BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

[lotti]

Hi Folks,

I spend some trial and error time figuring out how to bypass the BMP-1 Modular Preamp, so I can have 3 Fury Stacks using either standard passive wiring or with the turn of one switc an active signal path.

As I am far from being an expert in electronics I would like to take the opportunity to ask for your help finding the most elegant solution.

The following solution works fine, but could be improved and maybe of interest to others:

1. I installed a megaswitch so that I got 1 layer for each of the 4 pickup wires coming from the stacks.
   
   
2. the 4 "outputs" of the megaswitch connect to 2 latching relays
   
   
3. these either connect them to the bmp 1 preamp or the regular passive signal path
   
   
4. 1 further relay connects rather the passive volume control + tone or the active volume control + tone pot to the out jack.
   
   
5. i mechanically joined 250k pots and 25k pots on one axis so I can adjust passive an active volume / toner turning only one knob

As the relays are latching type the guitar will switch to passive in case the battery should be empty.

____

The same can be achieved using a 4 pdt Switch and 1 miniswitch instead of the relays, but one would have to turn 2 switches instead of one.

I just received a rotary switch providing 4 layers and 4 positions, so I am try in to figure out, wether there is a way to achieve this using only the rotary switch and the mega switch?

Can it be simplified?

 

[Artie]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

There are two versions of BMP-1. Do you have this one? (Two pots, short shaft.)

 

[lotti]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

Yes exactly


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[Artie]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

Ok. I just ordered one. Should be here Wednesday. Let me examine it more closely and then I can answer your question more intelligently.
(More accurately?) Take your pick.

 

[lotti]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

Ok. I just ordered one. Should be here Wednesday. Let me examine it more closely and then I can answer your question more intelligently.
(More accurately?) Take your pick.

Hope you will enjoy it as much as I do.
Looking forward to your findings!


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[orpheo]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

I have done this before, but just for ONE humbucker and that was plenty of work. I assume you want to be using just one jack? If so, don't forget the following.

1. the battery is hooked up to the jack too. If you're in passive mode you really want to short the battery so it won't drain itself via the jack.
2. you have two modes; passive and active, so you also want to select the final signal. one signal is active (goes through a 25k volume pot, mind you, preferably the BMP itself) and the other signal, passive, goes through 250k, so you kinda need to select which signal is routed to the the jack.

To do what I want, I got me a 12 pole 2 position switch.

ALSO, how do you wanna hook up 3 singlecoils (3 humbuckers, technically) to a switch that was designed to have just two?

 

[lotti]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

I have done this before, but just for ONE humbucker and that was plenty of work. I assume you want to be using just one jack? If so, don't forget the following.

1. the battery is hooked up to the jack too. If you're in passive mode you really want to short the battery so it won't drain itself via the jack.
2. you have two modes; passive and active, so you also want to select the final signal. one signal is active (goes through a 25k volume pot, mind you, preferably the BMP itself) and the other signal, passive, goes through 250k, so you kinda need to select which signal is routed to the the jack.

To do what I want, I got me a 12 pole 2 position switch.

ALSO, how do you wanna hook up 3 singlecoils (3 humbuckers, technically) to a switch that was designed to have just two?

I have done this before, but just for ONE humbucker and that was plenty of work. I assume you want to be using just one jack? If so, don't forget the following.

1. the battery is hooked up to the jack too. If you're in passive mode you really want to short the battery so it won't drain itself via the jack.

You are correct.
In my case the battery is not switched by the output jack, but by the switch.
The ground of the preamp and one relay are connected by the witch, which does what normally inserting the instrument cable into the jack would to.
1. It connects the ground of the active path to the common ground and connects the battery.
2. Therefor the preamp and the relays receive current
3. The relays are latching. Connected battery means that as they behave kind like a ON / ON Switch their input "active" is routed to the other pole.

2. you have two modes; passive and active, so you also want to select the final signal. one signal is active (goes through a 25k volume pot, mind you, preferably the BMP itself) and the other signal, passive, goes through 250k, so you kinda need to select which signal is routed to the the jack.

Again you are correct.
I simply desoldered the 25kpot from the preamp, glued it to a 250k Pot, drilled a hole in it and used a longer shaft (from a push pull pot) that now turns the 250k and the 25k pot at once.

So the on / on switch alternates between the ground and hot signal of the 250k pot and the 25k pot.

To do what I want, I got me a 12 pole 2 position switch.

ALSO, how do you wanna hook up 3 singlecoils (3 humbuckers, technically) to a switch that was designed to have just two?

I use a mega switch to choose one of the three pickups.



and 2 relays to rout the selected pickup to the preamp or the passive signal path.

I also achieved the same by using a 4pole / On / On switch, but in that case one would have to turn 2 switches to toggle between active and passive
Actually I use just one side of the preamp, the disadvantage is, that I can only have one pickup active at a time.

 

[Artie]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

I'm wondering if I'm misunderstanding what you want to do. This should be dirt simple. Your Fury's should just go to a standard 5-way. Then, you'd use a simple on-on DPDT to select between the BMP-1 and the passive volume control. Is this not what you're trying to do?



My volume controls are upside-down, but you get my point.

 

[lotti]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

I'm wondering if I'm misunderstanding what you want to do. This should be dirt simple. Your Fury's should just go to a standard 5-way. Then, you'd use a simple on-on DPDT to select between the BMP-1 and the passive volume control. Is this not what you're trying to do?

View attachment 98701

My volume controls are upside-down, but you get my point.

My understanding regarding the preamp is:

The preamp uses a differential amplifier, it is designed to be used with 2 Humbucker having 4 conductors.

There are 10 Inputs for pickup conductors: 2 x (Black, White, Red, Green and Ground)

There are two outputs for 1x for pickup one, 1x for pickup two

There is a 1 input and 1 Output for the integrated pot.

The image shows the standard wiring:

____

There for I thought, that in order to google between pickups, all 4 conductors would have to be toggled.
So I used a Mega Switch having 4 Output poles and 5 positions.

If I remember correctly like that (without relays):

 

[Artie]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

I'm pretty sure the BMP-1 is just a preamp added to the solderless Liberator pot. That means that green and bare are shorted to ground, red & white are shorted to each other, and only the black wires go into the actual dual-preamp. You're adding way more complexity than is necessary. But let me actually get mine in hand before I proclaim that too strongly. I'm still hoping it will arrive today.

Edit: Just arrived. Let me check this out.

 

[Artie]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

Quick side note: Out of respect for Seymour Duncan's intellectual property, I did not reverse engineer this. I simply snagged a generic circuit diagram of a differential op-amp circuit. The BMP-1 blurb openly admits to using a differential amp.

So, lotti, since you're messing with relays and such, I'm guessing you understand some electronics. Basically, here's what you're dealing with. Normally, with two humbuckers, black, green, and bare, (of both pickups), are all grounded. Then they use white as the positive input and red as the negative input to a differential amp. These feed outputs 1 & 2, which technically, you can feed anywhere you want. The "bottom" three terminals are the breakout for the internal pot.

From there, you could either feed outputs 1 & 2 to a 3-way, and then out to a master vol/tone, or if using LP style wiring, out 1 jumpers to the internal pot input, and out 2 feeds to your external vol pot and so on & so forth.

Now, lets forget for a moment about switching between active and passive, and just consider how you'd connect three single's to this circuit. The easiest way would be to take the output of a normal 5-way and connect it to input "A". Then you'd take the "grounds" of the three pups to terminal "B". This would, of course, waste half of your BMP circuitry. But this would get you closest to utilizing my previous diagram to go active or passive.

The other way, which really gets weird, would be to connect one pup to "A" and ground. One pup, (reversing its wires), to "B" and ground. Then the third pup to "C" and ground. Then ground the "D" terminal. Switching, tonal character, and output levels will be a virtual crap shoot here, but it's an option. At this point, you're on your own.

My personal 2-cents worth is . . . I wouldn't try using the BMP-1 with three singles. Much less, trying to switch between active and passive. I'll think about this some more, but I'd need to do some actual wiring to see what really works and what doesn't. (And that probably won't be any time soon.)

I hope this was of some help.
Artie



Edit: In my 2nd paragraph, where I say that "normally", black, green, and bare, go to ground, I mean only as it relates to BMP-1 wiring. Not in any other situation. Also, I'm not saying to ground all those edge terminals. I'm indicating that they are all internally grounded. You don't have an option here, if you connect black, green and bare to those terminals as per the supplied diagram.

 

[Artie]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

One bit of good news. I just watched an old Frank Falbo video on the BMP-1 where he says that the humbuckers can still be split. That means that it doesn't hurt to ground one side of the dif-amp. That also means that singles might be do-able.

 

[Teleplayer]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

Now, lets forget for a moment about switching between active and passive, and just consider how you'd connect three single's to this circuit. The easiest way would be to take the output of a normal 5-way and connect it to input "A". Then you'd take the "grounds" of the three pups to terminal "B". This would, of course, waste half of your BMP circuitry. But this would get you closest to utilizing my previous diagram to go active or passive.

That's an interesting idea. There seems no reason to use more than one amplifier channel, and that way is reasonably straight-forward to wire up. Have you tested the preamp board with a meter to confirm the connections for black and green wires are grounded at the terminals block?

To the OP, I'm kind of confused by some aspects of this project. I don't understand how the tone controls will work as it seems they would need to be duplicated for active and passive controls. Was the intention to have two separate master tone controls? I'm also really unclear about the objective of doing this. What were the circumstances that led to the conception of this idea?

 

[lotti]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

That's an interesting idea. There seems no reason to use more than one amplifier channel, and that way is reasonably straight-forward to wire up. Have you tested the preamp board with a meter to confirm the connections for black and green wires are grounded at the terminals block?

I just checked that, black and green go to ground, white and red not.

I'm also really unclear about the objective of doing this. What were the circumstances that led to the conception of this idea?

The circumstances were:
I had a nice Suhr custom with EMGs that I traded for a YJM Strat and extra cash.
I like that guitar and the Fury pickups a lot, but also kind of missed the sound of the active pickups.
Also I wanted to simplify my guitar rig and purchased a one channel amplifier. Because of that I wanted to have a switchable boost in the guitar.
Then I heard about the BMP-1, which would gives me exactly what I wanted: a boost and the sound of active pickups. Unfortunately it is not switchable by default.
So I tried two figure out how to get the option to toggle between the original sound of the stacked Humbuckers and the boost / active voicing.
As I have only very limited knowledge in electronics and because I could not find a proper solution online, that resulted in trial and error.
I achieved a good result, but think that with the help of people more knowledgebale as me a more elegant solution could be achieved and maybe of use to others too.

To the OP, I'm kind of confused by some aspects of this project. I don't understand how the tone controls will work as it seems they would need to be duplicated for active and passive controls. Was the intention to have two separate master tone controls?

I did not want / need 2 tone controls and / or 2 volume controls.

Therefore I "constructed" something like a double pot by gluing a 25 k Pot to a 250k pot and connecting they shafts so one shaft turns them both. The signal is switched between the 250k and the 25k "side" of the double pots. I did that to the volume and the tone pots, so the result is:

Under the pickguard:
Passive circuit:
1x 250k volume control
1x Capacitor
1x 250k "no load" master tone control

Active circuit:
1x 25k volume control
1x Capacitor
1x 25k master tone control

I just replaced the mini switch by a rotary switch, so from the outside it looks like an ordinary Strat pickguard having one pickup selector 1 volume and 2 tone controls.

 

[lotti]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

One bit of good news. I just watched an old Frank Falbo video on the BMP-1 where he says that the humbuckers can still be split. That means that it doesn't hurt to ground one side of the dif-amp. That also means that singles might be do-able.

I read in an old thread that someone connected 2x 2 conductor single coils to one side of the bmp-1. If I remember correctly he just connected one pickup to preamp black and white, the other to red and green. Somewhere was written, that the disadvantage would be that one would not have the additional noice cancellation of the differential amplifier. Someone also claimed, that there would be a slightly different voicing between black / white and red / green.

In order to get in between positions I connected the upper coil of the neck pickup to black / white and the upper coil of the middle pickup to red / green. It did work, there was more hum compared to a humbucker, and a volume increase compared to a stacked humbucker.

 

[Artie]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

Have you tested the preamp board with a meter to confirm the connections for black and green wires are grounded at the terminals block?

Yup. That's why I bought one. I like to have one in hand when I try to answer questions like this. Also, the terminals are labeled fairly clearly on the board. (If you have young eyes, or a magnifying glass.)

 

[Artie]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

I read in an old thread that someone connected 2x 2 conductor single coils to one side of the bmp-1. If I remember correctly he just connected one pickup to preamp black and white, the other to red and green. Somewhere was written, that the disadvantage would be that one would not have the additional noice cancellation of the differential amplifier. Someone also claimed, that there would be a slightly different voicing between black / white and red / green.

In order to get in between positions I connected the upper coil of the neck pickup to black / white and the upper coil of the middle pickup to red / green. It did work, there was more hum compared to a humbucker, and a volume increase compared to a stacked humbucker.

Now that I have one of these, I'm going to experiment with a few things myself. Trouble is, I tend to move slow these days.

 

[lotti]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

Hi Artie,

thanks a lot for your detailed answer.

Quick side note: Out of respect for Seymour Duncan's intellectual property, I did not reverse engineer this. I simply snagged a generic circuit diagram of a differential op-amp circuit. The BMP-1 blurb openly admits to using a differential amp.

So, lotti, since you're messing with relays and such, I'm guessing you understand some electronics.

Well I know that connecting a relay to a power source equals flipping a mini switch. Unfortunately I do not have any deeper knowledge in electronics.

My personal 2-cents worth is . . . I wouldn't try using the BMP-1 with three singles. Much less, trying to switch between active and passive. I'll think about this some more, but I'd need to do some actual wiring to see what really works and what doesn't. (And that probably won't be any time soon.)

The Fury pickups are 4 conductor stacked Humbuckers.

The other way, which really gets weird, would be to connect one pup to "A" and ground. One pup, (reversing its wires), to "B" and ground.

Would it be possible to connect a 4 conductor pickup in a way that not black + green get grounded but red + white?
In that case cutting the preamp ground from the common ground would equal joining the red and white conductors of the stacked humbucker as recommended by Seymour Duncan as factory default when used without the bmp 1? If possible one layer of the pickupselector would be needed for the black, one for green and in case of a 4 layer selector 2 layers would remain available i.e. for toggeling between the active and passive circuits?

 

[lotti]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

Now that I have one of these, I'm going to experiment with a few things myself. Trouble is, I tend to move slow these days.

Move slow? That better than moving fast, and breaking things by trial and error - what is kind of my approach ;-)

 

[Artie]

Re: BMP-1 Modular Preamp = 3 Pickups passive AND active in one guitar

I've got to run the dog to the vet, and then go pick up a great-grandchild. I'll go into some more detail when I get back. I actually appreciate that you asked this question. It inspired me to buy one of these, and it looks like it might be fun to experiment with.

Back soon.
Artie