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DIY Stompboxes => Building your own stompbox => Topic started by: Paul Marossy on May 29, 2007, 05:16:21 PM

Title: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Paul Marossy on May 29, 2007, 05:16:21 PM
Well, I got my dismantled Ebow in the mail today. Someone else did all the work for me and got all the goop off of it so we could see what's "under the hood".  :icon_wink:


The is showing how the PCB sits in the base and how the coils are held by the PCB. The LED is on the right side in the picture.
(http://www.diyguitarist.com/Images/EbowGutsA.JPG)

This is the other side of the PCB with the coils dismantled. The coils are about 1.3" apart from eachother (center to center)
(http://www.diyguitarist.com/Images/EbowGutsB.JPG)

This is a closer view of one of the coils. It is composed of a steel core, the copper windings, a steel ring approx. 1/2" in diameter and a magnet that goes on the bottom. The magnet is farthest away from the strings. The coils are physically identical, but one of them uses wire about the size of a human hair and the other one uses windings that are considerably larger.
(http://www.diyguitarist.com/Images/EbowGutsC.JPG)

Here is a little closer view of the PCB. The is what appears to be an LM386 on it, a 1N914 type diode, two resistors and four capacitors on the board. There are no magnets on the PCB as I thought there were, only the two on the coils. The PCB is 1.5"x.875"
(http://www.diyguitarist.com/Images/EbowGutsD.JPG)

This is showing how the coils fit into the bottom piece.
(http://www.diyguitarist.com/Images/EbowGutsE.JPG)

These are all the plastic parts as they look individually. I looked at the switch assembly. I think my theory about a multi-tapped coil might be right from studying the PCB and how the switch is wired.
(http://www.diyguitarist.com/Images/EbowGutsF.JPG)

Interesting, huh?  :icon_cool:
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: petemoore on May 29, 2007, 06:57:19 PM
  Very nice displays Paul !!
  Being the less than extremely adventuresome type who would like to try an Ebow, this is getting closer to where I'd actually try building one!
  So, being the shy type, I'd be as bold to say I'd be scared to try one until I had the layout and wiring where I had complete confidence/understanding, almost a step by step instructional or reference..not that I expect it, but it is getting close..
  Source the magnets/coils etc., building on perfboard from schematic, other things I might not be able to have real easy.
 
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: markm on May 29, 2007, 07:02:48 PM

Interesting, huh?  :icon_cool:

To say the least!
WOW!  :icon_cool:
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Paul Marossy on May 29, 2007, 07:07:47 PM
Yeah, as you can see, building an Ebow clone is not for the faint of heart.  :icon_eek: :icon_wink:

BTW, the PCB might look like it's broke on both ends, but it's actually made so that the hole for the magnets doesn't actually close. Don't know why, but that's what the deal is.
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Paul Marossy on May 30, 2007, 10:38:47 AM
One thing that has piqued my curiousity is the steel pole piece. The patent says it's a magnetic core of Alnico-5, but it's just a piece of steel. Isn't Alnico-5 a magnet?
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: markm on May 30, 2007, 10:40:21 AM
One thing that has piqued my curiousity is the steel pole piece. The patent says it's a magnetic core of Alnico-5, but it's just a piece of steel. Isn't Alnico-5 a magnet?

To my knowledge it is.
Isn't that the same type of Magnet Leo used?
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: petemoore on May 30, 2007, 11:11:23 AM
Alnico-5 a magnet?
  Alnico-5 is a type of metal alloy, which can be magnetized:
  Alnico-5: Any of several hard, strong alloys of iron, aluminum, nickel, cobalt and sometimes copper, niobium, or tantalum, used to make strong permanent magnets.
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: nephsuperman on May 30, 2007, 11:11:45 AM
alnico is a magnet made of and alloy of aluminum, nickel, and cobalt.  
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Paul Marossy on May 30, 2007, 11:41:31 AM
Quote
alnico is a magnet made of and alloy of aluminum, nickel, and cobalt. 

I know that much.  :icon_wink:

So then Alnico-5 doesn't necessarily have to be a magnet then? Interesting.  :o
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: MarcoMike on May 30, 2007, 11:42:48 AM
Alnico is an alloy of Aluminum nikel and cobalt, yes. but these are not the all the components. the main component is Iron, other metals may be present depending on the alloy (alnico X)
and it should be a permanent magnet, which means it retains its magnetization until it stays below a certain temperature (which is usually high). if yours is not magnetic, then I doubt it is ALNICO.
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: MarcoMike on May 30, 2007, 11:50:05 AM
mh, I wrote the previous post before your last post...
I guess ALNICO may exist as non-magnetic metal, but why woould you do something out of alnico when you don't deserve it as a  permanent magnet?
so, just to clarify my last post: if it was a permanent magnet it is not so easy to delete its magnetization. heating it over its Curie (or someone else) Temperature will allow you to change its magnetization by an external M.field. and I guess at higher temperature it will loose it because of internal thermal agitation.
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: mattpocket on May 30, 2007, 11:53:21 AM
You had to break this to get it apart! Your nuts man! It's great for us guys, but you just broke it! : :icon_eek:
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Paul Marossy on May 30, 2007, 12:08:26 PM
Quote
You had to break this to get it apart! Your nuts man! It's great for us guys, but you just broke it!

No I didn't. Someone else dismantled it in his quest to try a make a DIY sustainer system (like a Sustainiac), I just bought it from him for $10 plus shipping in order to satisfy my own curiousity.  :icon_cool:
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: mattpocket on May 30, 2007, 12:11:24 PM
Thats cool enough!

Interesting nethertheless.... are you going to build one, Paul?... You seem like the biggest fan of the ebow around here, and you know what it sounds like, so you are a good candidate in my opinion!  ;D

Matt
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Paul Marossy on May 30, 2007, 12:27:41 PM
Quote
are you going to build one, Paul?... You seem like the biggest fan of the ebow around here, and you know what it sounds like, so you are a good candidate in my opinion!

Yeah, I'm going to try making the circuit just for fun. I'm not really the biggest fan, I just find it to be a very interesting circuit. More so after I got a couple of working ones the last couple of weeks.  :icon_wink:
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: MKB on May 30, 2007, 01:15:55 PM
Yeah, as you can see, building an Ebow clone is not for the faint of heart.  :icon_eek: :icon_wink:

BTW, the PCB might look like it's broke on both ends, but it's actually made so that the hole for the magnets doesn't actually close. Don't know why, but that's what the deal is.

Thanks for posting the pics!!  It is very interesting, however they are doing quite a service to guitarists (and keeping themselves in business as well) by making such a strange circuit/device affordable.  Around $80 street price on such a thing is a good price.

The PCB's look like that as they are most likely panelized (many of the boards are supplied in one large panel); the panel is much easier to work with.  After stuffing the panelized boards and soldering them with a wave solder machine, the boards are then broken apart for use.  So they are broken, but were meant to do so.

Is there any other circuitry in the ebow, like up near the octave switch?  I find it hard to believe they can implement all those functions (automatic power on/off, octave switch, LED driver) with a single off the shelf part.  But the newer ones have the power switch and octave select in the same switch.  Maybe the older chrome ones had more circuitry in them. 

FWIW, I had both a chrome one from the seventies and currently have the new one with the blue LED.  The newer ones are WAY better in every way than the chrome ones IMHO.  Only down side to the new ones is that they no longer are supplied with the cool leather belt case.   :icon_sad:
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Paul Marossy on May 30, 2007, 01:33:40 PM
Quote
Is there any other circuitry in the ebow, like up near the octave switch?  I find it hard to believe they can implement all those functions (automatic power on/off, octave switch, LED driver) with a single off the shelf part.  But the newer ones have the power switch and octave select in the same switch.  Maybe the older chrome ones had more circuitry in them. 

Nope, it's just the opamp, two resistors, a diode, four capacitors, the input/output coils and the SPDT switch which apparently somehow reverses the current in the output coil for the harmonic effect. That's where my theory of the center-tapped coil comes into play. AFAICT, the schematic here looks pretty close to the Ebow circuit: http://logosfoundation.org/kursus/4047.html - I'll see if I can verify the resistor/cap values on the PCB.

EDIT: I looked carefully at the PCB. There are two tracks leading up to where one of the leads of the output coil connects. I think what the SPDT switch does is reverse the coils while simultaneously allowing the circuit to be powered up. That has to be how it's done, I can't see how else it could be done with a SPDT switch...  :icon_confused:

Yeah, it's a panelized PCB, I could tell that right off the bat.  :icon_wink:
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Thomas P. on May 30, 2007, 01:41:45 PM
Is it really non-magnetic or is the effect just really low?

If there are pickup builders in the thread they propably now that in the process of building a single coil the last step would be "reorientating" the magnetic dipoles via  two strong ceramic magnets. So if the magnetization is low (really low) it could be due to age. If that's not the case the dipoles can be randomly orientated by vibration.
To thermally randomize the magnet you have to get over ~800C which is the curie temperature of alnico
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Paul Marossy on May 30, 2007, 01:57:55 PM
Quote
Is it really non-magnetic or is the effect just really low?

If those pole pieces are magnetic, they are extremely weak magnets as they do not appear to be attracted to steel/iron in the least bit. The 1/2" round ones are pretty strong magnets, though. Not like rare earth magnets, however.
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Mark Hammer on May 30, 2007, 02:20:53 PM
FYI, Alnico, whether 2, 3, or 5 (common types for pickup polepieces and speaker magnets) is simply an alloy, and is magnetized for the purpose of use in pickups or speakers, etc.  Good thing too, because shipping magnets in any quantity must be a real nuisance.  Its non-magnetic nature in native form means that pickup manufacturers use a magnetizer prior to installing them.  Stew-Mac will sell you Alnico polepieces and has instructions on their website for how to magnetize them, using rare earth magnets.  Since rare earth magnets are ALSO a nuisance (now let's see, did I or did I not have my credit card and ATM card in my pocket when I was leaning over the bench?), manufacturers tend to use electromagnets for "charging" the polepieces.  Unlike rare earth (cobalt samarium) magnets, once those babies are off, they are OFF.

Because the slugs/polepieces have to be magnetized, that means they can be magnetized to varying strengths/gauss-levels.  I would imagine that anything which is intended to use in close proximity to strings, with the express purpose of keeping those strings moving, would be designed to have very modest magnetic "tug".  the use of Alnico is really more for the long term retention of magnetic qualities, I imagine, as well as machineability (prior to magnetization).
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Paul Marossy on May 30, 2007, 03:03:48 PM
Quote
Because the slugs/polepieces have to be magnetized, that means they can be magnetized to varying strengths/gauss-levels.  I would imagine that anything which is intended to use in close proximity to strings, with the express purpose of keeping those strings moving, would be designed to have very modest magnetic "tug".  the use of Alnico is really more for the long term retention of magnetic qualities, I imagine, as well as machineability (prior to magnetization).

Good points, Mark.  :icon_cool:
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: calculating_infinity on May 30, 2007, 07:34:05 PM
Thanks for taking the time and sharing with us Paul!  I remember seeing something similar elsewhere dunno if it was here or somewhere else.  Anways, keep up the good work.
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Paul Marossy on May 30, 2007, 08:20:03 PM
No problem. I thought others here might be as curious as me about it.  :icon_wink:
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: psw on June 27, 2007, 09:37:33 PM
Great thread and I'm glad the dismantled ebow fell into good hands. That Phil Keaggy video ebow demo is pretty inspiring...in many ways it would seem that the ebow is the ultimate sustainer (at least it is portable from instrument to instrument)...
http://www.youtube.com/watch?v=wwq0i6jP7dQ (http://www.youtube.com/watch?v=wwq0i6jP7dQ)
I have always intended to build my own (they are a little expensive down here for me! A$300!)...have shot you an email paul. I was wondering if any ergonomic improvements could be made to the design?

The circuit is ultra-simple and I already have plenty of similar ones for the sustainers I have been working on...and experience with coil making. Winding driver coils is not hard...a few hundred turns, if that of fairly thick enamel wire (0.2mm) will do the job...making the pickup coil may be a little harder...this hair like pickup wire needs to be bought in some quantity, is hard to source and really needs a machine (a drill would probably do it) to wind!

I suspect that the coils are simple steel slugs with magnets under and the steel rings (probably cut from a metal pipe...or at least could be) is there to allow some magnetic sheilding and allow the driver and pickup coils to be placed so close together. A device like this need not have a lot of power and a preamp would not be necessary if the pickup was an appropriate impedance for the amp (maybe 10k or so). People should keep there eyes peeled for suitable off the shelf coils for the pickup coils...some reed relays have interesting coils that could suit the purpose. The dutch DIY ebow site suggests a phone pickup...don't see too many of those around...hmmm Perhaps even speakers could be used as applied to intercoms for both the driver and pickup coils if suitably modified...

The real elegance in the design is in the enclosure...and that is hard to replicate. I wonder if anyone could come up with an alternative design or format that would work as well?

Anyway...interesting stuff and an invaluable reference...glad to see the pics have not been lost in the cyberspace...I'll let you guys know how any experiments I may try work out... pete
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Paul Marossy on June 27, 2007, 09:46:51 PM
Quote
I suspect that the coils are simple steel slugs with magnets under and the steel rings (probably cut from a metal pipe...or at least could be) is there to allow some magnetic sheilding and allow the driver and pickup coils to be placed so close together

Yep, they are just steel slugs similar to pickup pole pieces, with magnets on the bottom. But the rest of the surround appears to be a ferrite material.

Hey Pete, you should also check out the tune called "Sexton Demo 1" on my MySpace Music page, I have a cool sounding ebow part on there. Actually, it's a double ebow part... :icon_cool:

www.myspace.com/j201jams
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Jaicen_solo on June 28, 2007, 08:13:55 AM
Just a thought, but Alnico may be used because it will saturate much sooner than other steel alloys (it has a high magnetic reactance). Perhaps it helps to constrain the gauss strength of the coil when used on the lower strings?
This is something i've been wanting to try for some time. Although i'm more attracted to sustainer pickups,  having seen inside one of these things, I think an Ebow is certainly DIY-able, and I have the wire to do it too ;) !
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Paul Marossy on June 28, 2007, 09:42:11 AM
The patent documents say that the cores are Alnico-5. In the case of the ebow, the steel cores are not magnetized, so I don't know what to make of all that...  :icon_confused:
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: fafer88 on January 16, 2013, 05:18:35 PM
Hi,

I've just finished redraw schematic from pics. Could somebody check my schematic and pcb especially values of components and correctness of schematic? Maybe someone knows value of resistor in feedback? Instead of coils I want to use tiny computer speakers, just like this:
http://www.tme.eu/en/details/ld-sp-u15.5_8a/speakers/loudity/# -> instead output coil
http://www.tme.eu/en/details/ld-bzen-1205/electromagnetic-sounders-wo-generator/loudity/# -> instead output coil
Is this going to work?

(http://files.tinypic.pl/i/00235/gxuqrocbznz3_t.jpg) (http://www.tinypic.pl/gxuqrocbznz3)
(http://files.tinypic.pl/i/00235/3l4d09nvlnm9_t.jpg) (http://www.tinypic.pl/3l4d09nvlnm9)

greetings

fafer88(http://)
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Gurner on January 16, 2013, 05:53:45 PM
I can't help you on the value of the feedback resistor, but normally feeding back an audio IC output to its +ve input = oscillation.
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: PRR on January 16, 2013, 06:33:58 PM
> check my schematic

I have NO idea what resistor "?" is for. Or why you'd use a speaker output.

Why not use the good schematic?

http://logosfoundation.org/elektron/ebow_amp.gif
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: deadastronaut on January 16, 2013, 08:29:11 PM
^ yep i used that schematic and  it worked....

i made a really crude...and i mean crude ebow, way off spec on the hand bodged coils too, but it worked.. :)

http://www.youtube.com/watch?v=CO0dsElQ8Mk&list=UUGP0eO8ADt0H9FY5UcHTf8A&index=8

i wound 2 coils and just put magnets on the back of them...same polarity...

and had harmonic mode too by flipping the coils magnets....(can be done with a dpdt)... 8)


edit:  found my old diagram, ...have fun, i did.. ;)

(https://dl.dropbox.com/u/7464107/ebowdiy666.jpg)

if i tried this again, i'd go probably go for coils just wound round the magnets (no poles) and would probably be a stronger sustain,

but will likely want to stick to the strings though....on the real ebow the string guides prevent that.........hmmmm makes me want to make one again now.. :icon_idea:



Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Paul Marossy on January 17, 2013, 09:51:59 AM
^ yep i used that schematic and  it worked....

i made a really crude...and i mean crude ebow, way off spec on the hand bodged coils too, but it worked.. :)

http://www.youtube.com/watch?v=CO0dsElQ8Mk&list=UUGP0eO8ADt0H9FY5UcHTf8A&index=8

i wound 2 coils and just put magnets on the back of them...same polarity...

and had harmonic mode too by flipping the coils magnets....(can be done with a dpdt)... 8)


edit:  found my old diagram, ...have fun, i did.. ;)

(https://dl.dropbox.com/u/7464107/ebowdiy666.jpg)

if i tried this again, i'd go probably go for coils just wound round the magnets (no poles) and would probably be a stronger sustain,

but will likely want to stick to the strings though....on the real ebow the string guides prevent that.........hmmmm makes me want to make one again now.. :icon_idea:

You are the man!  :icon_cool:
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: deadastronaut on January 17, 2013, 09:58:42 AM
ha ha cheers paul....i had to try it.. :)
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: fafer88 on January 17, 2013, 11:50:29 AM
I drew my schematic using this PCB as exemplar:
http://www.diyguitarist.com/Images/EbowPCB.jpg
and guts posted in the beginning of this subject.
Schematic posted by PRR doesn't fit to this PCB.
I calculated feedback resistor, 62Ohm should be just fine,
I  ran simulation in Multisim and its looks good
In nearest future I want to build e-bow from my schematic,
the only thing I risk is a waste of time and a few $.
I will let you know what is the result.
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Paul Marossy on January 17, 2013, 11:53:38 AM
To me, the hardest part of a DIY ebow is the package it's in. You can build the circuit, but the thing that contains the circiuit is a whole other affair...
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: newfish on January 17, 2013, 02:08:22 PM
Thank you *so* much for this.

I love my Ebow, but would not remotely consider taking it apart for curiosity.

In terms of the 'package', I think this will become easier once 3D Printers become more affordable...

Thanks once again!
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: Paul Marossy on January 17, 2013, 02:33:04 PM
Thank you *so* much for this.

I love my Ebow, but would not remotely consider taking it apart for curiosity.

In terms of the 'package', I think this will become easier once 3D Printers become more affordable...

Thanks once again!

Me neither. Someone sent me one that was already dissected. Good point about the 3D printer.
Title: Re: Ebow Expose Part II - Ebow Anatomy Inside
Post by: deadastronaut on January 18, 2013, 03:08:48 AM

I will let you know what is the result.

please do, i'm interested to see how you get on.  good luck ;)


what is the feedback resistor doing then?....just curious.