Effects send noisy

[surbas]

I've been trying to figure out why when I use the effects loop I get so much noise. It seems to be coming from the send jack, as soon as I plug a cord into the send the VM becomes noisy. It's not as noticable on LDR. I have to use a noise suppressor to get the noise under control, which kind of sucks. I'm only using a delay and noise suppressor in the loop. I replaced all the preamp and power tubes recently but that didn't fix it. SteveD or anyone have any ideas what's going here?

If I don't use the effects loop at the all the amp is pretty darn quiet in LDR and HDR.

Scott

[SteveD]

The effects loop has a little treble compensation to account for high frequency loss when using the loop with cables and pedals but nothing dramatic. It shouldn't need a noise suppressor unless you are driving a lot of gain into the front end to start with!

[KevinOConnor]

Hi Guys

Lift one end of R52 to hear the loop without the treble emphasis.

Have fun
Kevin O'Connor

[surbas]

I understand I'll get a little noisy when using the loop but the noise I get is ridiculous so I have to use a noise suppressor. I'm only using a delay in the loop, no other effects involved. I've tried other pedals in the loop as well, same results. I've attached an mp3 so you can hear the noise I'm talking about. Like I said, I don't get this noise when I don't use the loop.

[MKB]

Listening to the clip, it sounds like the noise is primarily coming from the preamp, not the effects loop. Here's a few things to try:

1) Does the noise stop when you have the amp in HDR and you unplug the cable from the input jack?

2) When you connect the effects send and return together with a 1/4" shielded cable, and enable the effects loop, does the noise change or go away? If the noise does not change, but you still get signal, your effects loop is OK.

Since the noise changes significantly when the amp is switched from LDR to HDR, the problem is most likely either at V2, V1, or the input to the amp. That noise sounds like your guitar is near a CRT monitor, or you have pedals on the amp input that are being powered by a switching power supply. Setting up the amp so it is noisy with your guitar, then unplugging the guitar cable from the front of the amp, should tell you a lot. If the amp gets quiet with the cable unhooked from the input, the problem probably isn't your amp.

[surbas]

Ok, tried what you suggested and here's my answers to your questions:

1) Does the noise stop when you have the amp in HDR and you unplug the cable from the input jack? YES

2) When you connect the effects send and return together with a 1/4" shielded cable, and enable the effects loop, does the noise change or go away? NO, noise does not change .

Based on my answers what does this mean?

Is it just a electrical interference problem? The thing that's weird to me is I don't get that crazy noise in HDR when not using the effects loop. It only happens when effects loop is enable and connected to a pedal.

Thanks,

Scott

-- Sun Feb 06, 2011 5:17 pm --

Well, I found the problem. My preamp tube in v1 must have been going bad, I replaced it and now the amp is much quieter. It's weird because I just retubed the whole amp back in the summer and haven't really played it much. Must have been a bad tube :(

-- Mon Feb 07, 2011 4:30 pm --

forgot to mention I just replaced preamp tubes in V1 and V2, that made it better.