Wtf is this thing (warning ugly work inside)

[add4]

Years ago I bought a high level gypsy jazz guitar. With the guitar came a acoustic pickup and with the pickup a preamp. That gear was used for a long time by the professional guitarist who sold me the guitar. I actually used this pickup a few times and found it lacked output level and presence and moved on to a magnetic pickup for that guitar. Lately I thought about mixing both pickups and though I'd open the preamp to check what's inside.

This is what I found



Components are held in the box and together using this kind of paste.
There is a battery, but no active component (except a led?)




I'm actually not sure what the blue components are but they look like trimpots with long legs.

It looks like a passive network of resistors and caps to me

What I don't understand if that it the pickup is plugged directly into an amp.... Nothing happens so it's like there is some kind of amplification there. Or could it be that the pickup needs power like some kind of Fantom power and this is actually providing it to the pickup?

Anyway it's so ugly I thought I'd share it

[matmosphere]

If it doesn't work without a battery it's probably an active pickup. In that case I bet the trimpots are an eq. Plug it up and start twisting those knobs and see.

[m-Kresol]

the blue things also could be trim-capacitors. Can't see if the have three legs or just two.

[add4]

3 legs, 1 cut really close to the body of the component.

I would love to experiment but the lead from the positive side of the battery unsoldered itself from somewhere as I removed the paste. But u have no clue from where

[gordo]

I have to admit, I'm feeling much better about my builds now...

That goop is the yellow stuff you spray into walls and cracks to insulate.  Nasty stuff and a bitch to work with/clean-up.

[matmosphere]

3 legs, 1 cut really close to the body of the component.

I would love to experiment but the lead from the positive side of the battery unsoldered itself from somewhere as I removed the paste. But u have no clue from where

You could probably figure it out from looking at the led. The power goes to the anode right?

If there are three legs on those blue things I'm standing by my preamp/eq theory, but it's hard to say for positive. Any chance you could draw up a schematic from that? It would probably help.

[Willybomb]

Self expanding foam... Probably a good way to stop things moving around inside a pedal, if it wasn't so final.

[add4]

how can it amplify anything if it doesn't even have an active component?

passive EQ, i'd accept that theory, but the microphone doesn't give a sound of that thing isn't plugged in .. so? power for the microphone with some caps for the usual filtering?

i'll try to draw something, 1rst try ever

[add4]

Here's what I came up with.

the ? element are the mystery blue trimmable things it's written YA (not sure about the Y) 100K ?? on one and Y(?)A K7 (not so sure about K7 also) ?? on the other one.

they could just be trimpots to dim the led and, to control the lowpass filter on the other hand.
i have now idea where the +9v was supposed to be added in that mess. i guess directly on the input, to power the LED, and maye it powers the microphone too?

[matmosphere]

I was assuming there were active components in the pickup that are getting power from there, then all the passive stuff there was eq.

[add4]

The pickup is basically something like this:

jacl -> cable -> pickup looking like the pic

[drolo]

That looks like an electret microphone. These need to be connected to a supply voltage to work.


Here is a scematic of a simple elecret preamp to give you an idea:





But where's that transistor in that case :-)

[add4]

that might be exactly the reason why the volume is really really low and the sound not so sexy!

[add4]

that sounds like .... A NEW PROJECT
breaboard time guys let's try to make that shitty microphone work.

[matmosphere]

I was thinking it was something like this:

https://reverb.com/item/2022136-new-ghs-acoustic-sound-hole-microphone?_aid=pla&pla=1&gclid=CJaMtOiU-M4CFcEmhgodMY4DmQ

That had been modified with a passive eq, or had a passive eq that somebody took out of its case and covered in spray insulation?

Little different than the one in your picture though.

How long have you had the guitar? You could just ask the former owner.