Member Since 07 Jun 2010
Offline Last Active Jul 25 2016 09:05 AM

Topics I've Started

D-75 Amp -- Suspected fault in IOC

31 May 2016 - 07:48 AM

I haven't opened it up yet, but I figured I'd post here before diving in.

I have an original Crown D-75 amp, connected between a Tascam DM-24 mixer and a pair of Event 20/20 passive speakers.  Same setup I've been using for years.  Up until recently, the amp lived in a closet just outside the studio, in a rack with the noisy computer.  It has since been moved into the studio to join the rest of the outboard gear.  Still connected to the same gear, and powered from the same exact branch circuit.

I've noticed that the IOC indicators light up quite frequently.  I have each channel's level control set to about the 1 o'clock position, and I tend to monitor at reasonable levels (rarely louder than 90dB, measured at the mix position).  

It's not just when using the Tascam mixer.  I've also tried connecting right from the balanced outputs of the sound card, with and without a passive attenuator between them.

Usually, the IOC lights will sort of flicker with the music, acting almost like peak indicators.  But, I also notice that once there's sufficient level to make them stay on, they stay on long after the music stops.

Incidentally, the music sounds clean even when the IOC's are lit.  I'm not hearing any distortion.  I haven't tried just running pure tones yet.


P.S.:  Several years ago, I did have to perform the typical cooked resistor replacement, along with the attendant diode.  (Don't recall the exact part designations...)