# RF Interference with a boutique amp



## Super62 (Mar 15, 2010)

Hey guys

I got a new amp today, it's a 65 Amps Tupelo. So I loaded it in my car and went off to a jam and when I got there I set up and plugged in, and when I turned on the amp there was an FM radio station blaring through it. Tried switching AC cables, moving the amp around the room, plugged it in to different outlets, etc. and nothing helped. Then I brought in my Fender Supersonic and plugged that in and the radio interfernce was gone. So I took my amp home after rehearsal, and tried it out here only to find the same issue. However, when I unplug the cable from the amp's input, the RF interference disappeared. It was only when the cable was connected, regardless of whether or not there was a guitar on the other end, that the problem was occuring. Also, turning up the amps volume had a pretty negligible effect on the radio volume. Not sure if that matters much.

Any help or advice anyone can offer, I would really appreciate it. Hoping to gig the amp this week, and I'd like to know I can do something to prevent this problem from happening at soundcheck and having to cart out one of my old Fenders to stand in for it if need be! hah

Thanks in advance for any help you can give!


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## Chito (Feb 17, 2006)

Have you tried using another cable?


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## Wild Bill (May 3, 2006)

Super62 said:


> Hey guys
> 
> I got a new amp today, it's a 65 Amps Tupelo. So I loaded it in my car and went off to a jam and when I got there I set up and plugged in, and when I turned on the amp there was an FM radio station blaring through it. Tried switching AC cables, moving the amp around the room, plugged it in to different outlets, etc. and nothing helped. Then I brought in my Fender Supersonic and plugged that in and the radio interfernce was gone. So I took my amp home after rehearsal, and tried it out here only to find the same issue. However, when I unplug the cable from the amp's input, the RF interference disappeared. It was only when the cable was connected, regardless of whether or not there was a guitar on the other end, that the problem was occuring. Also, turning up the amps volume had a pretty negligible effect on the radio volume. Not sure if that matters much.
> 
> ...


There's two ways things can be wrong. Either something has gone wrong or being a boutique amp, the actual design has a problem.

Regardless, it has to do with the grounding of the input jack. The designer may have "floated" the ground from the actual chassis. This often is better for reducing possible hum pickup but can allow the guitar and/or the cord to act as an antenna and conduct radio signals into the input of the amp. The first preamp stage can act like a crystal radio and then the following stages amplify it.

If you are not a tech, there's not much you can do except to maybe check to be sure the input jack has not had its mounting nuts come loose.

A tech who understands such things can look at the input wiring and design. There are things that will eliminate the problem but it's not really something for the "unlearned" to try by himself.

If you have a tech background or if you have a local tech who looks after you, have him post in here and we can be of more help.

Does "Mr. Tupelo" have any service set up for his Canadian customers? Perhaps the store where you bought it might have another amp that you can try. That will settle the question about whether the design is flawed or if YOUR amp has developed a problem.

I would certainly expect the manufacturer to treat this as a warranty problem.

Wild Bill/Busen Amps


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## dcole (Oct 8, 2008)

Thats a tough one. In my experience, receiving radio signals was so tempermental that moving the amp or adjusting knobs caused the signal to go away. You seem to have a problem that occurs always. I would suggest with a nice amp like this to take it into an amp tech unless you have the skills to do work on it.


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## WCGill (Mar 27, 2009)

It's highly likely you need a grid-stopper on V1 from the jack input, or a larger one. When the cable is unplugged, the shorting jack grounds the grid to chassis so the RF signal can't be amplified. Shielded cable may also help.


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## Swervin55 (Oct 30, 2009)

Sorry, nothing technical to add but our second guitar player has a 65 Royal Albert that does the same thing. I have a 65 Soho and no issues. ??


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## jb welder (Sep 14, 2010)

Have you contacted them yet? TECH SUPPORT, WARRANTY & SERVICE: 818-766-4265 They may want to fix it, or they may have suggestions and be willing to reimburse a tech., that is their choice if it is warranty. One thing I saw mentioned is that is uses an EF86 pentode tube. I'm not sure if those tubes are more prone to picking up radio, others here may know. If so, maybe another EF86 would cure it.


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## Super62 (Mar 15, 2010)

Hey guys, I've got great local tech who can get on the problem for me so hopefully it will sort itself out. If not, I've heard the guys at 65 amps are pretty good to deal with.

Thanks!


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## WCGill (Mar 27, 2009)

jb welder said:


> Have you contacted them yet? TECH SUPPORT, WARRANTY & SERVICE: 818-766-4265 They may want to fix it, or they may have suggestions and be willing to reimburse a tech., that is their choice if it is warranty. One thing I saw mentioned is that is uses an EF86 pentode tube. I'm not sure if those tubes are more prone to picking up radio, others here may know. If so, maybe another EF86 would cure it.


I use the EF86 regularly in my amps as inputs, never had a problem, never had a problem with 12AX7's either.


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## Mooh (Mar 7, 2007)

I have a Traynor YCV50 that will pick up signals, but only in Bayfield Ontario. Renders it unusable there. Everywhere else it has been fine. Freaks me out. Stunning amp otherwise. 

Peace, Mooh.


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## Wild Bill (May 3, 2006)

WCGill said:


> I use the EF86 regularly in my amps as inputs, never had a problem, never had a problem with 12AX7's either.


Exactly. A tube is a tube.

I agree with your tips. There's a whole pile of other things he can try but no point in mentioning him if he doesn't have the background himself. We should wait and if perhaps his tech comes in we can talk to him about it, assuming he needs any help.

Wild Bill/Busen Amps


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## dcole (Oct 8, 2008)

Most of my RF problems have been with solid state gear. I once picked up a short wave station from Michigain. I think thats the farthest away radio signal I have ever received.


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## Adicted to Tubes (Mar 5, 2006)

Grid stoppers are 68k on that amp.It may be picking up the signal somewhere else in the circuit.


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## Wild Bill (May 3, 2006)

JUst curious if the problem was solved and what actually was the matter.

Wild Bill/Busen Amps


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## Super62 (Mar 15, 2010)

So far, the issue has yet to be resolved, because my tech lives a couple of hours away and has yet to come in to grab the amp. He has three of my amps right now (my 62 Super, 68 drip edge Super Reverb, and my JCM 800 Can. Import) for repairs right now. Once he brings back the finished work he's got done now, he is planning to grab the 65 and have a look at it. I will be sure and let all you guys know how it pans out! Thank you all for giving it some thought.


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## David Garry (Dec 15, 2016)

Hi
I have a 65 Amps Tupelo with the exact same issue. I was just wondering if you got this resolved and if yes what was the fix?
Regards
David


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## knight_yyz (Mar 14, 2015)




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## knight_yyz (Mar 14, 2015)

another double post.... smh


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## gtone (Nov 1, 2009)

I had the same problem with my '66 Blackface Bassman, both with receiving local radio stations and RF noise from my son's Xbox 360. The ultimate solution proved to be the TubeCages that the Tube Store used to offer, placed on the Bassman's sensitive preamp V1 & V3 positions (www.thetubestore.com - The Tube Cage). Unfortunately, these are unavailable thru their channels now, but it wouldn't be hard to bodge something similar up like these - basically some copper screening grounded to a tube shield to create a "Faraday Cage" and some rubber shrink-wrap covering for the aluminum tube shield.

Good luck!!


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## guitarman2 (Aug 25, 2006)

I only ever had these problems with Dr Z amps. My last amps was a 1965 Blackface Bassman, no problem. Other makers, Victoria, Tone King, Carr had no issues. I had this issue with a Dr Z maz 38 the head and combo versions had the problem. As well as a Mazerati and a Stangray. The Dr Z Carmen Ghia I had did not have this issue. So I assumed it was mostly a design problem. My Maz 38 head with reverb also had lots of noise that got louder as you turned the reverb up. I was told my Dr Z this was an issue with the reverb tank being in tight quarters with the rest of the amp.


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## David Garry (Dec 15, 2016)

Super62 said:


> Hey guys
> 
> I got a new amp today, it's a 65 Amps Tupelo. So I loaded it in my car and went off to a jam and when I got there I set up and plugged in, and when I turned on the amp there was an FM radio station blaring through it. Tried switching AC cables, moving the amp around the room, plugged it in to different outlets, etc. and nothing helped. Then I brought in my Fender Supersonic and plugged that in and the radio interfernce was gone. So I took my amp home after rehearsal, and tried it out here only to find the same issue. However, when I unplug the cable from the amp's input, the RF interference disappeared. It was only when the cable was connected, regardless of whether or not there was a guitar on the other end, that the problem was occuring. Also, turning up the amps volume had a pretty negligible effect on the radio volume. Not sure if that matters much.
> 
> ...


Super62 - Do you happen to know what the problem was that caused this issue? I'm still trying to get in touch with 65 Amps to try and get assistance to resolve the problem


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## David Garry (Dec 15, 2016)

Hi
I am still having this issue with this amp. I have however discovered that if I plug my cable into the FX loop and don't use the man input the interference nearly completely disappears. It is definitely still present but not close to the same level as if I plug a lead into the input. I don't even need to have a guitar connected for the interference to become shocking..


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