I want to build some sort of preamp to go from guitar level signal to line in level. Right now to run my lm3886 amp I need to plug into my practice amp and line out from it. Any sort of booster circuit that would bring it up to line level easily?

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Just a simple opamp is all you need, but you need one with a high impedance input to match a passive guitar (1Mohm or so). Using non-inverting format is best, you don't need much gain, 5 or 10 times should be plenty.

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Any suggested opamps I should look at, or schematics?

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So I'm thinking about using the TL072 preamp my dean markley uses.

http://www.deanmarkley.com/Info/Lega...tics/D1515.pdf

Can anyone help me get all the values, it seems some aren't listed. Also, whats the difference between a A10k pot and a B10k pot? Is the B one linear? And if so, why would the mid and bass EQ be alpha (log) and the treble be linear?

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The TL072 would be fine.

Again, that looks fine - notice that the first opamp gives a gain of about 5?, which is what I suggested. If all you want is a basic preamp, the first opamp part is all you need.

Which parts are you having problems with?, it looks pretty clear to me?.

It looks to me like B pots are log (as the volume is a B one). The reason the tone control pots are different types is because it's the strange 'Fender' type guitar tone control system - with baxendall tone controls the pots would be all the same, all linear for active, and all log for passive.

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PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Is there any other opamp that would be easier to work with or something? Or just better in general?

And I think there was a cap I couldn't figure out, but now I don't know which one lol.

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This shows another guitar pre-amplifier design:

http://sound.westhost.com/project27.htm

The TL072 is pretty decent, I often use it. I have used the NE5532 recently too, and its noise performance seems excellent to me, though its not always a suitable alternative (internal diodes and needs an input resistor I believe). Anyhow, breadboard it and just try some you have, a 741 and other cheap/old ones will probably be too noisy.

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Angry!? I'm absolutely electrolytic!

Will have to make do with myspace now I guess...

 

How could it be easier?, it's an 8 pin opamp, it's easy to use - there's no opamps easier than that.

I didn't notice anything, it all looked very straightforward.

As for noisy opamps, it's not at all a problem, MANY guitar amps have used them in the front end, as have microphone inputs, perfectly happily.

In fact I changed a couple of 741's in the front end of a mixer/amp the other year before a gig (to keep Audioguru happy!) - I couldn't tell any difference, and that was using 600 ohm mike inputs.

NOT that I suggest you use a 741, you can get far better opamps for less money, the TL072 series are FAR better chips.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Cool. I think I will do the dean markley preamp. It seems the easiest and best solution. Besides that, I know I like the sound, because I already have one :-)

**edit**
The caps I didn't know about are listed as 333M and 222M, whats that mean?

**edit again**
Think its perfable? I want to do it on perfboard since I don't make PCBs.

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A cap marked "333M" is 33,000pF which is also 33nF or 0.033uF. "M" is a tolerance of 20% (K is 10% and J is 5%).
"222M" is 22nF or 0.022uF at 20%.

Use Veroboard or stripboard instead of plain perfboard since half the wiring is already done for you on the copper strips.

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I'm thinking of doing a PCB for it since it seems several other people are interested in using this as a preamp for their chipamps.

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