Amp hiss/drone

  • Thread starter Thread starter Dorian Mode
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Dorian Mode

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Hello,

I'm having problems with amp hiss. It seems to get better and worse at different times. It increases as I turn the amp volume up, but it's still loud enough to be annoying when I have the amp volume low and the volume on the guitar up all the way. The amp is a Fender Blues Jr. It has the stock 12ax7 tubes (the amp is about a year and a half old, bought new) and new JJ el84's. I'm more concerned with this now because I've just started recording from the amp.

Here is a recording of the hiss: uploads.mailboxdrive.com/831815.mp3 [You have to copy it into your browser because the board won't let me post links]

Another problem is a constant low drone (that you can also hear in the mp3 file). It's usually much quieter than the hissing, and it keeps at a constant volume.
 
Bump. Does anyone know of another message board where I could find the answer to this? One with a few good electronics/gear geeks..
 
The hum is probably a sign that the body cavity of the guitar could use some copper foil tape to shield it better. The hissing... dunno. You might try switching temporarily back to the original tubes and see if the problem goes away.

Hmm. Now that I listen to it, the sound is much more mellow than a ground hum---almost like a bad filter capacitor in the power supply is letting a little 60 Hz mains hum leak in. You might crack it open and see if there are any obviously bad capacitors (bulged and/or leaking). You might also try a different outlet in case there is a grounding problem on the outlet.
 
Dorian Mode said:
Bump. Does anyone know of another message board where I could find the answer to this? One with a few good electronics/gear geeks..
Click to expand...

24 hrs is too long to wait???? no need to be insulting... are you using Real Cheap cables??? could be very bad shielding and /or molded plugs for the hiss...
 
I didn't mean to be insulting... I was just wondering if there was an amp-related forum somewhere which would specialize in this kind of thing (since this board is focused on recording).

The cables I'm using can't be the problem. The amp gives off the same hiss (and hum) even when there are no cables plugged into it. I also tried plugging it in to a couple other outlets in other parts of the house with no change in sound either (I don't know if grounding issues would be localized to a specific outlet though).

On the subject of tubes... I don't have the old power tubes anymore. Could the problem be the pre-amp tubes (it might not be a bad idea to replace them soon anyways)?

I will try to open up the amp later today and check the capacitors. Thank you both for the suggestions.
 
Thanks for the link, Milnoque. In further updates, I checked the capacitors and there is no visible damage. Everything looks clean inside.

I wonder what kind of problem the hissing is a symptom of. Is it most likely the result of a loose connection or a faulty circuit (since that's what it seems is being suggested here)? Or could it still be a grounding or interference problem? (I know nothing about electronics)
 
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