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the schemo John Hardy has on his page (990.pdf, page 4 top)? I think that's what you need.
Yes, that is probably the simplest way to use an idle 990. And it does use Kelly's pot.
Note that it only aims for electrical gain of 54dB. Several problems are less acute if you shave the maximum gain.
Also note that he calls the use of fat caps and offset trimpots "traditional", and offers a different approach that avoids big caps (though a lot more pins to wire, and still needing a trim; perhaps more than a spare-time DIY-er wants to wrestle with).
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cause the entire universe to implode. ...look at... http://www.johnhardyco.com/pdf/MPC3000.pdf
Another sweet one-990 plan. Note that this one uses two gain-pots: a 10K for low-mid gain and a 500Ω for mid-high gain. I think John has an essay explaining this technique, good reading.
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Perhaps it is time for a new discrete op amp---how long has the 990 been around and about now?
We should work on the StratoCaster guitar first: it is a lot older.
Some things are dead before they reach market, and other things are timeless.
The 990 is not stuck in 1979: wise men continue to work with it and judiciously modify it. See the
thread where several 990 gurus jumped in with some straight dope and a few hard-won hints.
Within its intended purposes, what is wrong with the 990? It is a crummy condenser-mike head-amp, and not good on batteries. Neither was part of the goal. There is a wide array of low-med-Z some-gain wall-powered applications where the 990 fits fine.
And people who are surely capable of working up a new design keep fiddling with the 990. Apparently they think it is still a darn-good plan, and better than any other they can come up with. Certainly others have designed very different amps and done well, but the 990 seems to hold its head up very well in the best crowds.
Personally, I was away from fancy audio for decades, and was quite astonished to learn that the 990 is still a leading-edge amp. I knew it was good. When I thought about it, I realized it was roughly unbeatable (in its niche). But a lot of good designs fall by the roadside over the years. Parts-supply, winds of fashion, economics. Jelly-bean chips with some of the 990's virtue at 1/100th the price. Nobody is getting rich making 990s (more profit in box and knobs than soldering 394s to a board), but it hasn't gone away and shows no sign of retiring.
If I were thinking of a "new amp module", I'd target the 5534/5532. It is very fine in its way, though some say recent production is not up to the old stuff. The world is FULL of 5532 sockets. If you can convince a wee fraction of those folks to pay, say, $25 to replace a $0.50 chip, with promise of adequate Class-AB current and low-low offset, there might be a self-supporting hobby in it.
