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Discussion Starter · #1 ·
Okay so I got my Framus cobra several months ago used, and it came with the stock tubes, so I assume the bias has never been changed. I noticed on the clean channel in particular if I strummed somewhat hard at all or at a normal pace it would make this odd scratchy break up sound like the channel is trying to distort. I tried all gain, presence, treble, etc. settings on the EQ to remedy the problem and it still remained. I resorted to pulling out a set of JJ tubes and preamps and re-tubed the amp. Unfortunately I don't have the faintest idea on how to bias it, and I refuse to send it to an amp tech due to the very few technicians here who due a horrible job with dropped off equipment, so I didn't bias it after re-tubing it. Even after re-tubing the amp it still breaks up on the clean channel and has that odd scratchy sound, does anyone have an idea why this is happening?
 

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NSLALP
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Is it literally cutting in and out? Does it have more to do with volume and bass than which channel it's on... that is to say, if the chassis is getting vibrated hard, the problem occurs?
 

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Discussion Starter · #5 ·
Is it literally cutting in and out? Does it have more to do with volume and bass than which channel it's on... that is to say, if the chassis is getting vibrated hard, the problem occurs?
It happens with any volume, low or loud. And it's just breaking up, like it's distorting somewhat when I strum with little force, it sounds awful. My clean channel is completely useless under the lowest of gain settings.
 

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NICE BLACKMACHINE YO
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Are you running any pedals? What are your leads like? Any chance they could be shorting out? Leads do some very funny things when they are dying - mine was shorting the signal out to earth so my volume control acted as a tone control. Very odd.

What you are describing sounds like a headroom issue, so if other guitars with low output passive pickups are doing the same thing and you aren't using any pedals are you using the right input on the Cobra?
 

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Discussion Starter · #8 ·
Are you running any pedals? What are your leads like? Any chance they could be shorting out? Leads do some very funny things when they are dying - mine was shorting the signal out to earth so my volume control acted as a tone control. Very odd.

What you are describing sounds like a headroom issue, so if other guitars with low output passive pickups are doing the same thing and you aren't using any pedals are you using the right input on the Cobra?
I do run a Boss NS-2 and a Maxon OD808, but they're off when I use the clean channel, that and I've tried just plugging straight into the amp with no pedals and still the problem occurs. Both my crunch channel and lead channel kinda do the same thing, though the crackling break up sound is harder to hear over the amps distortion.
 

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NICE BLACKMACHINE YO
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It really does sound like a battery problem to me, dude. Either the EMG's in your guitar or the batteries in your pedals (and, FYI, whether they are on or off they will impart the sound you describe on your amp if there batteries are low - such is the nature of non-true-bypass pedals - the signal is still 'touched' by the circuits!). If you've retubed it I fail to see how it can be the amp, and what you are describing is a preamp problem, not power amp - so biasing doesn't come into it.

I'd give everything you are plugging into the amp a good look. Maybe borrow a friends guitar and lead, and work back from there, slowly adding things of your own into the signal chain until you find the culprit.
 

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Discussion Starter · #10 ·
It really does sound like a battery problem to me, dude. Either the EMG's in your guitar or the batteries in your pedals (and, FYI, whether they are on or off they will impart the sound you describe on your amp if there batteries are low - such is the nature of non-true-bypass pedals - the signal is still 'touched' by the circuits!). If you've retubed it I fail to see how it can be the amp, and what you are describing is a preamp problem, not power amp - so biasing doesn't come into it.

I'd give everything you are plugging into the amp a good look. Maybe borrow a friends guitar and lead, and work back from there, slowly adding things of your own into the signal chain until you find the culprit.
I just tried using a single cable into the amp, several at that, and still the problem occurred. I know it's not batteries in the guitar cause I've tried 4 guitars on it over the time I've had and all did the same thing. Could the pre-amp slot that controls the clean channel be messed up in some way..?
 
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