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Post by ashcatlt on Oct 23, 2008 23:12:07 GMT -5
Before somebody comes along and jumps on me... I've been trying to keep this part of the discussion as simple as possible. The truth of the matter is that all discussion of phase is frequency related. Unless both pickups are in exactly the same place AND transducing the same thing (that is magnetic OR piezo) you will quite certainly have some phase related interference. Thanks to the fact that the wave must travel through some physical substance before getting to the piezo, which will cause a delay, I'm not sure that you will ever get them perfectly aligned in phase. In fact, I'd expect for the fundamentals of different notes to have different relative phases between the two pickups. I think what we're going to want is to be sure that the fundamentals are corresponding as closely as possible in order to avoid a very thin sound. Since these lower frequencies have longer wavelengths, they require a considerable amount of delay to create noticeable interference. Thus, you'd ought to be able to effect an audible difference in this area by reversing the wires on one of the two transducers. Higher frequencies will be more of a crapshoot. Once you've decided which way you need to wire the pickups to get the fundamentals to play nice, you then might have to move one of them (probably the piezo, since it doesn't require a router ) until you get a sound in the upper mids and treble that works well. That is, to find the spot where the phase related interference is least objectionable. I'm sure not much of that helps anything, and I'm a bit tired to go into further detail. Maybe somebody who knows what they're talking about will come along... Edit - Now you've ninja'd me! I intend for you to be aware that: IF you intend to mix the piezo and magnetic pickups THEN you might need to reverse the wiring of one of the two IF they don't sound good when mixed
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Post by ChrisK on Oct 23, 2008 23:32:45 GMT -5
True, two pickups can be completely in phase for the fundamental and out of phase for certain harmonics depending on their exact location as a ratio of the string length. Yes. Agreed! Yep. For a piezo not mounted in the saddles, the speed of sound in the body (and all other coupled components) will determine the delay time. It should be a relativly constant time for most frequencies and therefore will effect a differing percentage of phase shift for different frequencies. All of the guitars that I have with piezos have them in the saddles (Variax 500, MIM Nashville Power Tele, Godin xtSA, Parker P38). In this case, there should be virtually no delay since they are at the bridge anchor point for each string. I don't know whom (else) you were waiting for to come along that "knew what they were talking about". (Unless that was some form of a disclaimer.)
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Post by ashcatlt on Oct 24, 2008 0:26:23 GMT -5
Oh, that's right, I actually do have a clue. It was, I guess, an attempt at feigned humility by way of self deprication. I also thought maybe somebody could expand upon or translate my point.
Thanks for the second, though.
Wanted to mention, too, that JohnH has his connected to the trem block. In this case it is not in direct contact with the strings as they would be in the saddles, and we have to wait a (very) little while for the vibrations to get from the strings to the pickup.
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Post by newey on Oct 24, 2008 5:49:07 GMT -5
Before all of the late-night theoretical discussion ensued, Zuee asked:
No one is suggesting that you use the phasing of the piezo as an effect, that probably wouldn't be worth it. What we're saying is that you may need to play with the phase of the piezo to get a useable sound out of it when used together with the mag pups.
So, here's what you should do:
1) Post your revised diagram so it can be vetted.
2) Once the diagram is final, wire it up and see what you get.
3) Be prepared to move the physical location of the piezo, and also to swap the wires on it around, as you may need to tinker with it to get a usable sound. Since you will have 2 phase switches to play with, you can easily determine whether swapping the piezo wires will make a difference when the piezo is used in conjunction with the un-phaseable pickup.
Keep in mind that all this discussion of phasing only applies when the piezo is used in combination with the mag pickups. When the piezo is used by itself, the only variables are the physical position (and attachment) of the piezo, and the type of buffering circuit you use (if you elect to use one).
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zuee
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Post by zuee on Oct 24, 2008 9:28:21 GMT -5
Before all of the late-night theoretical discussion ensued, Zuee asked: No one is suggesting that you use the phasing of the piezo as an effect, that probably wouldn't be worth it. What we're saying is that you may need to play with the phase of the piezo to get a useable sound out of it when used together with the mag pups. So, here's what you should do: 1) Post your revised diagram so it can be vetted. 2) Once the diagram is final, wire it up and see what you get. 3) Be prepared to move the physical location of the piezo, and also to swap the wires on it around, as you may need to tinker with it to get a usable sound. Since you will have 2 phase switches to play with, you can easily determine whether swapping the piezo wires will make a difference when the piezo is used in conjunction with the un-phaseable pickup. Keep in mind that all this discussion of phasing only applies when the piezo is used in combination with the mag pickups. When the piezo is used by itself, the only variables are the physical position (and attachment) of the piezo, and the type of buffering circuit you use (if you elect to use one). Before I make another diagram, would using a potentiometer to pan from magnetic to piezo be a good idea? It can eliminate another switch from the guitar.
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Post by JohnH on Oct 24, 2008 14:43:35 GMT -5
I used a potentiometer to blend the mag and piezo, but to make it work right, I needed two transistors as a buffer/booster after the piezo to boost and EQ it, another to buffer the magnetic pickups, then the blender and a fourth transistor to buffer the output. It's great, but anything less would not have worked to my satisfaction. I found that the two signals are just too different in level, impedance and and response to blend well without that. I'm willing to share my circuit design, but such a preamp is not a first-time project, especially if reading schematics is new to you.
If you want to try piezo with less fuss, Id keep them seperate without blending, maybe with a simple buffer. Then you can set your amp for which ever you are using. Also, without blending them, the phase is not important.
There's one question Id like to ask you, since I think you have already experimented with your piezos. Have you already found a piezo sound that you are happy with, and what kind of amp did you cannect it to and how did you adjust it? I just want to see if you may be able to get a sound that you like with less electronics than I needed.
John
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zuee
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Post by zuee on Oct 24, 2008 19:06:24 GMT -5
I used a potentiometer to blend the mag and piezo, but to make it work right, I needed two transistors as a buffer/booster after the piezo to boost and EQ it, another to buffer the magnetic pickups, then the blender and a fourth transistor to buffer the output. It's great, but anything less would not have worked to my satisfaction. I found that the two signals are just too different in level, impedance and and response to blend well without that. I'm willing to share my circuit design, but such a preamp is not a first-time project, especially if reading schematics is new to you. If you want to try piezo with less fuss, Id keep them seperate without blending, maybe with a simple buffer. Then you can set your amp for which ever you are using. Also, without blending them, the phase is not important. There's one question Id like to ask you, since I think you have already experimented with your piezos. Have you already found a piezo sound that you are happy with, and what kind of amp did you cannect it to and how did you adjust it? I just want to see if you may be able to get a sound that you like with less electronics than I needed. John Ok, I'll stick with a switch for choosing between mag and piezo then. And about the piezo, I tried your method of putting the piezo behind the block of the trem bridge and it sounds great. It sounds great when it's clean, but it almost sounds like magnet pickup on clean too . I tried to get a more acoustic sound, but that might be hard on a solid body guitar. I'm still deciding on where I should place the piezo for my project guitar. I have a Roland Mini-Cube. It doesn't have a lot of tone options , but rather a lot of effects. I have the gain at halfway so it has less hum (I could go higher). I have the tone around high. I also tried taping the piezo on the pickups. On the neck pickup, it sounds VERY bassy, and I like it. On the bridge, it has less bass and sounds brighter, which I think sounds closer to an acoustic. Both ways sound good, but I want to know if the sound could be improved.
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