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Preamp For A Classical Guitar?


Steve Vai
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I'm going to do a project like this (http://projectguitar.ibforums.com/index.php?showtopic=6941), so I'd like some advice. It will be a semi hollow Strat with a spruce top and an undersaddle Shadow piezo (http://www.musicyo.com/product_specs.asp?pf_id=281) (unless someone can recommend a better one). I'm not sure what to use for a preamp. Should I make one like a simple booster, or should I buy an expensive one designed for acoustics with piezos?

I also have an extra Schatten soundboard transducer (http://www.stewmac.com/shop/Electronics,_p...Transducer.html) and I'm thinking of making a single coil route to put the transducer in the bottom of (attach it to the bottom of the pickup route), and using/making a mixer or blender preamp to combine the sounds. Would this be a good idea, or would I get better tone from running just the undersaddle pickup?

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Whew! That's a pretty ambitious project - my first instinct would be to recommend that you buy one of those Fishman blender/preamps or something similar, simply because it's going to be difficult to homebrew anything that can match the noise specs on the commercial products, and with the high impedances and low levels of piezos in general, noise is going to be fairly critical. How good are your electronic construction skills (and be honest, at least with yourself - this isn't the time for cockiness :D )? If you're not well above average, you're probably better off buying a preamp - I'm not sure I'd want to fool with it myself, but I haven't really looked into what it'll take, so maybe it's not as difficult as I'm assuming. I've got a nice low-noise dual booster/impedance converter for magnetic pickups that I've "designed" - let me see if it'll translate to piezos, and I'll get you the schemo if it's practical.

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OK, looks like I was overthinking the problem (as usual), and my little booster will probably work - I've got parts coming in this week (Thursday?), and I'll throw one together to try out and let you know if it's going to solve your problem. Two quick questions -

  • Do you have room for two 9 volt batteries in your plan, or do I have to work with limited headroom?
  • Do you want to use volume pots to set the level for each pickup, or do you want a fixed amount of boost (and if so, how much)?

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OK, looks like I was overthinking the problem (as usual), and my little booster will probably work - I've got parts coming in this week (Thursday?), and I'll throw one together to try out and let you know if it's going to solve your problem. Two quick questions -


  • Do you have room for two 9 volt batteries in your plan, or do I have to work with limited headroom?

  • Do you want to use volume pots to set the level for each pickup, or do you want a fixed amount of boost (and if so, how much)?

LPB1

darlington transistor and you will never need to turn it above 1 and will be shimmering and boomy and free of distortion. and it consists of 1 pot 4resistors and two caps.

with decent soldering skills and either 1/4watt or 1/8watt you can build it on the back of a dime or a quarter your choice. epoxy it all with lampblack and use double sided tape to affix to the back of a pot. with 1/8thwatt resistors andsome creative sodleering you could go ahead and just apply the resitors directly to the legs of the darlington with some smt caps it would be the size of a pencil eraser. :D

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Before I decide to do any of this or buy a blender preamp, I need to make sure that I want to add the soundboard transducer I already have it, I just don't know if it will add any worthwhile sounds if I install it. It should though, since I can mix between the two different sounds until I find one I like. I'll probably want to use more of the undersaddle pickup, but I can play around with the ratio later. I'd need a preamp that can bypass one of the inputs, in case I decide not to use the soundboard transducer.

I'm probably not good enough with electronics to make my own blender preamp yet. I could probably pull it off, but it looks like it will be more trouble than it's worth. Where are you located? I could buy a preamp from you through Paypal or ebay. That's probably the best option I have! :D

I should have space for two batteries. I'm going to get the body from Warmoth; it's just easier. I could get a double battery box installed, and even if I don't, it should fit under the pickguard.

I'd want to use trim pots to change the volume of each pickup, so I could get a set ratio to always use, and not have to worry about bumping into the knobs, and a master trim pot, so I can lower the maximum gain in case it clips. I would want a volume pot in the first position of a Strat pickguard, so I can change the master volume of both pickups, but I'd want the trim pots for each individual pickup and the gain trim pot internal.

Having an XLR output would be nice, but not required.

Someone recommended getting a preamp with a minimum 3 band EQ, and possibly sweepable mids, but it's not really necessary since I could get a seperate EQ unit, or change the settings on the amp.

Other than EQ, blending, and a good signal to noise ratio, what's the main thing that acoustic preamps offer that a simple booster doesn't? As long as I can get a nice natural sound out of my guitar, I'll be happy. I'd like to buy one from you, if you want to do it, and I'd be willing to pay whatever the price is for a similar LR Baggs preamp. I just want to get this right. B)

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Other than EQ, blending, and a good signal to noise ratio, what's the main thing that acoustic preamps offer that a simple booster doesn't?
:D Nothing, except perhaps robust construction - but what else is there? (now remember, I'm laughing with you, not at you!) B)

I'd like to buy one from you, if you want to do it...
I'm really not geared up for building items for sale, but we'll figure out how to get you one made - let me get one built with the new parts, and we'll see how it works before we worry about the rest! :D What's your estimate on completion of the rest of the guitar?
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I need to finish my amp before I start on another guitar, so it could take a couple months. I'm mostly just planning it out right now. Once I get started, the hardest thing will be the electronics, so there shouldn't be anything else I have to worry about.

If I can't do the preamp myself, which I'm guessing I can't unless it's really simple, then I'll just buy one used or something.

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  • 1 month later...

If you bought a piezo from radioshack and then added one of those stereo preamp cables and/or phantom preamp box, would that work the same as the peizos/preamps like fishman and L.R baggs uses?

http://www.till.com/articles/PreampCable/

http://www.till.com/articles/GuitarPreamp/index.html

-Jamie

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