Looking for Answers about Lepai 2.1 2x40W Amplifier + 1x68W Sub Output?

Well according to it's power requirements it would be 14.4volt 5 amp max. I don't know what you are planning to run with it but always get more amp than you think you need. As long as you don't try to power more than it was designed for then the included power supply should be sufficient.

car battery....really, or a smaller 12V gel-cel. Keep it charged thru lighter plug or AC maintainer charger [12V @ 1A].

14.4 v, 5 amp. tough to find, and expensive.

I was not happy with the sound when using the 15V 3A power supply from the package. I took the risk and use 16V 4.5A power source from an old IBM laptop power supply. The sound is definately improved with more punching bass and much clearer. The only issue that bothers me is the sub crossover. It does not work too well.

I forget mentioning that I have used the 16V 4.5A IBM laptop power supply for several months. It produces better sound. I can't tell the difference from the TA2020 little T amp after using the IBM power supply.

No, that really isn't a bi-amp. If a very small shift in phase of signal occurred damage to either amp or speakers could result. I would try one unit to see if your sound level is acceptable. If not, you could use this unit as a pre-amp. To drive a pair of larger amps by turning it down. One amp you could bridge for max power to the sub and the other in stereo to the satellites.

It's possible but probably not advised. I would suggest a board amp. They are just a bare amp with nothing but outputs and audio in. They are cheap considering how much power they deliver. You could get multiple board amps if u wanted to have a powered separate subwoofer. Take a look into it. You might want a volume control though.

What you are talking about is not bi-amping, if I understand you correctly. It sounds like what you want to do is bridge the 6 channels of 2 separate units down to 3 (2.1) output channels. This is possible, but not safe and it will likely damage the units. In order for this to work you would need a signal inverter on each of the outputs on one of the amps to make it bridgeable. Bridging two amps will increase the output voltage and may make the combined output louder than they are independently, but bridging these will cause the output current to be higher than either of the units can safely handle and fry the amps.
Don't do it. It would be a waste of money when you fry both amps.
If you find that one of these is not loud enough for your purposes, try getting more efficient 4 ohm speakers. If that doesn't cut it try a better amp. The Dayton 2.1 plate amp would be a good option. Even though it shows a lower power rating, it will out perform this Lepai by leaps and bounds.

Yep that was pretty much what I was asking.

I mean, I've seen people do that with home audio receivers and that seemed to work for them, and I'd expect them to be way more temperamental than Lepai amps

Is it something to do with imperfections in each amp that would cause failure?
I know that's what happens when you parallel diodes: one diode with a lower resistance does practically all the work then fries.

The amp is stereo and non-bridgable. If you use one channel you get 40 watts and the other channel goes unused. Some amps can be bridged, And there are mono amps. Take a look through PE if this amp isn't a match for your needs.

No, the amp will not send double power to one channel if the other channel is not in use.
Also, read some of the other Q&As to learn about this amp's limitations (i.e. 7 watts vs the reported 40, and the inability to bridge channels).

First off, the power rating is with a decent power supply behind it. This amp works great for a desktop unit. It is not bridgeable. What would be a cool build, using one 12" woofer to cover the lows, then use two mid range and two tweeters. Utilizing both channels from the amp (stereo). All in the same enclosure, this will work fine for a gym. Find a efficient sub woofer, preferably ported.

What you did with your midrange is drop the ohm load to half. It's probably a little brighter than it should be eh? Anywho, running odd ohm loads is never good and I would recommend using 2 way crossovers instead. To answer your question, you don't gain wattage by bridging this amp. (not sure if it's even recommended by the manufacturer). And don't expect 40w. That is an unrealistic "max" rating. This amp realistically produces about 50 watts total from all 3 channels based on the power supply rating.

The subwoofer output is mono, one channel. There are, however, two sets of connections that are in parallel with each other.

There is one sub channel. It has two speaker connections for the one sub channel that are connected in parallel.

Yup. it wud be perfect for that.

seems like a perfect choice to me.

no

The Lepai 2.1 2x40W Mini Amplifier has a dedicated powered sub-woofer output that is adjustable. Many powered sub-woofers have inputs that will accept amplified inputs to accomodate equipment that does not have a sub output or an electronic crossover. If your powered sub-woofer is capable of receiving amplified signals at it's input then this will work.

You could also install a line level adapter across the speaker outputs of the Lepai 2.1 2x40W Mini Amplifier that would drop the amplified level to headphone levels and use this to provide a line level input to your sub-woofer. I have included an example in this answer, the Metra IBLOC01. This unit would connect to the sub speaker output of the Lepai 2.1 2x40W Mini Amplifier and give you two RCA jacks that you can connect to your powered sub-woofer with standard RCA cables.

Good Luck

Yes. Although there is no information directly about the sensitivity of the inputs, you are driving it with a preamp, so your bass should be able to drive the amp to full output.
Your suggested use is far away from the intended use of the amp. You don't seem to plan to use the sub out or both sides of the stereo amp. But I think you see that the amp is small, extremely inexpensive, comes with a power supply, and according to reviews here, is surprisingly OK-sounding. If you don't expect more than a low volume practice amp, you have a clever (but a little odd) solution.

After the pre-amp yes.
I suggest the most sensitive drivers to get the best out of it.
The separate gain on the subwoofer channel might work to your advantage too, regardless of the reviewers complaints. A first order roll off is not a bad thing when it comes to music...

use a cheap, light 12" woofer on the sub channel, (with the crossover set to 200hz,) and a couple of smaller drivers on the satellite channels then twiddle the gain and volume knobs until it sounds right.

What a neat idea! look in buyouts for a nice 12" for cheap, otherwise below are some very likely candidates.

Though I haven't bench tested this amplifier to measure the crossover slope, it seems to be 6 dB/octave. I would recommend a 5.0 mH series inductor (listed below) be used with the subwoofer to further filter the output for use with most applications. This will allow you to dial in a frequency with the Lepai subwoofer crossover to precisely integrate a subwoofer with the stereo speakers.

The stereo output is full range and is discretely controlled with bass, treble, and volume adjustments separate of the subwoofer section.

Using the included power supply, I have tested this amplifier to produce roughly 7 VAC cleanly into an 8-ohm load, and a 4-ohm load, on both the stereo and subwoofer outputs using -0 dB white noise as the input signal.

With the included power supply you can expect up to 6 watts of clean output per channel into 8 ohms (including the subwoofer) and 12 watts of output per channel into 4 ohms.

This is a class A/B amplifier.

The output is designed as an output. I have found that the output is wired in such a way that it, in fact, does provide signal to the amplifier. I do not know the long-term consequences of using this output as an input (though I don't think it would do damage, but don't know).

Using the output to feed signal to a subwoofer is a perfect example of its intended use.

sure

The volume control on the far right controls the stereo output (top speaker level outputs on the rear of the amplifier) whereas the subwoofer output (bottom speaker level outputs on the rear of the amplifier) is controlled by the subwoofer volume control, on the far left, independently. This allows for precise integration of the subwoofer to the two stereo speakers.

The Lepai 2.1 2x40W Mini Amplifier + 1x68W Sub Output is actually a group of three mono amplifiers with two of them tied together as a stereo amplifier and the odd remaining amplifier is dedicated via an internal crossover as the sub-woofer amplifier. In as much a bass (low) frequencies require more power to reproduce then they have increased the power output of this amp accordingly.

You ask several questions within your inquiry so I will attempt to address each on separately.

Regarding the 7 volt AC output, I fail to find a specific listing of 7 volts. It does required DC input between 9 volts and 14.4 volts that nicely accomodates automotive use. The power output to a speaker is listed into an 8 ohm load and would increase with speakers of a lower impedence. It should be understood that an amplifier will generate increased heat at loads of lower than design impedences.

The reason the sub-amp has a higher output value was addressed in my first paragraph. You ask if all 3 channels actually the same in maximum output ability, and the answer is no, the output power specs are provided and accurate; 2 @ 40 watts & 1@ 68 watts for the sub.

You inquire about a 2 ohm load, what is your load on each speaker? I have not found very many 2 ohm sub-woofers. To calculate the audio AC voltage, it is necessary to use some advanced math and have an understanding of the exact load and the frequency at which you desire the volt rating at. In addition, it is also necessary to have an understanding that there existing a rating called RMS. The Root Mean Square (RMS) can be simplified as 0.707 x peak output, but this simplified calculation does not yield a definitive voltage because it requires much more data to be considered.

My reason for the detailed answer is to point out that perhaps you need a different question answered to consider the worthyness for your use.

Good Luck

The 2 stereo channels use a TDA7266S amplifier chip and the sub section uses a TDA7256 chip.

NO. Not on this amp. Apparently USB is provided as charging port only.

Probly about 45-50. Enough to hear but not enough to feel.

The subwoofer channel has a variable, 1st order low pass crossover. This crossover does not act as a high pass for the stereo channels, so no worries there.
It will attenuate the sub channel 6db/octave below the point you choose, between 50 and 200Hz. So, if you choose 200Hz it will be attenuated 6db at 400Hz, and 12db at 800Hz. If you choose 50Hz it will be attenuated 6db at 100Hz and 12db at 200Hz.
If you need a steeper curve, you can run an inductor in series with the woofer. This will give you the net effect of a 2nd order low pass crossover, 12db/octave. For a 4 ohm woofer I would use a cheap 3.5mH inductor, like the one below.

You might be better off to series wire them so that you can get the most watts out of the amp. You might want to consider just wirering one sub instead of two. Maybe not, just a matter of testing things out.

No, the 3.5mm jack on the front of this amplifier is an auxiliary input for iPods, cell phones, MP3 players, and the like. I'd suggest something like the Topping I've linked below.