"Ian Iveson" wrote in message
...
Keith G wrote:

OK, OK, I get it - 'neither one, go and fix the valve mic', eh?

Replaced this (probably perfectly OK) JAN Philips with a nice little
'Chelmer' badged short plate (for, er, low microphony) Sovtek 12AX7 and
thought I had at least significantly reduced the hum for a while, but
it's back now!!

http://www.moirac.adsl24.co.uk/showntell/AKG-1.jpg


(Guess I now know why the mic was on eBay!! :-)

Here is a shot of the orange LED that makes the valve 'light up':


Hum?

Power supply should supply regulated DC for heaters and HT. Does yours
have a "ground lift" switch?



Yes and I'm sure I've tried it both ways, but I'll have a more careful look
at it in the week. I don't think it is the valve, but if it was, there's
always the chance I've swapped one noisy valve for another!


AKG mics seem to be well supported with info such as he

http://www.akg.com/mediendatenbank2/...5d251a2cd0.pdf



Thanks for that - I have already got that somewhere but I don't think I'll
be stripping it down that far myself. If it comes to it, I'll send it off to
have it serviced by someone who knows what he is doing!

Reading some of the information about these mics on the Net I'm seeing a lot
of people have swapped the valve for the *exact same* Mullard I gave/loaned
to a friend for use in his Croft preamp which the *****ing idiot*
suddenly/surprisingly sold, letting the Mullard go with it!

Worth about 40 quid at the time, IIRC - I had forgotten that; now I am
reminded....