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Semi Acoustic Guitar Processor

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Nigel Goodwin

Super Moderator
Most Helpful Member
Buy one, such devices are cheap these days as they use DSP's - doing one in hardware is going to be FAR more complicated and expensive.

What sort of 'processing' do you want anyway?.
 

hemanthemma

New Member
Thanks Again!
I wanted an electronic system that could actually convert the piezo input to an electronic output.I tried various circuits(Guitar Fuzz etc.) but nothing worked.
 

gabeNC

Member
Sounds like you just need a basic preamp. I have a fishman matrix installed on my Taylor which has a piezo p/u under the saddle.

There is a wide variety of price and performance. I've even seen cheap $150 acoustic guitars with internal preamps and tone controls.... and yes they do sound like crap.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
If it's a bare piezo pickup, you need a preamp (as gabeNC said), a simple FET, two resistors, two capacitors, and a 9V battaery are all that's needed. However, it may be useful to add some gain as well, depending how low the pickup's output is.

What do you normally plug it in to?.
 

hemanthemma

New Member
I plug it into a small gain circuit using transistors but to no avail. I just got the guitar so I have nothing that I purchased for this purpose.
 

hemanthemma

New Member
Well, it does not work.I made the circuit on a PCB and then TRIED to connect the guitar cable to it but just like you guessed nothing came off it.
Thanks Again!
 

Mr RB

Well-Known Member
You can use any decent mic preamp. If you have an old "tape deck" you know the ones that were a component in 70's and 80's hifi stacks and have 2 VU meters etc. They usually have quite good mic preamps built in and a "Mic" jack on the front and line outs on the back.

Otherwise if your amp has a mic input you can use that.
 

hemanthemma

New Member
Thanks RB
I am currently trying to build a JFET based preamp for the guitar.I have an option of using an Op-amp for the same purpose but I am sticking to the JFET one.

Thanks Again
 

Nigel Goodwin

Super Moderator
Most Helpful Member
You can use any decent mic preamp. If you have an old "tape deck" you know the ones that were a component in 70's and 80's hifi stacks and have 2 VU meters etc. They usually have quite good mic preamps built in and a "Mic" jack on the front and line outs on the back.

Otherwise if your amp has a mic input you can use that.
You certainly can't, mike inputs like that are low impedance - a piezo needs a VERY high impedance, 2 megs is probably a minimum.
 

hemanthemma

New Member
I'll post the image of my guitar so that you can tell me what to do.
It does not have an inbuilt pickup or any other feature.Just a guitar cable that can connected to an amplifier.
 

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Mr RB

Well-Known Member
You certainly can't, mike inputs like that are low impedance - a piezo needs a VERY high impedance, 2 megs is probably a minimum.
Interesting. I have a number of piezo and dynamic mics and never had any troubles using my old Sanyo tape deck mic amp. It must have been designed for both impedance types (ie all mic types).

I've never had a loading problem with any decent mic amp and ceramic pickups.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Interesting. I have a number of piezo and dynamic mics and never had any troubles using my old Sanyo tape deck mic amp. It must have been designed for both impedance types (ie all mic types).

I've never had a loading problem with any decent mic amp and ceramic pickups.
Presumably the mikes had preamps built-in?, giving a low impedance output.

Mike inputs on tape decks etc. are very low impedance.

Try doing the maths on the attenuation, a 2 meg pickup output feeding a 4.7K (600 ohm) input. You also get a massive loss of bass as well as a massive loss of gain.
 

hemanthemma

New Member
I am sorry, but is there any other way to design a circuit for this guitar as it has no inbuilt pickups? I already am working on the preamp as Nigel had advised me to.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
I am sorry, but is there any other way to design a circuit for this guitar as it has no inbuilt pickups? I already am working on the preamp as Nigel had advised me to.
We still don't know what you've actually got, or if it even works - have you tried plugging it directly into a normal guitar amp?, if so what did you get?.
 
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