Weird noise

[YellowJacket]

Hi Everyone,
Here's the lowdown. After playing this amp almost every day for the last couple of years, I'm hearing a weird quiet almost electronic swishing sound intermittently that starts only after I have been playing for some time. If I put the amp on standby and then power it back up, the sound disappears and then comes back again. My first thought was 'preamp tube' but the sound does not get louder or quieter when I adjust the controls on the amp. It is the same volume if the amp is off with all the controls zeroed or if they are all maxed and it quickly gets buried as the amp levels go up. It is present on all modes and is not affected when I switch between them. It is also present when there is no guitar and patch cable connected. The fact that the sound is always the same level is what is causing me to scratch my head.

I did a test on the power source and speaker lead by running my Dual Rectifier through the same cab. It is a noisier amp being older but it does not have this unique swishing sound.

I'm still inclined to think this is a tube problem but I'm just wondering which tubes. Do you guys think it is the 'driver' tube in V7? Maybe impurities in a power tube? It shows up on 45 watts and 90 watts.

Being a tube amp owner, I suspect these sorts of issues but this one is just a little strange and it has me scratching my head for now. No blown fuses or the like here, just a weird little noise. (tube gremlins)

 

[elvis]

Bummer.

I'd look at V5 (effects return buffer), V6 (Reverb driver) and V7 (PI).

When I got my Dyne, V7 went bad immediately. Went all squonky, then no volume.

 

[screamingdaisy]

In addition to the above, look swap the inner and outer power tubes for each other. If it is a power tube it could've been one of the two that's on in both modes. If the noise goes away in 45w mode after swapping the tube pairs it'll indicate one of the two off tubes was the culprit.

 

[YellowJacket]

Well, now I'm getting sputtering that gets louder as I turn the master up. I swapped the power tubes so we'll see how that goes but I definitely suspect a preamp tube at this point. I'll most likely get around to troubleshooting next week sometime.

 

[topalchohol]

99% chance it is a preamp tube. I had the reverb tube go bad on my Mark III, and it turned the reverb contol into an extra EQ. :lol: Also check your power cord to make sureit isn't frayed, and also try a different wall outlet on a different circuit. Also are your tube shields on? When I took all of mine off,I got some radio station to come in. This will be a simple fix. :wink: Let us know what it is.

 

[YellowJacket]

Of course. I suspect the Phase Inverter in v7 for sure and that is the first tube I am going to try replacing. All the shields are on for now.

Which 12ax7 do you guys recommend for a phase inverter in v7? (Assuming that is where the problem is)

 

[wekiitoedzo]

I use stock mesa preamp tube in v7. However i recently put tung-sols in v1, and at the reverb as someone offered here. It sounds much better with them. I'd give a try to put it in v7 too.

 

[YellowJacket]

The tube testing has started. So far I found a 6L6 GC glowing brighter than the rest as well as a sputtering that only occurs on the clean mode....

So far I changed one 6L6 GC -the bright one- as well as the 12ax7 in v4. This made the amp much quieter. I'll have to play test tomorrow but things are looking good so far.

Well, the cleans sound a little thick and bloated with the new tube so I'll have to roll a couple of other ones through there when I have a chance.

Verdict: I swapped in a SP12ax7 that I had sitting around (Not sure what kind of tube it is) but it was a bit noisy for v1 in my Recto so I had not used it. It is a little less bassy sounding which is great for V4 in the Electra Dyne where there isn't a whole lot of gain. It's a hair quieter than the other mesa 12ax7a I have so I think I'm happy with that. Feels good to have the Electra Dyne up and running although I spend 30min playing when I was just planning on putting the headshell back together again.

Incidentally, while I love the Electra Dyne I HATE having to pull the amp out of the headshell just to change the preamp tubes. It's the only way I can actually see the tube sockets to line up the preamp tubes. GRRR!

Well, I am back in business now!! YAYS!!

 

[cradlefish]

You certainly have put the ED to full usage within a couple of years!

I recently had the same issues with my mark iv and triple rec.


I went and tapped each tube on both amps to troubleshoot.

Turns out to be two power tubes for the iv and one for the triple. I replaced the culprits and theres no ringing or swushing noises when I crank it now!

You shouldnt need to remove the chassis from the shell. Just aligned the pins of the sockets and carefully put it back in.