need help for preamp

[jogina111]

Hi, I got a tda2003 power amp built from the datasheet schematic. I'm wondering what would make a good guitar preamp for it. Is it good to just stick a distortion/overdrive/booster  in front or it should be something complex? I need your suggestions maybe something that can drive a tonestack.

[GibsonGM]

Speaking in general terms, what a preamp does is condition your signal to the tone you like (EQ...tone stack(s), etc)  and possibly add distortion, if your PA is designed to be clean in sound output.   The pre also sets the level of the signal the PA sees for best quality.

A stompbox really IS a preamp, just one that's operating at a low level designed to work in front of a complete amp.

I would say, by all means TRY a pedal before it...try plugging directly into it, too, as long as you have a DC blocking cap at the input and there are no DC voltages present at the input (TEST THIS FOR SAFETY FIRST!!!!!!).   My ASSUMPTION that you're not using high voltages is just that - an ASSUMPTION.    A quick look at the data sheet shows you could have up to 40V at 4.5A present in there, which CAN be considered dangerous.   Just making the point....

if this is the schematic you used:  http://www.futurlec.com/Philips/TDA2003a.shtml   then the 10uf/3v cap is your input cap, and no DC should be on the input. 

Anyway, you probably will want to build an input buffer, tone controls, and then output buffer before feeding the signal to the TDA2003, would be my guess.  Maybe even some distortion, with pre and/or post EQ - sky's the limit!

[lidbod]

i have built the pedal and the only thing that works is the led i get no sound when the effect is on just getting sound when bypassed
i,ve used gaussmarkov layout

[jogina111]

Thanks, I've built a plexidrive clone as a preamp. Do i still need an output buffer? I've read that fets have low output Z so I've put it in front of the tda2003 amp and its loud, very pleasing.. Not quite sure on the impedance part...

[jogina111]

Thanks, I've built a plexidrive clone as a preamp. Do i still need an output buffer? I've read that fets have low output Z so I've put it in front of the tda2003 amp and its loud, very pleasing.. Not quite sure on the impedance part...

[Kesh]

a pre amp raises the signal from guitar or mic levels to line levels as well as possibly coloring the sound

OP, distortion and overdrive pedals tend to raise the signal to line level as well as dirtying up the sound. something like a tubescreamer is perfect for this. you can use the volume and tone controls on it as you would a guitar preamp.

[GibsonGM]

Thanks, I've built a plexidrive clone as a preamp. Do i still need an output buffer? I've read that fets have low output Z so I've put it in front of the tda2003 amp and its loud, very pleasing.. Not quite sure on the impedance part...

If I understand you right, you are getting a good sound?  Well, if there is an output buffer there, and it sounds good, then fine, keep it!   

You may not NEED an output buffer, but it can be good to have there.    It helps keep the following circuitry from 'loading down' what comes before it.

[mistahead]

My POV here (I want to be corrected here when sketchy folks lol) and output buffer between pre-amp/tonestack and the poweramp is "Good if its good, but then sometimes not..." - in this case the buffer isn't a line driver and there is no obvious reason you want another active stage to seperate (buffer?) the preamp from the power-amp, the power amp is quite happily taking the input so buffering is "not required".

Last week I realised how little stands between "buffer", "preamp", "boost", "gain stomp" etc... application not design is a VERY big factor.