#1
Well, I finished 2/3 of my piezo pickup insanity, I made the piezo pickup itself (which sounds quite nice, listen to the clip on my profile) That I run through what I call a "tone" box where I can kill the signal, low-pass filter it, or decrease the volume. But I believe the last thing to do is build a preamp.

Now I KNOW that Jim has a schematic, but I like the way tillman's sounds:
http://www.youtube.com/watch?v=RDeJXaxguqU&fmt=18

Its very clean and chimy, and I like that :3

So I will document the process here for all to see!

But first I have a few questions.... Firstly

Q1 J201 N-channel JFET
R1 3.0M ohm 1/4-watt 5% resistor
R2 2.2K ohm 1/4-watt 5% resistor
R3 6.8K ohm 1/4-watt 5% resistor
R4 51K ohm 1/4-watt 5% resistor
C1 4.7 uF electrolytic capacitor
C2 10 uF electrolytic or tantalum capacitor

Thats the parts list. Now the 3mohm is easy to find on mouser but the rest of them are under the "precision resistor" category, is there anything special about them or is it simply harder to make resistance in that scale?

What type of resistors should I be getting that sound the best for audio? I have heard that Carbon Comp resistors are the preferred material.

What is the best material for capacitors?

Where does the negative terminal of the battery go on the schematic?

And what is the difference between signal ground and ground in this case?

So far I have the following as far as parts list:

5"x2" black project box
9v battery
9v battery clip lead
1" x 1" perfboard
60/40 rosin cored solder
Mad 1337 soldering skills ( )

Anything else fairly obvious I missed?

THANKS! I will take high quality pictures as I go through all the steps for future noobs to learn :3
Pain is an illusion.
Schecter Hellraiser C-1 w/ Seymour Duncan JB/Jazz Combo
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#2
i wanna come back to this later, but quickly:
im not sure why you are having a hard time finding resistors, they are standard values.
carbon comp resistors are fine
poly film capacitors are usually fine, but people say orange drop can be better for audio
signal ground is the ground for your input signal, ground is the ground of your circuit. the two are usually the same, unless im missing something (they are the same on that diagram)

ill be back later to elaborate if you have any questions.
#3
Ok thanks. Just one more little question, where the heck does the battery negative go?
Pain is an illusion.
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#5
AND if I had a stereo jack on the input how do I make it so that the battery only is used when there is something plugged in?

On a stereo jack there is what, jack, tip, plate? So I'd wire it how? As far as I know the battery lead has to go across it somehow so it only connects when there's something inside the jack.
Pain is an illusion.
Schecter Hellraiser C-1 w/ Seymour Duncan JB/Jazz Combo
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#6
Carbon comp's are great for tube amps, not so much for a preamp.

Ideally you want metal film resistors. They are less noisy.

For caps, if they aren't above 1-2uf, use poly film or a good film cap (like orange drops or mallory). If it is above 2, use electrolytic. They are less noisy than tantalum.

As for the jack, the easiest way to do it is go

tip connector -> signal (of course)
Ring connector -> negative side of battery
Sleeve connector -> ground.

That way, unless you plug something in, the circuit isn't complete (assuming you don't connect the negative lead from the battery to anything else)
#8
Polyester (thats what poly means no?) caps are really expensive!

Are ceramic caps that bad?
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Last edited by sesstreets at Mar 18, 2009,
#10
$2.13 each?

In contrast, 10 carbon film resistors cost 40 cents lol
Pain is an illusion.
Schecter Hellraiser C-1 w/ Seymour Duncan JB/Jazz Combo
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#11
Where are you seeing this? Link please...

edit: here. 30 cents each.

http://www.smallbearelec.com/Categories.bok?category=Capacitors%2C+Panasonic+Low+Voltage+Poly+Film
Last edited by Invader Jim at Mar 18, 2009,
#14
I saw it but why are the mouser ones so damn expensive comparatively?
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Last edited by sesstreets at Mar 18, 2009,
#16
Mf instead of a uf rating? What am I looking for here?
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#18
Oh... well I did not know that. Thank you for that and smallbear... ****ing mouser...
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#20


Things I learnt in this build:
uF and mF both are micro-farad
Mouser can be overpriced.
Smallbear ftw


But all the values on small bear are like .47 mf when I'm looking for 4.7 mf... unless they're the same thing and I'm just retarded AGAIN.
Pain is an illusion.
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Last edited by sesstreets at Mar 18, 2009,
#22
Xicon capacitors are cheap on Mouser, i think i've found them for about .11 a piece.
#23


My choices looking good?
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#24
Bump?
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#26
Ordering... now...
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#27
Any recommendations for a good solid push button spdt?
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#28
The 4.7 and 10 uf caps are electrolytic. They have those on Smallbear also.

EDIT: I see I was beaten to it... About any SPST switch is fine.
Last edited by end_citizen at Mar 19, 2009,
#29
I was considering making it a foot pedal, but I think I'm not going to and make it just a small little box with a flip switch.

So if I wanted to make it "true bypass" do I simply wire a spdt like this:
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#30
Ok... so after doing some research, I now understand that using a spdt switch; you can't get true bypass...

I understand why though. Since the path of the signal still goes to the circuit even though it isn't selected.





Makes sense to me. Add this to the list of "**** I didn't know before building this" lol
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