Hello all,
I'm trying to repair an older PS Audio pre-amp.
The problem is that even in lowest position of the ALPS potentiometer the volume is "very" loud. So I cannot turn the volume completely off. There is music on both channels.
The amp uses a 20K ALPS potentiometer. I measured around 17K.
I tested the volume with the protentiometer desoldered and even then I can hear music. For me it sound like no difference if the potentiometer is connected or not. When I turn up the volume the potentiometer is behaving normal.
Here are some questions:
- Is the potentiometer in a pre-amp normally connected to the input or to the output?
- Is there normally an additional resistor in series with the potentiometer? Or anything pulling it low?
- Do you have any idea what to look out for?
Thank you!
Regards
I'm trying to repair an older PS Audio pre-amp.
The problem is that even in lowest position of the ALPS potentiometer the volume is "very" loud. So I cannot turn the volume completely off. There is music on both channels.
The amp uses a 20K ALPS potentiometer. I measured around 17K.
I tested the volume with the protentiometer desoldered and even then I can hear music. For me it sound like no difference if the potentiometer is connected or not. When I turn up the volume the potentiometer is behaving normal.
Here are some questions:
- Is the potentiometer in a pre-amp normally connected to the input or to the output?
- Is there normally an additional resistor in series with the potentiometer? Or anything pulling it low?
- Do you have any idea what to look out for?
Thank you!
Regards
Perhaps it is located in the feedback loop for setting gain and not after the circuit / op-amp as a volume pot / voltage divider. Schematics would give You tremendous help. 17 is 85% of 20 so between 20% tolerance. If it is in the feedback loop, there could be a resistor in parallel, coupling the input to the output. Are You sure Your source isn't too loud, overloading the circuit ?
Which exact model of PS Audio preamplifier do you have?
Check the ground connection from the volume control with an ohm meter.
If this connection is open, the volume will always be at maximum.
Make sure that the outputs you are using are NOT the "tape output".
Those are fixed in level at full volume. The ones you should use are
labeled something like "main out" or "line out".
Last edited:
Hello MAAC0, hello rayma,
thank you very much for your answers.
I was also thinking it has something to do with an op-amp, but as far as I can say- they are OK.
I've fixed the problem. It's an PS Audio P200 Pre-amp. I bought it broken and I think someone already did some "work".
Finally I found two problems:
1. One connection from the potentiometer to the Board was broken
2. The potentiometer itself seem to have a problem with it's resistance at the first few millimeters of movement. I've added a 1K resistor in series with one of it's the pins. Now it's working fine.
Thank you!
Regards
thank you very much for your answers.
I was also thinking it has something to do with an op-amp, but as far as I can say- they are OK.
I've fixed the problem. It's an PS Audio P200 Pre-amp. I bought it broken and I think someone already did some "work".
Finally I found two problems:
1. One connection from the potentiometer to the Board was broken
2. The potentiometer itself seem to have a problem with it's resistance at the first few millimeters of movement. I've added a 1K resistor in series with one of it's the pins. Now it's working fine.
Thank you!
Regards
- Status
- Not open for further replies.