Hi,
With Xtmas holiday and new year's coming I am having some time to finish some (unfinish🙂 ) things.
I am using a preamp based on OPA627/BUF634 and a NIGC after it. Before the pre I have an Alps blue 100k. My problem now is that as I turn the volume up a very large hiss comes from the speakers.
I have the input connected to the volume pot with microphone shielded wire (~25 cm) , being the pot on the front of the standard 17" case. Then it goes to the preamp some (~7cms) with cat5 cable and to the NIGC (5 cms) again with cat5. If I ground the output pin of the pot the hiss is gone so the problem is between input and the pot. I don't want to move the pot to the back of the case, as it is a bit full (It is a 2.1 setup, with LM3875 for the main speakers and a OPA549 for the sub).
This hapens both with a source connected or not. Any suggestions on how to deal with it?
Miguel
With Xtmas holiday and new year's coming I am having some time to finish some (unfinish🙂 ) things.
I am using a preamp based on OPA627/BUF634 and a NIGC after it. Before the pre I have an Alps blue 100k. My problem now is that as I turn the volume up a very large hiss comes from the speakers.
I have the input connected to the volume pot with microphone shielded wire (~25 cm) , being the pot on the front of the standard 17" case. Then it goes to the preamp some (~7cms) with cat5 cable and to the NIGC (5 cms) again with cat5. If I ground the output pin of the pot the hiss is gone so the problem is between input and the pot. I don't want to move the pot to the back of the case, as it is a bit full (It is a 2.1 setup, with LM3875 for the main speakers and a OPA549 for the sub).
This hapens both with a source connected or not. Any suggestions on how to deal with it?
Miguel
The first thing that I can see is that there is no connection between the pot and the signal ground!
Sorry. The drawing is all from my head... The pot's ground goes to preamp's ground, then to NIGC ground and then to star ground. If I connect the output of the pot to pot's ground everything becomes quiet at full volume.
Miguel
Miguel
But that is only because you are shorting the signal to ground so none if it get's through to the amp!
About time we had some more help here! 😉 hint - hint.
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