Help with pseudo-ebow (working from patent document)

[coreybox]

patent # 4075921 (get it from google patents)

Schematic from this patent document:
http://engr.smu.edu/~cdcothru/ebowpatentschematic%20.png

Two general questions for you guys

(1) What is component 40 (op-amp thing with a arrow through it)?

(2) What pin of the op-amp does point 36 go to?

I'm wanting to build an ebow into a pickup, using the two coils of a humbucker as the input/output. I haven't experimented at all with this, and don't have any of the parts to build a little amp on hand.

I was thinking about using the little gem as the bulk part of this schematic, but I'm not sure about two things I asked about.

From what it sounds like in the patent specifics, the feedback loop might only be to initialize the string.. not sustain it. If that is true I don't care about that... if i have to pluck the string then that is fine.

So basically, will wiring up a little gem with two pickups from the input and output... will i get infinite sustain? Any obvious problems with this?

FWIW I actually want to do this for more of a functional reason than you guys might think! I want to use this on an acoustic guitar, to 'warm it up' before using it... and also to break in brand new strings to get rid of that metallic sound. Not as much as an effect, though that might be interesting too.

thanks guys,
Corey

[Paul Marossy]

Two general questions for you guys

(1) What is component 40 (op-amp thing with a arrow through it)?

(2) What pin of the op-amp does point 36 go to?

"Component 40" actually isn't a component at all, it's just a symbol to show that the circuit has a variable gain.

"Point 36" - Assuming the Ebow uses an LM386, Pins 2&4 go to ground, Pin 3 is connected to the input coil, Pin 5 is connected to the output coil, Pin 6 is connected to +9V, and Pins 1&8 is the feedback loop. Pin 7 is not connected to anything. "Point 36" would be connected to Pin 1.

You can see some pictures of an Ebow PCB by following the link at the bottom of this page: http://www.diyguitarist.com/DIYStompboxes/EbowTech.htm
I actually bought the PCB from the guy who attempted to get all the epoxy off of it. It satisified my curiousity about a few things to actually have it in my hands to examine it personally. Anyhow, I could not verify that it is using an LM386, but it is believed to be the IC chip that it uses.

From what it sounds like in the patent specifics, the feedback loop might only be to initialize the string.. not sustain it. If that is true I don't care about that... if i have to pluck the string then that is fine.

With an Ebow, you don't have to actually pluck the string. You can just set it above the string, and it will initialize the string vibration all on its own. Sometimes it takes a little coaxing to get it going, but that is something that you do with your right hand.

I'm wanting to build an ebow into a pickup, using the two coils of a humbucker as the input/output. I haven't experimented at all with this

It's a lot bigger task than you think to get something like that to work. Check out the sustainer thread here: http://projectguitar.ibforums.com/index.php?showtopic=7512
There's 227 pages of discourse and 3,392 replies. Simple in theory, but much harder to accomplish in the real world. 

I hope that helps...