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Skywalker83 30th November 2008 07:00 PM

Making and onboard bass guitar preamp
I have a passive set up on my bass. 2 soapbar pickups, 2 vol pots and a tone pot. I'd like to add an active preamp with a 3 band EQ with a mid sweep/freq select control. and also with a passive/active switch, so i can switch between the passive ciruit and the active preamp.

So in total there would be 6 knobs and a switch.

Bridge p-up vol (pass)
Neck p-up vol (pass)
Tone (pass)
Pup vol (activ) (push pull p-up select pot)
Treble (active)
Bass (active)
Mid/Mid Sweep (active) (stacked pot)
Active/Passive switch

Does anyone have a schematic for such a set up?

Skywalker83 30th November 2008 08:41 PM

Actually a slight change to the lay out...

Tone - for both Passive and Active
Treble - Active
Mid/Mid Sweep - Stacked pot- Active
Bass - Active
Pickup Blend - Passive and Active
Volume - Passive and Active
Passive/Active Switch

There's a preamp made by John East which is almost exactly like what i want , but i reckon if i can figure out how to make it (with my modifications) it would be alot cheaper. My design is a hybrid of the John East U-Retro 01 Deluxe and the U-Retro 5 Knob deluxe.

John East Preamps

unohu69 3rd December 2008 01:27 AM

go there and check out their build. Im not 100% if it will do the same thing for a bass. Some of the values may need to be changed to accommodate a Bass I believe a bass pick-up puts out a little more juice than a guitar.

I am A very new noob DIYer, but this is a build I plan on doing for my Ibanez SZ

Daveze 3rd December 2008 02:30 AM

Actually, all you really need to do is add is the 3 band preamp.

Have a squizz at the Aguilar wiring diagrams:

Look at the diagram with the bypass switch, all you're doing is adding a tone knob before the switch. Its been a while since I looked but you might have some drama finding the right pot to do the mid+mid sweep function, I had looked for one but gave up for an unknown reason.

In fact, using an OBP-3 (or similar 3-band) will save you the drama of tuning your DIY design for the right frequency responses and is a reasonable price (IMO). Have you looked at the Audere? The z-mode is rather tremendous (again, IMO).

Skywalker83 3rd December 2008 03:12 PM

in my search for some circuits for help with my preamp design i came across the circuit shown below.

My preamp is going to have

Passive/Active DPDT switch
Tone (pasive and active)
Bass and treble stacked pot (Active)
Mid with mid sweep stacked pot (Active)

I plan on taking the pickups into the blend pot then to the input (im going to change out the boost switch in the circuit for a trim pot that will go on the board) then throught to the preamp and EQ.

Where would i add the tone pot and the passive/active switch in this circuit?

How would i alter the "Mid" section to include a mid sweep?

Skywalker83 3rd December 2008 04:58 PM

forgot to attatch the image DOH!

unohu69 3rd December 2008 08:38 PM

O.K. well I went to radio shack (doh!!) and bought the parts I need to build this. However the T1 calls for a BC548. the closest thing I could find was a PN2907. Do I have anything to consider before wiring this up ?[IMG]<a href="" target="_blank"><img src="" border="0" alt="preamp ?"></a>[/IMG]

I didn't mean to commandeer this post, just figured since we were on the subject.

unohu69 3rd December 2008 09:42 PM

2 Attachment(s)
Darn wasn't sure if that image was gonna work... so here goes this .....

i was really disappointed in RS quality. +/- 20% WTF is that. how do I get better quality parts ? +/- 10 or even 1 % ?

AdamZuf 17th October 2012 05:28 AM

4 band all sweepable preamp
Suppose I want to make a preamp that all four frequencies act as bells (no shelfs) and have sweepable frequencies, something like:

Bass +-12db 60-600hz
Low mid +-12db 100-1khz
Hi mid +-12db 600-6khz
Hi +-12db 1kz-10khz
Passive balance (between passive mag pups before pre)
Active Balance (between piezo pups and mag)

Does anyone know a module or can come up with a schematic?

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