Booster for bass

[roknjohn]

I looking to build a simple booster for bass. Was wondering if I could used the MXR Micro Amp or EH LPB1 circuits and if I would need to modify them for better bass response. Keep in mind, I would like to boost levels only, not bass frequencies. I have already adjusted pickup heigth as much as I care too. Any input would be appreciated.

[Bernardduur]

Micro amp!

I use one now for several years (homebuild) and it gives that boost to my bass! Just love that unit!

[roknjohn]

Thanks for your input Bernardduar. Did you have to change the input cap for better low end response, or is it pretty much as seen in the schematic?

[grapefruit]

Whatever you build I'd recommend putting large enough voltage caps in so you can run it from 18V or higher, in case you run out of headroom. An op amp booster from a high voltage supply should be good for bass.

For the microamp, If you're not running it from batteries you may want to use a higher performance / higher current draw op amp like the LM833 or NE5532. If you do this the 10M bias resistor may need to be decreased to 2.2M due to the lower input Z of the LM833 pulling the bias voltage down.

Cheers,
Stew.

[funkbass187]

i built an AMZ Mosfet booster for my bass without any mods and i am very pleased with the results.

[roknjohn]

Thanks Garefruit. Great ideas. I will definitely test the 9V vs. 18V for headroom when I breadboard it. The op amps I do have on hand, so I will do a little swapping before boxing it up. In general, I dont run my stompboxes with batteries, so that is not an issue.

[roknjohn]

Thanks funkbass. I hadn't looked at that one. I'll check it out before making my decision.

Anyone else have one that hasn't been mentioned?

[Meanderthal]

 Yes. Tim Escobedo's CMOS Boost. Very simple, powerful, and sounds great.

Pretty much all the boosters mentioned are good choices... I'd go for the one ya already have parts for...

[roknjohn]

Thanks Meanderthal. I can't seem to find Tims site right now. I'll check it out as well.

I keep my parts box pretty well stocked, so I should be able to check them all out before deciding. I was leaning toward the Micro Amp to start with, but with these additional choices I will probably breadboard a few, and them make my choice.

I checked out the AMZ Mosfet boost schematic, and was surprised by the .001uF cap on the input. First impressions would suggest a healthy amount of low end loss. I'll definitely have to test that one out.

[Meanderthal]

 I'd bump that cap up to at least .1uf, maybe higher...

Here's Tim's site. The CMOS Boost is just past the middle of the page... lotsa cool circuits actually... but the CMOS Boost is the only clean  boost from this page I've built, and it sounds great on bass...

Circuit Snippets

[roknjohn]

Thanks again Meanderthal. It looks like the Cmos Boost would be quick to build. I'll have to give it shot.

Don't know why I couldn't get the site to work. Maybe I was following an outdated link. Oh well, got it now.

[Laus]

don't worry about the .001uF in the MosFet Boost. That is way big enough. That is, if you keep the input impedance at about 10M.

Please correct me if i'm wrong: if you use a 1M pulldown resitor against popping, you should raise the input cat. (I did some low/high-pass filter calculations a few weeks ago, make yourself an excel-sheet and you know them all).

[Bernardduur]

Thanks for your input Bernardduar. Did you have to change the input cap for better low end response, or is it pretty much as seen in the schematic?

I didn't change anything

The 22M resistor with the 100n cap has such a low frequency pass that you don't need it!

[roknjohn]

Thanks all. I'll be doing a little breadboarding this weekend to see which I like best. I appreciate everyones input.