Building an onboard preamp

[Phil Mailloux]

Not satisfied with building my own bass, I decided to also build the pick-ups and onboard preamp.

The pick-ups will be MusicMan Stingray humbucker copies (5-string).

I found a couple of websites with scematics of preamps:

http://www.albertkreuzer.com/preamp_onboard.htm

http://www.usq.edu.au/users/maxwell/person...ic/gear/rbx260/

I'm more inclined to build the latter's "series 2" preamp (vol, treble, bass, active/passive switch)

Does anyone have experience with building those or any other bass preamps?

Any tips anyone?

Know of any other sites where I can find other schems?

Thanks

[ansil]

how much gain do you want.. when you go active.. the bass and treble controls do you want them to share the active passive split.. so when active they act as selective bands instead of simple low pass or high pass filters.

i can draw up somethign for ya.. but i need to know how much output the pickups would have. other wise it could distort.. of course i can also put in interanl trimmers in the scheme.

most systmes go up to 10db boost availble when active.. is this satisfactory.

.

email me and i will try to draw up soemthign when i get home.

austenfantanio@yahoo.com

[lovekraft]

I like the fact that Kreuzer's setup buffers each pickup individually, but that makes the active passive switching more complicated, and the Big Muff style tone control isn't to my taste. I like Maxwell's tone circuit, but I don't see any provision for controls in the passive position. So, Kreuzer's setup with Maxwell's James/Baxendall tonestack would suit me best, and I don't see any sense in the active/passive switch, so I would leave it out (I have one on my Galveston 12-ver, but I've never found a need to use it). But that's just my take on it. You could also use Maxwell's circuit as-is, but put a blend pot or a pair of volume controls between the pickups and the preamp. It all comes down to what you like, I'm afraid. Either circuit should have enough gain to confound a decent amp. This link may help explain the design considerations:

Designing JFET Audio PreAmplifiers

[Phil Mailloux]

Thanks guys,

I should mention that i'm an electronics beginner. I've soldered a couple of small DIY velleman kits and also soldered other household things in the past but my theory of electronics is a bit low...

I was thinking of just using one of those online schems and just plain reproducing what I see there on perfboard.

I want to use only one MM humbucker but also have a three way switch like MM basses (single coil / parallel / series). Those 3-way switch schems are on their website so I think I can manage that, they're also on the bartolini website. I will obviously build the pups with 4 connecting wires to allow the 3-way switch.

I don't really care for the tone controls when i'm in the passive mode. They can be bypassed no problem in my opinion. I'll only use passive in case my battery ever goes dead in a gig, you can always fiddle with the tone controls on the amp.

Ansil: What you say absolutely fantastic!!!! If you can draw me up something I would definitely be the happiest man alive but unfortunately, like I said i'm not too familliar with some of those electronics terms you mentioned

I do understand that my pick ups with distort if the output is too high but then again, i've haven't build them yet.

I got specs for MM pups and other companies' MM replacement pups but they all have different different output specs so I was thinking of just messing around with what I get when I start building them.

You could also tell me what would be a good resistance that I could make, we could match the preamp to the pick-ups. My goal of course is to have pick-ups that will work either in passive or active mode.

here's some of the specs i've found on the net:

Japanese MM copies; D.C.Ohm(k) : 5.80, Inductance(L) : 2.34

Tone chart(Low):12,(mid-low):13

(mid-high):13, (high):14

(I don't understand what the tone chart is and if that is calculable wether with a multimeter of math solution) This is a passive pup but this company also sells active electronics that can be used with those pups, I guess that could be good specs for me...

Quote I got on the MM basses forum:

I believe each coil is approx 1.4H and 3.8K ohms. The two coils are in

parallel giving 700mH and 1.9K ohms.

Kent Armstrong MM copies:

D.C. =13K-

I'm not set on one of those yet, although I believe the original Stingray ones won't work passively.

[lovekraft]

I want to use only one MM humbucker but also have a three way switch like MM basses (single coil / parallel / series). Those 3-way switch schems are on their website so I think I can manage that, they're also on the bartolini website. I will obviously build the pups with 4 connecting wires to allow the 3-way switch.

If you're using a single pickup, then Andrew Maxwell's setup is ideal! Just hook up the output of your switch to the preamp.

I don't really care for the tone controls when i'm in the passive mode. They can be bypassed no problem in my opinion. I'll only use passive in case my battery ever goes dead in a gig, you can always fiddle with the tone controls on the amp.

Dude, I've been playing active basses exclusively since 1993, and I've never had a battery go dead on me at a gig. With any decent preamp design, you'll start to hear distortion on transients long before it stops working. I do always carry a spare battery, but I've never had to install one between sets - usually they end up in my wireless. http://www.projectguitar.com/uploads/emoticons/default_biggrin.png' alt=':D'> There's really no reason why either of these circuits should present a problem for a reasonably alert beginner. Check here and here for the skills and tools you'll need.

[Phil Mailloux]

Thanks for the sites Lovekraft, i'll definitely keep myself busy reading there for a while.

I've already done a good amount of research, also done lots of read-up on PCB design and etching. If it comes to that I don't mind getting the stuff and experimentinga bit.