Question about TH30 combo

[kmb8488]

Hi all,

My TH30 recently developed a somewhat subtle hum on both channels. I figure this is an indication that the power tubes should be replaced, but I first want to check in and see if anyone has had a similar problem, and if so, what worked for you? I replaced a preamp tube in the TH30 last October, but that's the only maintenance I've done to the amp.

Thanks!

[Blue Notes]

Mine did the hum thing as well from day one, changing the 12AT7 tube cleared it right up. Quite as a mouse now, only it has a micro phonic tube now, so more testing and tube changing ahead.

[Ronnie Robinson]

Hi all,

My TH30 recently developed a somewhat subtle hum on both channels. I figure this is an indication that the power tubes should be replaced, but I first want to check in and see if anyone has had a similar problem, and if so, what worked for you? I replaced a preamp tube in the TH30 last October, but that's the only maintenance I've done to the amp.

Thanks!

First I'd check each tube and reseat it in its position. Visually anything obvious? Do u have any spares you could swap in?. If tubes are over 2 years old they are probably ready for a change anyway if the amp gets used regularly.

Everyone has there own favourites but I've read that Ehx preamp tubes are good in reducing noise ....and I've had no issues using them.

If your changing power tubes Buy a matched set and install, it won't need additional biasing.

[Phlowen]

Mine did the hum thing as well from day one, changing the 12AT7 tube cleared it right up. Quite as a mouse now, only it has a micro phonic tube now, so more testing and tube changing ahead.

I had the same issue, but mine was always with the PI tube. I bought a whole round of new tubes when I got the amp (something I always like to do) and the hum started as soon as I replaced the stock tube. I went through 4 different, brand new replacements, and only replacing the stock tube fixed the issue. I've heard other people have some weird issues with the PI tubes in the TH30...I haven't consistently heard about any of the others being a problem.

[Blue Notes]

Haven't had any issues with the other tubes, all turned out to be the effects loop (12AT7) JJ tube, it had a loud low hum which one of my friends said was probably due to a short in the tube.

My dealer gave me a groove tube as a replacement, it quitened the amp down but I thought I heard some traces of micro phonics, but more testing proved it to be fine.

Since the amp came new with all JJs, I wanted to put a brand new JJ back in, so I bought a new (12AT7) JJ today, and put it in, and it's even more quieter than it was with the groove tube. The amp is so quiet, and sounds so amazing I couldn't be happier.

At first I was a little upset about having to work on a brand new amp, but man has it been worth it.

Blue Notes