Tube Amps / Music Electronics
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|7/15/2004 2:32 PM|
could someone please enlighten my on 'hex pickups' and the hexdistortion ones as well. id like to know how they work and also how to make one, thats if it doesn't infringe on anyones personal pickups.
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|7/16/2004 6:18 AM|
Basically, unless I am confused, you speak of a Dimarzio Super Distortion pickup.
|7/16/2004 6:21 AM|
No they use some sort of arrangement of transistors or relays to create a multiple of the sound and so distort it.
|7/16/2004 2:42 PM|
Hex pickups are divided pickups that assign a coil to each string. I suppose they can be used for multi-channel separation of the actual strin sound, but in geenral they are used for keeping individual string signals separate for the purposes of synthesis. By keeing each signal separate, you have greater assurance that any note-on/note-off information is coming from that string, that the envelope follower is responding to only that string, and that any pitch-to-voltage conversion is responding only to that string.
Since a big part of keeping such note information clearly differentiated by string is to reduce side-to-side bleedthrough, hex pickups are always situated where the strings wiggle the least, down by the bridge. I have an old Guild hex octave box that uses a proprietary divided pickup for directing each string to its own octave divider/fuzz. Unfortunately, its dimensions require it to be situated too far away from the bridge and the amount of false triggering due to sideways wiggle is noticeable.
Since one is interested in deriving "note information" and not the actual sound of the string and body in synthesis, the pickup doesn't have to be that hot. So the physical constraints imposed on coil size by having a coil per string and being stuck close to the bridge, are not that much of a problem as they would be if your intention was to sense the sound of the string.
Some compnaies such as Bartolini, and I think DiMarzio, have made divided pickups intended to sense the actual strings. The old Ripley guitar that Eddie Van Halen used to endorse on the back cover of Guitar Player used this and turned out not to be such a hit with consumers.
Harry Bissell telles me that these days one of the most cost-effective ways of obtaining a hex pickup is to checkon e-bay for the G-Vox unit. This was a hex-pickup/software combo for guitar training that connected the guitar to your computer. He built himself a terrific guitar synth with one that I had the pleasure of using. Great little unit.
|7/16/2004 2:55 PM|
Cheers thanks for the post it is very useful, but does anyone know what the distortion part of it is? im not sure if it means it uses a hex pickup tho?
|7/19/2004 10:56 AM|
The distortion part of the hexdistortion can be accomplished numerous ways. One way is to use a comparator circuit. In this configuration, there are two inputs to an op-amp or comparator chip (e.g., LM339) section. One of the inputs is a small steady DC reference voltage, and the other is what comes from the pickup. The moment the pickup signal crosses the reference voltage threshold it is "compared" to, the op-amp output goes high. And I mean high. Then it goes low when the signal drops below the threshold.
This accomplishes several things. First it keeps separate audio noise, hash, and incidental sounds, from intentional picking-derived signal, much the way a noise gate does. Second, it produces a squarewave output which any other parts of the circuit needing to convert an audio signal into a DC voltage indicating note pitch will find VERY handy. Third, it takes what may well be an audio signal of 50mv on a good day (with the widn at your back), and turns it into a much higher level signal on the order of several volts which other parts of the circuit appreciate and which keeps a decent signal to noise ratio down the line.
The squarewave output is, of course, fuzzy-sounding, so it is often used as a signal source itself, and not just a basis for pitch-to-voltage conversion for driving oscillators and such. If you look at Anderton's "Ultrafuzz" from the EPFM II projects book, this is precisely how it works, only it is applied to the entire guitar signal rather than individual strings.
As suggested, there are other hex distortion approaches too. On Harry Bissell's unit, he told me that he basically runs each coil's output into its own Big Muff, and from there into its own filter and VCA. I can attest that it provides a really nice, lively and responsive sound.
The advantages of a setup in which any distortion applied to the guitar signal are applied separately to each string is that there is considerably less intermodulation distortion. Moreover, since the signal level obtainable from one string varies over a much smaller range than the signal obtainable from anywhere between one unwound E and 6 strings slammed hard, it is possible to set the clipping threshold separately for each string to obtain a more consistent distortion sound across the strings. It also ends up yielding a much better defined sound since the strings don't interfere with each other. Finally, if one is intending to apply some sort of filtering to mimic other instruments or invent new tones, processing each string separately, whether clean or distorted, allows one to adjust the filters to be appropriate to each strings range of notes and harmonic content.
There are ways of achieving *some* of these outcomes without means of a divided pickup. For instance, Craig Anderton's "Quadrafuzz" he designed for Guitar Player (and still available from PAiA in kit form), takes a mono signal from normal pickups, and divides it into four bands, then clips each band separately, and mixes the four outputs back to mono. The intent is to achieve a fuzzed sound with better definition when playing chords, with no preparation or anticipation of synthesis and P-to-V conversion. Build reports are that it works okay for the money, and provides a lot of tonal flexibility, but is not going to revolutionize distortion.
|7/19/2004 1:28 PM|
I found that really helpful and I'll look into the whole thing in more depth now, although my electronic skills are rubbish i have some friends who im sure can guide me in a good direction in how to build the circuits. Now i know how it actually works!
really i was looking into it to see how i might incorporate it into a PU.
Just an idea, but i know that a distorted sound is basically multiples of the same output(right???). so i was thinking that somehow using capacitors or relays, or sumthing that u could boost the output somehow, without having to use another power source.
would this work or is there more to it?
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