Help needed- slight noise after mod.

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hi

I desided to convert my old Denon PMA925R into a power amp by bypassing the pre stage. The problem is that there now is a slight noise in both channels.

An externally hosted image should be here but it was not working when we last tested it.


I have used the tape/dat input, and chosen to run the ground through the original path, and then bypas the pre stage with two wires directly from the connectors. The old signal path has been terminated.
The noise is constant, and does not get higher when the volume is turned up. It stops when i switch off the input source. The noise is not that high, but it is anoying.
What can cause this? Should i run the ground directly from the connectors also?
 
Last edited:
Than it must be a problem with the signal path chosen for this amplifier, just for testing you could go in with the signal without using the conectors/plugs on the pannel, just connect a shielded cable on the input of the power amplifier and route it directly to the signal source, if this way all is good than you know for sure that the trouble is with the signal path, maybe with the ground, also make sure that you have a dc-coupling capacitor in series with the signal.
 
An externally hosted image should be here but it was not working when we last tested it.


Here is a picture of the signal path, and the red cirkles is where i have connected the signal. 1 is the signal in, and 2 is the ground.
I will try to connect both the signal and ground to these plugs.
How big should the dc coupling capacitor be? And should it be an electrolytic or a bipolar?

Sorry for the possible noob questions :)
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.