EH Memory Man Preamp

[Dimitree]

Hi 

I'd like to build the DMM's Preamp..could anybody help me?
What is the preamp part in the schematic?
could be the part that I've colored in black? Only this part? Does the Blend pot is needed?


thank you very much, I hope you'll help me..
Dimitri
ps. sorry for my bad english 

[Mark Hammer]

Why do you want to build this?  What do you want to use it for?

[Dimitree]

I'd like to use this preamp as a stompbox.. Could it be possible?

[Processaurus]

That looks right.  No the blend pot and switch is not needed.   Notice it runs on -15v though.  The preamp on the DMM isn't anything special, just a cookbook inverting opamp stage with variable gain.  The MXR microamp is a similar opamp preamp with variable gain that is set up for 9v already, if that works for you.

[Dimitree]

thank you..
So I can cut the blend knob and also the SW and the 150 ohm res. for the direct out? The signal goes from the 22uf cap to the 47k res. ..and then? Does the 1.2nf  cap and the 100k res. (after the first 4558 and before the 22uf cap) are needed?

thank you again

[Mark Hammer]

There is really NOTHING special about this preamp stage.  You are much better off building one of the many "clean boosters" that there are detailed projects for.  Go to www.generalguitargadgets.com and you will find many to choose from, complete with PCB layouts.

[BrianJ]

You may want to take a look at the adjusticator. It's one of RG's circuits on GeoFEX.  It's identical in function but his circuit is complete - start to finish.

At the very least you'll have a cleaner schematic to look at.

[Dimitree]

thank you for these alternatives..but I dont' need it..because I just want to build a 1:1 dmm's preamp.. Not because I could use only this preamp.. 

[slacker]

thank you..
So I can cut the blend knob and also the SW and the 150 ohm res. for the direct out?

Just get rid of everything after the 22uF cap except the 47k resistor to ground. The output is then where the capacitor and the resistor join.

[Dimitree]

Thank you very much slacker!!   

Does the 1.2nf  cap and the 100k res. (after the first 4558 and before the 22uf cap) are needed?

[slacker]

No you don't need them. If you build this, where are you going to get a -15volt power supply from? Or are you going to convert it to a positive supply?. Like other people have said it seems like a lot of work.

[Dimitree]

in the schematic there is also the schematic of the power supply.. Could I build it?

[slacker]

Yes you probably could. It would be easier to just use a +12 or +15 volt DC power supply though, that would be simpler than getting a 24 volt AC power supply and building the negative supply on the schematic.
The only thing you would have to do to convert the preamp is reverse the 22uF capacitor and where it says -15 on the schematic would be +15 or +12 or whatever you use. The preamp would sound exactly the same.

[Dimitree]

Thank you very much again Slacker!!