Dyna Comp RI Mods
Uncompressed oversized .wav; http://soundcloud.com/beckyjc/dyna-comp-attack
Despite the hate, i think these are really sweet sounding boxes for good money. I’m not too into compression, but i like it for making stuff fatter, funkier and adding a bit of shimmer. It might not be a ub3r transparent keeley or whatnot, but for me, compression is supposed to noticeably improve your tone. The dyna adds a little high end, which i like. After hunting for a bit of a more tweakable compressor, I just settled on modding my own.
First off mines quite an old one, marked with Revision E on the PCB, as far as Dyna RIs go, revision E is pretty much their prime. Good quality metal film caps and resistors, high gain low noise MPSA18s, CA3080 chip, so really, not much needs changing parts wise. If you have an earlier version its worth swapping the caps and trannies to match up to spec (Dont bother with ge components, make sure everything you buy is for low noise, high gain and clarity.), Revision F onward as far as i know are pretty different, and i’m not sure how much of my mods will apply, feel free to poke around if you know what you’re doing though.
You need; DP3T (on/off/on, or just a DPDT on/on could work if you change the resistor values.), 10k resistor, 2x 300k resistors
First off is the attack mod, a very simple mod that adds just a bit more tweakability to the comp, attack basically sets how fast/hard slow/soft the compression steps in, a slower attack works better with distortion I find as its more subtle, where-as a faster attack sounds more clicky and funky, this mod will also affect the release time of the compressor.
Using an on/off/on DP3T gives you 3 options, 9k (hard attack, 300+10k in parallel),300k (softer attack) and 150k (stock, 300k+300k in parallel). Mount one of the 300k to one set of lugs on the end of switch, another 300k to the middle two lugs and the 10k to the lugs on the other end of the switch.
The resistor that limits the signal to the opamp is the 150k resistor, which is the only 150k resistor in the circuit, so it isn’t difficult to locate with a multimeter, it should be R14. Remove the 150k resistor and replace it with 2 wires leading from the middle 2 lugs of the switch.
Make sure everything snug and the leads to switch dont short on any of the other resistors; some heatshrink and tape. Double check everything works and you measure where to drill the hole in the enclosure since it will be pretty snug.
Getting back the lows
Another very easy mod, basically this is just switching the output cap so you don’t lose too much low end with the pedal engaged. The pedal definitely suffers from too much low end roll off. Maybe its part of the vibe, but I like my low end.
This is a 0.05uF cap on the original schem, replacing it with a 0.47uF restores some much needed thump without making the bass too overbearing. (Try 0.68 for a little more) This makes it much better for metal and high gain too. The cap isn’t too hard to find, on my dyna its the cap underneath and to the left of the trimmer or C9, (its actually a 0.047uF on Rev E rather than 0.05 fyi) you should be able to trace it from the signal out -> output level pot -> 10k resistor -> cap.
And heres the finished thing.