What's the buzz on hum in old tube amps?

[Steve Conner]

Yeah, turn off the fan, then the engineer will complain about the sound of the electronics sizzling.

I just sold some old gear to a local guitarist who said that he did the cab-in-the-van thing too.

[Gtr_tech]

That is the most ridiculous thing I ever heard of. Maybe those cats *like* the sound of everything in the van (and the van itself) rattling like its about to explode.....sounds like a dumb idea to me......
And....you get no guitar/spkr interaction. You may as well play a POD into the PA....
Now GIT OFFA MY LAWN!!!!!

[Steve Conner]

It would be really cool though, if you walked out after the show, and the van actually had exploded.

[Enzo]

A while back now, I got a call from a guy who was in radio production, and he wanted to pay me to burn out electronic parts so he could record the sound. I think he had the idea that stuff makes all these great movie-like noises when it burns up. He was very disappointed when I told him that most parts when they burn out either do so with a simple "snap" sound or possibly a small FFFTT. I think he was hoping for some sort of BZZZZWZZZZTTTT kinda thing. he never called again.

[Chuck H]

Enzo, why didn't you just take the opportunity to create your own sound effects for the guy? As in alter the parts or burn them in such a way as to prolong and accentuate the effect. I know time is $$$ but when will you ever get another chance?

Twenty years ago my band had a regular at this awful club that was so cliche we literally had to load our gear through an alley stepping over broken Thunderbird bottles and sleeping bums. In that case a van out back with an amp in it would have just been rude.

[Mark Black]

Twenty years ago my band had a regular at this awful club that was so cliche we literally had to load our gear through an alley stepping over broken Thunderbird bottles and sleeping bums. In that case a van out back with an amp in it would have just been rude.

Ha! That brings back some memories, although the broken glass at the club I'm thinking about was in an interior hallway and there were no sleeping bums (not right there anyway). Funny - back then I just used to wonder why they never cleaned up that hallway - these days I would probably bring a shop-vac the second or third time through...

@MrEarl: Looking forward to hearing how this goes if/when you implement the great advice posted in the thread.

And on the topic of shielding the rear cover: Anybody have a good suggestion about where to find some adhesive-backed heavy foil, similar to what many of the amp manufacturers use? Or would metal screen & staples be the preferred method?

[Tom Phillips]

... Anybody have a good suggestion about where to find some adhesive-backed heavy foil, similar to what many of the amp manufacturers use? Or would metal screen & staples be the preferred method?

I just use heavy duty aluminum foil and attach it with 3M spray adhesive. Works fine but you do need to insure that at least part of the shield presses firmly against the chassis when the back panel is screwed down.
Tom

[Marc]

I bought a roll at Home Depot in the HVAC section to seal the duct in my kitchen vent, its duct tape made with metal not vinyl/cloth.

[Chuck H]

I just use heavy duty aluminum foil and attach it with 3M spray adhesive. Works fine but you do need to insure that at least part of the shield presses firmly against the chassis when the back panel is screwed down.
Tom

+++ That's exactly what I do most of the time. But aluminum doesn't provide much EM shielding. It does improve the ground plane though. I do it because I'm lazy. Copper would be a better choice. You can buy copper flashing at your local hardware store. There are different types. Some have a psuedo tar backing and others have a PVC backing. The PVC backing can be removed and the flashing can then be stapled in place. This is probably the best shielding. But, as noted, heavy aluminum foil and spray adhesive seems to work fine.

[Tom Phillips]

The foil is also a good way to seal up the asbestos used in the old Fender amps and add shielding at the same time.

[Mark Black]

The foil is also a good way to seal up the asbestos used in the old Fender amps and add shielding at the same time.

Ah yes - there is indeed asbestos of some sort stuck to the back cover of some of the old amps. Some people freak over this (and that's not necessarily wrong mind you). I just look at it and think back to my days as a shipyard worker & later motorcycle mechanic where I used to be exposed to aerosolized asbestos in the form of pipe lagging & brake dust and figure "meh - I've seen worse..."

Not a bad idea to cover it up though, regardless of shielding. Definitely don't scrape it up into lines with a razorblade & snort it! (Not that I would know about such things - probably read it somewhere...)

[Tom Phillips]

I have always wondered why the asbestos in the Fender amps has not become a hot topic. Especially since people seem so concerned about it when it turns up in other places.

[Chuck H]

In the architectural coatings arena the common knowledge is that back in the day there were four basic asbestos product forms that were either turned into textiles or incorporated into other textiles. Only one of the four has ever been proven to cause asbestosis. And it wasn't used much. But all I know for certain is that the asbestos product that was once used in acoustic cieling texture (often called "popcorn" cielings by laymen) isn't the one thought to be harmful. Still, all the usual regulations and hazmat requirements for handling still apply. You can't be too careful but I hope this takes the fear level down a little.