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

[lotti]

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

Hi Artie, hope your dog will be fine. Reminds me that mine would like to have a walk now.
It's a lot of fun. Hope that you also like the sound of it.

 

[Teleplayer]

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

So how is the tone different between the active and passive? I'm guessing the active one will be brighter since there is lower inductance with each coil of the stack is wired to the BMP-1, not connected in series like a passive installation. I never used the FURY pickups, so I'm going to ask if you actually need to use tone controls in a passive installation. IOW, is there a situation where the FURY pickups are too bright?

When using an onboard pre-amp you are missing one passive component that greatly affects the tone of the pickup. That's the guitar-cable capacitance which is no longer loading the coils of the passive pickup. Its one of the biggest effects on the tone for passive pickups. The active preamp isolates the cable capacitance from the pickup so the effect is nullified. However in the case of active preamps there is also capacitance that is designed into the amplifier module. When you buy an active pickup you are buying a device that has a particular coil spec and matched preamp that is engineered to deliver a particular resonance frequency. With some active pickups, the resonance frequency is specified on the manufacturer's information sheet. When you buy a BMP-1, there will some uncertainty about what resonance frequency you will end up depending on what pickup you are using. To get a proper understanding you need to know the input resistance to the preamp module, and also the amount of input capacitance loading each coil.

I experimented before with active preamp (an EMG), by adding small capacitors in parallel with the input of the preamp around 68pf, 100pF, 150pF etc. In my case I was trying to combine 2 Dimarzio Cruisers with an EMG active humbucker in a HSS guitar. The capacitor sometimes helped for getting a good high gain tone at max volume, but I wasn't really happy with the way it sounded when rolling off the volume control. I favoured a volume control with treble bleed, and I found the passive approach ended up working better. I basically gave up on the idea of mixing active and passive pickups.

 

[Artie]

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

^^^^ Good info. I'll keep that in mind as I experiment with this. There's some good videos about the BMP-1, with Frank Falbo too.

That one will lead you to others.

Hi Artie, hope your dog will be fine. Reminds me that mine would like to have a walk now.
It's a lot of fun. Hope that you also like the sound of it.

She's fine. Doing a follow up on an ear infection, and then shampoo, grooming, and overall pampering.

I'm going to draw up a couple diagrams that hopefully will clear up the red/white as hot, or black/green as hot question. Stay tuna-ed.

 

[Artie]

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

Would it be possible to connect a 4 conductor pickup in a way that not black + green get grounded but red + white?

Absolutely. I'm guessing that Duncan did the red/white thing for no other reason than they already had the connection artwork done for the Liberator, and didn't feel like redrawing it.

So this would be electrically, and polarity wise, the same.



Note also that the position of red, white, and bare, doesn't matter. They're all in "ground" sockets. Only green and black matter, and even then, only for phase purposes.

 

[lotti]

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

So how is the tone different between the active and passive? I'm guessing the active one will be brighter since there is lower inductance with each coil of the stack is wired to the BMP-1, not connected in series like a passive installation. I never used the FURY pickups, so I'm going to ask if you actually need to use tone controls in a passive installation. IOW, is there a situation where the FURY pickups are too bright?

The video Artie posted describes the tonal difference a bit. Obviously active delivers more output. Hard to describe maybe less throaty, the "feel" is different, a bit smoother, clearer, the noice floor is even lower. More like a regular humbucker less than a stacked one?

I never used the FURY pickups, so I'm going to ask if you actually need to use tone controls in a passive installation.

Malmsteen disconnected the tone controls on his guitars, Fender put a "no - load" tone pot for the bridge pickup in the YJM Strat and a regular tone pot for neck and middle.
I prefer to adjust treble at the amp after the gain stages. So you are right, I could skip the passive tone controls. The active tone control is useful.

When using an onboard pre-amp you are missing one passive component that greatly affects the tone of the pickup. That's the guitar-cable capacitance which is no longer loading the coils of the passive pickup.

If the active volume controls output and ground would be connected in parallel to the passive volume but not to a pickup would the active side still effect the capacitance of the passive one ?

 

[lotti]

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

Absolutely. I'm guessing that Duncan did the red/white thing for no other reason than they already had the connection artwork done for the Liberator, and didn't feel like redrawing it.

So this would be electrically, and polarity wise, the same.

View attachment 98731

Note also that the position of red, white, and bare, doesn't matter. They're all in "ground" sockets. Only green and black matter, and even then, only for phase purposes.

View attachment 98733

Could I connect the red and black wires of all pickups to each other (kind of like a star grounding), and would then only need one cable from the joint to the preamps ground for active and for passive that wire disconnected from ground?

 

[Artie]

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

Could I connect the red and black wires of all pickups to each other (kind of like a star grounding), and would then only need one cable from the joint to the preamps ground for active and for passive that wire disconnected from ground?

Well, definitely not red & black. Remember, that black is not ground when in the active mode. It's the input to "-" side of the preamp. While in the active mode, you could connect all the red & whites together, and then star ground them. But, each red/white pair would need to disconnect from ground, and from each other, when you went to the passive mode.

Again, let me doodle up a couple things before I go farther.

P.S. I'm going to initially approach this from the point of view of two 4-wire pups. (Two Fury's.) I just don't see any good way to connect three humbuckers to the BMP-1. But I'm not done yet.

 

[lotti]

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

Well, definitely not red & black. Remember, that black is not ground when in the active mode. It's the input to "-" side of the preamp. While in the active mode, you could connect all the red & whites together, and then star ground them. But, each red/white pair would need to disconnect from ground, and from each other, when you went to the passive mode.

Again, let me doodle up a couple things before I go farther.

P.S. I'm going to initially approach this from the point of view of two 4-wire pups. (Two Fury's.) I just don't see any good way to connect three humbuckers to the BMP-1. But I'm not done yet.

Hmm something in that direction? I do not have the red and white pairs disconnected in passive mode and black and green of the coils of the pickups not in use at a time are disconnected?



EDIT: Sorry I forgot to draw the black wires from the pickups to the pickup selector. They should be conected in the same manner as the green ones, but on layer 1

 

[Artie]

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

At a glance, with all red/white wires shorted together and grounded, all three pups will be split when in the passive mode. You won't have the original character of the YJM's. Is that what you want?

 

[lotti]

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

Sorry for not being more precise and the misleading diagram.

At a glance, with all red/white wires shorted together and grounded, all three pups will be split when in the passive mode. You won't have the original character of the YJM's. Is that what you want?

No, I do not want to split them.



The switch is a rotary type similar to that PRS uses. It has 4 layers / poles and 4 positions.

I would use the switch's first position for active mode connections and the second for passive.

Something like:

Active volume pot's ground is wired to layer 1, position 1
Passive volume pot's ground is wired to layer 1, position 2

Layer 1 output / pole would be wired to the output jack.
Additionally everything supposed be grounded both in passive and active mode (i.e. 9v batterie ground, pickguard shielding, strings bridge, etc.) is connects here too.


Indented Result:

Switch position 1
As red/white wires connect to the preamp's ground wich is wired to the volume pot's ground, grounding the pot will connect all of these to the output jack's ground?
As the 9v batterie's ground also connects here that will be connected to the preamp's ground and the preamp receives current?

Switch position 2
Th above would be cut off the jack's ground but the passive volume control is connected. The red and white wires will not be grounded and the coils not split?

 

[Teleplayer]

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

If the active volume controls output and ground would be connected in parallel to the passive volume but not to a pickup would the active side still effect the capacitance of the passive one ?

If you connect the output of the two volume controls in parallel, then there will be unwanted interaction which would be a problem. However in your latest diagram (post #28) the output of the 2 volume controls go through the active/passive selection switch, so there will be no interaction between the active and passive sides. The capacitance would only have an interaction if you somehow connected the pickup to the passive volume control and the active preamp at the same time, but you can avoid that if all the 4 pickup wires being switched between modes.

EDIT: I wrote before "You shouldn't connect all the red and white wires together in a star because the hum-cancelling part of the stack would not work properly, even if you have solved the grounding problem that Artie wrote about". That's actually not true. As long as the black and green pickup wires go though the pickup selector, the hum cancelling will work fine in both Active and Passive mode. It works because in Passive mode, you must only ground the Green wire for the pickups that are selected, and the hum cancellation coil for the stacks not being used will be open circuit.

In my lastest thinking you only need 2 poles of switching for the pickup selection:
Pole #1 Green pickup wire.
Pole #2 Black pickup wires.
If I'm right, that can be done with a regular 5-way blade switch to conveniently get notch position selections as well.

Red/white wires should all be connected together in a star, and get switched to ground only when Active mode is selected, otherwise left to be floating in Passive mode.

Hopefully I got all that correct after my initial post had errors in it.

 

[Artie]

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

There's another problem here too, but it's late, and my brain hurts.

I'll go into more detail tomorrow.

 

[Teleplayer]

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

Here is my suggestion for the 3 humbucker wiring. However this untested and not guaranteed to work!
I have to say this is not my original idea, as it is based on ideas from lotti and Artietoo in this thread with some minor additions.

In my opinion its not necessary to use a low impedance volume control. The volume pot value is 250k for both Active and Passive modes.
I have included a small treble bleed capacitor with series resistor to minimise the treble loss due to cable capacitance.

 

[Artie]

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

That looks similar to what I've done here, except that I include the twin volume pots and also switch the 9-volt power. That way, you don't power up the BMP when in passive mode.
If you switch the 9-volts with the jack, and use one volume pot, a DPDT will do it.



And now, purely as an intellectual exercise, here's what you ultimately want:



While not at all practical, it's not totally undo-able. If you switch the 9-volts some other way, a 10PDT switch will work with some clever DIY engineering. (They are available: https://www.citrelay.com/view_switch.php?series=DL)

Also note, this version requires two BMP-1's. Again, feasible if you unsolder the pot from one, and then stack them. Maybe not cost effective, but doable.

But I have to go back to my bottom line: while this is an interesting and thought provocative project . . . I wouldn't actually do it.

Artie

 

[lotti]

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

Here is my suggestion for the 3 humbucker wiring. However this untested and not guaranteed to work!
I have to say this is not my original idea, as it is based on ideas from lotti and Artietoo in this thread with some minor additions.

In my opinion its not necessary to use a low impedance volume control. The volume pot value is 250k for both Active and Passive modes.
I have included a small treble bleed capacitor with series resistor to minimise the treble loss due to cable capacitance.

View attachment 98766

Looks interesting!

A few thoughts:

In the drawing you use a 3 position pickup selector, so I guess in passive middle + neck will be no problem?

Would be great if the 250k volume control could be used for both active and pasive. Would the positive effect of the active signal being "buffered" be lost?

Will you test it?

 

[lotti]

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

And now, purely as an intellectual exercise, here's what you ultimately want:

View attachment 98773

While not at all practical, it's not totally undo-able. If you switch the 9-volts some other way, a 10PDT switch will work with some clever DIY engineering. (They are available: https://www.citrelay.com/view_switch.php?series=DL)

Also note, this version requires two BMP-1's. Again, feasible if you unsolder the pot from one, and then stack them. Maybe not cost effective, but doable.

But I have to go back to my bottom line: while this is an interesting and thought provocative project . . . I wouldn't actually do it.

Artie

Why would you need 2 BMP-1? Do you need to have more than 2 Humbuckers active at a time?

 

[Artie]

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

Why would you need 2 BMP-1? Do you need to have more than 2 Humbuckers active at a time?

You're right. And that makes it easier. I need to redraw this, but it might not be today. Stay tuna-ed.

 

[lotti]

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

As I already got a 4 pole 4 position rotary switch and a 4 pole 5 position selector switch, I will try if I can get the following:

5 Positions:
Bridge
Bridge + middle
Middle
Middle + neck
Neck


Rotary switch:
Pos 1: active mode
Pos 2: passiv mode, humbucking coils in series
Pos 3: passiv mode, humbucking coils in parallel
Pos 3: passiv mode, coil split



Worst case I still have some relays.

 

[Teleplayer]

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

Looks interesting!

A few thoughts:

In the drawing you use a 3 position pickup selector, so I guess in passive middle + neck will be no problem?

Would be great if the 250k volume control could be used for both active and pasive. Would the positive effect of the active signal being "buffered" be lost?

Will you test it?

The pickup selector is a normal 5 way blade switch, so you get all the normal strat combinations: Bridge, bridge + middle, middle, middle + neck, neck.
They should all be hum-cancelling in both active and passive modes.

By using a single 250k volume control there is potentially some reduction the benefit of buffering. I expect the tone aspect should not change very much. At full volume there is no loss at all. However when rolling off the volume there will be some effect depending on what cable length you use. Its better to use a 10 foot cable length if at all possible. The 250k pot with resistor and cap combination as I have shown makes it less sensitive to cable capacitance than a 500k control without any treble bleed. Some people notice the difference while others probably don't.

I've been thinking about buying a BMP-1, but its not a priority for me at the moment so I won't be able to test it unfortunately.

 

[Teleplayer]

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

I also drew up a HSH Auto-split version of this Active/Passive wiring. So the combinations are:
1. Bridge humbucker.
2. Bridge Split + Middle
3. Middle
4. Neck Split + Middle
5. Neck humbucker.
They should all be hum-cancelling except for the Position 3.

This is a bit more complex, so it definitely needs someone to check before its ready for use.