#1
I don't have a lot of experience with fixing amp problems, so hopefully somebody here can shed some light for me...

I bought a Double Muff pedal (basically a Muff with 2 gain stages) used at Long and McQuade because it seemed like a good deal, came home and plugged it into my Jet City head. It was sounding real good, until I flicked the pedal into "double Muff" mode. I may have had the gain on my amp too high at the time, but all sound from my amp immediately stopped as soon as I flicked the switch. Now, if I completely crank the volume and gain on the amp, I get barely a whisper of my signal to come through the speakers.

It happened as soon as I engaged the 2nd mode on the pedal, so I know that was the culprit, and I know the problem lies in my amp as I've tested different guitars and cables that are known to not have any problems. I emailed EHX and they told me that the only possiblility was that I might have blown a tube IF the gain on the amp was up too high when the pedal was engaged.

I've since switched out the preamp tubes to no avail. Does that sound like it could be a power tube problem to anyone? Or am I going to have to take my amp in to a tech for some costly repairs? Any help will be appreciated, thanks.
#2
What JC model?

If you plug your guitar in the FX return can you hear it?
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#4
Maybe.. havent had that happen to anyone i know. But that might be the culprit. If worse comes to worse just take it to local repair shop after you've tried everything that you yourself are comfortable trying.
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#5
Not having an FX loop hurt diagnosis.

You replaced all the preamp tubes? Or just bought one and switched in different places?

How old is the amp?

You have not replaced the power tubes correct?
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#6
I bought one preamp tube and tried switching each tube out seperately. Do you think its possible I blew more than one?

Its probably just over a year old... Its my backup to my JCM, so it doesn't get a whole lot of use.

And no, I haven't yet touched the power tubes. I figured I'd try the preamp tubes first.
#7
Its really hard to say.

If it were me I would retube the whole thing. However that may be past the cost of taking it to a tech.

How much can you get a full set of tube for minus the preamp tube you already have?

How much for a tech diagnosis?
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#8
That's something I haven't really looked into thus far - I don't think it would cost much to retube the whole thing, Its only got 2 power tubes and 3 preamp. So I'd be looking at maybe another $80? I haven't yet talked to any techs about it, but the prevailing shop price for techs here in Edmonton seems, from what I've seen, to be about $70/hour.
#9
I highly doubt your pedal caused the amp to break.
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#10
Yeah but it might have overloaded the preamp circuit that allready had a weak tube. Its not unheard of but not that common either.
The Rig of Joy:
Stiff Amplification Dirthead 20w
Bugera 2x12 Cab
Fender Partscaster Korean Made
Epiphone Prophecy
Washburn Southern Cross 34 of 100
Ibanez TS9,AD9,GCB95, Multi Chorus and TU2
#11
Quote by bburritt1
Yeah but it might have overloaded the preamp circuit that allready had a weak tube. Its not unheard of but not that common either.

Now this is probable. I was just letting TS know that a pedal is not going to ruin an amp
2002 PRS CE22
2013 G&L ASAT Deluxe
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate
#12
Quote by Robbgnarly
Now this is probable. I was just letting TS know that a pedal is not going to ruin an amp


I wouldn't have thought so - maybe there was some sort of underlying problem, I was just explaining what exactly was going on when it broke. So you think the fault is within the circuitry then?

I was under the impression that when a power tube blows, the amp is likely to blow a fuse. The Jet Citys dont have external fuses so I'm unable to check, but it still turns on, so I don't think a fuse was blown.
#13
Quote by bburritt1
Yeah but it might have overloaded the preamp circuit that allready had a weak tube. Its not unheard of but not that common either.


Actually, it pretty much is unheard of. Most pedals won't even come close to a 9V output swing, which is an order of magnitude lower than what the tube is operating at, plus the input impedance of the tube tends to drop pretty sharply when larger signals are presented at the grid, compressing it to a lower level and causing clipping.
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