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Author Topic: pre-amp suggestions  (Read 4243 times)

troublerat

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pre-amp suggestions
« on: June 28, 2009, 12:55:55 PM »
This is one thing that I may be able to give some suggestions on. If you need 9+9- go to http://www.geofex.com/ the circuit sweeping section and look for 9+9- from an 9 volt supply. Go to http://runoffgroove.com/doubled.html and use the jiggle side for an clean to overdriven fenderish type sound. Then theres my favorite  http://www.muzique.com/schem/projects.htm  the mosboost can be built from radio shack parts and gives an excellent fat clean boost [ you can use bs170, irf511, 2n7000]  Heres one chain to try it involves an boss comp. cs-3 with wampcats mods www.wamplerpedals.com   guitar/cs-3/mosboost/chip amp. I am probably going with the mosboost[one knob booster] [and the rog double d , just the jiggle side.and put the mos on an dpdt to switch it in and out in front of the jiggle. I am seriously pondering on the classic fuzz face circuit, I built one from the schem. at geofex with no variance from the schematic was very pleased with sound. Go to geofex at the top of the page "The tech of series".  Theres just to many good workable circuits  to bang my head and try to reinvent the wheel. All the above work well. I have use them in front of several amps. The hardest thing you have to do is deciding what kind of tone you want. I prefer the one or to knob types and try to keep the face of the amp from getting to cluttered with knobs.

edvard

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Re: pre-amp suggestions
« Reply #1 on: April 22, 2021, 01:15:22 AM »
This is one thing that I may be able to give some suggestions on. If you need 9+9- go to http://www.geofex.com/ the circuit sweeping section and look for 9+9- from an 9 volt supply. Go to http://runoffgroove.com/doubled.html and use the jiggle side for an clean to overdriven fenderish type sound. Then theres my favorite  http://www.muzique.com/schem/projects.htm  the mosboost can be built from radio shack parts and gives an excellent fat clean boost [ you can use bs170, irf511, 2n7000]  Heres one chain to try it involves an boss comp. cs-3 with wampcats mods www.wamplerpedals.com   guitar/cs-3/mosboost/chip amp. I am probably going with the mosboost[one knob booster] [and the rog double d , just the jiggle side.and put the mos on an dpdt to switch it in and out in front of the jiggle. I am seriously pondering on the classic fuzz face circuit, I built one from the schem. at geofex with no variance from the schematic was very pleased with sound. Go to geofex at the top of the page "The tech of series".  Theres just to many good workable circuits  to bang my head and try to reinvent the wheel. All the above work well. I have use them in front of several amps. The hardest thing you have to do is deciding what kind of tone you want. I prefer the one or to knob types and try to keep the face of the amp from getting to cluttered with knobs.

I love MOSFET preamps!  Here's two more for your grab bag:
- Use a CD4011 2-input NAND or CD4001 2-input NOR (unbuffered versions, of course) instead of a CD4049 for the "jiggle"; tie the two inputs of each gate together and wire each like an inverter. The internal structure shifts the bias point for asymmetrical clipping that sounds pretty darn good, and you don't have to worry about "throwing away" all those unused inverters in a 4049.
- Find a complement for the 2N7000 (BS250 probably) and wire the two together like the innards of an inverter.  It actually works, and again you don't have to worry about all those unused inverters, just build as many as you need!
Bonus: Same inverter-from-two-MOSFETs idea, only add another 2N7000 in parallel with the other one so you have a BS250 on top of two 2N7000s in parallel.  That shifts the bias point for asymmetrical clipping like the NAND/NOR gate.

Loudthud

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Re: pre-amp suggestions
« Reply #2 on: April 22, 2021, 05:33:27 AM »
You can connect the MOSFETs in a CD4007U to be NAND and NOR gates. The 3 input NOR with a gain of about 2 is the most like a tube. Run the gates on 8 to 10V.
« Last Edit: April 22, 2021, 05:39:35 AM by Loudthud »

phatt

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Re: pre-amp suggestions
« Reply #3 on: April 24, 2021, 04:14:47 AM »
Thanks , interesting. Q Will a 4007UBE work in this application?
Phil.

Loudthud

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Re: pre-amp suggestions
« Reply #4 on: April 24, 2021, 07:44:16 AM »

phatt

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Re: pre-amp suggestions
« Reply #5 on: April 27, 2021, 02:00:16 AM »
Ta mate ,,Yep I found some of your circuits on MEF and when time permits,,, one day :(
I notice your circuit also uses a CD4069UB which I can find locally but I'm a little lost as to how the pins are all wired up. ???
Anyway no hurry as my Bread board is full up with another project at the mo and once I've resolved a couple of small issues on that circuit I'll try it out. :tu:
I'm not looking for the metal Shred grind ,,more like a sweet smooth OD if that is possible.

My experience is limited but I do recall using a small Laney HC15R (I think) which has something similar to get the OD effect. It sounded ok but like a lot of Amps as well as a lot of those all in one pedal boards there is just way too much bandwidth giving that brittle edge which is just horrible. (to my ears at least).
I'm really happy with what I've designed and achieved over many years and it does a darn fine job,, but always interested in other ideas.
Phil.

Loudthud

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Re: pre-amp suggestions
« Reply #6 on: April 27, 2021, 06:03:57 AM »
4069s can definitely sound buzzy. There are conflicting characteristics that you need to balance. As the rail Voltage goes down, the gain goes up and the clipping gets sharper, less rounding at the top and bottom of the waveform. Also, bandwidth goes down as the Voltage goes down. Loading is one way to control bandwidth. A cap to ground on the output or from input to output should do the job.

The preamp I posted over at MEF really doesn't sound very good. I've got something I want to try but just haven't had the time to get it done. The layout sketch I did is difficult to follow, I used mostly 1/8W axial resistors on 0.1 inch centers. I call it hairpin lead dress like those old transistor portable radios from the 60's.