After a few months of non-use I plugged in my Arcam CD72 today and find the analogue output greatly reduced in level. I have to turn my amp right up to hear it, though the quality sounds as normal. What can cause this? Surely the failure of anything in the analogue stage would lead to silence? Is there some sort of mute low output mode that can be engaged? I can't find any such thing on the remote...
Sounds odd. Both channels affected ?
As ever, you have to be sure... and that means measurements. Are you simply swapping the RCA leads over between this player and another to 'determine' and prove its its low (which is basically OK as a method) or is it all an unknown set up and you think the output is low but could in fact be an amp/amp input issue.
If it is the player then looking at the circuit and muting arrangement (typically one or two pairs of transistors) and seeing if they are indeed turned on by the system control is the next step.
As ever, you have to be sure... and that means measurements. Are you simply swapping the RCA leads over between this player and another to 'determine' and prove its its low (which is basically OK as a method) or is it all an unknown set up and you think the output is low but could in fact be an amp/amp input issue.
If it is the player then looking at the circuit and muting arrangement (typically one or two pairs of transistors) and seeing if they are indeed turned on by the system control is the next step.
Arcam CD72/92 uses mute transistors which actually short the signal to the ground when logical command MUTE is on (function: STOP, PAUSE, SKIP, etc.). Although it would be very unlikely that the logical signal is opening mute transistors only partially (normally it is either 0V or full TTL swing), try measuring the voltage on TP13 which is common L/R base of mute transistors and you should get 0V in PLAY.
I would also check voltages on operational amplifiers in analogue stage.
I would also check voltages on operational amplifiers in analogue stage.
My CD 72T has a mute relay on the op amp outputs.
The CD 72 has a mute transistor.
The CD 72 service manual is easy to find on line, but I have never found a CD72T manual.
CD72T output stage is fairly simple The only thing I found out of the ordinary with my CD72T was the output op amp stage was biased class A with a single resistor to a voltage rail.
The CD 72 has a mute transistor.
The CD 72 service manual is easy to find on line, but I have never found a CD72T manual.
CD72T output stage is fairly simple The only thing I found out of the ordinary with my CD72T was the output op amp stage was biased class A with a single resistor to a voltage rail.
Thanks for the replies!
It's both channels and it's definitely the player - it's my regular setup (Roksan Caspian amp) and I definitely didn't have to have the volume turned right up previously. I tried a Rega Planet CD player into the same amp input- back to usual level.
Thanks for the suggestions - will get into the case with DMM as soon as I can (might be next weekend though).
Ian
It's both channels and it's definitely the player - it's my regular setup (Roksan Caspian amp) and I definitely didn't have to have the volume turned right up previously. I tried a Rega Planet CD player into the same amp input- back to usual level.
Thanks for the suggestions - will get into the case with DMM as soon as I can (might be next weekend though).
Ian
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