I know this is a super old thread but none of these answers are correct in reason, the answer is if course NO, but the reasons given aren't exactly correct.
The NHT SA-1 is a mono subwoofer amp. It's not a 2.1 or even a 2.0 it's a 0.1 and it only will play frequencies from 20Hz to 150Hz. I read their manual on this amp and it's simply the worst example of a manual I've seen that wasn't an obvious Chinese to incorrect English. It's written in English but they show ways to connect the amp that just make no sense at all. Example being, using the amp as part of a bi-ampified speaker on a typical tower speaker. I'm not sure how NHT towers are set up but most speakers that are typical 2 or 3-ways, the woofer driver in that speaker will reproduce frequencies well beyond 150Hz making this amp useless for any typical speaker. I'm running hybrid electrostatic speakers that have one of the lowest crossover points I know of for the woofers. They're 2-way with the woofer covering 0Hz to 250Hz. So how can this amp work when it can only send a signal that stops at 150Hz and there will be nothing from 150Hz to 250Hz coming out of the woofers if this amp is used?
I came looking for a mod that could "up" the highest crossover point up to 259Hz (if possible) I checked the manual hoping that theyd have an amp spec that showed the amps true rating as far as a full range output amp and then show why they only allow it to go up to 150Hz based on the output curve with distortion per watts into different loads. Class H amps don't always have any set limit until it hits 20KHz where they purposely stop the signal so the amps won't go into runaway oscillation. These old ones have high distortion kick in at some point but usually not until it's up over 8KHz or so. Meaning that the amp has a circuit that controls the highest Frequency through a series of resistors and caps like an analog crossover does but much simpler.
I'm looking to find out which pieces can be changed to do this or if there's a resustor that can be changed to set the adjustment to read x10 so the highest output frequency could be as high as 1500Hz even though it would never be asked to do that normally, it could be a real possible bi-amp system amp. Example could be a set of Klipsch Heresy's, where the woofer could be directly connected to this amp and set the high pass at 800Hz and then a second amp connected to the NHT amps passthrough outputs (running at full range) connected to a second full range stereo amp that will be connected to the internal analog crossovers and it would power the skwauker (mid horn) and the tweeter together as one and powered by a separate amp to gain more control over the sound,
The manual also shows a system that using a typical receiver that has no separate pre amp that requires a jumper between the pre out and the amp in. The receivers or ore amps that have a pre out will be controlling the volume for the amp, since most power amps will be running at full output (they may also have an input control that sets the overall output, this is the voltage matching control) and the pre amp does the cutting of the signal before the amp. On a receiver that uses the jumper bars between the pre out and amp in is doing the very same thing as I just described, but if it only has an RCA output (like a monitor loop in and out) that output has no volume control and will out out whatever the receiver is set to send in the loop, making the amp run at whatever that voltage is and that's the settings it sees. The only way to control the volume would be to cut the signal using the amps voltage match setting, That negates the use of any external amps that have no pre output control.
They do show using the speaker level output of the receiver to the speaker terminal input on the NHT amp but they are oncd again forgetting that the frequency cut off is only going up to 150Hz! So trying to use it in a 2-way system to biamplify a tower speaker will only work if that woofer is set to cross over at 150Hz or lower. That rules out any 2-way speakers I know of, there's no tweeters or high frequency drivers (capable of reaching a flat response up to 20KHz or even an unven response) that can cover from 20kHz to 150Hz and could require a bi-amp set up. Of course this could be done if you ran a high powered tweeter and supplied it with 10 watts, it might not burn up instantly but it would sound awful and make no sense to even try it.
That's why I had to write this response to this post. They must be buying the amos from an unknown Chinese maker and having their name slapped in it since they seem to know nothing about the amp and how it could be used. This is audio class 1.0 the most basic things people must know about amplifiers before they even consider buying an amp. The idea that they are showing this in their manual immediately made me forget about buying any amplifiers they have their name on no matter how good people rate it, it seems they're gearing sales for those users who know very little about amps and audio ststems, I would expect their buyers to leave raving reviews saying how awesome their amp is based on comparing it to nothing. That's the Amazon affect on ratings, Amazon ratings are useless because of this fact and also due to how Amazon won't publish too many bad ratings to keep sales moving on the junk they sell. I know this first hand because I was only allowed to post 2 bad ratings on 2 pieces of garbage that they don't allow returns and stuck me with that junk and then blocks me from giving an honest rating. Im no longer allowed to leave any ratings there.
Don't trust NHT for amplifiers, it's obvious they have nothing worth buying, I mean, who makes a subwoofer amp that is rated at only 100 watts at 8 ohms and I'm very much doubting it puts out anything more than 150 at 4 ohms, not every amp doubles it's output into halved ohms. Many D and H amps will have lower output for any loads less than 4 ohms. Since this is a mono amp, it should be rated to 2 ohms (even if it puts out less watts at 2 ohms) like most all mono amps. This is an early model, but I've owned the same class amps made near the same date as this (im using a QSC GX5 right now) that are full range amps and they don't claim double output into halved ohms but it is rated to 2 ohms with minimal gain in watts but it won't shut off or go into protect if it's powering low impedance loads. Mine runs 24/7 at 2 ohms and has the fan slowed to barely spinning without any issues. The QSC GX5 specs show 500w x 2 at 8 ohms, 700w x2 at 4 ohms but only 350w at 2 ohms , so the 8 ohm rating is higher than the 2 ohm rating and it doesn't double into halved loads ever, it puts out half the power at halved output from 4 to 2 ohms but it's capable of running 2 ohms all day if needed,
