Where shall I place the potentiometer?

[Axelvilhelm]

This might seem like a dumb question, but I'm a total newb in electronics. I built this preamp to amplify the signal from a small speaker that i use as a pick-up element in a DIY spring reverb. The preamp works fine but i would like to be able to adjust the gain, because often the level of the output signal is too high, so the signal distorts in the line input. So, i shuold probably add a potentiometer to the circuit, but exactly where in the circuit should i put it? Here are the schematics: http://www.eleccircuit.com/wp-content/uploads/2010/09/A-microphone-from-the-speaker.jpg

Thanks in advance!

 

[Zen Mod]

at output

 

[Axelvilhelm]

Thanks for answering! Then, another question: What value should the pot be?

 

[Arty]

good question, if i was you i would try 50K linear one.
but that's just me, and i em not expert.
I prefer linear pots over log.

 

[Zen Mod]

question :

line inputs usually have pots right after selector ;

how's the case that this one is clipping line stage that way ?

give us more data , something is fishy there

 

[knutn]

Too high gain?

If the signal distorts in the line input, then your gain is to high. You have made yourself a common base amplifier with high gain; so you will have to reduce the collector resistance, i.e. place a pot in parallel with R2 (you will need a capacitor too).

 

[Axelvilhelm]

Yes, that's just the problem, as I see it, too much gain. It's not a problem if I connect it to a line input with a pot following it. But, if I, for instance, connect it to a line input of a A/D audio interface with no input level pot, then clipping will occur.

So, a pot parallel with R2, right? And what about the cap? Should that also be parallel to R2 and what about it's capacitance and should it be a polarized one? Sorry all this question, but this is all really new to me...

 

[knutn]

My first thought was this (C= 1000u ? and Pot=5k ?)

 

[Zen Mod]

if you need less sensitivity from circuit - do like this

if you need to maintain sensitivity - place pot on output

 

[Axelvilhelm]

I tried both, and realised that placing a pot in the circuit resulted in noise in all potentiometer positions but full throttle, so I'll just go without the pot. Maybe the circuit is generally sensitive to noise, or perhaps the power supply is poorly filtered. Anyway, I think I'll be fine just adjusting the volume before the pick-up. Thanks to everyone for helping, my deepest appreciation!!