Digital Tone Control, and Audio Switches

I think I would look at multiplying DACs and volume control chips and make my tone controls somehow depend on the gain.

If it wasn't hifi, I would perhaps use a micro as a DSP.

An analog switch PWMed at 100KHz or so can also work as a variable gain.

The digital pot mentioned elsewhere will be far simpler than setting up a DSP, presuming you only want single pole filters.

I would suggest going full digital. The Digital Audio Processors (DAPs) are available from all major vendors such as TI, ST, AKM, AD, Cirrus logic, NXP, etc. Some of them have the integrated audio codec, but most require the external codec.

I like TAS3103 from TI.

Use the generic HC4053 or like.

Don't use Maxim parts. Anyone who designed in any parts from Maxim had to regret about it later. AD has the nice selection of high performance switches/muxes, but you generally don't need them for audio.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

For his application, Maxim would be acceptable. He's not going to manufacture a billion of the things. If he can get enough for the prototype, he's made a lifetime buy. ;-)

Bob

Bit of a twist, but you might look at using one of the chips that they make sound cards with.