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Old 9th November 2009, 07:08 AM   #1
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Default small preamp design for a bass guitar

Iím trying to locate a small preamp design for a bass guitar with potentiometer controls for: volume, bass, treble and midrange.

This must be small enough to fit into the guitar body.

Are these designs very popular, in other words if something is available, how many people want one in addition to me?

Thanking everyone in advance for the help.

Gene
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Old 10th November 2009, 03:25 PM   #2
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This is a popular bass preamp design, not for inbody use, but you could easily take the parts you want and make it so.

Bass Preamp
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Old 10th November 2009, 07:19 PM   #3
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Thanks Nigel,

I appreciate the help.

I'm looking for something a bit smaller that fits into the guitar body.

I'd like to limit the current requirements to a single nine volt battery if possible.

Gene
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Old 11th November 2009, 07:34 PM   #4
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A number of these onboard electronics designs are floating on the internet. Mr. Hugsley on this forum has designed on with a two or three band tone control. There's the schematic of the preamp for the ashbory bass (but that's for use with piezo bridges). And if you register at freestompboxes.org • Index page , you can find the onboard electronics of the musicman stingray and sabre basses, which use a extreme low power opamp (LM4250).
Alternatively, you could tack a tonestack between two halves of a dual opamp.
I've made a preamp with a sallen-key lowpass filter and have also made one using a state variable filter (a la Alembic). The state variable one you can find on the musikding.de forum, but it's in german.
Is a active tone control necessary? You could also make just a buffer, I've tried the fet buffers, but I didn't like the simple single JFET ones for bass. Opamps I did like, however, especially the opa2134, although that does draw a bit of current.
To increase the tonal options, you could add switchable caps and resistors, to make a Z-modes preamp like Audere does, I did this with my Precision. Finding the right capacitance and reistance takes some time.

Good luck!
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Old 12th November 2009, 06:41 PM   #5
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Thanks Jarno,
Great information!! I can see some very bright people have been hard at work. The interesting thing is, a good portion of the examples you provided seems to indicate, these very bright people are engineering better electronics that what is provided by the guitar manufacturers.

I have found an example of exactly what I’m trying to locate. It’s a schematic for an onboard 3-Band bass equalizer (with integrated onboard preamp).

An example of this 3-Band Bass Equalizer was available from Ibanez in their 2002 Sound Gear 400.

What follows is the Ibanez wiring diagram link: Ibanez :: Electric Guitars : Wiring Diagrams

Thanks again,
Gene
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Old 12th November 2009, 09:47 PM   #6
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Regarding the preceeding link i.e. - Ibanez :: Electric Guitars : Wiring Diagrams

Instrument = Bass
Year = 2002
Model = SR400


Sorry! This information must be inputted to pull-up the wiring diagram.
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Old 12th November 2009, 10:45 PM   #7
Minion is offline Minion  Canada
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Well thats not a schematic so there is no hope in just copying it , but it does show that it uses just a single 8 pin opamp probably a dual which means it probably is just a 3 Band active tone controll like this one but with the other half of the opamp used as a buffer ...

Click the image to open in full size.


or

it"s a 2 opamp stages with a 3 band tone stack stuck in between simular to this one .... (This one is only a 2 band , I use this one in my bass but it has adjustable gain to get those fuzz bass tones but it super clean with the gain down)

Click the image to open in full size.


Cheers
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Old 12th November 2009, 11:33 PM   #8
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Quote:
Originally Posted by Gene_Johnson View Post
Iím trying to locate a small preamp design for a bass guitar with potentiometer controls for: volume, bass, treble and midrange.

This must be small enough to fit into the guitar body.

Are these designs very popular, in other words if something is available, how many people want one in addition to me?

Thanking everyone in advance for the help.

Gene
There isnt a lot of room inside a guitar body for electronics.
Also you have to get in to change the battery which isnt a quick job.
I would go for a seperate box.
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Old 13th November 2009, 04:50 AM   #9
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Thanks for the schematics Minion. I appreciate the information. Minion, if I really grovel could you email a larger drawing of you Guitar Pre w tone controls schematic? I have a tough time reading some of the smaller notations.

Nigel, youíre right, not lots of room. But the guitar is an Ibanez with a cavity for the electronics and another for a nine volt battery. So there is some extra room.

-----

There are also three pick-ups so I think if I use something like a single shaft (or even a dual shaft) dual body I can control the pick-up input signal.

Thanks for the help guys.
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Old 13th November 2009, 07:26 AM   #10
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And you can always break out the router and make a bigger cavity. A separate battery compartment is also a good idea. But you should be able to make a fairly compact version of the preamps, use 1/8watt resistors, small filmcaps. Even the state-variable filter from Musikding, with a quad opamp, fits in most instruments.
the standard cavity in a P-bass fits nothing, those are a bit of a pain, but nothing chisels and a router can't solve.

Edit:
By the way Gene, you did "click" on the pictures minion posted? :-)
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