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Post by ajent__smith on Aug 13, 2006 22:35:15 GMT -5
I have this idea to use 2 guitar mounted switches in place of the footswitch for the Delux Reverb reissue that i plug into. i know how to wire it, i was just wondering if there would be any problem with squealing if the wires from the footswitch out where that close to the pup wires and whatnot. could i isolate them with tin foil or somthing? any ideas? thanks in advance, ajent
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Post by sumgai on Aug 14, 2006 16:06:14 GMT -5
ajent,
You could do this, but you run the risk of making the reverb sound like crap. That long a cable run will introduce much capacitance into the return line (the switch is connected directly to the output of the pan). Yes, it's in parallel, and therein lays the problem - you are adding a significant amount of capacitance directly across the signal line, right to ground. This can, and will, create the Mother Of All Tone Sucks.
Not to mention, what if the cord gets stomped, and your signal goes south? If it shorts, the reverb is off forever, if it breaks open, the reverb is on forever. Quite the opposite for the vibrato (or to be accurate, the tremolo) switch.
You will need some very high quality cabling, and some rather heavy-duty connectors, perhaps of the locking variety. Other than that, there are no worries about high voltage or anything, so hug a nut!
HTH
sumgai
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Post by ajent__smith on Aug 15, 2006 2:19:41 GMT -5
The cable run isnt going to be any longer then the cable on the footswitch (i dont use very long cables), so i dont think that the tonesuck would be any stronger.
Also, i plan to have 2 seperate cables running into my axe, 1 for the guitar signal, and a second for the amp controls.
In addition, im not to worried about the cable getting stomped, because the reliability of the footswitch isnt too great either (ive had to repair the footswitch once already). If it does get stomped, however, I can always replace the cable.
I dont think i understand why i need heavy duty connectors, the amp footswitch in is a stereo 1/4" jack. I planned on using a 1/4" stereo cable in this instance too, is there a reason why i shouldn't?
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Post by ChrisK on Aug 15, 2006 16:56:31 GMT -5
Is this an unnecessary optimization or have your feet recently stopped working?
I ask because you're messing with internal amp circuits. These were designed prior to the current period of litigious life safety concerns. I wouldn't do it since the life that I may save just might be my own.
The tag line below may well NOT apply here.
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Post by ajent__smith on Aug 15, 2006 17:28:50 GMT -5
Chrisk,
The amp is a reissue, and includes some safety features such as a grounded power cable, and the switch itself will be grounded, so i dont exactly understand why this is dangerous. i understand that if one of the tubes fails in either effect that i might end up with a high voltage coming up through the cable, but other then that I don't see how this could be dangerous. I looked at the schematics, and i see no danger, but im young and stupid, so i might have missed something.
PS ( i don't know if this any different from the origonal deluxe, but the footswitch just has 2 buttens that ground out there respective live lines.)
Thanks for your concern, A__S
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Post by ChrisK on Aug 15, 2006 18:13:42 GMT -5
The DRRI has the tremolo switch control point derived from the bias supply ("C-") which is typically -49 VDC. While this point normally varies from -0.2 VDC to -6.8 VDC, a single point failure regarding R37 (a 390K resistor) would present -49 VDC at the tremolo switch point.
One of the UL requirements is that a single component failure won't present a shock hazard. This design does. The fact that the presented voltage in case of a failure exceeds 42.2 VDC relegates this node to Class 1 voltages in failure.
I ain't going there.
Due to the often questionable wiring in venues, you don't need the additional shock risk. If you have to do this, make a new footswitch/control box with a couple of ultra low power relays in it and switch an isolated battery supply to the coils. Let the contacts assume the risk.
See digikey.com
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Post by UnklMickey on Aug 15, 2006 18:37:59 GMT -5
"a single point failure regarding R37" i think you can do better, Chris. what happens if C17 shorts? 100~200v DC. granted, this is at the switch, but if the switch on the guitar is closed, and the ground on the cable is broken..........................yikes!
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Post by ChrisK on Aug 15, 2006 19:15:56 GMT -5
(Duh-) uh, ok. C17 fails and Homer Simpson peas on the control panel at the nuke plant and causes the mains to go to 100 KV.
The user does the same on the floor (the ground plane) and.......
Snap, Crackle, Pop, a new genre is (briefly) born.
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Post by UnklMickey on Aug 15, 2006 19:26:09 GMT -5
Homie don't eat no peas.
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Post by ChrisK on Aug 15, 2006 20:06:05 GMT -5
I was being somewhat PC.
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Post by UnklMickey on Aug 15, 2006 20:14:07 GMT -5
unlike the pervs with the hidden cameras in the ladies rest-rooms.
(pee-see)
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Post by sumgai on Aug 15, 2006 21:16:41 GMT -5
unk and Chris, My undies are in a state of shock, after seeing what you two guys can do to an innocent topic like this! ~!~!~!~!~!~!~!~ ajent__smith, Sadly, they are both correct. While I said that there are no dangerious voltages present, I did mean this to be "under normal circumstances". I should have said that up front, sorry for the omission. If a part fails (and they do fail, make no mistake; after all, that's how I make my pin money, repairing those failed parts), then you are definitely in danger. It's not a matter of a tube blowing up, the parts are there to protect against that. But under otherwise normal circumstances, even if a tube is operating with no problems, you could still be exposed to potentially lethal voltage(s), should other parts go haywire. Now, that said, Chris makes a valid suggestion - let a pair of relays do the dirty work for you. In fact, I could suggest that you might even consider using opto-isolators as control points, and then running the signals onto your main cord - no modifications would be necessary to that cord (or to your guitar's output jack). But that's a lot of work, and probably more expense, than you need for basic functionality. Stick to normal wiring for standard relays, use good quality cabling, and you should be good to go. And we were (or I was) referring to using high quality cables and connectors more for endurance than signal quality. Even if you say they're gonna be short, it's still a good idea to design for prevention than it is to fix stupid mistakes afterwards. ;D sumgai
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Post by RandomHero on Aug 19, 2006 5:10:28 GMT -5
Just of curiosity, Smith, why would you want these features to be on the body of your guitar? Don't let me discourage you, if you know for sure that this wouldn't be an issue, but one of the things that brought me to GN was the idea of putting my distortion pedal into my axe. A wiser man than me pointed out that if I ever wanted to kick on that distortion mid-song, it would be much easier to do with a free foot than a flailing pick hand... just my 2 cents.
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