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FDP Forum / Amp Mods, Repairs, and Projects / Is my PRRI behaving badly or is it normal?

Rob Jai

Northern California

"Jai" pronounced "J"
May 20th, 2012 10:42 PM Edit Profile Print Topic Search Topic
I have a two year old PRRI that I've not been able to tame. Even after recommended mods, I still get some serious speaker farting and just recently starting getting some crackling sounds when first turned on. The crackling seems to go away once the amp is warmed up a little.

I've really wanted to love this amp, but it just never sounds right. Twice I've tried to sell it and both times potential buyers would try it out and ask "where that rattling is coming from"? Needless to say, no one has been interested once they demo it.

I think this amp was produced AFTER Fender fixed the baffle rattle that was common on earlier versions, so I don't think that is a problem although I'm not 100% sure about that.

The mods that I've tried are replacing the output transformer with a Heyboer TO20, replaced tubes with some JJ6V6s,(corrected) and did "the stokes" mod and the amp still sounds "defective" for lack of a better word.

I WILL say that at low volume, it sounds just fine but once you crank it up a bit it just sounds wonky.

I'd seriously like to figure this out so that I can either decide the amp is worth keeping or pass it along to someone who can live with the sound that comes out of it.

Do I really have a problem amp, or is this just normal for PRRIs?
(This message was last edited by Rob Jai at 03:33 PM, May 26th, 2012)

Liquid Smoke

USA

May 20th, 2012 11:07 PM Edit Profile Print Topic Search Topic
The crackling is probably just a tube/socket that needs cleaning (or even just pulling out and re-seating).

The sound you call speaker farting...no that's not normal. It could very well be the baffle rattle. I believe that was "normal" in the reissues...at least the earlier ones like mine.

Try pushing in on the top/middle of the baffle while somebody else plays it. On mine I could even see the baffle vibrating while I played it.

Look inside the amp at the top of the baffle. Is it a flat piece of wood? or does it have a reinforcement?

Rob Jai

Northern California

"Jai" pronounced "J"
May 20th, 2012 11:10 PM Edit Profile Print Topic Search Topic
At the top of the baffle there is a half inch square piece of wood that runs all the way across the width of the cabinet.

Modal Magic
Contributing Member
****

MBJ, Highway Hound.

You Can't Bend It Aussie!
May 20th, 2012 11:10 PM Edit Profile Print Topic Search Topic
Well... I've had mine for almost five years and I have'nt had any of the problems as stated. I've never had the baffle rattle and I tried extensively to replicate it after reading a bunch of posts about it. I've never had the farting or crackling on either.

Don't know, but it sounds like it could be a bit dodgy to me.

Rob Jai

Northern California

"Jai" pronounced "J"
May 24th, 2012 04:31 PM Edit Profile Print Topic Search Topic
So, I thought I might be on the right track by beefing up the baffle support. I added some half inch square hardwood strips so that the baffle now has extra support on all 4 sides. Nothing has changed.

The funny thing is that when playing through my single coil guitars (Strat and/or Tele) an E or F chord hit hard has an annoying "rattle like" noise to it. It could almost be described as an over tone of some sort Yet, when playing though a P90 or humbucker guitar, I don't hear the same thing. Doesn't make any sense.

This amp is fast becoming either a nice amp;for playing softly at low volume or an expensive door stop.

JJuran

Boston Area

May 24th, 2012 05:31 PM Edit Profile Print Topic Search Topic
Try connecting a different speaker to the amp, preferably a separate cabinet. This will at least help you determine if you've got a bad speaker or baffle in the PRRI.

As Liguid Smoke said, the crackling sound could be loose contacts in a tube socket.

But then you mention a rattle but it's not clear from your posts whether the rattle and crackling are the same noise. You might be hearing filament rattle in your rectifier tube, power tube, or pre-amp tube. Again, replace the internal speaker connection to an external speaker and listen.

Hammond101
Contributing Member
*

So. Cal. USA

May 24th, 2012 05:31 PM Edit Profile Print Topic Search Topic
Plug it into an extention cab and see what it sounds like. Might be the speaker and not the baffle.

I tried to buy one of the PRRI amps when they first came out. I tried three amps at different stores. They all sounded farty to me when cranked and broke up way too early.

I had a '66 back in the day that unfortunately an ex wife made me sell. It was farty with the stock speaker. It got a EV Force 10 that cured the flatulance (sp?)

Rob Jai

Northern California

"Jai" pronounced "J"
May 24th, 2012 06:15 PM Edit Profile Print Topic Search Topic
The rattle and the cracking are two different things. I re-seated the tubes and the crackle went away.

The extra baffle reinforcement made no difference and now I'm convinced that it's NOT the baffle rattling

I just tried the advice to run through a different speaker. I unplugged the stock Jensen in the PRRI and connected the amp to the 15" speaker in an extension cab. There IS a difference, but he noise is there, although maybe not as pronounced as with the stock speaker.

Then I tried hooking the stock internal speaker back up and also running with the extension cab. Again, somewhat better but not what I would think is right.

Maybe I'm just being overly critical - maybe this is just the way PRRIs sound. All I know is that I'm not the only one who has heard this. As I stated above, when letting two different potential buyers play through this amp, both asked "what is that weird sound"?

Gene Dunn

USA, Sacramento, CA

Ono Boy says: "good n' swampy"
May 24th, 2012 08:09 PM Edit Profile Print Topic Search Topic
Hey Rob! Bring that gal over to my house and let me help you investigate the source of that noise......

I've had lots of experience with my old silverface Princeton Reverb, so I have a point of reference for your amp......Although I also put an Electrovoice Force 10 in mine, I think I have a good idea of what's normal breakup for that amp.

Geno in Sacramento

Rob Jai

Northern California

"Jai" pronounced "J"
May 24th, 2012 09:53 PM Edit Profile Print Topic Search Topic
Geno - thanks for the offer. I'll send you an email and we can talk about it. Should have thought to ask you in the first place.

Gene Dunn

USA, Sacramento, CA

Ono Boy says: "good n' swampy"
May 25th, 2012 08:50 AM Edit Profile Print Topic Search Topic
That's great Rob.....we can try tube swaps and check the sockets, if need be.

I have a couple of cabinets here that we can try out also.

Peegoo
Contributing Member
**********
**********

That chicken

is WRONG, baby.
May 25th, 2012 04:45 PM Edit Profile Print Topic Search Topic
I've seen a few that have a weird resonance due to a noisy rectifier tube. Never ran into that issue with recto tubes on any other amp. Worth checking out.

Fritz_D_Cat
Contributing Member
**********
*

better living

through chemistry!
May 26th, 2012 02:36 PM Edit Profile Print Topic Search Topic
Rob - dunno if I'm any closer than Gene, but light's on if you want to work on this. Have lots of cabs and speakers, and the gear, parts, and ability to repair.

One question: You really have 6L6's in there? Or did you mean JJ 6V6's?

Rob Jai

Northern California

"Jai" pronounced "J"
May 26th, 2012 03:31 PM Edit Profile Print Topic Search Topic
Fritz,

Thanks for the correction - I DID mean 6V6 and not 6L6. Thanks also for all of your previous email advice. Gene lives just across town from me. We'll see what we can come up with. If we can't solve the problem a trip to the North Bay Area may be in order.

Fritz_D_Cat
Contributing Member
**********
*

better living

through chemistry!
May 28th, 2012 02:57 PM Edit Profile Print Topic Search Topic
Well the JJ 6V6's DO punch bass more like the bigger 6L6, and so a weak speaker or insufficient filter cap reserve will show up more readily.

Gene Dunn

USA, Sacramento, CA

Ono Boy says: "good n' swampy"
May 31st, 2012 12:17 PM Edit Profile Print Topic Search Topic
Never mind about the PRRI behaving badly..... I've heard YOU'RE NO ANGEL! (^_-)

Rob Jai

Northern California

"Jai" pronounced "J"
May 31st, 2012 08:54 PM Edit Profile Print Topic Search Topic
What you MAY have heard is all lies - NUTHIN' BUT A PACK O' DANGED LIES. I TELLS YA'.
:-)

UPDATE: Gene's cure for the rattle that I was hearing was to replace the first 12AX7 with a 12AY7. I found an old GE 12AY7 and it made a big difference. The amp now sounds more like I feel that it should.

Thanks, Geno.

And, Fritz - you could be on track about running a stronger speaker. When I tried bypassing the stock Jensen and running through a larger 15" extension cab speaker (a Jensen Neo) there was also a noticeable difference although not as much a difference as the tube change.

Gene Dunn

USA, Sacramento, CA

Ono Boy says: "good n' swampy"
May 31st, 2012 09:30 PM Edit Profile Print Topic Search Topic
One of the sweetest tones I've had was generated by a 69 Princeton Reverb (12AY7 in V1). I loaded the combo cabinet with a high power handling Electrovoice Force 10, and often connected a closed back 1x15 cabinet loaded with an EVM 15L....another high power handling speaker.....

No chance of farting out there! With that kind of robust arrangement, I could practically dime the amp and stay relatively clean...... But still, for larger gigs, I felt the need for a bit more power, so ended up with a 40-watt amp.

Fritz_D_Cat
Contributing Member
**********
*

better living

through chemistry!
May 31st, 2012 10:30 PM Edit Profile Print Topic Search Topic
Didn't think much about tube rattle, but it's more common in the smaller combo amps just due to proximity to the sound of the speaker.

12AY7 is softer edge gain and just a bit sweeter on top than 12AX7.

Glad it's better and that no one is in jail...

Dying to find out what a Celestion Gold 10 could do in one of these things. Now that this is all fixed up you should bite the bullet. I mean, for research purposes and all.

mullardgz34

USA

Jun 8th, 2012 12:01 PM Edit Profile Print Topic Search Topic
Yes tube rattle in those things are very common. Straight out the box v1 was noisy and one of the 6v6 had a bad rattle too. You can do what I did and replace the 10" baffle with a 12" baffle and put a cannabis rex in. Holy cow what a beast of an amp now.

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