CTS pots.

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CTS pots.

Postby jdrpicker22 » Fri Feb 22, 2013 7:12 pm

So this summer i bought a hollowbody 5120 copy from guitarfetish and this thing buzzed like a swarm of bees after i put my bigsby with the wire arm on anyway i just got it back on Wednesday from a friend who rewired it for me like it was supposed to be (i spent like 40hrs trying to rewire and ground stuff) anyway i put new CTS pots in it from RSguitarworks.net and the taper is wierd like between 8-10 huge volume jump and 1-8 hardly noticeable volume increase 0- off. SO i pretty much use my master volume the most and i want a good taper in that one because my i play at differnt volumes not wide open all the time (my parents tell me to turn it down, its really only loud enough for good tone though :D) So does anyone know of some good pots with good taper, i bought CTS after research and thinking that was my best choice, but if i put a new pot in id like to eliminate my neck pup volume and just wire it like a Nashville Classic. any suggestions will be greatly appreciated.
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Re: CTS pots.

Postby alexjones » Fri Feb 22, 2013 8:27 pm

What your describing sounds like typical Audio taper pots. I notice the same behavior on my Country Gent. I would like to have uniform control of the bridge pickup volume, but the current pots are not set up that way. I am pretty sure that the pots in my Gretsch are Audio taper. I guess most folks prefer this type of taper. If you want to try something else - get a linear taper pot. I bought one to put in my Gretsch but I haven't gotten around to tearing all the wiring apart to change a pot. I'll probably change it out when I get some unpotted pickups from TV Jones. I want to see if I notice any difference. I suppose Chet's pickups were unpotted, so it might be an interesting experiment. Call me crazy, but chasing a tone can be fun!
Alex
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Re: CTS pots.

Postby Brian Ingram » Thu Feb 28, 2013 1:50 am

Audio taper is the correct taper to use for a volume pot, because your hearing is logarithmic so the pot taper matches the way we hear.

I think the problem is the way the pots are wired on some of these Gretsch's.

Normally, one outer lug of the pot is connected to ground (often by soldering to the case of the pot), and the pickup hot is connected to the other outer lug. The the middle lug (the wiper) taps some portion of the signal, and passes it to the next part of the circuit.

I noticed the 5120 (and even the 6122-1959) have the pots wired "backwards". The pickup hot is connected to the wiper, and the output is the un-grounded outer lug. It reduces volume not by acting as a voltage divider (like standard volume control wiring), but by loading down the signal when the volume is turned down.

I think that rewiring as in a standard volume control will cure the effect of all the action happening at the top of the volume control movement.

I just bought a 5120 myself last weekend. I have some TV Jones pickups on the way, and a Tru-Arc. Once they arrive, I'll install them and "correct" the volume control wiring. If it seems to cure the taper issue, I'll report back. Only catch is TV Jones sent me an e-mail that their Supertron is backordered, so it might be a couple weeks before I get the pickups and get the wiring done.

Schematic of Tone Pot Circuit wiring, as used in the 5120
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Re: CTS pots.

Postby Brian Ingram » Mon Mar 25, 2013 8:40 pm

So I apologize for this taking nearly a month, but my pickups were held up in backorder that long.

I just replaced the entire wiring harness in my 5120, while I was in there swapping pickups and adding the new bridge. I have a discovery that should help you.

First, I was wrong earlier when I thought your issue might be related to how Gretsch wires the volume pots in the 6120/5120 and other Tone Pot models. In fact, what I found out is the "odd wiring" actually ensures that when both pickups are selected you can roll down the volume of one without it reducing the volume of the remaining pickup.

That sounds obvious, but every Gibson I can think of is wired differently, and if you turned off the volume of the bridge pickup with the selector set for both pickups, you'd get no output at all. No that is actually helpful to a rock guitarist playing a Les Paul with no master volume (because it's an easy mute when playing through screaming amps), but I get how that is dysfunctional for Chet music.

So now that we know I guessed wrong on the wiring harness setup, what about the taper?

Well, I outsmarted myself again. I knew the 5120's tone control worked fine, the circuit diagram I linked earlier has the tone control marked as an audio taper, but I wasn't sure the 5120's harness matched the circuit diagram. I ordered a linear taper for my tone control when I got the parts for my harness.

Guess what? The linear taper tone control behaved exactly like you described earlier: all the action is at 8-10 on the knob. So, the 5120 does have the correct wiring and parts as indicated on the diagram for American-made Gretsch models, and all of the pots are audio taper.

That tells me you got a linear taper mixed in with your parts somehow. If you installed it yourself, maybe you got a wrong taper sent with your others. If you had the pot out of the guitar and had a meter, the easy test is to set the pot at half-rotation and measure resistance to one end. If the pot is linear taper, that mid-point will measure roughly half-resistance. If the pot is audio taper, a 500kΩ pot will measure ~50kΩ from the middle lug to one end, and about 450kΩ to the other outer end.

So it sounds like if you get an actual audio taper in your guitar, you'll be happy with the performance. FWIW, CTS is no better or worse than anyone else on the taper of their audio pots. I used Bourns pots in my guitar, but really I only swapped because I like those and I wanted to put in parts I knew would last several decades at least.

(BTW, nothing magical about Bourns either. You may not like them if you try them, as there is very little physical resistance when you turn the knob. Some folks want a pot that's a little bit stiffer so it's less likely to be jarred on stage.)
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Re: CTS pots.

Postby Norm » Tue Mar 26, 2013 12:05 am

alexjones wrote: I suppose Chet's pickups were unpotted, so it might be an interesting experiment. Alex




Why would you "suppose" Chet's pickups were unpotted? Bigsby potted his pickups and I would imagine Ray Butts did too due to his radio repair background. Potting defeats a certain high frequencey feedback
...that's how it looks to me...The opinion expressed above is my own and does not necessarily reflect the views of this station. Your mileage may vary...

Audio samples: http://www.youtube.com/user/acountrygent/videos
That should do it.
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Re: CTS pots.

Postby alexjones » Tue Mar 26, 2013 8:58 am

I am under the impression that the early Gretsch pickups were not potted. And then again, Chet's pickups were not true Gretsch pickups either - they were modified. So I guess the only way to find out is to open up the pickups and look around - not going to happen. I wonder if Paul ever knew - has this been talked about on the board before?
Alex
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Re: CTS pots.

Postby Norm » Tue Mar 26, 2013 10:04 am

alexjones wrote:I am under the impression that the early Gretsch pickups were not potted. And then again, Chet's pickups were not true Gretsch pickups either - they were modified.
Alex


Well, as you say, there is no definitive answer.

Just thinking off the top of my head it is possible that the pickups on the 59 weren't potted but, again, it seems to me that Ray Butts and Shot Jackson (the guy who rewound Chet's bridge pickup) would have seen to it that they were potted, again, for the noise factor.

Chet not having his pickups potted is something I hadn't heard before. Could be they weren't. The only mention of potting I've seen Paul make was referring to Bigsby who potted his pickups to help keep them quiet. I don't think there would be a discernable tone difference and, again, you'd be opening yourself up to possible feedback/microphonic issues down the road
I'll check with the guys at gretschpages.

Meanwhile let us know how yours come out. Did TV Jones make any comment on what the end product might be like?
...that's how it looks to me...The opinion expressed above is my own and does not necessarily reflect the views of this station. Your mileage may vary...

Audio samples: http://www.youtube.com/user/acountrygent/videos
That should do it.
Norm
 
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Re: CTS pots.

Postby Norm » Tue Mar 26, 2013 11:52 am

Responses so far...

Brian Setzer's pickups are "lightly potted" and Jones said the standard potting has some effect on tone although he doesn't specify just what. Tone is really hard to describe anyway.

Another guy said "none" of the pickups of the day were potted 'except Fenders' but, as already cited, Bigsby potted his.

Chet's could very well have been unpotted. The double bar pickup was an experiment that Chet liked and it may be Ray was just trying the idea and didn't take the time to pot it. Not sure what Shot Jackson's policy was on potting pickups. A Sho-Bud owner might know.

A well made pickup might not need potting as cited here:

Any guitar with a pickup that is microphonic but otherwise a good sounding pickup is a good candidate for potting. If your pickups aren't microphonic then there is little point to potting them – and they may even have been potted at the factory. Many better-quality pickups are potted at the factory, and some others are so solidly constructed that potting will provide little or no improvement. Often a pickup that has been fine will become microphonic as handling and environment take their toll. Such a pickup then becomes a good candidate for potting. Even a pickup that was potted from the factory might become microphonic after much use. If the pickup was potted with wax it can be repotted.

So, you may well be (and probably are) correct. And unless we see a direct quote about Chet's 59 pickups we'll never know for sure.

That does it for me. I'll pass along any further gretschpages comments.

Interesting stuff... We still need to practice the guitar to sound better though... :D
...that's how it looks to me...The opinion expressed above is my own and does not necessarily reflect the views of this station. Your mileage may vary...

Audio samples: http://www.youtube.com/user/acountrygent/videos
That should do it.
Norm
 
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Re: CTS pots.

Postby Norm » Tue Mar 26, 2013 2:02 pm

Looks like you were correct, Alex...
From gretschpages:

_______________

Yeah, old FilterTrons were not potted. The way I understand it, the cause of a microphonic pickup is internal vibrations, either in the coils or something else, like a loose cover. Apparently Gibson-type humbuckers are notorious for loose covers causing microphonics. All I can say is I've never had an issue with microphonic FilterTrons. I wonder if the whole pickup apparatus being screwed directly into the top helps to prevent microphonics in Gretsches? If vibration is the cause, I can see how Gibson humbuckers might have issues, being mounted on springs and basically just floating in the cavity.

And FWIW, some people claim that you lose some "airy quality" in a pickup when you pot it. I have no idea how much truth to that there is, or even what exactly "airy" means, but it's something I've heard.
...that's how it looks to me...The opinion expressed above is my own and does not necessarily reflect the views of this station. Your mileage may vary...

Audio samples: http://www.youtube.com/user/acountrygent/videos
That should do it.
Norm
 
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Re: CTS pots.

Postby Norm » Tue Mar 26, 2013 4:03 pm

...and more:

In my opinion the lack of wax potting is the HUGE reason that there is such a market for "vintage pickups".

people talk all day long about wire gauge, number of windings, the alloy of the magnet, scatter winding vs uniform winding, even the alloy of the casing......but no one ever talks about potting. It makes a HUGE difference in the sound of a pickup.

Potting ruins all the high end of a pickup. Humbucking pickups like Filters and PAFs NEED that high end because it's lost a bit due to the separation of the coils in humbucking design.

Why would wax make such a difference?

Basically mechanical vibrations from the guitar shake the coils in the pickup. These small movements in the coil wires change the positional relationship between the coils wires and the moving strings. When you wax the coils, you kill this.

Yes a pickup that is NOT wax potted will feed back more. But so will a $1,000 microphone. It's more sensitive to sound. You could dunk the microphone in wax I guess....but why do that?

I order all my Filtertron style new pickups from TV Jones without wax potting. I never have feedback problems....but then I don't use them in high gain situations....and if i DID I sure as hell wouldn't be using a hollow body Gretsch for the job anyway. The sound is definitely improved and exactly like vintage Gretsch pickup. it's the missing ingredient.

Pickup manufacturers like Seymour Duncan are hip to all this. His Seth Lovers PAFs are not wax potted to get a sound closer to original Gibson PAFs
...that's how it looks to me...The opinion expressed above is my own and does not necessarily reflect the views of this station. Your mileage may vary...

Audio samples: http://www.youtube.com/user/acountrygent/videos
That should do it.
Norm
 
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Joined: Wed Aug 31, 2011 12:36 pm
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