Dual Op-amp for Pre-amp

[Hank Grizzly]

Hey,
I recently designed a pre-amp for my harmonica, using a dual op amp chip at the center. I foolishly thought that choosing a chip and making a power supply (from a 9v battery) would be childs play.

After looking it up online however, I see that there is allot more to it than a couple of 1k resistors and any old chip that fits. But because I am a broke, jobless student, I cannot indulge in such decadence as "trial and error."

Anyone know what to do here?

 

[Left_Hand_Strat]

Re: Dual Op-amp for Pre-amp

What Op amp do you have? that the starting point.

 

[Hank Grizzly]

Re: Dual Op-amp for Pre-amp

I don't yet, I'm open to any suggestions.

 

[Left_Hand_Strat]

Re: Dual Op-amp for Pre-amp

Ok, go for something cheap and available, and I know you don't have lots of money but if you buy two op amps you have a spare just in case you balls one up.

It also depends what wattage you are looking at, this can alter what op amp you use and the nominal voltage input rating for it. basically we need some more details from yourself about your design and what you had in mind

 

[Rich_S]

Re: Dual Op-amp for Pre-amp

Start browsing through the popular DIY effects sites. There are dozens of op-amp based preamp circuits out there, ask questions of FX forums to find out what sort gives the kind of sound you want. Are you looking to build something with just a volume knob? Volume and tone? 2-band EQ? Overdrive?

Freestompboxes.org/ has tons of schematics for all sorts of pedals. For many of them, people have already develpoed perfboard layouts, which is probably the cheapest way to build a one-off pedal, provided it's not to complicated.

However, you are going to find that it IS more involved than just an opamp and a few resistors. You're going to need capacitors, pots, knobs, a box, jacks. I generally find that packaging the thing up costs more than the circuit. Of course, if you're happy building it into a Altoids tin, then you'll save on the enclosure.

Since you're using this as a harp preamp, you may be able save yourself the most expensive component - the 3PDT switch. As long as you can leave it on all the time, you don't need the stomp switch and will save about $10 right there.

Also check in at the "Burnt Fingers" room at the TDPRI (Telecaster) forum. Lots of good guys there, doing all sorts of boxes from Altoids preamps to fancy boutique-quality stuff.

 

[Hank Grizzly]

Re: Dual Op-amp for Pre-amp

The design is for volume, gain, and a 3 band eq. My electronics teacher has also kindly let me use the colleges equipment to make a PCB for it (yet to be made, so I can change that).
With regard to the voltage, I still haven't chosen what microphone to use. I was just going to grab one out of a headset, maybe get a piezo transducer from rapid.

 

[DankStar]

Re: Dual Op-amp for Pre-amp

I'd use something off runoffgroove's site - they have a lot of DIY opamp pedals and tiny amps with perfboard diagrams.