Treble bleed on JP6 with piezo

[nerdstradamus]

Hi,

As the title says, is this possible? Do I just ground the tone capacitor and then install the treble bleed mod on the volume pot? I'm not good with electronics, so forgive me if I sound stupid. Thanks.

 

[beej]

Backing up a bit ... a treble bleed is a work-around to retain higher frequencies that are lost due to the loading effect on the pickups, largely due to the capacitance from your cable.

With the piezo version of the JP6, you have an on-board preamp that will negate this effect. So simply by using the active output (mono I believe) and selecting magnetic pickups only on the selector switch, you'll have a buffered output from your magnetic pickups that won't lose treble as you turn down the volume.

If you still want to put something in place for when you use a passive output, you'll can wire up a treble bleed on your volume pot. You'll have to experiment a bit to find resistor/capacitor values that work though- perhaps someone can recommend something.

Another option to consider is "50's wiring", where you change where the tone pot connects to the volume pot. This results in less treble loss when you reduce the volume, though it changes the interaction of the tone pot somewhat. (I prefer this approach, and have it wired up on most of my guitars.)

 

[DrKev]

As beej said, with a passive guitar circuit if high frequency loss is an issue when turning down the volume, adding a resistor/capacitor combo to the volume pot is the way to go.

This is my list of the value recommended by the various pickup manufacturers....

Treble Bleed Mod Round-up | DrKevGuitar.com

Based on my recent circuit simulations I recommened that if you use a 10 ft cable from your guitar to your pedla board or amp, choose the Mojo, DiMarzio, or Suhr values. If you use a 30 ft cable choose one of the versions with 1 nF or 1.2 nf capacitor.

The DiMarzio treble bleed vlaues are working great for me (560pF capacitor and 300kΩ parallel resistor).

Note that doing this mod will also change the taper of the volume pot somewhat. Try it and see if suits you.

 

[axeel_b]

Backing up a bit ... a treble bleed is a work-around to retain higher frequencies that are lost due to the loading effect on the pickups, largely due to the capacitance from your cable.

With the piezo version of the JP6, you have an on-board preamp that will negate this effect. So simply by using the active output (mono I believe) and selecting magnetic pickups only on the selector switch, you'll have a buffered output from your magnetic pickups that won't lose treble as you turn down the volume.

If you still want to put something in place for when you use a passive output, you'll can wire up a treble bleed on your volume pot. You'll have to experiment a bit to find resistor/capacitor values that work though- perhaps someone can recommend something.

Another option to consider is "50's wiring", where you change where the tone pot connects to the volume pot. This results in less treble loss when you reduce the volume, though it changes the interaction of the tone pot somewhat. (I prefer this approach, and have it wired up on most of my guitars.)

Hello @beej,
a little revamping on an old thread....
I purchased a second hand JP6 piezo (2014) and it seems to have this (and maybe others) issues, also on the buffered mono output with both magnetic and piezo pickups. Indeed the cable type, length and quality is quite an issue when using this guitar respect to other passive guitars I own (Fender, Ibanez, PRS).

Unfortunately I do not have the opportunity compare my guitar to a brand new one here - I'm from Italy, there are some issues with the italian distributor and the result is that Music Man instruments can only be purchased in 3 stores across the entire country (...) none of them less than 300 Km from my place.

Anyway, another thing seems a little strange to me, which is not an issue by itself but rather a "different" behavior from what expected: I remember some other users on this forum, stating that there may be slight tonal differences when using the buffered output instead of the non-buffered connection (see: this thread) : buffered output may sound a little less good while the stereo output is always better. I never experienced anything like that: when using the magnetic pickups both outputs sounds exactly identical to my ears in terms of volume and tone, equally full, same dynamic and headroom - not sure this may be the right word - anyway they sound good to me when the volume is fully open. In fact, both outputs suffer the same issue about treble loss when turning down the volume pot.

The last issue I have is about EMI (electromagnetic interferences). I mentioned this issue on another thread (here). Basically magnetic pickups on this guitar are way more subject to EMI than any other guitar I use, specially for EMI coming from laptops, mobiles, monitors or other electronic equipment such as wireless devices. As a side note, the guitar has an insane hot output level, especially on the bridge position - hotter than a Seymour Duncan Distortion as an example - and this can remarkably push the amp input stage harder and consequently engage higher distortion levels, i.e. more noise.

Is there some sort of electrical test I can perform on the outputs or on the internal board to verify everything is working properly? I'm thinking about replacing the preamp board, but due to the problems with the supply chain I mentioned above, I would like to better detect the root problem if any or else update the circuit by introducing a treble bleed (relatively to the first issue on this thread) and maybe provide a stronger shielding to the cavities and the preamp board.

Thanks in advance.
Alex