Digitally adjusting gain

[futz]

I do have another newbie audio question.
In systems where you can plug in headphones, it will usually shut off the speakers when you plug in the headphones.

How is this acheived?

It's simpler than you think. When you push the headphone plug into the jack, it connects the headphone tip and rings on the plug to contacts in there. And in the process of contacting it pushes the speaker contacts apart so they're no longer touching.

 

[firewater]

Xicor X9C103 Digitally Controlled Potentiometers (XDCP)
http://www.datasheetcatalog.com/datasheets_pdf/X/9/C/1/X9C103.shtml
http://www.attiny.com/x9c103.htm

 

[alvinyow]

Volume Control help!!

Hi to all the gurus here,
I'm new to this forum. I hv been using TDA8424 Volume chip in my project. I manage to control the level using a pic controller.
However the problem i'm facing are... lots of noise. When the music are paused. Turn the device to a maximum level. The noise level is unacceptable. Beside when i sendind the data to the chip, while it is ramping the vol up or down, I can here some "ramping noise". I dunno how it called. It should be ramp smoothly without any additional noise.
I built this unit using 4 pcs of regulator 7812/7912 for the balance-unbalance input and unbalance-balance output. The ground of this circuit is analog ground and is supply from 1 transformer 909Vac. The other similar transformer 09Vac will supply 5V and 12V from 7805/7812 regulator respectively. The +5V/+12V will supply to the PIC and TDA8424. So here will be a digital ground. I had split the digital and analog ground before they join in certain spot of the board. Is there any problem with the power supply section? I'm quite happy with this chip. The only problem is i wans to get rid of those noise.
Even when i sending the data to increse the bass or treble.... the output will somehow mix with "some unwanted digital sound".
Please help....
Many thanks