Wix Posted February 27, 2007 Report Share Posted February 27, 2007 hum were is the diagram? Quote Link to comment Share on other sites More sharing options...
rhoads56 Posted February 27, 2007 Report Share Posted February 27, 2007 hum were is the diagram? hum, what are you talking about?? Quote Link to comment Share on other sites More sharing options...
erikbojerik Posted February 27, 2007 Author Report Share Posted February 27, 2007 OK mods....this is the second time I've started a new thread, only to have the forum software delete the first post in its entirety. Not leaving a post by me with a blank or edited window.....my first post is just plain GONE! ___________________ So...I think I am going to eventually jump onto the pickup winding bandwagon. And it has got me thinking about what's under cover. Can anyone come up with a circuit diagram for an active EMG pickup, like 81 or 85? I know they use some kind of buffer circuit/chip to drop the output impedence of the pickup, anyone know what they use? I'm not talking about the wiring harness....what I'm after is a diagram for all the stuff that lives in epoxy underneath the hood. And while you're at it if you know the DC resistance of the coil(s) alone (sans buffer) and the gauss strength of the magnet, that would help too. I know they list the resistance at ~10kohms but I have a feeling thats with the buffer. They also talk about their pickups having a low-strength magnetic field, and I'm interested to learn about how this all fits together with their buffer strategy. Alternatively....if anyone has a dead one they'd like to send me, I could deconstruct it and post the results. Quote Link to comment Share on other sites More sharing options...
Robert_the_damned Posted February 27, 2007 Report Share Posted February 27, 2007 As to my knowlage no one has deconstructed an EMG pickup. Mainly because they're expensive and that puts people off and secondly because they're completely sealed in epoxy so you're likely to end up with a load of trashed internal componets that you'll never be able to reverse engineer because they're knackered. Alternatively....if anyone has a dead one they'd like to send me, I could deconstruct it and post the results. Reverse engineering something that's not working is even more difficult. Not only have you got to work out what everything is and where it goes you've also got to work out WHY it doesn't work otherwise all your clones of it wont work either! All in all if you have the skills to reverse engineer and debug the EMG circuit you should be able to design one yourself. Then you could go for whatever options you like and customise it to be connected to what ever coil configuration you're using ect. Quote Link to comment Share on other sites More sharing options...
unklmickey Posted February 27, 2007 Report Share Posted February 27, 2007 ...never be able to reverse engineer because they're knackered.... hi Robert, i don't speak much English. my native language is "Merkin". is knackered a (more polite?) way of saying "stuffed"? Quote Link to comment Share on other sites More sharing options...
erikbojerik Posted February 27, 2007 Author Report Share Posted February 27, 2007 (edited) As to my knowlage no one has deconstructed an EMG pickup....because they're completely sealed in epoxy... Vee haff our vays...seriously, if I can get a dead one, I can at least get an idea of how full the bobbins are (even weigh them), measure the magnet strength, etc. That part I have no worries about. I'm more interested to see if any of you electronics gurus have a rough idea of what the circuit diagram would look like. Edited February 27, 2007 by erikbojerik Quote Link to comment Share on other sites More sharing options...
Robert_the_damned Posted February 28, 2007 Report Share Posted February 28, 2007 ...never be able to reverse engineer because they're knackered.... hi Robert, i don't speak much English. my native language is "Merkin". is knackered a (more polite?) way of saying "stuffed"? Its a very english way of saying 'it doesn't work anymore' OR it can mean your very tired. Its not used that much other than by me so don't worry about it Vee haff our vays...seriously, if I can get a dead one, I can at least get an idea of how full the bobbins are (even weigh them), finding out what gauge wire it is though is going to be tricky. Measuring the diameter directly of something that small is virtually impossible let alone trying to work out what the thickness of the insulating layer is! measure the magnet strength, etc. That part I have no worries about. I'd be interested in hearing how you'd plan to measure magnet strength. I'm more interested to see if any of you electronics gurus have a rough idea of what the circuit diagram would look like. It'll be something with op-amps in it....probably two op-amps. The first acting as a high impedance input buffer for the signal and the second providing the boost to normal signal level. Or at least that would be my guess. There might be some tone filtering circuitry in there too. I can't see there being much more than that though. Quote Link to comment Share on other sites More sharing options...
Saber Posted February 28, 2007 Report Share Posted February 28, 2007 (edited) Seeing that they're active pickups, I've always wondered if EMG didn't just use identical coils (of a very wide, flat frequency response) for all their models and just use different tone-shaping active circuitry to give each model its own sound. It makes one think. Edited February 28, 2007 by Saber Quote Link to comment Share on other sites More sharing options...
erikbojerik Posted March 1, 2007 Author Report Share Posted March 1, 2007 Robert, that's pretty much what I would guess as well. I did get some info from another forum, looks like they use a PCB as a baseplate and they have an op-amp-looking chip on there with their name engraved on it. From the photos, looks like normal 42 or 43 AWG with maybe fewer turns. No gauss data on the magnet though. finding out what gauge wire it is though is going to be tricky. Measuring the diameter directly of something that small is virtually impossible let alone trying to work out what the thickness of the insulating layer is! Calibrated microscope and/or SEM (I love my job!). I'd be interested in hearing how you'd plan to measure magnet strength. Gaussmeter with Hall probe. I'm more interested to see if any of you electronics gurus have a rough idea of what the circuit diagram would look like. It'll be something with op-amps in it....probably two op-amps. The first acting as a high impedance input buffer for the signal and the second providing the boost to normal signal level. Or at least that would be my guess. There might be some tone filtering circuitry in there too. I can't see there being much more than that though. Quote Link to comment Share on other sites More sharing options...
badsnap Posted March 1, 2007 Report Share Posted March 1, 2007 As a professional robotics engineer, I deal with control circuitry as well as electro-mechanics and pure mechanics on a daily basis. I would suggest that you try not to reinvent the wheel. In other words, odds are that inside that device is more than just a few op amps. My guess is that is a circuit on a chip, complete with muti stage buffers, waveshape circuitry, and multiple cascading output (power, if you will) amplifiers. Your best chance at sucess is to browse the catalogs of circuit on a chip manufacturers and find a COC that would seem to meet your needs. There are many audio amplifier and waveshaping COCs to choose from. Before attempting to mount it with the coils as a unit, mount it on a prototype board and connect the externals (coils, power, resitors and capacitors) to it and see what you get. If you like the sound...cool, go on to the next step. If not, tweak it (change external components) or go back to the catalogs and find a different COC to try. Manufacturing on a circuit board should be easy and then you pot it with the coils and see what you have got!!! You seem to have a good understanding of the phyical parameters of the PU (wire, wraps etc.) so I won't even go there...you probably know more about that than I do anyway. I guess what I'm saying is even if you get that chip open you would need a SEM and a 1070nm laser based probe (several million dollars for each) to "see through" all the layers to reverse engineer...most likely more work and less fun than just trying to make your own. Remember, that COC is their trade secret, their bread and butter. It will not be easy to copy. I'm sure there are enough technophiles out there for you to partner up with to acheive your goal. Good luck, and keep us posted. Peace...Rog Quote Link to comment Share on other sites More sharing options...
crafty Posted March 1, 2007 Report Share Posted March 1, 2007 I *highly* doubt that it's as complex a chip as you're thinking. 30 years ago, EMG was still pretty much a garage-based company when the current line of pickups was developed. I'm pretty sure they had neither the budget, engineering capacity, and equipment to develop such a complex COC circuit. More likely, it's a two-stage, op-amp based circuit that's been custom burned on a little chip that they just solder on the little baseplate before the pickup is assembled. Great design, but I think it's as simple as that. Quote Link to comment Share on other sites More sharing options...
badsnap Posted March 2, 2007 Report Share Posted March 2, 2007 Perhaps you are right...I have no real experience with EMG pickups per se so I really don't even know what they sound like. I was under the impression that their was waveshaping going on, but that could easily be done with a few stages of amps. If they do indeed use a multistage amp, that would actually make it easier. Yous could even prototype with discreet compents and experiment until you find the right sound, then choose components to reduce the size. Choose your own 2 stage amp chip (much cheaper), mount it, provide the necessary external components and see what happens. I still believe that it will be difficult at best to find out what they are actually using, so have fun and experiment. This is what I love about this forum, there is always a voice of reason (another valid take on the subject) to get you thinking. Peace...Rog Quote Link to comment Share on other sites More sharing options...
Saber Posted March 2, 2007 Report Share Posted March 2, 2007 Here's another picture from that other forum. If someone had this board in their possession, it shouldn't be too difficult to trace out the circuit, measure the surface-mount components, and see if it matched typical op-amp circuit configurations. Quote Link to comment Share on other sites More sharing options...
erikbojerik Posted March 3, 2007 Author Report Share Posted March 3, 2007 Thanks for the comment badsnap. In removing the rubber, I was thinking it would just reveal something simple (op270 for example) and we'd be done. But what you are suggesting is actually more the direction I'm thinking. Design one from the ground up. Quote Link to comment Share on other sites More sharing options...
scottyd Posted March 3, 2007 Report Share Posted March 3, 2007 Hey Erik Im in the same boat with you, Ive wondered about what emg uses but havnt found any info. Ive found a butt load of schematics to build different buffers and pre's if your interested. Ive built a couple of jfet type buffers but they are lackluster to say the least. Opamps are the way to go and the circuits seem pretty simple. I just built a set of neo magnet passive single coils that worked out great, so Im really burning to build a set of actives. Let me know if you find any more info on the emgs. Quote Link to comment Share on other sites More sharing options...
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