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low noise pre-amp required

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flexagon

New Member
hi all, i've just made my first electronics project; an audio optical compressor, i'm pleased with the sound from this, but i have to put my guitar through a mixer and push up the gain before it goes into the compressor as it won't drive the circuit.
can anyone suggest a simple but quality preamp circuit i can put on the input, i'd like it to be as low noise as possible. i have a few spare lt1028 opamps i could use?
cheers
 

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flexagon

New Member
i have googled & found so many variations of pre-amps that i'm more confused as to what to go for.

any help much appreciated.
 

Sceadwian

Banned
Try searching the forum here, but use Google's advanced search and limit the domain to electro-tech-online.com search for low noise pre-amp, your post will show up but I'm pretty sure Audioguru has posted schematics for some simple low noise pre-amps before.
 

flexagon

New Member
yeh, thanks for that, 500 results for audio pre-amp on this forum, many, many more from my old friend google, all combine to confuse the noob!
i pulled this from the lt1028 data sheet (attached). which one would suit my requirements best do you reckon & why? i'd like to learn a little as i go along if anyone fancies sharing a bit of knowledge. cheers
 

audioguru

Well-Known Member
Most Helpful Member
The LT1028 opamp produces extremely low noise when the source impedance is very low, the example has only 7.5 ohms. Its input resistance is also very low.
It is noisy when its source resistance is high.

A guitar pickup should feed a high impedance of about 3M ohms so an LT1028 opamp should not be used.

An OPA134 FET-input opamp produces very low noise when its source resistance is high. It would make an excellent guitar pickup preamp.
 
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