*CLOSED* PGA4311x4 PCB

[dj3nk]

Hi people, if there is anybody how wants to build a MB Mixer here is something I've got for you. If you are interested in this layout just let me know. If its OK for LyleHaze  I'll add this to the wiki.

;D  greetz  ;D

4311.JPG

[Ashiman]

some people still dont get the basic idea : PGA series are STEPPED ATTENUATORS. MAN WTF YOU THINK WHY "ZERO CROSSING DETECTION" IS THERE?

[dj3nk]

and what is so bad about this ? 31.5 db in 0.5 db steps are 64 voulume settings. It's enough for me since i dont want to do any volume slides with it. or do i dont know somethin else what is mattering ? and what is that zero crossing detecting ? i also wondered what that pin is for.

[Ashiman]

please try to think about it , what happens if you got a nice sine wave , and you start to attenuate back & forth , totally out of sync!! Thats right,  a CLICKS& POPS ! Inside there is resistor ladder, like in other digital pots resolution is limited. Try to read those digipot threads, and you get whats the problem.  You have to spend effort to fight off crosstalk. This layout offers itself for crosstalk big time .

Typical mixer application is something like - overdriving the signal adding second and other harmonics, PGA is totally transparent, its usually employed as preamp before ampllification.

[dj3nk]

hmm that sinewave issue is a good explanation. but i just need it to mix several stereo line signals into one stereo  signal. It should be connected between my synthezisers and the audio input of my soundcard. every time every channel is on by default. sometimes BETWEEN parts I could change the volume and/or pan. So I wouldnt have to expect any clicks in my example or do I ?

thank you for your help

[Ashiman]

Midi controlled mixers never catched on . What you propose I dont see much use either. You can feed the soundcard with -10dB signal and not loose any precision, then if you already talkin about PC, why dont just do it once you ' re inside ?

I would just wait for the AOUT guys, once they have VCA you re set and you can build your mixer with generic parts, and the sort of with the distortion you want  plus you can fade it as you wish.

[lylehaze]

Yes, of course you can add it to the WIKI!

Also, the PGA chips have a range from +31.5dB to -95.5dB

in 0.5 dB steps, so that's actually 255 separate levels

plus MUTE.

Since I'm using CC7 for control, I only have 127 active

levels (plus MUTE), but the additional resolution is

used by the LOG conversion for smoother final resolution.

I hope that helps,

LyleHaze

[dj3nk]

:D

please use that thread from now on for the discussion of this pcb

http://www.midibox.org/forum/index.php/topic,7280.msg79516.html#new

*THREAD CLOSED*