Just for everyone's benefit, I believe that PE now ships these amps standard without any boost. And even if there still is boost, simply state in the comments when you place your order that you want it removed.
I did this several months ago (before they started shipping without the boost) and they removed the boost at no extra charge. The technician even included his business card stating that he had done the mod.
Does anyone know the Fc of the rumble filter with the R26=56Kohms, R27=120Kohms no boost configuration? I'm currently using R26=50Kohms, R27=150Kohms, which results in a Fc=16Hz, but it's too low to protect the driver on hideously low bass material.
Okay, I cancelled my order for the same basic amp from adireaudio.com and got this one. The .pdf file does say that the default resistor setting is for NO bass boost, but I am concerned with sub-sonic bass hurting my woofer. I assume NO boost also has NO sub-sonic filter? I think the Aidre version of the amp has a 1 dB boost. I may go for that. Now, the Shiva is backorder a couple of weeks. Is the Dayton 12" Titantic just as good? My box is approx 3.5 cubic ft. (minus volume of port, driver and amp) w/ a 17" x 4" diameter port.
The "bass boost" circuit is really a hi-pass filter with Q > 0.7 So the frequency response is pretty flat until you get near the boost frequency. At that point theres a hump in the response that boosts a small range of frequencies. Below that it falls off pretty quickly. I haven't seen the schematics but I'm guessing its 2nd order so that's a 12dB/octave slope that filters out the reeeally low stuff.