V/-2.8V.

 

[Analog_Fan]

CD standard is 2V RMS maximum output, which is just a little more than +2.8V/-2.8V.

You made me scope the output of my pc.
I played a track on my pc on full loudness with the scope on 1V/div and i measured 2 V.p.p.
I have "faders" on the inputs it should work, it doesn't have to be a hi-end thing, but just a thing that allows me to hear audio experiments made by a MCU along the pc audio output.

 

[ruffrecords]

the values where Falstad standard, the actual values of the resistor in the circuit is 10K, i only have 100K(A) dual gang pots.

In which case I would advise you to change all the resistor values to 100K. SInce this is a non-critical application a little extra noise will not be an issue.

Cheers

Ian

 

[Analog_Fan]

Powering audio devices from a desktop PC isnt a good idea at all , you'll almost certain have noise issues in the analog signal path .
A small standalone mixer with USB connection to the PC will do exactly what you want .

What if i put a 78L10 voltage regulator on the 12 V (Molex) connector?
Than use 100nF and 100uF capacitors after the voltage reg. to filter the noise from the ATX psu?
Would that work?

 

[gyraf]

..10nF is too small for smoothing your virtual-ground reference - better make that at least 10uF..

 

[Analog_Fan]

..10nF is too small for smoothing your virtual-ground reference - better make that at least 10uF..

Well, i saw Don Buchla do it on the Buchla 259 complex wave generator and copied the value from that "ever" since.
But many thnx for the suggestion.