which diy bass preamp?..

[deadastronaut]

Hi guys,  i' ve looked around for a diy 'stompbox' bass preamp schematic to tinker with...but have no idea of how they might sound!..

i have a 5 STRING BASS, into DI box into mixer,but sounds flat and lifeless still,  i just need something to lift it up and stay clean, and have a bit of tone control too maybe.......

as its a 5 string i'd like something that can cope with the low end well..

which diy bass preamps do any of you guys use?.....or have used....and would recommend?..(not onboard)

cheers in advance..

[JebemMajke]

Fet version of bassman 135 and or sunn 200's. AMT type of conversion, with schottky diode. Both are killer.

[deadastronaut]

cheers, have you a schematic?...for either.

[Gus]

Here is a thread about a circuit I simmed.  I have not built it yet.  Input at C6
http://www.diystompboxes.com/smfforum/index.php?topic=96621.0

Note the 39K collector resistor at the first stage and the controlled gain for 9VDC operation.
Bootstrapped gain stage inputs and a Fender type tone section

[deadastronaut]

hi gus, cheers man, looks nice and simple to breadboard..

where are the lug 2's of bass/mid?..or are they wired 2-1 connected?

[JebemMajke]

cheers, have you a schematic?...for either.

No, but i can draw them.
You ll have them both tonight.

[deadastronaut]

cool, nice one misa

i'llbreadboard it/them and have a tinker..

[JebemMajke]

Top one is bassman

[Mark Hammer]

The late Albert Kreutzer was a bass player and musical electronics enthusiast.  His website is still up, and he had a number of fully-fledged original designs, with layouts.  Do it for Albert.

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

[roseblood11]

His preamp is really great.

Someone should mirror that site, as long as it's online...

[deadastronaut]

@misa:  thanks man, but is it just me or is it really hard to read....

i'll be using 3pdt bypass too.

@mark: looks great thanks, but i'd like to keep it to 9v.  

[Mark Hammer]

Fair enough.  Just keep in mind that bass can generate some serious peaks, necessitating the sort of headroom that the Kreutzer preamp amps for.

[Gus]

Mark brings up a very good point about bass pickup peak to peak voltage.

You can turn down the volume control on a passive bass but you lose the high end resonance of the passive bass and cable capacitance and input resistance of the preamp when you add enough series resistance with the input.  NOW this can be what you want.
 
Think about the passive bass volume control as it is turned down the wiper is the output so you have the resistance of the wiper to the input of the volume control in series with the input of the preamp.

I set the gain of each stage in the sim at about X10 inverting as a compromise for the 9VDC power supply and the output of a passive bass.  You could increase the output gain if needed.

[deadastronaut]

@gus: 

hmmm , well i'll give yours a go on breadboard and see how i get on. i like the idea of 9v as i'll have it in my chain (but just used for bass)

i'm only looking for something to use for home playing/recording bass, so anything has got to be better than just DI /mixer.

was  i right about those bass/mid lug 2' pots on your schematic?..


i also found this..any thoughts?..
http://www.diystompboxes.com/smfforum/index.php?topic=73173.0

[Gus]

JebemMajke circuits look interesting. 

deadastronaut
I have not built the simmed circuit I posted.  The cool thing is you could build tone volume sections and try the different gain stages

The 9VDC supply and the input gain stage vs the passive bass output is what need the most attention,  Do you want to stay "clean" at all settings of the bass and get distortion latter in the circuit or do you want distortion from the first stage?

You could build a circuit with a Jfet input dual opamp and a tone section volume control between gain stages.

 

[deadastronaut]

@gus:   i'd  like it to be clean really,

going from warm non toppy  to spanky/slappy

and maybe a little 'optional'  grit/drive to it...but mostly clean.

[deadastronaut]

ok i re-drew the bottom one of jebem's preamps, just a bit easier on the eye..

are the bat 85's essential in this...or is there an alternative?...if not i'll just order a couple..no probs.   (edit just got some bat85's )

@gus: i couldn't get that scheme to work...it was late and i was tired though...so probably human error on my part.




i redrew the bassman schematc as well, but for the life of me i couldn't see some values with my x ray eyes.. ...could someone fill those in for me?..  R5/C4/C5

i think the rest is right?....(apart from ground on 1M pot)  

[deadastronaut]

oh man, just breaded the bassman (bottom)...guessed the values

my bass is finally alive after all this time.....brilliant. kicks ass.....more tinkering to do...but yep it kicks properly now!!

[JebemMajke]

I've used bat 85, bat 42, bat 43, bat 41 ... pretty much stays the same. Fets that I;ve used on bassman were q1 bf245b and q2 2sk30 and on the sunn ( the bottom one xD ) q1 2sk30 and q2 bf245c. Now the b version of bf 245 provides really nice, glassy kind of sound. More highs and mids. But also more distortion and more noise. The C version is low gain, low noise but lots of bass. 2sk30 is somewhere in between. If you find that it has more gain than you would like than remove the D1.

On bassman values are
R5 10k
C4 and C5 are 0.47 uF
Also vol pot on bassman should be connected to the ground.
Bassman is great for slap and all that jazz bass madness. That fat switch is for a bit more bass sound. It's a nice option to have. There used to be a bright switch, but I've found it to be useless. Both with bass and guitar.

It's a killer isn't it?

[deadastronaut]

ahh nice one jebem, brilliant. thanks man,

i used 2n5457's on both Q's...sounds sweet, goes from nice n bright, but still with a thump to it too...which i love.

to warm soft rounded bass.....lots of output level on this too....my mid isn't working at the mo, but i quickly breaded it...i'll check it over in a bit,

if i wanted a bit of 'grit' in there too, are there any mods i can do to it, but still retain the original too?.

anyway,  what a difference, when i bypass it, it sounds so dull and lifeless, god knows how i put up with that since i bought it........i highly recommend this build,  

thanks again man, you brought my bass to life.. .....yep got the 1M pot to ground.. ....



when ive finished tinkering i'll knock up a pcb/layout for those interested too.