Speaking A*P*I....
I'm currently busy with many projects, but one of them is some kind of rebuild of a dual 15 band graphic EQ, into a dual 15 band 560.
The graphic EQ that I have is a low cost old unit, belonged to a local radiostation. I used this EQ years ago for soundshaping of distorted guitars. It's very easy to use, but the sound gets degraded, and that's also the reason why I haven't used it anymore. There were also a couple of sliders broken, so I had to use a screwdriver for setting these sliders, haha. This week I have repaired the sliders (replaced the sliding part with new ones, because I couldn't find sliders with the same taper and size).
Anyhow, the beauty of this EQ, is that the filters are built the same way as the 560, including the slidertapercurve and value. So, the only thing needed, is to replace the line amp, which currently consists of a few 4880 opamps. I have bought the parts for getting it A*P*I. a pair of gar2520's, 6 LF356 opamps, C's 'n R's. I do have a pair of Jensen outputtransformers, similar to the 2503 outputtrannies, but they probably don't fit in the enclosure. Maybe I'm going to use a pair of Lundahl's instead. But I still have to design a PCB for it.
I'm curious what the result will be.