In SX Microcontrollers, SX/B Compiler and SX-Key Tool, dpaton wrote:

Andrew-

Oh man, were those Alesis things MEQ-230s? If they were, I feel sorry for you. They're probably the worst designed pieces of excrement I've ever laid my ears on. The phase interferance and the fader interaction make true tuning impossible without a TEF or SMAART or something like that.

I have a PH15 that will be living in the trunk of my 95 Civic Coupe this winter, and an MTX500D driving a JL Stealthbox that's already in. Components up front are Infinity Reference 6.5"s in the stock locations (mod'd tweter pods, XOs hidden in the doors). It's an addicitve hobby, and while I don't have any aspirations to compete (my house sucks up my time and money), I do plan to stealth everything in really clean, and probably leave all the processing to a DBX DriveRack 260. Right now the only way anyone knows I have a partial system is if they catch the Infinity logo on the tweeter grilles. I like it that way.

As far as the preamp goes, I'd say jump in and experiment. Order some samples of the PGA2310/2311 from TI, drop them into a breadboard, and start messing around with a Stamp. For something like I described above, the topology would go like this:
Single input from the tape monitor out of your existing stereo
Buffer that input with some high quality ultra-low offset opamps
Run it into as many PGA231Xs as you like, with the inputs paralleled left to left and right to right with the other chips, but start with one.
Buffer each output with the same high quality opamps used as the input buffer. BYpass caps ont he power supply and the PGA231Xs should be liberal.

Build an LM386 circuit to test with, and use a small speaker. It's best to blow up a $1 speaker or a $3 amp than a more powerful LM3886 design, if you have the option.

Once the preamp is working well, without DC offset, etc, build a single LM3886 module. Test, verify, fix as required, then repeat as much as you like.

I bet if you ordered samples today and dug up the right power supplies, you could put together a 4 or 6 ch controller over the weekend with some pushbuttons and LEDs for control. If you want to put input switching into the preamp, it's a little more tedious, but not complicated. I'll see about posting some of my older PCBs here later in the week if you're interested.

-dave

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