Digital Potentiometers

[THChrist]

Hi everyone. I'm about to built a 3-channel SS amp. Since i want different EQ & gain controls for each channel, i wanted to know if there's a way of doing it without using  18 pots (vol, bass, mid, treble, gain & presence; x3). I thought about using LDRs, but that led me to use (again) 18 pots.

Another thing with the regular pots is, since i'd use relays to switch from one pot to another, the signal will be cut for a while (producing a big pop).

For what i want, i need some kind of digital potentiometers and some "memory device" (to save at least 3 presets). I don't need to save a gazillion of presets, only 3.

Pretty much like those new Marshall MG Series 4, they have a "simple" panel (and my amp is inspired by the beast of a billion pots, the JVM).



Please excuse my lame english

[J M Fahey]

Hi Tchrist. Have a good look at the JMP1 Marshall rack preamp. It does exactly that using a TDA or TCA-something (I'm quoting from memory) which is a "digital pot" application, controlling a tone control. I guess it can also be used to control gain and distortion if needed. The great advantage about it (for me at least) is that it´s not digital but analog. The only digital part is the control one, but not the sound part. The JMP1 is quite complex, with sophisticated Midi control, decoding, and patch storing, but if you want "only" 4 or 5 sounds, you can "hardwire" them and select them in a relatively simple way. Your relays needn't pop or click, if you are careful. Have a good look also at CD4053's, each of them has *three* SPDT "relays", in a cheap, compact and easy to drive package.
Good luck with your (ambitious) project. :tu:

[THChrist]

yeah, i saw the JMP-1, and it was too much of a mess. i wanted something more in the vein of those Caswell #39 amps (with motorized pots, but it uses some CPU thingy). I guess i'd go with the analog and simple solution (buy those 18 pots). my brain hurts...