Tube amp noise

[suave eddie]

I have a Mesa Boogie Subway blues purchased new in 1994. It is the first generation model with the two separate inputs (not the toggle switch).

I know at least two other board members have this model amp and I have a few questions. I am pretty ignorant regarding maintenance of tube amps.

Does anyone else here have the same model I have with the two inputs? This particular model has a known issue with a loud hum that starts after warming up for about 40 minutes, and the issue was resolved with the subsequent ‘toggle switch’ models. Apparently the easiest fix for this is to bypass the effects loop. Has anyone here done this modification, and if so do you have detailed instructions on how to do it? Since I was not generally gigging or recording with the amp, it’s never been worth my while to fix the hum issue, but I might want to finally resolve it.

The next question is regarding general noise coming from the amp. In the 17 years I have had it I have only used it in a gig situation a few times. Most of its use has been in the home and the volume rarely goes above 3-4. I recently brought it to a jam and noticed that when it was cranked up to 7-8 it seemed to be pretty noisy. This is general noise, not the hum that appears after warmup. It’s been so long since I’ve been able to crank it up loud that I can’t remember if this is a new development or not. How much noise do your Subway amps produce? I realize tube amps are generally noisier than S/S.

I had the original tubes in it until a couple years ago when I replaced them all just on general principal and kept the old ones as I don’t think they are defective in any way.

What sort of general maintenance do you do on tube amps? I know that caps can wear out and leak and create problems. Should I be concerned about having a tech go through the amp for any sort of general ‘tune-up’? Do capacitors give any warning before they fail?

I’ve seen in previous posts that yowhatsshakin and southpawguy have Subway Blues amps.

[sickbutnottired]

eddie,

I don't have any experience with Mesa, but I play a lot of old stuff!

In my experience caps don't just 'go bad' all at once. They seem to 'degrade' before they totally meltdown. I have had somewhat knowledgeable people tell me that caps have about a 10 year life expectancy at peak performance.

In my experience, I often wait until I have an acute problem. But after I get the recap done, I realize that the amp hasn't been what it should be for quite some time.

Noise is a common symptom of filter caps going bad on Silverface Fender stuff, and usually it's not to long after the noise gets annoying (to the point that you can't ignore it) that you have a major problem.

I don't do my own recaps, it's easy to ruin caps by getting them too hot; and in some spots you can have to solder multiple things at once. My brother does mine, he is not a pro amp-tech but an EE and generally good mechanic.

So anyway, check the easy stuff, replace key tubes, etc. but it might be worth it to get a once over by a tech.

Cheers

[yowhatsshakin]

Hey eddie,

My Subway Blues has the fat switch. It is not all too noisy (yet) but in my case the reverb circuit has conked out. I have to have it checked one of these dayas but never got around of doing it. As far as noisyness of tube aps is concerned you should see how noisy it is without anything connected. Guitars as well as effects can pick up RF or other stray signals that seem to make these amps very noisy when cranked. Just FYI.

- Jos

[suave eddie]

As far as noisyness of tube aps is concerned you should see how noisy it is without anything connected

Yeah, the noise I noticed recently is without anything connected--when I crank the volume up. I have a feeling it is normal to this amp but it has been quite a while since I have been able to play it loud that I really noticed it.

You have the second generation Subway, so the other "hum" issue I mentioned has been worked out already in your case.

Just out of curiosity, do you ever use the "fat" setting?

Get that reverb fixed--it's one of the nicest reverbs I've heard on a small amp.

[louis cyfer]

it's time to recap. some of the caps are starting to go. it is a gradual process. a good tech will only replace what is out of tolerance, not everything. makes a big difference, i just had my 57 deluxe recapped, love the results. noise is gone now.

[suave eddie]

Yeah, well I figured it's probably time to have it gone through. I will have the "hum" problem sorted out also. I never use the effects loop so that's no problem.

[yowhatsshakin]

Just out of curiosity, do you ever use the "fat" setting?

Yeah, depends on whether I use buckers or single coil. Whenever I switch guitars I'll tweak the controls if necessary and sometimes that includes the fat switch.

Get that reverb fixed--it's one of the nicest reverbs I've heard on a small amp.

I will Michael. One of my new years resolutions

- Jos