#1
I've been looking at diagrams of a Mesa emulator and a JCM-800 emulator and was trying to figure out what kind of capacitors I would use in these builds. I've heard all about the different kinds of caps, but I am just looking for some second opinions on what caps would sound best as well.

In addition to this, I was wondering what VR1 on the diagram represented. Thanks guys.

#2
I've built a number of these pedals and I just use mylar caps. Like these:

http://www.futurlec.com/CapMylar.shtml

The VRs are Variable Resistors. You use them to bias the FETs. Its easy. Technically you are supposed to tune each FET to 4.5 volts (if you are using a stable 9v power supply). Sounds confusing but its super simple. Just wire it all up and twist the VRs until you can hear your guitar coming through. Then you can go through each one until it sounds just the way you want. Thats tuning "by ear".

One thing that is a bit more complex about this pedal is the pot wiring. I usually use this layout:

http://gaussmarkov.net/wordpress/circuits/dr-boogey/
Last edited by samhell at Aug 15, 2011,
#3
C20 and C21 would be electrolytics as they have a higher capacitance. Other than that, the rest could be anything. Certain types are better are better suited to certain circuits (well, parts of circuits).

The best for audio path capacitors are Polypropylene and Metal Film. No doubt they cost more. Ceramic caps are best avoided for the audio path.

I'd have a look through here: http://www.banzaimusic.com/Film-Foil/ even if you don't buy from there.
Guitars & Gear:
Parker Nitefly M
Sumer Metal Driver
Ibanez RGD2120Z
AMT SS-11B
Two Notes Torpedo CAB
#4
Ok, one more question then. Is this preamp/pedal going to sound good once it is built? For instance, is the gain unusable or is there a nasty treble spike or other nasty things like that? Or does it have a decent sound?

And thanks for all your help.
#5
Quote by Fuzz93
Ok, one more question then. Is this preamp/pedal going to sound good once it is built? For instance, is the gain unusable or is there a nasty treble spike or other nasty things like that? Or does it have a decent sound?

And thanks for all your help.



Check it out on youtube, theres a ton of vids. People have their own names for it (like dual resistafier, etc). I've built a few for people because when they hear mine they love it. By default its just a dual rectifier type of sound but theres some easy mods to give it more channels and some vintage tones. All that circuit is is one of the preamp channels of the real dual rectifier but using FETs instead of tubes.
#6
not to mention some of those characteristics can be attributed to pups and amps. The circuit just uses Triode to J-FET conversion, does it not?
Guitars & Gear:
Parker Nitefly M
Sumer Metal Driver
Ibanez RGD2120Z
AMT SS-11B
Two Notes Torpedo CAB
#8
Quote by Emperor's Child
not to mention some of those characteristics can be attributed to pups and amps. The circuit just uses Triode to J-FET conversion, does it not?


Yep, pretty much.

to the OP, you don't have to use J201's for your FETs. You can swap around any other FETs with the and just be sure to bias them with your VRs. If you look through other forums you can find popular combos.
Last edited by samhell at Aug 17, 2011,
#9
^ any other JFETs (not Mosfets)
Guitars & Gear:
Parker Nitefly M
Sumer Metal Driver
Ibanez RGD2120Z
AMT SS-11B
Two Notes Torpedo CAB