Ebow Guts Shots and Some Various Info

[Paul Marossy]

Well, I finally found some photos of a gutted Ebow - at the Project Guitar Forum! It's laid out differently than I thought it would be. The consensus seems to be that it was always designed around an LM386. I was wondering how on Earth they could pack all that stuff in the base of the enclosure, but the pictures show how it's done. Warning: it's been terribly disfigured during the process. Not for the faint of heart! 

http://projectguitar.ibforums.com/index.php?showtopic=7512&st=1245&p=261912&#entry261912
Look around half-way down the page.

My curiousity is somewhat satisfied now. 

[Dan N]

Thanks, Paul!


"Your earlier coil is a lot neater than the one I made that caught on fire!!!"  Oh lord!

[tcobretti]

I need to build a ebow!  So, is there a schem floating around for it?  It looks like a pretty simple circuit, which of course makes sense, but I guess the problem is the coils.



This is my favorite part:

[Paul Marossy]

"Your earlier coil is a lot neater than the one I made that caught on fire!!!"  Oh lord!

Yeah. The Ebow expose is something that popped up in the middle of that DIY sustainer thread. I just happened across it while trying to track down some Ebow guts pictures. I was following that particular DIY sustainer thread for about the first forty pages. PSW did quite a lot of work and research on developing his own DIY sustainer. It just keeps getting better and better in terms of what others are doing with it.  

So, is there a schem floating around for it?

Yeah, right here:

http://logosfoundation.org/kursus/4047.html

[QSQCaito]

Patent files of the ebow in that link too

[tcobretti]

Thanks, Paul! 

[Paul Marossy]

There's also links to the two US Patents associated with the Ebow at the bottom of my Ebow page, too. http://www.diyguitarist.com/DIYStompboxes/EbowTech.htm

One's for the circuitry and concept. The other is for the enclosure itself. 

[Paul Marossy]

Looks like those pictures have been taken down from the Project Guitar forum. You can see them here instead. Looks like I found those pictures just in time! 

[QSQCaito]

Hi guys, sorry for my ignorance. But.. could someone guide me to a web, or briefly explain how this thing makes my strings vibrate(if that's what it does), thus, provide sustain..??

Thanks a lot

DAC

[tcobretti]

There's also links to the two US Patents associated with the Ebow at the bottom of my Ebow page, too. http://www.diyguitarist.com/DIYStompboxes/EbowTech.htm

One's for the circuitry and concept. The other is for the enclosure itself. 

QSQ, the link above describes what the Ebow does.

[Paul Marossy]

I've been studying the schematic on the web posted above, the schematic in the patent and the LM386 data sheet and have come up with a theory on how they do the harmonic/regular mode switch. I think it's a center tapped output coil and the setting on the SPST switch determines which direction the current is going in. Any opinions on that?

[John Lyons]

I have a dead original black ebow and a newish one with the harmonic switch. I guess I should dig in and see if I can figure out what went wrong with the old one. Thanks for the links paul1

John

[Paul Marossy]

I have a dead original black ebow and a newish one with the harmonic switch. I guess I should dig in and see if I can figure out what went wrong with the old one.

Trying to repair it would be very difficult at best. I guess that potting is a real PITA to deal with. If you're lucky, maybe it's just a broken wire or something. I think I have worked out a deal where someone is going to send me a circuitboard from a gutted Ebow for my examination. I love doing this reverse engineering stuff once in a while.

[Fp-www.Tonepad.com]

The 'not ebow' that I built (seen on other thread) could vibrate the strings VERY strongly, but I never got to really experiment with it, it's in a box with dozen other half finished projects that I'll probably get back to sometime.

That schematic will work, observe winding polarity and magnet polarity too. Probably variable gain could be useful or a way to fine tune it, since it seems that it will do the job with less power than shown.

Fp

[Paul Marossy]

Yeah, I think in a DIY Ebow, the variable gain control might be useful. I've discovered something else that is interesting - there's four magnets on the PCB besides the magnets at the cores of the input & output coils. I was able to verify this with a little magnet - there's definitely six magnets in the locations shown in this picture:



I wonder what they are doing there... I have some ideas, but they are purely speculative.

EDIT: I think the four magnets probably serve two purposes. One is to help position the EBow correctly on the strings, as the magnets would be attracted to the steel strings. The other purpose I would surmise is to dampen the adjacent strings from any sympathetic vibrations from happening. That's my theory, anyhow.

[Fp-www.Tonepad.com]

That's very interesting. Can you tell what polarity are all the magnets oriented?

[Paul Marossy]

That's very interesting. Can you tell what polarity are all the magnets oriented?

No, but when I get my gutted Ebow PCB, I should be able to figure all that stuff out. 

[Fp-www.Tonepad.com]

Paul, that's really cool.

When I tried to build it I found that the actual enclosure is a big part of the ebow's design, I think that now that you've found out about those 'positioning magnets' most of the details are revealed. I don't see why it couldn't be done with all sorts of variations and mods. I potted the coils with super glue, that helped a lot in making it stable, and I used thicker wire for the output coil to be able to get a lot of turns with little dcr. as for the shape of the whole thing, that was the tough part, I did mine using black bondo paste. If I were to make another one I'd probably use a single AlNiCo pickup pole piece cut in half for the coil cores and magnetize it after assembly to try a few polarity combinations, it is critical that you get the winding and magnet polarity correctly for it to operate.

Once you know the dimensions it's a pretty quick layout, there aren't that many parts or choices as to where to put them.

The switch does intrigue me with the harmonic and regular modes.

IMO the ebow is as elegant as it can be, and I'm sure I'll buy one as soon as I'm able.

[Paul Marossy]

When I tried to build it I found that the actual enclosure is a big part of the ebow's design, I think that now that you've found out about those 'positioning magnets' most of the details are revealed.

Yeah, it's a package deal, that's for sure. I drew up a PCB layout last night and this morning based on the basic circuit from what I can see on those PCB pictures and I just etched the PCB tonight to mess around with. I'm not sure how I'm going to do the coils. I'm going to try and replicate what they have done as much as I can. I have a hunch that the size of the coils make some difference in the overall sound, too.

I think the magnets are connected into the circuitboard somehow, but I have to verify that. It seems like the magnets in the coils repel my little magnet while the four little ones seem to be attracted to it. I also wonder if they are there to create some kind of magnetic field in a specific manner...

[Fp-www.Tonepad.com]

I'm going to try and replicate what they have done as much as I can.

I tried to replicate the functionality, I don't think the size/shape of the coils would have a big influence in the operation, but if you're going for a closer copy, I guess it's worth it. The coils being so low profile may make it easier to 'pack' too.

The connection of those magnets to the circuit board may just be mechanical, part of the construction process. I haven't had a chance to compare mine with the original one, but it does exhibit some of the 'features' the original one has, specially the fact that the string vibrates so much more with the ebow than with a regular pick that you have to turn the guitar volume down to keep it at a regular playing level.