Volume Control Clicks

[Koenjer]

My Rotel RSP-1068 surround processor uses a Toshiba electronic volume control.

The volume control works fine but on louder volumes you can hear small click/pops when you change the volume.
I assume this has something to do with the topolgy of the volume control IC. (stepped ladder maybe?)

I allready added a 100n capacitor on the +/- 18V lines (directly soldered them on the pins of the IC)

The internal PSU of the rotel is based on the 7818/7918 and the offset is quite small (100mV).

Used volume control:
TOSHIBA, SYSTEM ELECTRONIC VOLUME CONTROL - TC9482F

Does anybody know if there is a way to minimize the clicks/pops?
Or is it something I have live with

 

[fotios]

My Rotel RSP-1068 surround processor uses a Toshiba electronic volume control.

The volume control works fine but on louder volumes you can hear small click/pops when you change the volume.
I assume this has something to do with the topolgy of the volume control IC. (stepped ladder maybe?)

I allready added a 100n capacitor on the +/- 18V lines (directly soldered them on the pins of the IC)

The internal PSU of the rotel is based on the 7818/7918 and the offset is quite small (100mV).

Used volume control:
TOSHIBA, SYSTEM ELECTRONIC VOLUME CONTROL - TC9482F

Does anybody know if there is a way to minimize the clicks/pops?
Or is it something I have live with

Hello Koenjer
I don't know exactly what happens with your preamplifier, but this offset of 100mV is not so small. Can I suppose that you have measured it on main outputs? For example, in power amplifiers the max permissible output dc offset was years ago less than 50mV and today is less than 20mV and many modern designs have just 0.3 to 1mV output dc offset.
Consequently in preamplifiers dc offset should be... unmeasurable.
I hope this will help you by some way. Check all ICs in the signal path for possible dc offset.
Happy Easter

 

[Koenjer]

Hello Koenjer
I don't know exactly what happens with your preamplifier, but this offset of 100mV is not so small. Can I suppose that you have measured it on main outputs? For example, in power amplifiers the max permissible output dc offset was years ago less than 50mV and today is less than 20mV and many modern designs have just 0.3 to 1mV output dc offset.
Consequently in preamplifiers dc offset should be... unmeasurable.
I hope this will help you by some way. Check all ICs in the signal path for possible dc offset.
Happy Easter

Wrong description from me.

What I meant is that there is a +/-100mv difference between the +18 and -18v.
It's actually +18.07 and -17.96.

There is also a capacitor on the audio input of the Volume IC to elliminate any DC.

 

[AndrewT]

But is there a similar DC blocking cap on the output of the vol pot and/or selector?

 

[Koenjer]

But is there a similar DC blocking cap on the output of the vol pot and/or selector?

after the volume IC there is an buffer opamp and then a dc blocking cap to the output sockets.

 

[Leon08]

This is probably a design flaw, although Rotel has good reputation, they can make errors too.In the datasheet of TC9482F is mentioned that noise from digital signals can mix with analog signals if digital lines are not properly shielded.