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AquaRegia

Valve Mk I - "presence" issues and software questions

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Last summer I traded in my Spider III 1x12 combo for a used Valve Mk I 1x12 combo, and I'm very happy with the improvement in tone the tubes give.  However, after a few weeks I started having intermittent volume issues (or so I originally thought): amp volume seemed to decrease for no reason.  I think I traced the problem to the presence knob.  That function seemed to cutting on and off.  If I simply turned it all the way down, volume stays constant, although my tones were somewhat lacking.  Now the knob appears completely dead - it does nothing to the tone no matter where it's pointing.

 

I assume the odds of finding and fixing a physical problem like that are near zero, but I thought that if it's a software issue, I might be able to address it via a software fix.  I'd never used any Line6 interface software before, but now I see they have the software for Mac OS... but not for the Mk I?  Am I seeing this correctly?  My OLD Spider III could be accessed via software, as can the Valve Mk II, but NOT my Mk I?  What a drag.

 

Any thoughts or advice appreciated.

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The presence knob is actually an analog control  directly controlling the tube power section, so it's not something that's going to be fixable via a software flash or something like that. It might end being a relatively simple fix, so it's probably worth having a tech look at it.

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Thanks, phil, for the quick reply!

 

Obviously I know next to nothing about the software end of things, and little more about hardware.  I guess now I have two separate issues:

 

1)  Taking the amp somewhere to have it looked at will be a chore.  I live in hickville central PA, three hours from any real civilization; I don't know anyone who actually FIXES electronic equipment anywhere near me.  But I will try.

 

2)  I really need to know if my impression is correct - that the Valve Mk I CAN'T use the Line6 patch software.  If that's true, I'm in a tough spot.  I've got 9x4 sounds in that sucker for 50+ songs we play, and without it, the show can't go on.  We've got paying gigs almost every weekend now.  I don't use any effects except what the amp has built-in, so it's essentially irreplaceable if it dies.  If I'm wrong, and it CAN use that software, I need to back up my sounds ASAP just in case... at least then I could buy another used Line6 amp.

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Yeah, found the answer to 2):

 

"The MkI has a reasonably large number of factory presets (about 300 in all at a rough estimate) and factory user presets that you might find useful, however you cannot connect the amp to a computer to: update the flash memory; edit presets on a computer; store presets on a computer.  The MkI can only be edited from the front panel."

 

Well, crap.  As this thing will not last forever, I guess I'd better start shopping for another amp.

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Are you suggesting that replacing all the tubes will fix the function of the presence knob?  What makes you think so?  If it doesn't, haven't I taken out perfectly good tubes?

 

(I assume that you don't mean replacing tubes will help me get my patch info out, which is my most pressing problem.)

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AquaRegia,

'...odds of finding and fixing a physical problem like that are near zero'
 Your odds just went up by visiting this forum.

'...haven't I taken out perfectly good tubes?'
 No, because by your own description, it's a 'used Valve Mk I 1x12 combo'.

'...so it's essentially irreplaceable if it dies'
 This is a possibility with any gig. Although the tones may not be exact, always have a backup. Consider something that works with the same foot pedal you already use, like a Line6 Pod HD (plug into PA).

I agree with tscoolberth, but just replace the two 12AX7-B preamp tubes in the back. You can do this yourself.

I assume you are talking about your SV MKII 1x12 combo.
Bad tubes can cause all kinds of inconsistent tonal and volume problems that appear similar to what you describe. (see appendix C1 in the manual http://line6.com/support/manuals/sv112)
 

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One thing you can try is what we used to call "Zero Parking". See, on the combo amps the thing gets loud enuff to vibrate the knobs just enuff to reset the amp volume. Okay, first thing is make sure you have the floorboard controller connected. Get to one of your presets you know, now set all of the knobs to zero except the Presence and Master Volume (the two knobs this does not affect) then use the floorboard controller to change patches. See if that works for you, good luck bro...

 

cgtrox B)

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"'...so it's essentially irreplaceable if it dies'
 This is a possibility with any gig."

 

No, if I still had my Spider III (or if I had a Valve Mk II) I could plug it into my computer and save all my tones.  Then I could buy another similar amp and load them in, zing, done.

 

Because I naively bought a Valve Mk I, I can't do this, and I'll eventually have to manually recreate all 9x4 of my presets on another device... hours of work.

 

"One thing you can try is what we used to call "Zero Parking".... See if that works for you, good luck bro..."

 

Thanks, but I'm not even sure what this is supposed to be doing for me.  I'm not having any problems while playing; my amp works fine, except for the presence knob, which does nothing.  Are you saying "zero parking" might fix the nonfuctional presence knob?  Phil_m (5500+ posts) implies the knob may need a hardware fix.

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Sorry, I was reading the intermittent volume issue then I noticed the parenthesis. Zero parking usually fixes the bouncy volume issue but I can't see why the Presence control would fix it as it is not even connected to the digital preamp section. Just something else to try that's free! ;)

 

cgtrox B)

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Yes, presence is 100% analog in the SV. Parking knobs it for digital jitter for the pots that convert digital. Does not apply to the presence or master volume pots.

 

There is a little harness that runs from the power amp board to the control board that carries the master volume and the presence signals to the front panel pots...tiny molex headers...You will have to forgive me as it has been several years since I did a major modification on my SV MK1...But anyway, it could be that that the little header pins have become oxidized....Pretty easy to unplug the header, add some contact cleaner and plug it back in. If that doesn't bring it back, I would suspect a dead cap...That is all there is to a presence knob...

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