To put the problem as simply as possible: The input impedance of a classic fuzz or booster design is very low, usually lower than 20kohms. Together with the pickup inductance (usually 2.5 H up to 8 H) it creates a low-pass filter, a happy accident with an ear-friendly result. When a fuzz pedal, for instance, receives a kind of neutral carrier signal, it results in good, harmonic-sounding overtone content. But this balance is very fragile, so if the fuzz receives an input signal containing a lot of high end (caused by a treble-bleed network, buffer, active guitar signal, etc.), that balance is disturbed. A lot of intermodulation distortion will be generated between the overtones of the input signal and the generated overtones of the distorted signal. Sum tones and difference tones will be present, which sound dissonant and not very pleasant. So, we can say that the natural filtering of the guitar signal at the input of the pedal is essential for the typical, well-known fuzz tone.
“A treble-bleed network can help you to cut through the mix when you play with reduced volume, so this is definitely a mod to consider.”
I’ve tried to simplify this complex subject wherever possible, hoping that it’s not too much theory. But I think you get the problem. So, what can be done to get rid of it? Don’t worry, you don’t need to remove your beloved treble-bleed network; we will simply make it switchable. This way, you can have both options in your guitar: treble-bleed network engaged and treble-bleed network completely shut off. This mod is not very complicated. All you need is a push-pull or push-push pot with a DPDT switch of your choice or a stand-alone DPDT switch. We will break down the mod into two possibilities:
Fig. 1
1. Replacing the volume pot. The easiest way to make the treble-bleed network switchable is by replacing your standard volume pot with a push-pull or push-push pot of your choice. The benefit of this method is that all connections are made on the new volume pot, so you will have no extra wires running through the circuit. A downside in a passive circuit can be that it’s hard to find a new pot with a good working taper as a volume pot. Usually, manufacturers only stock one version in 250k, 500k, and sometimes 1M, but only with one given taper.
Start to remove the treble-bleed network from your volume pot; we will reuse it with the new pot. Disconnect the wires from the pot and remove it. I prefer to solder all possible connections on a push-pull or push-push pot outside the guitar, which can make things much easier. Here is the wiring diagram for this operation (Fig. 1).
After installing the treble-bleed network to the switch and soldering the two wires from the switch to the pot, you can install the new pot and reconnect the wires. In the diagram, the treble-bleed network is engaged when the pot is pushed down and in its normal position, assuming that this is the standard operation, and you only want to shut down the treble-bleed network when using a fuzz or booster. If for any reason you want the treble-bleed network to be engaged when the pot is pulled up, this is easy to do. Solder the wire on A1 to C1 and the wire from A2 to C2 and you are done.
Fig. 2
2. Adding the treble-bleed network function to a tone pot or using an additional switch. If you want to add the mod to one of the tone pots rather than to the volume pot, the basic operation stays the same: Replace the pot with a push-pull or push-push pot of your choice. But now you can’t do all connections on this pot; the wires from A1 and A2 will have to go to the volume pot. This is also the way to go if you want to add an additional DPDT switch to the guitar, so you don’t need to replace a pot. Here is the wiring diagram for this option (Fig. 2), showing a DPDT switch. If you want to replace one of the tone pots, you naturally have to reconnect the wires and the tone cap from the pot to the new one.
All the rest stays the same. If you want the treble-bleed network to be engaged when the switch is up, simply solder A1 to C1 and A2 to C2.
This mod is also for all players who want to have both options but do not plan on using a fuzz or booster. Without a treble-bleed network, the tone gets noticeably warmer when rolling back the volume and a lot of players regard this as a kind of second tone you can have from your guitar. But in some cases, a treble-bleed network can help you to cut through the mix when you play with reduced volume, so this is definitely a mod to consider.
That’s it! Next month we will have a closer look into the PRS sweet switch and how to substitute it, so stay tuned! Until then ... keep on modding.
RatingsPros:Great-sounding Marshall-inspired overdrive in a pedal form. Flexible boost channel. Superb for rhythm-to-lead transitions. Cons: Can lean toward bright for some tastes. Street: $229 Carl Martin PlexiRanger carlmartin.com | Tones:  Ease of Use:  Build/Design: Value: |
You can use this wiring for any guitar with the same layout. The Duo-Sonic uses a Gibson-style pickup selector toggle switch, but if you want to transfer the switching to a Fender-style, 3-way pickup-selector lever switch, you can use a guide made by Seymour Duncan, which you can find linked in this article online.
To start, let's make a list of what can be done with two pickups and a 3-way pickup-selector switch for an overview of the possibilities:
1. Neck pickup by itself
2. Bridge pickup by itself
3. Both pickups together in parallel and in phase
4. Both pickups together in parallel out of phase
5. Both pickups together in series and in phase
6. Both pickups together in series out of phase
This results in a proud list of six basic combinations instead of the typical three, which makes such a guitar much more flexible.
There is also another option with both pickups half out of phase in parallel and in series. We've discussed the basics of the half out-of-phase thing before, and I'm actually working on a useable design for this and will come back to this in a later column. The goal is to have a switch to toggle from half to full out of phase, because with a master volume and master tone configuration, you can't use the volume pot to dial in the amount of phasing you want on a Les Paul. For this you need a volume pot for both pickups, so a switch will be a suitable solution for a Duo-Sonic, Telecaster, etc.
More about the half out-of-phase basics can be found in two of my previous columns: “The Bill Lawrence 5-Way Telecaster Circuit" from October 2015, and “Decoding Jerry Donahue's 5-Way Telecaster Wiring" from June 2020.
Besides the possible pickup combinations, there are some add-ons we can implement to make such a guitar even more flexible. Something that I think makes sense would be:
1. Direct-through switch
2. No-load tone pot
3. Kill/standby switch
4. Treble-bleed network on the volume pot
There are many more add-ons we've discussed over the years, for example, TBX tone control, Grease Bucket tone control, etc., but it's easy to get lost in all the possibilities and overdo it. Who wants to end up with a guitar wiring that needs a written manual in order to operate it?
I've discussed all of these possibilities before, but today we'll combine them in one guitar. Here's a short rundown of what tones you can expect from these combinations:
Neck and bridge pickup by itself / both pickups together in parallel and in phase: I don't think we have to say anything about this combo as this is a classic guitar tone we all know.
Both pickups together in parallel out of phase: a thin, hollow tone that can be cool for playing reggae and ska music when using clean tones, or with tons of overdrive and distortion to prevent getting lost in the mix. For more details, have a look at “Adding an Out-of Phase Switch to a Telecaster," from August 2014.
Both pickups together in series and in phase: a loud and beefy tone, perfect for lead playing. For more details, read “Stratocaster Parallel/Series Switching" from December 2011 and “Telecaster Series Wiring" from June 2015.
Both pickups together in series out of phase: a very interesting sound that's much fuller and warmer compared to its parallel mate. Can be used for clean playing to add a special flavor but also for overdrive sounds. Brian May's “Red Special" guitar is one of the wirings that's able to give you this sound. See “Inside Brian May's Red Special" from October 2014.
Direct-through switch: Your signal is routed directly to the output jack, bypassing all controls for a louder tone with more high-end. Can be found under various names like “blower switch" and the like. See “Stratocaster Direct-Through Mod," from October 2009.
No-load tone pot: With the pot fully opened at 10, it will be out of the circuit, so it's half between normal operation and direct-though mode with only the volume control being active. See “The Fender Delta Tone System, Part 1" from January 2011 and “The Fender Delta Tone System, Pt. 2" from February 2011.
Kill/standby switch: This can be used to shut down the entire guitar when you're not playing, like during a break (standby switch, very similar to the standby switch you know from tube amps), or to produce a stutter-effect while playing (kill switch). See “The (In)famous Stratocaster Kill Switch" from December 2009 and “The (In)famous Stratocaster Kill Switch, Part II" from January 2010.
Treble-bleed network on the volume pot: preserves the high-end from getting lost when rolling down the volume. Check out “Deep Diving into Treble-Bleed Networks" from March 2019.
Fig. 1 — Image courtesy singlecoil.com
To prepare and fully understand this wiring, you should plan some time to read all the articles about the individual mods and what they do. That's the reason for so many links this time. It's simply impossible to cover all these individual mods again for one column—it would take up half the pages in this magazine!
For better clarity, I skipped the treble-bleed network in this diagram (Fig. 1). I described in detail in the treble-bleed article how to connect it between input and output of the volume pot. It's also up to you to use a no-load tone pot or not: I simply refer to it as “tone" in the drawing. For the parallel/series switch, the phasing switch, and the direct-through switch, you need a DPDT on/on switch. For the kill switch, you need to decide if you want a standby switch or a momentary kill switch, as described in the corresponding articles. Two of the switches can be substituted by push-pull or push-push pots, so your pickguard doesn't look like the main control unit from Apollo 11. There are even special kill-switch pots named “kill pot" that are available from the Shadow company. When you replace your tone pot with a push-pull or push-push pot, you'll have problems finding a no-load type if you want to keep this option. Your best bet is to mod your pot as described in the corresponding article.
As always, you can experiment with the type and value of the tone cap. Maybe you want to implement another mod here, like the warmth-control mod, which you can learn about in “Swap That Tone Knob for a Warmth Control" from November 2018.
If one of your pickups has a metal cover that's connected to the pickup's ground, like on most Telecaster neck pickups, you need to separate it to perform the series mod. I describe how to do that in “Preparing Your Tele for Future Mods" from May 2013.
For a better overview, I used individual switches for the diagram instead of push-pull pots. So, there we have it. Next month we'll return to our DIY relic'ing project and focus on the metal hardware, so stay tuned.
Until then ... keep on modding!