Preamp design schematics done

[Skywalker83]

Ok here are the 2 schematics for the passive and active sections of an internal bass guitar preamp i've done. Comments and crits welcome people!

[Skywalker83]

Ok , i''ve revised the schematics.

Athough, im still not very sure how to set up the first Op amp so that the input gain can be adjusted via a trim pot.

And also im not sure where the 2 outputs from the battery section go to.

can anyone shed some light on it for me?

thanks.

[Bill622]

Hum... if there is a connection between R1 and R2 and C2, it looks like a +4.5V DC offset. Your opamp will have single supply of +9V instead of a dual supply, example: +9V and -9V. This means you need to rise the input signal with a DC offset of 4.5V (middle), which can be done with the first op-amp.

Read this documents, they talk about it and alot more (20 sec, search on Google )
http://instruct1.cit.cornell.edu/cou...ngleSupply.pdf

Good luck!

[Skywalker83]

Thanks for the reply. Since i posted last i've manged to get the schematic completed. It took a while , but i got there!

[Bill622]

I would like to see your schematic, I plan to make myself a preamp too.

Thanks!

[Skywalker83]

Here it is.

it uses 2 dual LM4562 op-amp chips. I'm not sure what the frequency cut offs for the bass, treble and mid are, as i took the EQ section from a mixer styled set up. This circuit will also run along side my passive electronics in the bass.

I'm currently using some PCB designing software to try and get the preamp made on as small a board as i can that will fit easily into the bass cavity with minumum routing.. using standard components it will fit onto a board about 125mm x 35mm. but i want to try and do it with surface mount components, as this will cut down the size even more.

If you have any input or ideas i'd like to hear them.

[Minion]

I like your design but I would re-think useing the LM4562 at the input as it is a Bipolar opamp and won"t like the 2m2 input impedance , I would use a Fet opamp at the input and use the Bipolar ones at the output...Pluss I believe useing those nice LM4562 in a Guitar preamp curcuit is a bit over kill as you will never be able to utilize the great specs in the LM4562 as the Noise intruduced by your patch cord will swamp all other curcuit noise.....

I also suggest that you put the Bias voltage on the input of every opamp not just IC1a.....The input bias voltage will also be on the output of the IC1a but it is Blocked by C6 so the next opamp doesn"t get a bias voltage which will cause the curcuit to be non functional...The Bias Voltage must be maintained on every opamps input (or on the Non-inverting input in an inverting configuration).....


Cheers