Pre-amp circuit diagram

[Bobzilla]

I want to build my own pre-amp for a bass-build. I'm good enough with a soldering iron to do it, and its a nice little project for me. I've got a design for a MM 2EQ, but I want 3EQ, and if possible sweepable midrange so I can pick the frequency to cut/boost.

So, what designs out there? I want full boost/cut control, not just a boost function. And for the mid I am planning on using a concentric stack pot.

Thanks all.

[brensabre79]

Nice little circuit above seems to fit the bill...

Interesting article [url="http://myweb.ecomplanet.com/TOWN8019/mycustompage0019.htm"]here[/url] on the original MM ones (these are not Boost/Cut on all bands though).

If that's too much hassle, you could do alot worse than the [url="http://artecsound.com/pickups/electronics/se3.html"]Artec preamps[/url] which are really cheap, but not nasty. You might have to dig around for one though, they come up on eBay quite often.

[Passinwind]

[quote name='Bobzilla' timestamp='1429261613' post='2749712']
I want to build my own pre-amp for a bass-build. I'm good enough with a soldering iron to do it, and its a nice little project for me. I've got a design for a MM 2EQ, but I want 3EQ, and if possible sweepable midrange so I can pick the frequency to cut/boost.

So, what designs out there? I want full boost/cut control, not just a boost function. And [b]for the mid I am planning on using a concentric stack pot[/b].

[/quote]

You just made doing a swept mid frequency a much taller order, since a dual section pot is often required just for the frequency sweep. Concentric pots like that do exist though.

Edited April 18, 2015 by Passinwind

[Bobzilla]

[quote name='Passinwind' timestamp='1429386622' post='2751054']
You just made doing a swept mid frequency a much taller order, since a dual section pot is often required just for the frequency sweep. Concentric pots like that do exist though.
[/quote]

So I would need a dual sweep for the frequency (guessing because it is the resistors either size of the boost/cut pot that determine the frequency, dual sweep for bass/'treble, dual sweep for mid and volume, so three dual stack potentiometers? Have I got that right?

[Passinwind]

[quote name='Bobzilla' timestamp='1429605678' post='2753004']
So I would need a dual sweep for the frequency (guessing because it is the resistors either size of the boost/cut pot that determine the frequency, dual sweep for bass/'treble, dual sweep for mid and volume, so three dual stack potentiometers? Have I got that right?
[/quote]

You would need dual stacked pots for many of the more common sweepable tone control configurations, which generally split the bands up into separate sections, both to minimize interactivity and to improve headroom. Have a look at Rod Elliot's new bass preamp project for a different approach though: http://sound.westhost.com/project152-1.htm . The tradeoff here is more opamp sections in lieu of a dual pot -- as usual, there's no free lunch.