I need to make a X5 preamp to boost a signal after some volume and balance controls and send it off at a nice low impedance to a power amp. It needs to be happy running off a single 12 volt supply.
I thought google or ebay would throw up something but so far I have not had any success.
Does anyone have a circuit to share, it need not be fancy, transistor or IC, inverting or non inverting will do. Variable gain would also be fine as long as it included around 5 times in its range.
I can make stuff but not confident enough to start from scratch.
Cheers, Tim
I thought google or ebay would throw up something but so far I have not had any success.
Does anyone have a circuit to share, it need not be fancy, transistor or IC, inverting or non inverting will do. Variable gain would also be fine as long as it included around 5 times in its range.
I can make stuff but not confident enough to start from scratch.
Cheers, Tim
Something like this would work. Change C3 to 100u and reduce R4 to 2K4 for 5x gain.
However note that if your input signal is more than 700mV p-p it will clip due to the limited swing of the opamp (about +/-4v with the NE5532 shown on 12V supplies). To get more headroom you would need a higher supply.
You should be able to do this on stripboard easily.
edit: Oh, if you like bass (this for a car amp?) then make C2 at least 33u.
However note that if your input signal is more than 700mV p-p it will clip due to the limited swing of the opamp (about +/-4v with the NE5532 shown on 12V supplies). To get more headroom you would need a higher supply.
You should be able to do this on stripboard easily.
edit: Oh, if you like bass (this for a car amp?) then make C2 at least 33u.
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It will make a little more than 8Vp-p on the output at clip. That's more like 1.6 Vp-p on the input with gain at 5. Remember that's only a little .5V rms.
Personally I'd run a little higher feedback components to place less load on the output. 7K5 for R4 and 30K for R3 will get you the gain of 5 and still be reasonably low impedance.
G²
Personally I'd run a little higher feedback components to place less load on the output. 7K5 for R4 and 30K for R3 will get you the gain of 5 and still be reasonably low impedance.
G²
Thanks guys, just what I was looking for. It is nearly for a car system jaycee, I use a car amp for a portable PA and have to use the -10dB outputs from the mixer. Creating a suitable output with controlls has cut down the output enough to limit the audio to the power amp so it needs this boost. A gain of 5 may even be excessive but controllable.
For use in a car I would use a differential input and ties the '-' input to the ground of the source. Any ground loop noise gets subtracted out of the signal as the signal is actually 'signal + ground noise'. In stereo you'd simply tie the 2 '-' inputs together and connect to the source ground. It would be the same general circuit but with a few more resistors and a cap.
G²
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