transient

Hi guys, A longer explanation for iscaryoth's "1": I like to think of it this way: A magnet (or an electromagnet in our case), can only pull metals, it can not push. The ideal way to cause a string to vibrate would be to pull and then push it, however it's not possible. So we try to do the next best thing; which is to pull the string for half a cycle and then let it go (not pull) for the other half cycle. Now, if you don't use a magnet together with your driver, this is what's going to happen: it's going to pull the string for the first half of the cycle (N), and then it's going to pull it again for the other half of the cycle (P) - obviously this pull-pull action won't make a string vibrate. However, when you add a magnet to the driver, the following happens: when the driver is the same polarity as the magnet, we get a pull; but when it takes on the other polarity (remember that the polarity of our driver constantly alternates, because it's fed by an alternating current) then it's going to be somewhat disturbed by the reverse polarity of the magnet and won't be able to have much of a pull effect. And this is why it works with a magnet. Things are probably a lot more complicated at the electromagnetic level - this is just an overly simplified explanation which may not be completely true . e

Hi Pete and guys, While i don't have anything to add to the thread (yet), i just dropped by to say hello. I'm following your progress, keep up the good work ... emre

Yes Pete, i folded it But i haven't wound the coil yet, and since you say that attaching seperate isolated pieces together would work better, i'll do it that way and then wind the coil. I first need to get a tool to cut it though, although it's soft, it's not easy to cut unless you're using the right tool. By the way, this is the guitar to be the victim of my experiments: http://d940841.u31.0web-hosting.com/pics/fless_01.jpg ... emre

Well, LK would explain this better but: There can be a huge variance in characteristics between two FETs of the same type, which is why you need to do the biasing. This is what Don Tillman says about the subject: "I should point out that FETs in general suffer from a serious lack of manufacturing consistancy. The FET VGS and IDSS, the parameters that determine the bias point, can be anywhere over a 5-to-1 range and still be within spec. That's pretty awful, but such is life. It's an engineering accomplishment to design a circuit that can function exactly the same over a wide variation of component parameters. But I can't guarantee that in this situation; there's not enough supply voltage headroom." On the other hand, when it comes to regular transistors, the variance between units is not much. This makes it possible to design a circuit that will work with all transistors of the same type, without the need for re-biasing. By the way, i started building the driver. As an experiment, i'm using tinplate from a tea tin for the core. It's easy to find, easy to cut and shape, and highly magnetic. . e

You can use any pot value (100k, 250k, 500k or whatever) *after* the buffer. . e

I'm using this preamp with my Ghost piezo saddles, works great: http://www.scotthelmke.com/Mint-box-buffer.html You could also use the Tillman preamp as Devon suggested. I think it would work even better if you use a 10M resistor instead of the 3M in that circuit. . e

A 5M pot is suggested for passive installation, if you don't want any loss in tone. A lower value pot will cause loss in high & low frequencies, resulting in a "thin" sound. An active preamp would work even better. . e

Yes, LK is right (isn't he always?) about that. I thought you wanted to build a single circuit for yourself. When it comes to manufacturing, FETs are hard to bias, as every unit will have to be biased differently. I plan to use the piezo output for the sustainer. I want to install the sustainer in the middle pickup position on my fretless, and it would be hard to get it to work fine there if i feed the magnetic pickup output to the driver. . e

Well Pete, you can use a trimpot (or a regular pot) at first to measure how much resistance you need for biasing the circuit, then replace that pot with a fixed resistor. You won't need to re-bias the circuit unless you replace the transistor, so a resistor will do the job. By the way, i'm now officially working on a sustainer ... emre edit: Forgot to mention that there are also some circuits that bias themselves, like AMZ's mini booster. But they're more complicated (more than one transistor) circuits as a result of self-biasing.

Jim, you may not necessarily need Ruby. Have you tried using only one of those 1.5W amps instead of two in series? I have a feeling that one would work better than two. I had tried a similar thing months ago, using cheap computer speaker circuitries. I first had used two in series like you, but using only one seems to work better. ... emre

There's a difference. While magnetic pickups have high impedance, it's not as high as piezo pickups. This means that you can't use all magnetic buffer circuits for piezo's. The circuit should have around 5-10 Megs of input impedance for the piezo pickups to sound "right". Those two circuits i've linked both have high enough input impedance. Most magnetic preamp circuits have around 1M input impedance, which wouldn't be enough for piezo pickups. I don't know about the MIMF preamp, but you can use it if its input impedance is high enough (>3M). ... emre

I think the 5M pot is used because of the very high impedance of the piezo pickups, so using a lower value pot will probably result in a loss in tone. I recently have bought Graphtech's Ghost piezo saddles, but did not get their preamp, nor the passive wiring kit (which consists of a 5M pot and a 330pf cap). What i did was, to build a simple piezo-preamp and connect it directly to the saddles. It handles the impedance part, and you can use a regular pot after the preamp without the tone-loss. This is the preamp i've built: http://www.scotthelmke.com/Mint-box-buffer.html But you can also use this one if you want more boost, it also has a volume control by itself: http://www.muzique.com/schem/mosfet.htm ... emre

Sounds pretty good . e

I had designed a superswitch wiring diagram for the following configuration: 1) bridge humbucker, in series 2) bridge split 3) one coil from bridge, one coil from neck, in series 4) neck split 5) neck humbucker, in series I can post it if it will be of any use. But don't miss LK's offer . e

You don't necessarily need a pickup coil. You can use the guitar output for that purpose. It wouldn't be an exact ebow copy then, but will work. You'll just have to be careful not to hold the driver close to the pickup (bridge preferred) feeding it. . e

Yeah Pete, there's a lot of experimenting to be done with 'em . e Sorry, this has put your post on the previous page. Take a look at the previous page guys

Hi guys, I'm still a bit busy, but a lot of experimentation planned for this summer I now have Graphtech's piezo saddles, which would allow me to make a sustainer without the magnetic feedback problem. Good luck with your experiments ... emre

I know Tillman can build them into cable. I wouldn't be able to fit all those components there, even if they weren't wired at all I guess Tillman uses SMD components, but i don't know how he manages to hand-solder them and fit into a plug housing and still have it working fine . e

I can't make it that small The smallest i've built is on a 1" square perfboard. . e

Try the Tillman Preamp. . e

I thought you wanted use a single switch for both pickup selection and sustainer activation. If you'll have a seperate switch for the sustainer, a dpdt too might do the job. Here's the information on how a superswitch works, you can figure out the wiring yourself once you learn how it works. . e

I guess you could use a superswitch for that purpose. ... emre

Great tutorial Mike. Just a correction, you actually meant "no neck pickup" when you said "no bridge pickup", right? . e

Yes, he only sells JJ tubes. I actually replaced all the tubes in my amp with JJs, it sounds better now. I'm planning to purchase one more JJ 12AX7 for my upcoming ShakaTube build . e

You can get higher-gain 12AX7's from eurotubes. I've installed one of those in my amp, they do have more gain than the stock tubes. . e