Mini-Preamp Search

Replies to This Discussion

Permalink Reply by Nick on December 15, 2008 at 6:09pm

this was my first amp. it not very expensive or hard to build. it doesn't have any nobs, but you can add some on if you want. it has a good overdrive sound.
http://www.cigarboxguitars.com/workshops/CigarBoxAmp.php
-Nick

Permalink Reply by Whiskey Bob Taylor on December 15, 2008 at 7:19pm

Thanks. This is a good simple and cheap amplifier circuit. It's hard to beat op-amps for audio applications, but I'm actually looking for a preamp that would go in between the CBG and an amp or PA to give it a more reliable sound. When I play my CBGs out, I'm usually at the mercy of the house PA and most sound guys/open mic emcees don't want to get too adventurous when they see the CBG.

This could probably be used as a preamp with a minimum of modifications. Would the output of the amp still be considered a low-level signal or would it be line level? Anyhow I'll try it out. My son's been bugging me for a homemade amp anyway.
Thanks.

Anybody else have any ideas for a compact preamp?

Permalink Reply by Nick on December 15, 2008 at 10:41pm

there are some good schematics for amps and preamps on http://runoffgroove.com/articles.html like the "Ruby" and the "little gem amp"

My family is the other way around. i am the son and i build amps and effects, and my parents don't really want me building electrical circuits because they know nothing about electrical stuff, and they're afraid of me being electricuted.

Permalink Reply by BrianQ. on December 16, 2008 at 3:29am

Hey Bob, try this, it's super simple and it's small enuff
to fit into anything you wanna put it into.

Attachments:

• SimplePreAmp.gif, 16 KB

Permalink Reply by Whiskey Bob Taylor on December 17, 2008 at 10:08am

Pat Cook shot me this comment to my page after trying to post it here. The picture in the link actually shows the curcuit mounted in an Altoids tin. Here is his comment:

Howdy Bob,
I tried to post this in the "It goes to 11" group, but it won't let me join for some reason. So here is a link to a piezo preamp/buffer in an altoid box.
http://www.scotthelmke.com/Mint-box-buffer.html
Have a good one, Pat.

Permalink Reply by Mark Vickroid on January 2, 2009 at 11:48am

I posted detailed instructions for a < $10 preamp I called a rat-shack preamp at the old place. someone even made a stripboard layout. lemmie see if I can find it real quick..

Permalink Reply by Mark Vickroid on January 2, 2009 at 11:50am

http://launch.groups.yahoo.com/group/cigarboxguitars/message/55275

there's the main msg. it's got pics and everything

Parts list [everything avaliable at rat shack]
> 2N3819 FET transistor [the round thing in the middle]
> a FET has source gate and drain. Look it up, it's important you get
> those connections right.
> 56k 1/4 watt resistor
> 10meg 1/4 watt resistor
> 22k 1/4 watt resistor
> 10uf capacitor, polar [electrolytic]
> .1uf capacitor, nonpolar [ceramic]
> 9volt battery and clip
> 1/4" mono jack
>
> wire the red wire from your piezo to the gate [middle] of the FET
> wire the black wire to a common ground point
> wire the 10meg resistor from the gate to ground
> wire the 22k resistor and the 10uf capacitor together in paralell as
> shown. Wire this assembly so the + side of the capacitor is wired to
> the source [look at the diagram on the transistor package to determine
> which is source] and the other side is wired to the common ground.
> Wire the red side of the 9v clip to the 56k resistor and the other
> side of the resistor to the drain
> wire the black wire of the 9v clip to the ground point.
> wire one side of the .1uf capacitor to the drain, and the other side
> to the tip of your output jack. Wire the ring to the common ground.
>
> This circuit provides unity gain, with no controls, but as I said, its
> as simple as it gets and it will really improve the sound of your
> piezo pickups.
>
> You MUST use the parts and values specified, as the circuit was
> optimized to use those components with that FET.
>
> good luck, let me know if you have any questions
>

Permalink Reply by Dennis Menard on January 2, 2009 at 3:47pm

Check my website, www.fuzzboxworld.com for a pre-amp kit specifically designed for CBG's and will fit in an Altoids tin. Don't feel like building one yourself, email me and make me an offer and I might just build it for you!

Permalink Reply by BrianQ. on January 3, 2009 at 2:12am

Radio shack doesn't carry 2n3819 transistors anymore, they only carry MPF102 jfet transistors.
Mark Vickroid said:

http://launch.groups.yahoo.com/group/cigarboxguitars/message/55275

there's the main msg. it's got pics and everything

Parts list [everything avaliable at rat shack]
> 2N3819 FET transistor [the round thing in the middle]
> a FET has source gate and drain. Look it up, it's important you get
> those connections right.
> 56k 1/4 watt resistor
> 10meg 1/4 watt resistor
> 22k 1/4 watt resistor
> 10uf capacitor, polar [electrolytic]
> .1uf capacitor, nonpolar [ceramic]
> 9volt battery and clip
> 1/4" mono jack
>
> wire the red wire from your piezo to the gate [middle] of the FET
> wire the black wire to a common ground point
> wire the 10meg resistor from the gate to ground
> wire the 22k resistor and the 10uf capacitor together in paralell as
> shown. Wire this assembly so the + side of the capacitor is wired to
> the source [look at the diagram on the transistor package to determine
> which is source] and the other side is wired to the common ground.
> Wire the red side of the 9v clip to the 56k resistor and the other
> side of the resistor to the drain
> wire the black wire of the 9v clip to the ground point.
> wire one side of the .1uf capacitor to the drain, and the other side
> to the tip of your output jack. Wire the ring to the common ground.
>
> This circuit provides unity gain, with no controls, but as I said, its
> as simple as it gets and it will really improve the sound of your
> piezo pickups.
>
> You MUST use the parts and values specified, as the circuit was
> optimized to use those components with that FET.
>
> good luck, let me know if you have any questions
>

Permalink Reply by Mark Vickroid on January 4, 2009 at 5:31pm

Well, I guess I'll have to tweak the resistors a little for the MPF102 then..
Or one could use McMaster Carr to order the proper transistor..
Or course, then it wouldn't be RatShack friendly anymore, would it?

Permalink Reply by BrianQ. on January 6, 2009 at 12:13am

I think your preamp and my preamp are the same, just the transistor is different?
Mark Vickroid said:

Well, I guess I'll have to tweak the resistors a little for the MPF102 then..
Or one could use McMaster Carr to order the proper transistor..
Or course, then it wouldn't be RatShack friendly anymore, would it?