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here is a trace i have made from my charvel model 4 actives in case its of interest to anyone.

Its a vol,tone and mid boost.

i90.photobucket.com/albums/k243/lenny1dog/P7160001.jpg (dead link, see below)

That one with a ? is 220k in the schematic i have.

nickthemen wrote:That one with a ? is 220k in the schematic i have.

Does your schematic check out the same as mine. (I RE'd mine from my own guitar, would be great if yours is the same which would verify mine)

is there any chance someone has the je2000 bass preamp schematic?

Yep my schematic is the same!

The following pics/work are not mine so, I can take no credit and don't know of any mistakes. I downloaded them yonks ago and found them on a disc the other day.

I was going to build it but, never got around to it.

Thanks!
Is that verified!

Don't know if it is verified but, the layout and traces are very very close to the original (looking at photos), ie this is almost exaclty a je-1200.

pic from brochure

found this in google japan

Just what I've been looking for!!

I am currently building a Keeley Katana pre amp. Awesome pedal, which takes my amp (local Australian built modern plexi) to new heights. I am looking to incorporate a switchable mid boost following the preamp (I might even try to incorporate a pre/post switch, but first things first....).

Anyway, I have a few questions/proposals if someone can help:

- given this will be following a pedal pre amp, I am assuming I omit VR1
- what is the purpose of R2 @ 220k?
- I am going to replace VR2 with a fixed 50k resistor, as I don't need a volume control (level will be dictated by the Katana)
- I am going to omit VR3, as I simply want a fixed mid boost and don't need a mix control. I am assuming I simply take the output of R4 to the Pot of my Katana level control. Although I could wire this post the Katana Pot, which I guess would apply a mid boost to an attenuated signal vs attenuate a preamp/mid boost signal.

Any help on the above would be appreciated!

One for the breadboard tonight.......

Cheers

what you wanna do sounds cool, i'm gonna have a think about what you've written.

for now though, i wouldn't leave out any pots, but put trim pots in so you can muck around with some settings.

I've just finished breadboarding it - relatively high component count (for me anyway, say compared to the Katana), so a little time consuming!

Off to the studio tomorrow night to have a listen (and make sure it works/I've done it right)!

Will report back......

a mi me funciono perfecto se escucha muy bien.

Hi,

schematic reup possible?

Thanks in advance.

I am not sure if it's correct, I found it in a russian forum.

It works closer to Demeter Fat Control.

Hi,

Thanks. Finally I found that thread too. There ist a hand drawn schem going with the shown PCB further above in this thread all from that Russian forum.

Perhaps someone can verify this schem. OP Amp = LF442CN

95H wrote:Hi,

Thanks. Finally I found that thread too. There ist a hand drawn schem going with the shown PCB further above in this thread all from that Russian forum.

Perhaps someone can verify this schem. OP Amp = LF442CN

P7160001.jpg

jax_top.gif

Yeah, I traced that hand drawn schematic from my own model 4 charvel the LF442CN is correct, it is a low power IC which helps with the battery power consumption.

I have charvel 475 and it had jrc 062D as opamp.