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Post by lunaalta on Jul 1, 2014 6:38:41 GMT -5
Ok, so I've been cleaning up a friends '72 LP Deluxe and I noticed that there is a constant 'repeating click'. This is present with all control positions, volume up or down.... It's not so loud as to be noticed at conservative levels but if liberal gain is given to the amp it becomes very apparent (apologies for the political terms.... LOL). Also, when 1 PU is selected and the volume off a hum appears, for either PU. When both PUs are selected the hum appears when both volume pots are off. There is no hum if one pot is left up. I noticed this when plugged into my Fender (s/s) Sidekick Reverb 25, wwhich I recorded, by taking the line output from the amp. When the LP is plugged direct to my computer the hum is almost unheard but the clicking persists. I have attached a pick of the wiring cavity and a sound file of the noises with the Fender amp in the equation. In the sound file I dished the volume of each PU separately to indicate the hum. If I touch both a PU and the strings all noises disappear. These noises do not appear when I have my '73 Fender Strat connected. [a href="http://s112.photobucket.com/user/whitestrat73/media/72_lp_deluxe_wiring_cavity_zps6d3c4723.png.html?filters[user]=140712028&filters[recent]=1&sort=1&o=0"]pic of wiring cavity[/a] (sorry, you'll have to cut and paste the image address... ) mp3 of hum and noise 72 LP deluxeI wonder if anyone here can help me to find and fix this. Apart from the hum/clicks the guitar is awesome!
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Post by sumgai on Jul 1, 2014 11:24:47 GMT -5
la,
In a Gibson guitar, the volume controls are wired backwards. Thus, the wiper is not taking the input of the amp to ground, as it does in a normally wired guitar. Instead, the wiper takes the pickup's "hot" lead to ground, thus shorting the pickup, thus rendering no sound output.
The upshot here is, the input of the amp is now "seeing" that volume pot's resistance, which for all practical purposes, is an complete and functional circuit with a high resistance (the vol pot's total resistance). When you turn the volume up, the wiper starts introducing the impedance of the pickup, which is much lower, and in parallel with that vol pot resistance for at least some portion of the rotation. This drastically reduces the load that the amplifier "sees", thus reducing the amount of apparent noise coming out of the speaker.
The last culprit here is your environment. There has to be something for the amp to sense when the pots are turned down, or otherwise every Gibson owner in the world would be complaining! I suggest that you take the amp, guitar and cable(s) to another room, or another house/wherever, and test again.
Don't forget, it could be nothing more than a cheap quality cable. Try a known good one, if such is available.
HTH
sumgai
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Post by lunaalta on Jul 1, 2014 14:49:30 GMT -5
Thanks for the reply, sumgai, much appreciated! OK. Well, I eventually turned the Strat up loud, in the same set up, and the ticking sound appeared......... so, I'll check it at the owner's house. I live in a small village, kinda in the backwoods, with old Spanish wiring, and I have a radio station set up a couple of doors away..... I'll check it out elsewhere, as you suggest. I have pretty good quality cables that are not so old, but they are looked after. I must have spent a fortune in cables, over the last 45 years or so..... LOL. Thanks again, for the look see, I'll let you know what I find..........
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Post by JohnH on Jul 1, 2014 16:12:26 GMT -5
It looks like a multimeter test of the guitars resistance across the jack, as you sweep the volume pot from max to min, might be very revealing.
It does seem like it could be as sumgai describes. But i dont think that type of wiring is common. Certainly not on stock Gibsons from recent decades (including mine), but I dont know about a '72 Deluxe.
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Post by lunaalta on Jul 5, 2014 5:39:52 GMT -5
I tested resistance, as you suggested, JohnH, and got 0 in all positions........ For some reason, I've been thinking this is a problem shared across all PU positions, equally, so it must be someplace else...... or at least something that is common to both PUs... Then, and I feel stupid for not trying it earlier, I tried the 2nd amplifier input, which has 1/2 the sensitivity (according to the manual), the amp connection being the first part of the chain and common to all settings. Bingo! No more hum, in any position............ Now, I know this isn't record breaking science, but I did learn a big lesson (So, please don't laugh too loud ). Always, but ALWAYS check everything in the chain, from start to finish......... then do it again..... LOL. The ticking/clicking is still there, but, so far in my recording exploits, it is negligible. So, thanks again for the help! I learned something, and I'm pleased about that..... hope I didn't waste anybodies time.......
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