New Princeton reverb 65 - reverb humming

[Yreva]

In my experience Princeton Reverbs that hum when the reverb is turned up past 3 1/2 is normal. Anything past 4 is a lot of reverb ; more than I would use. Welcome to the world of tube amps.

 

[GreatGaudy]

Edited due to error. The reverb circuit in Fender reissue export amps are tube circuits. The tremolo circuits are digital.

Tremolo is digital ? Are you sure ?
... I'd be pissed.

 

[Wally]

Tremolo is digital ? Are you sure ?
... I'd be pissed.

I am sure. And….having the tremolo in the solid state domain not a bad thing since all that any trem circuit does is vary the amplitude of the signal at one point or another. It has no tone processing function.

 

[bradpdx]

I've dealt with this issue in Princeton reissues. I presently use a '68 Custom Princeton Reverb reissue.

The problem isn't tubes, and the tube circuit is pretty much unchanged for many decades. It's the proximity of the reverb tank to the power transformer combined with mediocre shielding - it's simply too close in the little Princeton, and the tank picks up this inference in it's receiving coil.

My solution: I created a grounding plane from some sheet metal with snips and covered the open half of the tank with that plane, making sure it was well grounded with a wire soldered to the jack. Back in the amp, most of the hum is gone.

 

[Beachbum]

They all hum

Now it doesn't

 

[Beachbum]

On top of those issues I absolutely hated the C-Rex speaker. Too dark, sounded horrible with dirt pedals, and very boomy. I replaced it with an Eminence GA-SC64 and couldn’t be happier.

Yep. Hated the C-Rex in mine as well. That one and the Legend 1258 that I went with are the way to go.

 

[PoorNoodle]

This sounds similar to my old PRRI…

 

[Sea Devil]

Towel under the tank, thickish ferrous metal plate on top (in the bag), hum reduced 75%. That's in a DRRI.

The speaker magnet was as much the culprit as the proximity of the transformer.

 

[D_Malone]

Towel under the tank, thickish ferrous metal plate on top (in the bag), hum reduced 75%. That's in a DRRI.

The speaker magnet was as much the culprit as the proximity of the transformer.

Interesting. Thanks for the tip!

 

[SJerseyDevil]

Hey guys! After years of playing directly through my audio interface, I finally got my first tube amp, a princeton reverb 65 (the 12" version with a c-rex speaker). It sounds great! However there is noticable humming when I turn on the reverb, andgets louder the more I turn up the reverb. The noise is also effected by the tremolo down the line, as you can hear on the video. I've tried unplugging the reverb tank, turning it 180 degrees so the rca connectors of the tank are facing either the front or back, and tried removing the tank from the cabinet whilst being connected. The hum did not disappear though. I am not sure if I should send it back or not.
Again, it's my first tube amp, and first amp with an actual spring reverb, so I was wondering whether this is normal behaviour. Thanks !

Take it back and get another one, don't settle for them having it repaired

 

[ETMusic777]

I am sure. And….having the tremolo in the solid state domain not a bad thing since all that any trem circuit does is vary the amplitude of the signal at one point or another. It has no tone processing function.

I actually like the tremelo on the one that I played and did not know it was digital.

 

[burntfrijoles]

I have a special edition 12” Jensen speaker PRRI and I have never encountered that. I would return it.

 

[SnidelyWhiplash]

In my experience Princeton Reverbs that hum when the reverb is turned up past 3 1/2 is normal. Anything past 4 is a lot of reverb ; more than I would use. Welcome to the world of tube amps.

It's not normal for a PR to hum when the reverb is turned up. I'd start with the tubes, but since it's a brand new amp, I'd send it back.

 

[Sea Devil]

I think some noise is inevitable. I've tried to completely eliminate it many times, and had considerable success, but never got it to zero. I'm talking bedroom levels with reverb above six; it's totally negligible at higher volumes and lower reverb settings.

 

[Wally]

So, I've done some troubleshooting and here are a couple of observations I made.
I checked the hum with a frequency analyser, and there are two large peaks at 100hz and 200hz (I live in Europe, so 50hz mains). The loudness of the hum depends on which outlet I put it in, volume of the hum changes up to 10dB's depending on which outlet I use. I've tried a different RCA cable for the reverb tank, this did not change anything, and the wire connections from the spring to the rca sockets looked fine to me as well. Leaving the RCA cables completely unplugged made the noise worse. I have given the two tubes (12AT7 and 12AX7A) corresponding to the reverb a good wiggle to make sure they were seated correctly. I've also tapped both tubes with a wooden stick with the amp on, and they were both pretty much silent when tapping. Any ideas on this?

This is the last post by the OP…from December 2, 2022.
From the quoted post above…
“The loudness of the hum depends on which outlet I put it in, volume of the hum changes up to 10dB's depending on which outlet I use.”

This is the best clue given as to the source of the hum. This problem may likely not be in the amp.

 

[Jasonpatrick]

This is the last post by the OP…from December 2, 2022.
From the quoted post above…
“The loudness of the hum depends on which outlet I put it in, volume of the hum changes up to 10dB's depending on which outlet I use.”

This is the best clue given as to the source of the hum. This problem may likely not be in the amp.

Yep. It ain’t the amp. Watching him crank the verb to 10 and then wonder why it hums is kinda entertaining though.