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Preamp or Compressor


 
6/3/1999 6:22 PM
Lee MacMillan
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Preamp or Compressor
I'd like to put something at the front of my effects chain (overdrive, chorus, flanger, delay) to boost the guitar signal. I figure it should be either a preamp or a compressor. I've used the latter a couple times and was never too fond of the sound. Can your typical Boss or DOD compressor be used as a preamp by just setting the attack and sustain controls to zero? Any recommendations for a preamp if I decide to go that way? I built the Craig Anderton version and it was OK but needs 2 batteries so the case needs to be a little big. (Plus I was making some very minor changes to it recently and now that damn thing doesn't work. Can't find the problem to save my life.)  
 
Thanks.
 
6/3/1999 9:35 PM
R.G.
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Lee, I'd just use a single JFET gain stage after the guitar, maybe IN the guitar. It'll give you somewhere between 4x and 20x gain on the basic guitar, use only one battery, and be a great cable buffer.  
 
There was one that floated through alt.guitar in the old pre-web internet days. I'll see if I can find it.  
 
You might also want to look at the Dallas Rangemaster clone on GEO. This has a nice lift, you can make it a flat, not treble boosting, gain stage by changing one cap, and most people love the sound.
 
6/4/1999 6:48 AM
Lee MacMillan
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Sounds like what I'm looking for. If you can find it, that would be great (and a source for the JFET too!).  
 
Tried to pull up the Rangemaster stuff. The two pics came up find but I got a blank screen from the "how to build..." link.
 
6/4/1999 8:08 AM
R.G.
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My long-limping ISP was recently acquired by another company. In talking to the new sys admins, I find that they wonder how eden ever limped along at all.  
 
Although they are making a lot of changes, they still have not completed moving the site to a new server farm. I believe the problem with the PDF file stems from the odd setup on the old servers, and they do too.  
 
Try downloading the pdf file and browsing it with acrobat or ghostview locally. That has worked for everyone that's tried it.
 
6/5/1999 9:57 AM
Lee MacMillan
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Got the manual. I would use a .15uf input cap instead of .005uf to make the boost uniform across the guitar audio range? Do the pulldown resistors go from the hot lugs of both jacks to ground? I have a silicon fuzzface transistor with a gain of about 65. Would that work OK? I only want a gain of 2-5 or so.
 
6/5/1999 6:40 PM
R.G.
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quote:
"I would use a .15uf input cap instead of .005uf to make the boost uniform across the guitar audio range?"
 
Yep.  
quote:
"Do the pulldown resistors go from the hot lugs of both jacks to ground?"
 
I always put pulldowns on the effect board itself, outside the coupling caps. In this case, yes, you could put them on the jacks, but many effects disconnect the effect from the jacks (that ol' devil true bypass!) so pulldowns on the jacks don't help effect-induced pops at all. I just print spaces for pulldowns on all my effect boards for this reason.  
quote:
" I have a silicon fuzzface transistor with a gain of about 65. Would that work OK?"
 
Probably not, at least not for how you plan to use it. The Austin Treble Blaster/Rangemaster depends on the shutoff in gain of germanium devices near cutoff; silicon hits cutoff more abruptly than germanium. What you might do is to use the silicon and bias it away from cutoff a bit - put the collector at maybe 6V instead of 7 by diddling the resistors I note. As shown, the gain is higher than 2-5, so you might also split the emitter resistor into about a 2.2K and a 2.7K and bypass the 2.7K to ground with a big electo cap. That would run the gain down and linearize it more.  
 
In any case, Frank Clarke found the JFET buffer I was alluding to in a Harmony Central archive. Look at that as well.
 
6/5/1999 2:25 PM
Frank Clarke
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Hi Folks,  
This may be the document R.G. was referring to, I have used the FET circuit successfully, gain depends on the individual FET obviously.  
Frank Clarke.  
 
http://www.harmony-central.com/Guitar/Faqs/faq/faq.buildPreamp.txt
 
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