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Old 30th November 2008, 06:00 PM   #1
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Default 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?
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Old 30th November 2008, 07:41 PM   #2
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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
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Old 3rd December 2008, 12:27 AM   #3
unohu69 is offline unohu69  United States
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Join Date: Dec 2008

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
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Old 3rd December 2008, 01:30 AM   #4
Daveze is offline Daveze  Australia
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Join Date: Jun 2004
Location: Sunny Queensland, Australia
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).
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Old 3rd December 2008, 02:12 PM   #5
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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?
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Old 3rd December 2008, 03:58 PM   #6
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forgot to attatch the image DOH!

Click the image to open in full size.
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Old 3rd December 2008, 07:38 PM   #7
unohu69 is offline unohu69  United States
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Join Date: Dec 2008
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.
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Old 3rd December 2008, 08:42 PM   #8
unohu69 is offline unohu69  United States
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Join Date: Dec 2008
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 % ?
Attached Images
File Type: gif preampsch.gif (17.1 KB, 708 views)
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Old 17th October 2012, 04:28 AM   #9
AdamZuf is offline AdamZuf  United Kingdom
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Location: London
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Default 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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