noise in speakers as long as mute is enabled eT3/Cl 62

[Jack]

Hello, I am Jack from France, may I ask a question about a noise that appears in both speakers (Harbety 30.1) when my preamp is on « mute » and then disappears as soon as the preamp is no longer on mute, with a display of volume level different from zero!

I have a ET3 SE and a Classic 62 SE, 2 years old. I noticed that a few months ago.

The noise is not loud but you can really hear it in the room, it looks like a endless serie of clicks (////////) with a medium tone. (I have recorded it but I don’t know how to post the recording).

I have tried many things:

Different main power leads → still the noise

New tubes in both amp and pre → still the noise

Amp alone without any cable with preamp → no noise

The noise comes again when I switch RCA cables (Cardas blue sky) between pre and amp. In this case the ET3 is alone without any main power lead nor other input cables.

And when the ET3 is plugged and switched on, and when lit is no longer on mute after 90 seconds, the noise disappears, and comes again when mute is enabled…

Does it looks like a ground issue? Where ? On the preamp? Has anyone ever noticed that once?

Thank you for your opinion on a subject that is not very easy to expose for me!

[admin]

It could be a ground loop. If it is, the frequency of the sound would be 60 hz. If you have a recording of it, you can upload it as an mp3 file. Just use the "full editor and preview" button below and you can attach files as needed.

It does sound like it's a preamp issue. Not sure exactly how the ET3 handles the mute function, but perhaps the signal path is manually broken with mute vs just incremental higher resistance as in units with a volume pot. This may explain why it is only with mute.

[Jack]

Sorry but I get this message, but my file is a valid mp3 file (I think)

[admin]

Please try it again. I have updated the attachment settings. The file size does still have to be less than 15 mb.

[Jack]

It works! The previous file was too big...

[admin]

Not sure if the previous file was too big, but I also had the settings wrong for mp3 attachements.

Anyway, that does not sound like a ground loop to me. Ground should be a pretty consistent 60 hz "buzz".

Audacity frequency analysis maximum peak at 145 hz, but the "click" are not regular like a ground loop should be. There is something else going on that is not a fully repeating noise.

[AnotherJohnson]

That sounds like interference.

[AnotherJohnson]

The noise comes again when I switch RCA cables (Cardas blue sky) between pre and amp. In this case the ET3 is alone without any main power lead nor other input cables.

Does this mean that if the preamp is unplugged, but the rca interconnects are installed between the preamp and amp, that the noise is present?

I’m wondering if it’s not interference coming in via these interconnects.

Take some aluminum foil and wrap them loosely to shield them. Or, use a really cheap pair like what used to come with a DVD player (they’re lousy, but well shielded).

If either of these measures solves the problem, at least you’ll know where to put your effort.

[Jack]

Thank you for your answers, I think it was interferences mainly from my home electric current; I have reorganized all my cables behind all my stuffs and it is now better. I am glad that my CJ gears are ok, as my dealer is in London (and me in France)!

[admin]

If simply moving cable position influences the sound, it pretty much guarantees that it is an interference issue. Getting some shielded cables may be a good idea in this particular situation.