WM8816 digital volume control (WM STAMP)

[veteran]

This project should be placed somewhere between Digital and ChipAmps It's my new volume control module basing on WM8816 from Wolfson. I call it 'WM STAMP', because executive part of it is very small.

Some details and basic functions:

- gain range from -111.5dB to +15.5dB
- gain step size: 0.5dB or 2.5dB

controls:
- IR remote (program can learn every RC5 remote commands)
- encoder
- standard, analog pot (ADC)

- optoisolation
- LCD or VFD 2x20 display
- backlight adjust

- output for 8 relay selector
- mute
- optional name for every input (like 'CD', 'DVD', 'TUNER', ...)

WM8816 is similar to PGA2310, but... opamps are outside This give many possibilities:
- many single opamps can be used
- discrete stage
- using some high power opamps we get good, headphone amp

Schematic diagram



I found WM8816 chip in:
Marantz PM-15S1 Reference Series Integrated Stereo Amplifier
Marantz PM-11S1 Reference Series Integrated Stereo Amplifier

[Upupa Epops]

Very nice, good choice - Wolfson is much better than PGA...

[veteran]

Thank you Upupa Epops .
Placing some pins like this change this wmstamp into non - standard chip with wm8816 and optoisolation and can be used for volume control in some designs where standard op-amps can't be used.
This way I can integrate my module with OPA1632 to control XLR signals.

[skappy]

Hi Veteran
very nice job, it looks great !!!
(1) I've just a small question concerning this device, do you think that updating it to 6 channels represents a lot of work ?
I'm trying to do it with pic , encoder and vfd display with no real success since now ...

(2) Could you check the link with your schematic in pdf, it seems to not work ...

Thank you very much, have a nice day

[paulb]

Originally posted by skappy
...
(2) Could you check the link with your schematic in pdf, it seems to not work ...

Link should be http://www.audio.webd.pl/pdf/wm_stamp_analog.pdf

I like the idea of the optoisolators.

[veteran]

Look at the board Skappy - there is place for 3 jumpers. This way we can control 3 x WM8816 using the same cable = 6 channels

[Raka]

What's the purpose of the optoisolators?

[tobias_svensk]

Been waiting for this baby!

Nice work Damian

[veteran]

Originally posted by Raka
What's the purpose of the optoisolators?

To separate controller (digital) ground from (analog) ground on wmstamp board.

[skappy]

Hi Veteran,
thank you very much for your answser

I have just another small question ;
Do you think that selling such a kit is a possible thing ?

I'm trying to obtain the same result as yours with pga2310 and pic16f877, vfd and encoder but i encountered lot of problem with the rotary encoder so buying something which has been tested would really save me money (and time as my level in the electronic field seems not to be enough ...)

Thank you verty much for your help