Princeton Reverb - Reverb Hum

[UncleChewy]

I just picked up a used 2017 68 Custom Princeton Reverb (all tube) and noticed on the second day that a hum appears when the reverb is turned on and gets louder as the reverb is turned up. The hum disappears completely when the reverb is turned off.

I'll skip ahead and say I just replaced the spring tank with a new one hoping that would get rid of the hum, which it didn't, but did manage to reduce it by about 80%.. which is great. I'm wondering maybe there's a ground issue elsewhere causing the hum, cause I'd like to get rid of it completely if I can.

I guess my question here is.. Should it be possible to eliminate this hum? Or is it normal for the reverb to cause a little bit of hum? And yes.. it still gets louder when as the reverb is turned up?

 

[Willie Johnson]

Mine did this and a new driver tube took care of it. I used a 12au7 and I liked the more gradual control that it gave the reverb knob.

 

[UncleChewy]

Mine did this and a new driver tube took care of it. I used a 12au7 and I liked the more gradual control that it gave the reverb knob.

Interesting..I'll look into that.
Would you say your reverb is pretty much silent now? Even on 10?
Thanks

 

[UncleChewy]

I just found this old thread which seems to suggest that some amount of hum from the reverb is normal.
https://www.tdpri.com/threads/new-princeton-reverb-65-reverb-humming.1120585/

 

[Willie Johnson]

Interesting..I'll look into that.
Would you say your reverb is pretty much silent now? Even on 10?
Thanks

It was pretty quiet after that--before that it had a weird sympathetic ringing as you turned the knob up past 5 or 6. You do get a little more hiss the more you turn up, but nothing abnormal. It's guitar equipment--it's never going to be stone silent.

 

[UncleChewy]

It was pretty quiet after that--before that it had a weird sympathetic ringing as you turned the knob up past 5 or 6. You do get a little more hiss the more you turn up, but nothing abnormal. It's guitar equipment--it's never going to be stone silent.

Fair enough.. In a perfect world I'd love to line my amp up with 10 other princeton reverbs and compare them, but right now I'm pretty happy that replacing the spring tank has made things much quieter than they were. This is my first all-tube amp in some years and I guess I just wasn't sure what I should expect for noise. I appreciate your response.. thanks again.

 

[UncleChewy]

Went to the local music store today and checked out the same amp they had on display and was pleased to find the same noise from the reverb that I experience from mine. Good to know I guess. If/when I really need silent reverb, my Strymon Flint pedal does the trick.

 

[SoK66]

There’s something of a compromise between production efficiency and noise in Fender’s PCB amp designs. I have what started out to be an absurdly noisy new ‘68 Custom Deluxe Reverb. After recapping the amp, removing the heater circuit and power section grounds from the PCB completely, changing the NFB resistor and eliminating reverb / trem from the “Custom” channel it’s now the quietest I can make it. IOW, I can’t hear it at idle if I’m in another room in the house. But side by side with my vintage BFDR it’s still noisy. It does sound quite good so I’m satisfied to just enjoy it as it is.

 

[slider313]

Just a thought: I wonder if the old style shielded reverb cables would help?

 

[Paul G.]

Just a thought: I wonder if the old style shielded reverb cables would help?

The cables on the reissues are shielded.

 

[fretknot]

Mine did this and a new driver tube took care of it. I used a 12au7 and I liked the more gradual control that it gave the reverb knob.

I did the same thing with good results.

 

[fretknot]

There’s something of a compromise between production efficiency and noise in Fender’s PCB amp designs. I have what started out to be an absurdly noisy new ‘68 Custom Deluxe Reverb. After recapping the amp, removing the heater circuit and power section grounds from the PCB completely, changing the NFB resistor and eliminating reverb / trem from the “Custom” channel it’s now the quietest I can make it. IOW, I can’t hear it at idle if I’m in another room in the house. But side by side with my vintage BFDR it’s still noisy. It does sound quite good so I’m satisfied to just enjoy it as it is.

I agree, there are options for tweaking this amp to make it quieter and sweeter. I did some tube rolling with NOS valves and it made a big difference. Lower mu valves reduced the gain and tamed the reverb. That transformed the beast into a glorious tone machine.