Fender Princeton Reverb '65 RI

[edwardofhuncote]

My Princeton Reverb Reissue is making a weird sound... I would describe it as a harmonic distortion, that seems to be most noticeable on a high A note, but also present in frequencies on either side of that. (think; 2nd string, 10th fret)


This obnoxious little ringy-thing is happening even a low volume. It's happening whether I'm pushing the gain stage or not, but more obvious when pushing towards overdrive. The whatever-it-is dissipates if I let the offending note sustain... it will eventually fizzle into a clean decay.


It's a fairly new amp; 2019. Groovetubes tubes, Celestion Cream 90w 8ohm speaker, both supposedly upgrades. Has not been abused. I got it from a keyboard player. It was "too much amp for his home studio". It just started this aggravating racket a couple weeks ago.


I've read as much as I can find online. Nobody seems to be describing what I hear. It isn't the backboards loose. I tried swapping preamp tubes one at a time. What does this seem like to you all- Power tubes? Rectifier? Sockets? Speaker? I love the amp when it's right. Can't suffer this foolishness though.


TIA. ~Ed of H (who Thanks to Alembic, has a whoop-ass set of rabbit ears)

[lbpesq]

I’d try swapping the power tubes first.  A good general rule of thumb is try the easiest stuff first.

Bill, tgo

[edwardofhuncote]

Power tubes (I have learned) are best acquired in matched sets.

I'll go ahead and ask the obvious (possibly stupid) question... with tubes, how much difference is there between this brand and that? In shopping for sets, I see this set voiced for Silverface, this set for Tweed, that set for Marsh... my only experience is replacing the preamp tubes in my Mesa WalkAbout. (the fine folks in Petaluma sent me a new Mesa-branded pair of 12AX7 tubes)

Anything wrong with a set of J/J's ? For instance-

https://reverb.com/item/27890603-jj-tube-set-fender-princeton-reverb

[lbpesq]

Do you have an old tube lying around or another amp using the same tubes?   I don’t believe you need to worry about matching tubes just to do some trouble shooting.

Bill, tgo

[edwardofhuncote]

Nah. I had a couple spare 12AX7 preamp tubes only because that's what the Mesa bass head takes. I don't have any 6V6  tubes, and never owned any other Fender tube amp. I wish there was someone around here that could listen to it and tell me definitively what it is I'm hearing. It's just odd to me how these certain frequencies seem to be setting it off.

[rv_bass]

Can you connect it to another speaker to see if it is the speaker causing the noise? 

[edwardofhuncote]

That's a good idea. I don't have another guitar cabinet though. I know someone who has a couple... for the purposes of a test, I could try an 8 ohm bass cab. I have a Bag End S10D that is coaxial... I'm not sure the sensitivity will allow for hearing it though. They actually advertised that thing as being perfect for amplifying a banjo. Worth a shot.

[BeenDown139]

well as my boss at the amp shop where i cut my teeth fixing big tube amps many moons ago said after he watched me chase my tail for a coupla hours trying to track down a similar problem using scope, knowledge and finesse - "sometimes ya just gotta change all the tubes!"

i've found that to be sage advice through the years in a varity of tubular and non-tubular situations.

HTH

BD139

[gtrguy]

I am not a fan of Groovetubes, new Tung Sol either. They seem to have a high failure rate and to my ear are not very musical. JJ's are new tubes I really like. Try both inputs, another cord, another instrument, etc too. However, tubes are the usual suspect.

[edwardofhuncote]

Thanks for checking in guys... I figured you might have a couple thoughts too David.

Well here's the update-

per Rob's suggestion I dug out my little Baggie 10, (it provided the 8 ohm load) I disconnected the onboard Celestion from the amp, and hooked up the Bag End and rung it out. The distortion is still there, same spot, just harder to discern using the little cube with a a bass driver in it rather than the much more articulate Cream speaker in my Princeton cab. It was lower, more warble-y, and less fizzle-y on the note's decay, but definitly still there. The closer you play to that high A note the more pronounced it becomes.

Of course I have tried both inputs, every cable in the house, 2 Les Pauls, two Telecasters, and another nameless beast. Every one produced the same results. I think this eliminates the speaker, and the cabinet, or some random piece of hardware like a screw being loose, maybe ever negates user error.

I believe it's time to buy some new light bulbs for my Fender and swap 'em out. Thanks for the insight on GT David. There's a whole 'nother world of keyboard jockeys out there saying this tube or that is great/sucks. I'd much prefer to take my advice from here.

*any thoughts on Tube Amp Doctor? Stew-Mac sells a variety of retube kits for Fender amps... I notice they like these.

[rv_bass]

I had an old Peavey Deuce amp from the 70s, great amp but heavy, sold it a couple of years ago.  I changed the tubes in it once, I just took one of the tubes down to a local electrical supply place and said I need six (or however many it was) of these, went back and installed them all and it worked great.  So you never know

[cozmik_cowboy]

It's a crying shame that they no longer have a tube tester (and tube sales) in every department store, hardware & pharmacy.

Peter

[edwardofhuncote]

It's a crying shame that they no longer have a tube tester (and tube sales) in every department store, hardware & pharmacy.

Peter

We used to have a 4- foot tall contraption at the Fret Mill for testing tubes... had all kinda' different sockets and chicken-head dials on it, I don't think anybody but Ken knew how the blame thing worked. It never occurred to me until you posted that, but I don't know what ever became of it. They may even still have that thing upstairs somewhere. I know it hasn't been on the sales floor for at least 20 years. I'll have to ask Aaron, he'd be the only one who would remember it.

[David Houck]

How about these guys:  http://www.uptownaudio.com/about.htm

[JimmyJ]

Perhaps this is what we need:

https://www.ebay.com/itm/B-K-Model-700-Dynamic-Mutual-Conductance-Tube-Tester-Nice-Working/313484205242?hash=item48fd1d5cba:g:IIMAAOSwvCdgbjrf

Is that not a fine looking piece of kit?  Tempting.  And I'm not even a tube guy. 

Also, I don't know if these testers could ever tell you when a tube went microphonic - which may be what's happening to Ed's.  Give a gentle tap on the glass and see what comes out of the speakers.

Jimmy J