Roland JC 40 Hiss - Any way to fix this?

[ribas]

I can look into it. Do you have the schematic or service manual for it?

Hello!

I'm also really interested in investigating if there is a way to mod the JC-40 to remove the base noise hiss like you did with the JC-120 ( :handsdown: )

Here are some pictures of the circuits inside the JC-40, maybe it gives you an idea how it should be moded or maybe if it's not doable at all. (Very tiny components and complex circuit in comparison to the old JC-120 you moded)

HIGH RESOLUTION: https://mega.nz/folder/jUcHna4b#hE3tZSJLaBNUoWZ4I0KsPg

[Payne]

I am sorry, I cant help you without the schematic. Tiny components is not a problem....?

[pcjazz]

I always understood that hiss was part—perhaps most—of the JC’s charm.

[jads57]

Sell It?

[jazzfrog]

See details in this mod post here, it worked for me on a '85 JC-77.

I got rid of the hiss by swapping ONE resistor, giving up some volume (it's fine, that amp is loud) and some eq effectiveness (fine as well).

Newer JCs (JC-40 etc) use surface mount and my mod does NOT apply unfortunately.

Also, Payne's post shows transistors mods (thanks for your work Payne, it definitely helped directing and inspiring my solution).
My JC-77 uses opamps, not transistors. So again, this works on my mid-80s JC-77.

[PMC63]

I've had reduced the hiss by using the effects loop. I believe it disables the panel controls
a trade off but I feel it's worth it.

[ElRay]

Our JC-40 has developed "The Hiss", but it seems to be entirely pre-amp related. On another forum, somebody recommended to just pull the board and re-flow all the solder joints. Has anybody here tried that? Does that should like it would help, or at the very least, do no harm?

[sgosnell]

It should do no harm, but anything that can possibly go wrong, probably will. Wires can jump from the joint when the solder is melted, and other unintended consequences. Use care and all should be fine, but there are no guarantees.

[whiskey02]

The idea of buying a product and then opening it up to do/fix something the manufacturer did not do strikes me as absurd. Maybe doing something small to tweek things a bit to your exact needs is one thing but having to FIX something as it comes out of the box; No, I wouln't do that.