The consequences of changing a JB to v-t-t

We are fortunate to count Paul Gagon as a member here, so it seemed natural to give him a home to stretch out in and relax a little. Maybe exercise the grey matter and present a little history of the guitar and bass (amps too!) from his perspective as one of the eminent designers of our time.

Got questions? Great! Good questions might be, "What are the EQ mappings for the M Series preamps?" Or, "What was the thought process behind the MJ-4?" Troubleshooting questions should remain in the regular forums (he reads those too). Finally, please be mindful of how I feel about tech questions via PM or email.

Moderator: Paul Gagon

The consequences of changing a JB to v-t-t

Postby Ricky Rioli » Tue Sep 29, 2020 10:58 am

I'm imagining the three knobs of a JB reallocted to be master volume, neck pickup tone, and bridge pickup tone. Somewhere would be located a three way selector switch giving neck-both-bridge.

One benefit of this would be the ability to go from neck pickup only with 100% tone to bridge pickup only with 0% tone just by flicking the switch

If knobs were set up for that - one tone knob on 100% and the other on 0% - what would happen when the switch was at the middle position, selecting both pickups?

The question is asked in a spirit of learning, not because of any actual plans.... :geek:

(ps after I wrote this, and with the thoughts still in my head, I went back to practising, and decided what I would quite like would be for the switch's three positions to be (1) bridge with tone 0% (2) both with tone 0% (3) neck with tone knob in action)
User avatar
Ricky Rioli
 
Posts: 24
Joined: Thu Sep 17, 2020 7:50 am

Re: The consequences of changing a JB to v-t-t

Postby Ken Baker » Tue Sep 29, 2020 4:52 pm

Ricky Rioli wrote:One benefit of this would be the ability to go from neck pickup only with 100% tone to bridge pickup only with 0% tone just by flicking the switch

If knobs were set up for that - one tone knob on 100% and the other on 0% - what would happen when the switch was at the middle position, selecting both pickups?


You'd probably end up with some interaction between the tone controls because the signal chain is common to both pickups. Would it work - yeah probably. Would it work to your expectations - maybe. Would be a worthy experiment.

The question is asked in a spirit of learning, not because of any actual plans....


That is a damn fine reason!

(ps after I wrote this, and with the thoughts still in my head, I went back to practising, and decided what I would quite like would be for the switch's three positions to be (1) bridge with tone 0% (2) both with tone 0% (3) neck with tone knob in action)


How about this: Leave the stock controls as-is; V-V-T. Set up switching to toggle a .047µF cap (or even a .1µF cap) onto the hot lead of each pickup upstream of its associated volume control. Then you'd have a bone-stock set of normal controls plus the ability to dump off a pile of treble from each pickup individually.

Ken...
User avatar
Ken Baker
Site Admin
 
Posts: 4402
Joined: Sat Oct 10, 2009 10:33 am
Location: 12 miles WSW of Fender Ave. Fullerton

Re: The consequences of changing a JB to v-t-t

Postby Ricky Rioli » Wed Sep 30, 2020 2:27 am

Ken Baker wrote:
If knobs were set up for that - one tone knob on 100% and the other on 0% - what would happen when the switch was at the middle position, selecting both pickups?


You'd probably end up with some interaction between the tone controls because the signal chain is common to both pickups.


So the net effect would probably be roughly equivalent to having both tone knobs set at 50%?

Ken Baker wrote:
I would quite like would be for the switch's three positions to be (1) bridge with tone 0% (2) both with tone 0% (3) neck with tone knob in action)


How about this: Leave the stock controls as-is; V-V-T. Set up switching to toggle a .047µF cap (or even a .1µF cap) onto the hot lead of each pickup upstream of its associated volume control. Then you'd have a bone-stock set of normal controls plus the ability to dump off a pile of treble from each pickup individually.


I'm amused by the difference in the direction of our daydreams: yours towards greater versality, mine .... kinda opposite ;) I feel distracted by unwanted options, as if I'm having to decline them over and over.

Here's another way (I think?) of getting what I want without being being so brutally restrictive: the v-v be left as they are (or replaced with a master vol + blend / three-way switch) and, in place of the tone knob, two tone knobs, with a toggle choosing one or the other. If I were using this, one tone knob would be permanently parked near 0%; the other would only get swapped to when I was on solo neck pickup. For tidiness, the two tones could be stacked.

Once I had had this idea, I thought of my Yamaha, with its 5 knobs and 1 switch, and imagined two volume knobs and a neck/both/bridge switch, with each of the three options being sent to its own dedicated tone knob. I've no idea how much the person with the soldering iron would enjoy building that.
User avatar
Ricky Rioli
 
Posts: 24
Joined: Thu Sep 17, 2020 7:50 am

Re: The consequences of changing a JB to v-t-t

Postby TDR1138 » Wed Sep 30, 2020 9:59 am

Ricky Rioli wrote:If I were using this, one tone knob would be permanently parked near 0%; the other would only get swapped to when I was on solo neck pickup. For tidiness, the two tones could be stacked.


Easiest way I could think of to accomplish this would be to put a push/pull knob in the system to bypass the tone pot. Play with your tone rolled back and then pull the knob up to bypass the tone and keep an unfiltered signal.

Or, if you wanted, use a P/P to switch from tone pot A to tone pot B (which you could stack). Keep tone A active when the pot is down, roll it off as much as you feel needed. Keep tone B wired when the pot is up/pulled, and open it as bright as you feel needed. For efficiency sake, put the P/P on the bridge pickup volume. As you roll off the volume on the bridge pickup, pull it out and switch the tone from A to B.

Or, better yet, I suppose you could wire it to just pull up and bypass the bridge pickup volume and tone A altogether, go straight from the neck into tone B.

Or, you could also do it the other way around - pull up and get only bridge pickup through tone B (which you would roll off completely) by bypassing the neck pickup and tone A (which you would keep more open). To Ken's point, if you did this, you could keep tone B with a fixed capacitor and bypass the tone B pot completely (just a big cap to ground) inserted into the circuit).

Or....
User avatar
TDR1138
 
Posts: 958
Joined: Mon Oct 19, 2009 8:06 am

Re: The consequences of changing a JB to v-t-t

Postby TDR1138 » Wed Sep 30, 2020 11:19 am

Ricky Rioli wrote:Once I had had this idea, I thought of my Yamaha, with its 5 knobs and 1 switch, and imagined two volume knobs and a neck/both/bridge switch, with each of the three options being sent to its own dedicated tone knob. I've no idea how much the person with the soldering iron would enjoy building that.


Just thought of this...

Both pickups feed into a 4 pole double throw switch. Switch up puts the two pickups out from the switch into your VVT or VBT circuit, using three of the pot holes (and the switch hole). Switch down puts just the neck pickup into a separate VT circuit (using pot holes 4 and 5) and disconnects the bridge pickup.
User avatar
TDR1138
 
Posts: 958
Joined: Mon Oct 19, 2009 8:06 am

Re: The consequences of changing a JB to v-t-t

Postby Ricky Rioli » Wed Sep 30, 2020 11:54 am

TDR1138 wrote:Or....


...replace the tone knob with a stack of tone and blend.

Start with solo neck and 100% tone. First turn the tone gradually down; once that journey is complete, slip down the stack and keep turning in the same direction, going from neck solo to both to bridge solo. (Is there such a thing as a stacked knob with a detent?)

On classic JB controls, to go from neck 100% tone to bridge 0% tone you have to turn one vol all the way down, the other all the way up, and the tone all the way down. With the tone/blend stack just turn both parts of the stack together from one extreme to the other.

TDR1138 wrote:
Ricky Rioli wrote:.... I thought of my Yamaha, with its 5 knobs and 1 switch.....


Just thought of this...

Both pickups feed into a 4 pole double throw switch. Switch up puts the two pickups out from the switch into your VVT or VBT circuit, using three of the pot holes (and the switch hole). Switch down puts just the neck pickup into a separate VT circuit (using pot holes 4 and 5) and disconnects the bridge pickup.


Once I had read this for a third time, I managed to get my head around it, and the elegance of the solution suddenly became clear. Pootle around decorously on low tone, flick the switch and BLAM.

The VBT circuit already exist when it's on passive: all that would need doing is turning the two currently redundant knobs into the VT circuit, and changing the switch. Amazing!

Ps, after some more thought: this solution could be fitted on a JB: (1) Stacked v/t on bridge only circuit (2) Stacked v/t for both pickups circuit with (3) smaller blend knob. Move the jack to the side and put the switch in its place.

Pps, only after yet more thought did I realise that this is simply having both a p bass circuit and a j bass circuit in the same instrument. It's amazing how slow-witted a brain can be sometimes :?
User avatar
Ricky Rioli
 
Posts: 24
Joined: Thu Sep 17, 2020 7:50 am

Re: The consequences of changing a JB to v-t-t

Postby Ricky Rioli » Sat Oct 17, 2020 1:54 pm

I've continued to think about all this, about how I use my pickups, and how my plan might be fitted into the three knobs of a JB.

I was wondering about the abilities of rotary selectors. Would be possible to have one which did the following:

Position 1: pass the signal through the neck pickup, then send it to the 1st v/t stacked knob
Position 2: pass the signal through both pickups, then send it to the 2nd v/t stacked knob
Position 3: pass the signal through the neck pickup, then send it to the 2nd v/t stacked knob

During my attempt to educate myself with google I found the term 4 pole 3 way rotary switch. Am I barking up the right tree? :roll:
User avatar
Ricky Rioli
 
Posts: 24
Joined: Thu Sep 17, 2020 7:50 am


Return to Paul's Technicalities

Who is online

Users browsing this forum: No registered users and 0 guests