I've created a TONE MONSTER!!!

[soulfeather]

I bought my '02 McCarty back in '06. The previous owner had removed the McCarty pups and the push/pull pot. Over the years I have experimented with new pups and configurations. The current setup is how its been for the past 2 years, and how it's going to be forever. I put a push/pull pot in both the volume and tone pots so the pickups can be split independently. This adds two additional pickup combinations: 1. Bridge Humbucker + Neck Single Coil 2. Bridge Single Coil + Neck Humbucker. After doing this I realized that I wanted to blend the pickups, because the hums dominated the sound with their higher output. Without having two volume knobs to blend pups like a SC or a DGT, I decided to place a pan pot in the pickup selector position. A pan pot rolls the volume of the two pups up and down as it rolls from 0 to 10.

0 = Bridge FULL ON, Neck OFF
1 through 4 the volume of the Neck pup rises
5 = Bridge FULL ON, Neck FULL ON
6 through 9 Bridge volume drops
10 = Bridge OFF, Neck FULL ON

This IS THE BEST THING I HAVE DONE to this guitar. As complicated as it sounds, the guitar is very intuitive and natural to play. In live settings one can find the perfect tone to cut through the band by just tweaking the pan pot. I thought I was putting in another volume knob, but it plays more like another tone knob. Instead of cutting highs like a conventional tone knob, the pan pot works by adding and subtracting the natural highs of the bridge or the natural lows of the neck. One unintended plus is when the pan pot rolls over 5, from a single to a hum, the harmonics that are added give it a wonderful chorus/pan/tremolo effect. I don't really know how to describe it, but it works well with some jammy sounds.

I have been wanting to show PRS this configuration for some time. With the release of Paul's Guitar, and the mini toggle switches that split independently, I finally decided to come here and show my girl off. I know I'm not the first person to use a pan pot, or independently coil split the two pups, but I haven't found one yet that has this configuration. (I admit I haven't looked very hard) My one concern is that I often hear PRS brag (justifiably so) about how well the volume knob works and cleans up nicely with no tone loss. Well, with the push/pull in the volume knob I lose that quality. Its not bad tone loss, but does not compare to how well some of the newer PRSs work. Does anyone know a high quality push/pull pot that this tone loss would address? I plan on doing a video of this guitar, and will surely let you guys know when its up. Pics and Vid are on the way.

Thanks,
Reid: The Soulfeathers
https://www.facebook.com/TheSoulfeathers?fref=ts

 

[]-[@n$0Ma☩!©]

That sounds very interesting, Reid. Thanks for the write up and welcome to the forum! I assume you did the mods yourself?

I'm looking forward to the pics and video.

 

[soulfeather]

[/IMG]

 

[docbennett]

Very interesting, and the sole reason why I spec'ed out my new CU-24 PS with a 2 X 2 volume and tone layout, with separate coil splits for each pickup....and obviously the ability to blend the volume of both pickups in any combination desired. Only problem is that they still don't know how they are going to place the piezo controls with this brand new layout. but...for some time, i've wanted that "Les Paul" ability to control each volume knob separately and distinctly.

Looking forward to your subsequent posts. Wish I had something to add that was technically what you're looking for...but, alas...you lost me at "I decided to place a pan pot in the pickup selector position"

 

[soulfeather]

This guy Warren, Lead Guitarist of The Soulfeathers, did some of the mods. You'll see more if him in the demo.

[/IMG]

 

[sergiodeblanc]

Nice! I'm in the middle of deciding how to deal with coil splitting options for McCarty electronics as we speak!

 

[soulfeather]

This would be a "before" picture from '09 with Zebra Fralin Unbuckers and the selector switch

[/IMG]

 

[soulfeather]

docbennett,

There was no discernible tone loss with the addition of pan pot, and you can roll from 0 to 10 and back just as fast as a selector switch. Maybe there is something I'm missing. Is there a particular reason you don't like pan pots, or am I reading this wrong?

 

[docbennett]

docbennett,

There was no discernible tone loss with the addition of pan pot, and you can roll from 0 to 10 and back just as fast as a selector switch. Maybe there is something I'm missing. Is there a particular reason you don't like pan pots, or am I reading this wrong?

My lack of knowledge.....lack of ability to solder....lack of experience with the technology...reliance on guitar techs. Nothing personal. You just lost me with the technical talk...that's all.

 

[László]

Nice post!

 

[soulfeather]

Gocha! After putting the pan pot in I'll probably customize all of my future guitars (dreaming) to this spec. I'm just curious as to why its not more common, or even a standard on some models. Doc, I like you, rely on guitar techs to work on my guitars, and am a novice, at best, when it comes to soldering. Thanks for your replies.

Peace,
Reid.

 

[soulfeather]

It's fairly complicated to describe on the screen, but is pretty simple to manage on the guitar. The future video will show this.

 

[justmund]

My one concern is that I often hear PRS brag (justifiably so) about how well the volume knob works and cleans up nicely with no tone loss. Well, with the push/pull in the volume knob I lose that quality. Its not bad tone loss, but does not compare to how well some of the newer PRSs work. Does anyone know a high quality push/pull pot that this tone loss would address?

Great idea and excellently executed!

As for your question, I don't think you can go wrong with the OEM PRS push-pulls:

http://www.prsaccessories.com/collections/parts/products/push-pull-tone-pot

and also the "tone loss" you are experiencing may be attributed to different tone caps/treble bleed circuit, plus you might want to experiment with resistors between the "dead" coil and ground, when coil tapped. Take a look at the latest DGT wiring schematic:

http://www.prsguitars.com/csc/schematics/2012/dgt_2012.pdf

Hope this helps! Can't wait for the vid :top:

 

[soulfeather]

Thanks Justmund.

 

[zamsden]

Great idea and excellently executed!

As for your question, I don't think you can go wrong with the OEM PRS push-pulls:

http://www.prsaccessories.com/collections/parts/products/push-pull-tone-pot

and also the "tone loss" you are experiencing may be attributed to different tone caps/treble bleed circuit, plus you might want to experiment with resistors between the "dead" coil and ground, when coil tapped. Take a look at the latest DGT wiring schematic:

http://www.prsguitars.com/csc/schematics/2012/dgt_2012.pdf

Hope this helps! Can't wait for the vid :top:

The tone loss is probably due to the different wiring of the output capacitors, the PRS output configuration is fairly unique.

I'm actually in the middle of a similar modification for my PRS Custom 24. Previously I had replaced the 5 position rotary switch with a 6 position switch that allowed Neck, Neck + Bridge parallel, Bridge, Neck + Bridge series, Neck + Bridge parallel out of phase, and Neck + Bridge series out of phase. It also allowed coil tapping of either the slug side or screw side via two push pull pots.

That allowed for a wide variety of tones, but I discovered over time I disliked the series sounds, the only series sound I liked was when coil tapped, and I didn't find them all that compelling over my go to sounds. I also found very little difference between individual slug and screw side coils, so I didn't need that option. I did however really like the out of phase sound, to my surprise. So I recently decided to do almost exactly what you have done, I added a pan pot which can blend the pickup volume from neck to bridge, with both pickups on full at center detent. When I started drawing the schematic for the circuit, I realized quickly there was a problem. If you keep the original master volume and tone controls (as I want), you now have three potentiometers all at 500K going to ground. This means your resistance to ground is only 166k instead of the 250k you want with passive humbuckers. That will cause a fairly noticeable tone loss, this is what will happen if you do wire up a new master volume in your guitar. This could very well be the tone loss you are experiencing when you wire in the push/pull on the master volume - it doesn't have anything to do with the push/pull, it has everything to do with having three pots to ground instead of two.

Fortunately, there is a solution - upgrading the volume and tone pots to 1M-ohm pots and using a 500k blend pot will put your resistance back at 250k. I currently have some 1M ohm pots on order and will post a schematic of what I did when I'm finished. I plan to keep the original PRS style master volume and tone, you might want to do the same if this works out.

My setup is actually a bit more complicated, as I want push/pull volume and tone pots, this way I can use one to coil split, and I plan to use the other one to invert the phase of one pickup - a little bit different than your approach of splitting the pickups independently, but you could wire it that way too. I like the idea of using one pickup to subtract from the sound of the other (what the phasing will do), especially with the blend pot this will give me a lot of tone color without a lot of unnecessary controls.

Wish me luck, hoping the parts arrive soon. Hoping to trade notes on how this worked out.

 

[zamsden]

I've heard of another related modification, where people use the blend pot to blend from single coil to full humbucking mode. In effect, you are blending the amount of (usually the screw coil) the humbucker. While this sounds useful (think 3/4 humbucker mode...), I don't think the tonal range you can get from this will be nearly as dramatic as the range you can get from blending both pickups in parallel. In addition, you would need either a 4th control, or give up the ability to use pickups in parallel (which is a feature I could not live without). You also won't get perfect hum cancelation anymore, so you could end up dialing in the hum along with your tone in high gain situations.

One other mod I've heard of was blending from series to parallel. I have not heard it described as usable at anywhere but the extremal settings.

I think what you're doing is pretty cool, I really like the fact that you can independently split coils on each pickup, this or the out of phase option I am going for I believe will give the widest variety of tones. Ideally, you could split coils independently and invert phase, but it is rather hard to find a push / pull pan pot and I don't want to drill more holes or worse, route more cavity in the interior of my PRS to add a 4th control. It could, very remotely be possible to find a dual-ganged push / pull pot that could be used as a pan pot, (these are used as stereo master volume / power with push / pull turning it on), but you would have to use linear taper and I don't think there exists one with a center detent. Ideally, an MN taper center detent pan pot with a push / pull phasing would give you all these possibilities.

 

[zamsden]

You might find this useful for playing around with wiring. The base circuit is a simulation of stock PRS electronics circa 2008. They've since changed to a .033uF tone cap if I am reading the new schematics. Sweeping V8.R from 0.01 to 1 will show you frequency response curves for various values of the tone pot.

The reason I made this is so I can run those sweeps and validate the change to a blend pot doesn't lower the signal level unacceptably.

https://www.circuitlab.com/circuit/za4mra/prs-custom-24-custom-wiring/

Coming up: circuit with blend pot installed.

 

[zamsden]

And with the blend pot:

https://www.circuitlab.com/circuit/9qm9e8/guitar-custom-wiring-blend-pot-mod/

After doing some circuit simulation, I have an explanation for your tone loss. I don't think it is tone loss, I think you are losing a bit of volume, somewhere between 10-20%. You lose a couple dBs of signal with the blend pot, even if you bump the volume and tone controls to 1M. The reason for this (which I didn't see at first) is that the blend pot when properly wired drains your signal to ground not once, but twice, as the outputs are combined in parallel, you are effectively getting a 250k resistance to ground across the blend pot.

The proper fix is to use a 1M blend pot.. but they seem to be hard to find. If anyone can find them, let me know... otherwise you would have to use active electronics to get a clean blend with no volume loss over a stock guitar.

Still, I think 15% volume loss for the tonal flexibility is acceptable, especially considering you are probably going to boost your signal anyway before the amp, which can make that 15% loss right back up.