Digital/analog volume control experience

[audioPT]

Has anyone built or listened to this ?

http://www.decibelhifi.com.au/prod10.htm

Do you know what that 6ch Vol Control on decibelhifi uses? The wolfson wm8816?

Guys,

I think that equipment is like one that I saw in a Silicon Chip magazine.

If it's so:

Volume control made by 3 x LM1973 and a PIC16F84A, witch controls the LED indicators, receive and decode IR from a remote control and, of course, the audio level of the LM's.

If it isn't... sorry

Regards,

 

[AudioWizard]

Hi Jan,
Surely digital volume controls are not being developed for the benefit of stereo listeners ?

Well, some are. The DS1808 was explicitely developed for this use. It sports a very low distortion figure over the whole audio spectrum. But it's not a "digital volume control". It's a digitally-controlled attenuator.

Granted it's better not to use anything at all ;-) (or just a few very high precision resistors), but I'm convinced that if you use a purely digital control of the volume (ie., multiplying the individual samples with a scaling factor), you'll get worse results than using an attenuator such as the DS1808. Not only in terms of dynamics (obviously), but also in terms of distortion. Unless you have a good digital overhead - that is, for instance, if your original audio signal was quantified in 16-bit, then you'd compute the final signal in 24-bit and output it on a 24-bit DAC. And even so, simply scaling the signal numerically might create nasty side-effects. You may need some kind of dithering to improve this. Not trivial.

As for using resistors and a switch: why not. But if you use standard resistors, that will most likely be worse than a laser-trimmed integrated attenuator. Even regular 1% metal film resistors might not cut it in terms of precision (you might not care) and temperature drift (that you would care).

My 2 cents.

 

[bowdown]

Hey guys you can buy that 6 ch vol control from here cheaper, i think its in kit form. it seems like a pretty good unit, i got the issues of silicon chip magazine at home somewhere, its got all the specs on it, will see if i can dig it up, but i wont be able to post any schematics on here due to copright stuff.


http://www.altronics.com.au/index.asp?area=item&id=K5600

cheers

Bowdown

 

[audioPT]

People,

About my last post (3 ago), I post here one pic of what is inside the 6 ch Vol control...

Bowdown: yes, it's the one in Silicon Chip!

Check out the LM's

 

[JoshK]

Thanks Pedro,

Looks like a good kit for the money, although Altronics has it much cheaper than Decibelhi-fi. Anyway, not a bad place to start, but I really need balanced in/outs.

Will the LM's control vol on a balanced channel if I change the corresponding opamps to deal with this?

 

[audioPT]

Hope nobody kill me for this...

Look in the schematic:

You have 6 inputs and 6 outputs.
If you need balanced, with one kit you get 3 ch volume control.

Just make another pcb with LM1973 and connect the data wires from the original pcb to the cloned.

Get the idea?

 

[MACKIE]

WM8816 - PIC uC

Dear All,

does anybody have any experiences in WM8816 to PIC processor connectivity using SHIFTOUT command in PICBASIC?

Thanks

Peter