On 19 Mar 2005 04:44:50 -0800, wrote:

Hi,

I have an audio mixing desk from the 80's that is a bit 'hissy' (i.e.
background noise with no inputs). Would I be able to reduce this by
replacing the op-amp ICs with lower noise versions ? ...or is this
sort of noise nothing to do with the op-amps ?

I have obtained and scanned the schematics, in case anyone fancies a
quick look. It's only a 1Mb PDF file, located he-

http://homepage.ntlworld.com/anengin..._Schematic.pdf

The vast majority of the op-amps are physically labelled:-
'4558 DD'
' JRC '
' 1266B '

I'm presuming these were made by the Japan Radio Company. (The
schematic refers to them as 'TA4558NB')

The desk incidentally, is an 'INKEL MX-1410' made in Korea.

Any help would be very much appreciated.

Cheers,

Kev.

The mic inputs are discrete - you need to be looking at Q101 and 102
and so on. I'm presuming the line level stuff is quiet enough.

d

Pearce Consulting
http://www.pearce.uk.com