JoeMeek JM27 (SDC) mod-with samples

Hi gang,

Recently purchased a JoeMeek JM27 SDC. It's a pretty neat single transistor, transformer output circuit. It had room for improvement (very scooped sound), so I looked inside for potential weak links.

It has a ceramic capacitor at the capsule which I changed to the Polystyrene recommended for the MXL 603 mod (they're both 1000pf). And replaced a couple of other ceramic caps with Panasonic metal films. There are a couple of 4.7uf tantanlum caps that I might upgrade with a better brand if I can find them in stock.

Tried on acoustic guitar and compared to samples recorded without the mod, and the difference was pretty dramatic. The low end was rumbling before, and now has tightened up quite a bit, and the mids are much more present than before. Way less scooped.

Made me curious about finding a real nice transformer and see what would happen.

Craig

hi, It's a good idea, really not expensive and it looks to be efficient.
Could you send samples? :green:

Yeah, it's cheap enough. I'll post the samples later.

Samples:
http://www.angelfire.com/ky3/craigorris74/jm27before.wav
http://www.angelfire.com/ky3/craigorris74/jm27after.wav

8 inches from the 12th fret on a Korean acoustic through a Baby Animal with JLM14 and JH 990.

hold a tic. didn't you post over the weekend that you was having problems and not getting sound to pass through or was that another lab member?

Yep, that was me. I think I just burned up the first 1000pf capacitor. I put another in and it was fine.
Craig

atta boy :thumb:

A very familiar comparison. I can pick out individual strings in the "after" sample instead of it sounding like one big blur in the "before" sample. Amazing what a little cap change can accomplish. :wink:

WIMA polypros can work wonders too.

The difference isn't small. I thought mic was incredibly boomy before and would need serious eq to be usable, especially in a denser arrangement.

Try this: WIMA FKP2-1000/100/2.5 (get them from Mouser in the US)

Very similar sound to the polystyrene to my ears, but more consistent and less susceptible to soldering damage.

I'll give em a whirl on the next one I do. I've actually got some of those around.