Amp is squealing. Help?!

Alex W

Alex W

Pork and Beans connoisseur
I bought a Jet City custom 22 head from reverb in mint condition. I just got the thing yesterday. When I turn the gain up past 5 on the overdrive channel it squeals like a feedback sort of squeal as soon as I lift my hands off the strings.

I took the pedalboard out of the signal chain, still happening.

I tried all my electrics and it's not specific to one guitar.

I tried playing as far away from the amp as my guitar cable would allow and it's still happening.

I checked to make sure the tubes were seated correctly and they were.

I read on a forum that to check if the tubes are microphonic you should turn the amp up full blast with nothing plugged in the input and tap the tubes. I heard the tap through the speaker on every single tube, preamp and power. Did I check them wrong?

These are the unbranded original tubes. It was sent through the US Mail from Kentucky in this cold ass weather.

Is this likely due to bad tubes? Is there anything else I could could check?
 
Alex W said:
I bought a Jet City custom 22 head from reverb in mint condition. I just got the thing yesterday. When I turn the gain up past 5 on the overdrive channel it squeals like a feedback sort of squeal as soon as I lift my hands off the strings.

I took the pedalboard out of the signal chain, still happening.

I tried all my electrics and it's not specific to one guitar.

I tried playing as far away from the amp as my guitar cable would allow and it's still happening.

I checked to make sure the tubes were seated correctly and they were.

I read on a forum that to check if the tubes are microphonic you should turn the amp up full blast with nothing plugged in the input and tap the tubes. I heard the tap through the speaker on every single tube, preamp and power. Did I check them wrong?

These are the unbranded original tubes. It was sent through the US Mail from Kentucky in this cold ass weather.

Is this likely due to bad tubes? Is there anything else I could could check?
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You might want to email Soldano. I a podcast he said he’s still providing assistance with any issues with them.
 
my first thought it preamp tube. That is easy to determine, if you have any extra 12ax7s (or you can pull one from another amp) just use that one to replace each preamp tube one by one until the noise goes away. Hopefully that's all it is.
 
I’m also thinking it’s a tube. Then again I could be 100% wrong. The last time I had this problem it was a bad output tube though.
 
Smacks of a microphonic preamp tube. Try Chad's approach. If you don't have a spare 12AX7, they're less than 10 bucks unless you go bonkers. It's good to have a spare or two around anyway.
 
Alex W said:
I read on a forum that to check if the tubes are microphonic you should turn the amp up full blast with nothing plugged in the input and tap the tubes. I heard the tap through the speaker on every single tube, preamp and power. Did I check them wrong?
Click to expand...

Advice from forums? WTF. :old:

Hearing a noise when tapping tube is normal. If the tube goes into runaway oscillation, that would be a sure sign it was microphonic. But that test may not find all microphonic tubes. A microphonic tube has a loose part(s) that is prone to vibrating against other parts. When tapping the tube, we are trying to get it to vibrate.

This may also be just a case of a tube that just can't handle a high gain application. Too much gain at a stage can result in oscillation, this is why the JCM 800 2203/2204 uses a cold clipper second stage.
 
I played around with the amp for a bit then took it to a local tech. 2 of the preamp tubes were bad, there was a piece of sheet metal floating around inside the amp, and the transformer was loose. I told him to retube the whole thing with JJ's. The only thing that's left is for me to pick out a new speaker cabinet to match the head. I plan on playing heavier stuff with this thing and so far Vintage 30's seem like the ticket.
 
I took a day and tried a handful of speaker cabs. I did not like the Marshall origin (?) 2x12 with seventy 80's in it. The orange 2x12 with creambacks was delightful but a bit out of my price range.

I ended up buying a Panama cab on reverb that is loaded with their take on a V30. I know V30's are harsh to a lot of people but I think I've probably lost some of the upper range in my hearing and they sound fantastic to me.

20190325_040718.jpg
 
Alex W said:
I took a day and tried a handful of speaker cabs. I did not like the Marshall origin (?) 2x12 with seventy 80's in it. The orange 2x12 with creambacks was delightful but a bit out of my price range.

I ended up buying a Panama cab on reverb that is loaded with their take on a V30. I know V30's are harsh to a lot of people but I think I've probably lost some of the upper range in my hearing and they sound fantastic to me.

View attachment 47003
Click to expand...

Vintage 30's are A-OK by me and apparently many other guitarists. If they (or any speaker ) is new, be patient until they get "played in". Much like a good acoustic guitar as the top wood ages, the tone gets better.
 
As far as I’m concerned the orange ppc212 with v30s is the best sounding cab I’ve owned. A 4x12 cab of v30s is heaven. V30s FTW!


Sent from my iPhone using Tapatalk
 
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