ENGL sudden microphonics/nasty feedback problem...amp gurus please help!

[Young Angus]

I rehearsed last week and all was well...come this week after not even having touched the settings on my amp because I didn't play it since, I turn it on and straight away it starts howling at the moon (if it could see it anyway). There was just uncontrollable feedback everywhere, even when on the clean channel with a light gain from a pedal. I also swapped guitars to make sure it wasn't them and nope, same thing...all with humbuckers mind you (one JB and one BBpro). I couldn't even silence it by playing or muting the strings, it just went bananas and I didn't even have the gain cranked as I never do anymore.

This was on my ENGL Savage 120 by the way. What could cause this? My guess is a tube that's gone bad/microphonic...the question is though would it be a preamp or poweramp tube, and can I pick it just by looking closely at them? I didn't notice any strong glowing or anything.

 

[Young Angus]

Re: ENGL sudden microphonics/nasty feedback problem...amp gurus please help!

Okay well I pulled all the preamp tubes one by one replacing them in turn with a good tube and still no answer. One thing I did notice though was that when I had the amp on and at feedback volume, i stepped on my cord and it fell out...and no matter how much I touched the tip of the cord it would not feed back at all even though it made some horrible noises...but that probably doesn't mean anything!

Also I tried the tap test on the tubes and the only one that I can hear at the speaker is V1...but I can hear that tap from V1 no matter what tube I put into the amp so I'm guessing V1 is just a sensitive spot in the amp where you will hear a tap anyway and it doesn't mean something is wrong. Is that correct?

 

[StrangeSound]

Re: ENGL sudden microphonics/nasty feedback problem...amp gurus please help!

I think it could be the power tubes. Do the tubes glow?

I'm no expert sorry..consider this as a bump

 

[StrangeSound]

Re: ENGL sudden microphonics/nasty feedback problem...amp gurus please help!

How's the amp doing??

My Screamer produces a light hiss in the clean channel..stock power tubes in there..already switched the preamp tubes around..didn't improve it.

Do you think a power tube swap would stop the hiss in the clean channel?

 

[Ray 911S]

Re: ENGL sudden microphonics/nasty feedback problem...amp gurus please help!

Hmmm. I was considering buying the Engl E530 preamp, but it seems that the two of you have had problems with hiss. Is this a common thing with Engl preamps?

 

[Young Angus]

Re: ENGL sudden microphonics/nasty feedback problem...amp gurus please help!

Mine is not a hiss problem, and no I wouldn't say it's a common thing.

 

[Marinblues]

Re: ENGL sudden microphonics/nasty feedback problem...amp gurus please help!

Hmmm. I was considering buying the Engl E530 preamp, but it seems that the two of you have had problems with hiss. Is this a common thing with Engl preamps?

I generally found that they are silent amps so, if any unexpected hiss turns up, it gets noticed.

For example, my friend has a vintage Vibrolux which hisses and hums as soon as you switch it on (it plays beautifully though!), so any additional hum doesn't get noticed that much.

M.