JohnH Posted January 4, 2006 Report Share Posted January 4, 2006 Heres is a prototype design for an on-board booster and overdrive circuit. I have it built into a Strat and it is alot of fun to play with. It can range from a clean boost, through some smooth crunch to a farly high distortion. Take a look at the circuit, and the words that describe it. I'd be grateful for any comments and suggestions. Feel free to point out any electronic sins that I may have committed! http://people.smartchat.net.au/~l_jhewitt/...ueDriverMk2.gif http://people.smartchat.net.au/~l_jhewitt/...verMk2words.pdf John Quote Link to comment Share on other sites More sharing options...
psw Posted January 4, 2006 Report Share Posted January 4, 2006 (edited) That's great JohnH All those sounds from a little 3 way switch, fantastic. If you have had a look in at the sustainer thread, preamping has always been a question. The "thin driver" model that I've been promoting seems to work pretty well and the power amp of a LM386 seems to be adequate (though I'm sure there are newer chips). I'd alway's liked the idea of on board active electronics like this to which you could just add the power amp and driver to get a fully functional electronic sustainer plus, when not in sustain mode, effective active electronics as well... thanks a lot...you wouldn't happen to have a perfboard layout or anything kicking around, would you?? psw BTW...I've posted a link to this as I'm sure the sustainer guys would be interested! Edited January 4, 2006 by psw Quote Link to comment Share on other sites More sharing options...
JohnH Posted January 4, 2006 Author Report Share Posted January 4, 2006 you wouldn't happen to have a perfboard layout or anything kicking around, would you?? thanks psw. but I havnt got a board layout drawn up. I just tend to start at the left and solder components onto the board until I get to the right. Here is a picture of the board before adding the wires to connect the switches and other connections. Most of the eq parts and diodes were mounted on the switches and pot http://people.smartchat.net.au/~l_jhewitt/.../BlueDriver.jpg BTW. For a simple one FET buffer , the circuit around the second transistor is what I reckon is best, basically as Tillman with increased resistor values. John Quote Link to comment Share on other sites More sharing options...
lovekraft Posted January 4, 2006 Report Share Posted January 4, 2006 Nice implementation - what JFET did you use? Quote Link to comment Share on other sites More sharing options...
psw Posted January 4, 2006 Report Share Posted January 4, 2006 That's great John. My two transistor preamp is bigger than that...and it's on a printed circuit board. You could less than double that for the complete sustainer circuit by the way, just a little IC and a couple of capacitors. Tell me though, I can't see the diodes...is that the complete circuit or just the first stage...there doesn't seem to be enough components there. I know I've seen something like this...here's a link to a site that sells them but I'm not sure who makes them now...Preamp rotary controls...guess you can do that with SMT's. I remember that someone posted a better link somewhere early in the sustainer thread, but at 75 pages now, I wont be searching it out, same product though. Neat idea, but a lot cheaper and not much larger to DIY from your circuitry. Quote Link to comment Share on other sites More sharing options...
JohnH Posted January 4, 2006 Author Report Share Posted January 4, 2006 Lovecraft - the JFETS are 2N5457. I got the idea by mixing up a Tillman preamp with various circuits at http://www.runoffgroove.com/, then adding the idea of diodes where you can control the crunch using a pot. The best sounds, other than simple clean boost, are in position 2, setting an input level that just maxes out the first JFET stage short of clipping, then lets the second, which has no negative feedback, make a soft clipped overdrive. To that recipe I add a touch of diode compression with the tone/crunch control,but not too much. This adds a sort of breathy sound in the background - kind of smoky. psw - The circuit board is mainly the gain stage, and the other parts are mounted on the pot and the switch, which is a 4P3T rotary. These and the wiring are bigger than the main circuit!. This is a first prototype, I got the main circuit going first, then experimented with the eq, level settings and diode arrangements for the three switch settings. Next time, more will go on the board. Further development will be to tune position 3 - it needs some better shaping to make it less raw. Also, I think the low bass may be better if it is curtailed slightly. at the moment it has a very low cutoff frequency and 'burbles' a bit on heavy bass input psw - That circuit you posted I believe is also sold by gfs see : http://store.guitarfetish.com/activepreamps.html Its neat - but its more fun to brew your own. John Quote Link to comment Share on other sites More sharing options...
lovekraft Posted January 4, 2006 Report Share Posted January 4, 2006 Excellent - I just happen to have a sleeve of 2N5457s around here somewhere, so this one goes on the list! Thanks!! Quote Link to comment Share on other sites More sharing options...
JohnH Posted January 6, 2006 Author Report Share Posted January 6, 2006 Excellent - I just happen to have a sleeve of 2N5457s around here somewhere, so this one goes on the list! Thanks!! ← Thanks Lovecraft - ill be interested in any feedback. Anyone else - any off the cuff suggestions from electronics experts to fine tune it? Quote Link to comment Share on other sites More sharing options...
oatmeal Posted January 16, 2006 Report Share Posted January 16, 2006 (edited) I am by no means an electronic guru, so this may be a stupid request ( ie: all guitar resistor voltages, cap types... are all the same) . I would love to see a detailed (and idiot proof) parts list for this. Could you post one? Another thing, is the pot notched so you can tell where one effect stops and the next one starts. thanx. Edited January 16, 2006 by oatmeal Quote Link to comment Share on other sites More sharing options...
JohnH Posted January 16, 2006 Author Report Share Posted January 16, 2006 I am by no means an electronic guru, so this may be a stupid request ( ie: all guitar resistor voltages, cap types... are all the same) . I would love to see a detailed (and idiot proof) parts list for this. Could you post one? Another thing, is the pot notched so you can tell where one effect stops and the next one starts. thanx. oatmeal. thanks for your interest. The tone/crunch pot was a 100k dual gang with a centre detent. It would in fact be easier to use a seperate controls for tone and crunch, but I was trying to reduce the number of knobs for this built-in version. The resistors are all standard 1/4w 5%, but any type will do, there are no signifiacnt power dissipation requirements. For caps, I used polyester, but only because that was what was available. The FETS were 2N5457. I could do a parts list, but all the values are on the schematic diagram, The circuit as posted is built into an old Hondo Strat, which I have reqired to give series/parallel and phase options The circuit is a propotype, and I am currently working on a version with even lower current consumption (about 50 microamps instead of 250), with a better bass response, by reducing one of the source resistor bypass capacitors. I posted it for comment, in case anyone else might try it. Ill add my next version when I have it, and do a parts list for that. John Quote Link to comment Share on other sites More sharing options...
ebun Posted January 16, 2006 Report Share Posted January 16, 2006 wow this is a great idea Quote Link to comment Share on other sites More sharing options...
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