Looking for a decently simple Bass Amplifier schematic

[Opencan]

Hi all.
I'm looking to get into bass playing pretty soon and bass amps are too expensive for me.
Considering that I have some soldering skills and a bit of electical knowledge and soon will have a 1x12" speaker cabinet I though I might just go and make my own amp.

I'm looking for something pretty simple. I'm working with perfboard and looking for about 30W of output as that should be my speaker rating.
My bass-to-be will be active so only high-gain input is needed.

I can work my way with around 100 parts item count from what I tried up until now.

Transformers are an issue as well - I can only get 12\24\36V balanced DC trasformers for a reasonable price around here. (Israel)


As the demands from the circuit are pretty tough I'm not picky. A single\dual OpAmp Power Amp circuit with volume and tone control that works well is good for me


Thanks in Advance - Ron.

[Ripthorn]

I would suggest something like the ROG Flipster or maybe the FET-2B(my jfet version of the Alembic F2B) as a preamp and then look at the LM3886 for a power amp.  The 3886 has a max of 60W output, but if you make sure that your transformer doesn't provide more than 30W, you should be fine.  I've never actually done a 3886 amp, but there is documentation all over the web about it.  Should be relatively simple.

[Opencan]

Could you please link me to your FET-2B? couldn't find the schematics, only the layout.
As for the Flipster, what are thoes 1MA VOLUME, 100kA MASTER etc written by the ground points?

I found that the schematic at the LM3886 datasheet is the one mainly reffered to. I guess I'll try it up and mod it up a bit as nesecery.


Thanks

[Ripthorn]

Here is the FET-2B thread http://www.diystompboxes.com/smfforum/index.php?topic=73173.0.  The 1MA, 100kA etc. are pot values for the controls.  So a 1MA gain means a 1 megaohm audio taper potentiometer to control the gain, etc.

[Cliff Schecht]

Go hard or go home!

http://www.freeinfosociety.com/electronics/schemview.php?id=974

.

[petemoore]

http://www.generalguitargadgets.com/index.php?option=com_content&task=category&sectionid=6&id=13&Itemid=99999999
  As you can see in the LM3886 and other amps, they look relatively simple.
  And they are...once you get the power supply, mounting, layout, chassis, and heat sinking done, IIRC the preamp likes to have a supply that is isolated from the amp.

[Opencan]

Ripthorn, thanks
Can I use other FETs instead of the J201 in your circuit? Its imposible to get them in here.

Pete, i'll remember that. Thanks

[Ripthorn]

Yes, you can use MPF102 and it should be fine.  Basically, you just need a good general purpose jfet, I believe.

[brett]

Hi
the MPF102 is a fairly different JFET to the J201 (Vgs(off) of -1V and -5 or -6V, respectively).
A 2N5484 is much closer.  A 2N5485 might be ok.
But why not get them in the mail?  Small Bear or Futurelec will ship them for a few $$.
You can use them for lots of projects.
cheers

[Opencan]

Hi
the MPF102 is a fairly different JFET to the J201 (Vgs(off) of -1V and -5 or -6V, respectively).
A 2N5484 is much closer.  A 2N5485 might be ok.
But why not get them in the mail?  Small Bear or Futurelec will ship them for a few $$.
You can use them for lots of projects.
cheers

Shipping cost to Israel.
I don't have enough projects to justify the purchase.

[Ripthorn]

I suppose a 2N5457 might also work.  You could socket different fets and see what works.

[petemoore]

  Perhaps pick a different type of active [more available] for the pre-amp.
  Leave room or make the layout so the pre-amp circuit board can be swapped.
  Note that many of these boosters use the same volume control [or similar enough]...and many of the other offboard parts [ power supply, switching, jacks] can stay with the chassis/layout.

[andymac1962]

Rod elliots excellent site has a guitar amp which may be suitable.   http://sound.westhost.com/project27.htm
Remove D1 - D4 for bass, and you may want to increase the value of C1, maybe up to 470n or 1u

Any power amp that uses LM3876 should be ok for your power amp,   or there is a lower power alternative LM1875
refer http://sound.westhost.com/project72.htm for details

Cheers