Digitally controlled analog (audio) mixer

[BrianHG]

The pcm3168a I recommended is an I2S controlled chip, except it has 4 bit lines for 8 channel audio instead of 1 bit line for normal I2S stereo mode.  It also has a separate I2S buss for ADC and DAC.

It also supports other interface modes if you want to run it the in and out buss merges with fewer IOs.

For the FPGA, you literally program your own input/output serializer / deserializer port, so you may use any mode you like.

[BrianHG]

If you prefer analog devices, they have their AD1937/AD1938/AD1939 which contain 4 ADCs and 8 DACs each.

There is no question if you use discrete separate stereo ADCs and DACs, your SNR on the ADC side will improve drastically.

But remember, you were thinking of feeding 16 analog audio signals through 16x16 analog switched/volume controls.  Even with a separation of 90db between everything, all that cross-talk and board routing will have summed up with a total system THD+N only in the 85db range unless you only had 1 or 2 audio sources running.

The FPGA solution would also offer you a free digital 16 channel TOSSLINK / ADAT audio interface output.  (hmm, you are approaching 100megabits/sec for uncompressed full 192k/24bit/16channels.)


If you want an Analog devices 8 channel sampler with studio grade performance, use this guy: AD7768
All you need are 2 of those ADCs and choose an 8 channel studio grade DAC for the other side.
Careful and do not order the -4 version, that one only has 4ADCs in it...

[BrianHG]

For your DAC, go for the analog devices ADAU1966A or ADAU1966, 16 channels...

Note that the Analog devices ADC and DAC have an un-filtered 192khz modes designed for minimum pipeline delay.

something like 192000/8 for the adc, 192000/4 samples for the fpga and 192000/2 samples for the dac.

Though, to get better ADC performance, you will need to turn on its sinc filter increasing it's latency by approximately 4x.
This would be nothing anyone could hear, we are still in the microsecond domain.


Obviously read the datasheets and double check everything I said.

[Saimoun]

Amazing, that's very clear thank you! Looking forward to starting to learn about FPGA then ha ha 

EDIT: Oh and thanks for all the ADC/DAC recommendations as well!

[BrianHG]

Amazing, that's very clear thank you! Looking forward to starting to learn about FPGA then ha ha 

EDIT: Oh and thanks for all the ADC/DAC recommendations as well!

For an FPGA, you are literally coding the logic gates and their wiring as functions.  It is basically describing a gigantic TTL schematic with words and how its wired to each pin.  But, you also get tools to see your code simulated logic analyzer images as well as real-time scope shots of you functioning circuit for most better FPGAs.

Note that dedicated audio DSPs can also get really fast performance if coded properly and you get the advantage of normal C language development.  You just need to make sure you have one fast enough to handle 32 audio channels at 24bit, 192khz.  The high end ones can do this without issue.