Md441 repair

[rightintheface]

I bought an md441 cheap off the 'bay a while back, and the seller described it as having a very low level buzz compared to his other 441's. This was never a problem with my Profire 2626 or Ta@#$% m512 preamps, but I recently picked up a Gap Pre 73 and it's a very obvious buzz. Makes any quiet source (ie NOT drums or guitar amps) all but impossible. Sounds like a ground hum to me. I unscrewed the filter/xlr section and purposely disconnected the ground connection, then listened through headphones as I touched it against the body of the mic. The sound was louder with the ground connected but is the same actual sound.

I know the obvious answer is "don't use that preamp" as it works perfectly with my other preamps, but that's not the point: there's a fault somewhere I'd rather fix if I can. Anyone had experience fixing these thing? Maybe the filter module has developed a problem?

Just weird that it only happens on the GAP pre. I changed cables, tried different mics etc. no other mic had the buzz, and plugging the md441 into the Ta@#$% showed no buzz.. Very odd..

Thanks lads

[jkhuri44]

hmm, a friend of mine in the USA fixed a 441 himself. Not sure if i can convice him to write a tutorial for you on it....

[rightintheface]

Jamil,
Any help would be great! I feel it's a problem with the HPF/XLR module, as I just discovered another mic that has the buzz - an unbalanced Akai dm13 mic from a R2R. Thinking maybe there's aproblem with the cold connection in the MD441, will have a tinker today.

[rob]

I've fixed a few of these but not with your symptoms
They are annoying to work on as all the shock absorbing internal mounts are covered in a sticky goop. There is a sealed can joined to the back of the capsule that has equalising components in it. The circuit board often breaks. Everything is glued up tight.

But do check you have good continuity between pin 1 and the body and check for open circuit between pins 2 or 3 and the body

[rightintheface]

Hey Rob,
Thanks for the comment mate. During the day I unscrewed/removed the XLY/HPF module from the bottom of the mic, and used bare wires touching the hot/cold pins at the bottom of the mic connected to a separate cable - no hum! I guess there is something wrong with the xlr module (which I have read about on the interwebz that the HPF filter can go south). SHame that it's 33 +shipping euros for a replacement part WITHOUT the filer section (77 euros for that one) as I find the HPF pretty handy.

I might try cracking into the XLR module (seems impenetrable though) and see if there's a wire loose somewhere