I've been trying to identify the source of a popping noise in one channel when the amp is idle. It appears to be mostly positive excursions that last around 1ms or less and are about 1V on an unloaded output. The amp has a jfet input using 2SK170/2SJ74 put those are difficult to find so I have not swapped them out. I've replaced the 2SC2240 and 2SA970 in the differential pair with KSC1845 / KSA992 and the issue continues.
Power rails seem ok and I've tested the caps on the differential section which is regulated. I believe that it is either heat or voltage related as the issue happens more often as the rails approach the 60v limit of my bench supply and it almost never happens in the first few seconds after applying power.
The amp is direct coupled so it is more difficult to isolate the stage that is causing this. I'm hoping to get some suggestions to track it down.
Power rails seem ok and I've tested the caps on the differential section which is regulated. I believe that it is either heat or voltage related as the issue happens more often as the rails approach the 60v limit of my bench supply and it almost never happens in the first few seconds after applying power.
The amp is direct coupled so it is more difficult to isolate the stage that is causing this. I'm hoping to get some suggestions to track it down.
Do you have a Service Manual or Schematic for this Parasound A52?
I doubt the problem is in the input stage of the amplifier itself.
I doubt the problem is in the input stage of the amplifier itself.
I agree -- it sounds like a bad soldered connection related to the output devices when heated but I have come across this in an amplifier that was unstable and giving off insipid oscillations when heated.
I have a schematic but don't have permission to post it. I've also have an ltspice simulation to help with troubleshooting so that may be an option. Are you looking for an overview of the design or something specific?
Without a circuit, and without an amplifier, it is difficult to understand something in words alone. ltspice will go too. but there most likely everything will be simplified, without a relay and a power supply.
Here's my ltspice file. It's very similar to the HCA-1205 which has a schematic available with a quick search.
You can handle such a detailed diagram faster than any of us. At the very least, you still have the ability to replace the tensions at the control points.
Deo99 it it possible to have you PM me the A52 schematic? I have an A52 with, at the very least, bad supply caps.As long as I am in there I might as well see if anything else needs replacing.