"I bought a bunch of Thomas Henry books from Magic Smoke and I got really curious about the circuits in the 'Making music with the NE570 compander' book. I decided to make a compact module with as much as I could fit from the book. And then the 570 Galore was born: 5 separate dynamic functions that are normalled to the first input (only the first input has a gain control, if you need more than you need to change the levels with other modules). It features a Compressor, Expander, AGC (automatic gain control, some sort of compressor), Limiter and an Envelop Follower).
It is a tight build, only for the experienced builders and putting it together will be a little puzzle, but it is a fun and versatile module packed with sound shaping tools (and the envelope follower is also very good), especially for drums!
This is not a hi-fi project, but the functions it performs can be still be useful. Be aware that when you have noise in your system a module like this can highlight the noisefloor.
There is not much to tweak so it is possible that for some materials it doesn’t sound good (changing levels already makes a big difference).
Here is a demo
Acquiring the book is recommended for understanding, tweaking and debugging.
I have permission from Thomas Henry to sell this project.
There are 2 versions of the chip: 570 and 571. The 571 is said to be lower specced, but I think for this project it doesn’t matter so much which one you choose (I built them with both the 570 and the 571 and didn’t hear a noticable difference)."
Solder these first (ordered from top to bottom):
C1c (1µF), R4 (27k)
The reason for this is that they are between the ics (and one half under a trimpot) and very hard to get to if you don’t do them first.
The following smd parts are on the top side:
C1,C2,C3,C5,C6,C7,C8,C9,C10 (all 100nf) and Cda (560pF)
Maybe the best moment to do this is when you are done with all the smd on the bottom side.