low-end boost

Why not just use an EQ pedal?

 

BEE sonic stomp does this well, the boost in volume isn't huge but it does boost your bottom nicely, I find that with distortions for keeping [adding] lows it works better than a blend, although I still keep it in my blend with my distortions because I like the faux bi-amped sound I get with the blend.

 

Most EQ pedals are fine for boosting lows.
The Sadowsky outboard preamp has an excellent low boost, that's my recommendation.
There are a number of "preamp" pedals out there with bass boost. Practically every pedal that calls itself a preamp has that option.

Aside from that, bear in mind that lows which have been removed at some point in the chain cannot be put back with any kind of boost, EQ, or enhancer. There are two ways those devices can "work" for this purpose: one, if the original lows were not cut off, but only reduced in overall level a bit; or two, if you're content boosting the low mids above the rolled-off point, as that will give the impression of massive sounding lows even though the actual frequencies affected are higher than you'd think.

 

if you like the DIY option:
http://www.schematicheaven.com/effects/eh_hogsfoot_bassbooster.pdf

 

Everything mentioned so far would get you what you want. +1 on the Sonic Stomp for me.

 

You're probably going to get a more natural sounding result if you roll off some highs and then boost the overall level a bit. IME FWIW... You would be well served experimenting a bit to what sounds best with the equipment you're using.

 

my amp (a behringer) has a nifty ultrabass effect that reinforces low end a good amount. Problem is that im not sure if they make a pedal.

 

I designed a little bass booster that uses one dual opamp. It is basically the bass side of a Baxandall tone control with no bass cut. At the time I was really into "one knob wonders".

http://seanm.ca/stomp/bassbooster.html

I really didn't have an application in mind. I just was fooling around.

 

Bongo makes a great point. A low-fequency boost may work, but it will probably be boosting frequencies other than what you are losing. A good buffer before the pedals in question might help a little, but the best remedy is always to eliminate the tone-sucking items!

That said, there are many great eq & pre pedals that do boost low frequencies. My favorite is the Frantone Thunderhead. Just bass boost & overall volume. It's true-bypass & preserves your "sound" while adding up to 25db below 300hz. It's probably not the best "bang for the buck", since it only does one thing - but it does that one thing perfectly!

 

Havent you checked this out yet? http://www.aphex.com/demo1402.htm

 

Frantone Thunderhead?

 

the Ibanez PD7 and The Boss ODB3 can both be set up to do this.

 

E-H Hogs Foot can be found on the 'bay for not a lot of scratch and also ProTone Lo-Gear Thruster is affordable and effective. Good luck.