Teeny little BMP-1 circuit analysis.

[Artie]

In the process of answering a question for someone else, I got to looking closer at my BMP-1 Blackouts Modular Preamp. The wiring is a bit unusual. Black and green are both grounded, with red and white used as the outputs, apparently in a differential input configuration. (See attached image.) Trying to figure out if this puts the pickup in series or parallel is starting to get above my pay grade.

It's just unusual and unexpected.

 

[idsnowdog]

Isn't the BMP a summing amplifier where you're amplifying both coils and the amplifier inverts one signal to create phase cancelation?

 

[Artie]

I'm not sure. There's a fair amount of surface mount components hidden on the other side of the board, and I don't want to tear mine apart to see how it works. But that definitely could be.

 

[Spaghetti Bolo]

https://www.electrosmash.com/emg81

The BMP-1 is a more sophisticated take on this concept. The coils are loaded equally unlike the EMG preamp, resulting in greater noise cancellation.

 

[Artie]

Somewhere, in my archives, I have a Yamaha bass schematic that does this same thing. Each coil is grounded on one end, then fed into the differential inputs of an opamp. Seems to work well. I suppose I should install mine and try it out.