This is a review and detailed measurements of the Outlaw Model 7140, seven (7) channel home theater power amplifier. It is on kind loan from a member. The 7140 seems to have come out a few years ago and is shown as discontinued. At the time it was out, the cost was a reasonable US $1,100. The new replacement series, 7000X looks just like this so not sure what they have changed.
The 7140 is a beast of an amplifier, nearly breaking my back carrying it up to my lab:
The design is highly modular with a massive toroidal transformer powering 7 independent amplifiers, each with their own power supply on board. The heatsinks are rather beefy with plenty of distance between them and top of the unit. The feet are also quite tall allowing better ventilation from bottom to top.
The back panel shows the inclusion of XLR inputs which I appreciate:
The inclusion of a grounding terminal was interesting. It did no good in my testing with XLR inputs as it should not.
During use, the 7140 was quite stable, never complaining, shutting down or anything as Audio/Video Receivers (AVRs) tend to do. Clearly then this is a more robust solution than internal amps in those units.
Power Amplifier Measurements
As usual we start with our dashboard view of 5 watts into 4 ohm load using a 1 kHz tone:
I was surprised to see such high mains hum at 60 Hz. A prior review of another unit with just RCAs complained about the same thing and recommended a ground terminal on the unit which they have added. But as I mentioned, it made no difference. I have to think this is magnetically coupled into the amplifiers.
Fortunately or unfortunately the distortion spike from 2nd harmonic is bit higher still so didn't impact measured SINAD (combination of noise and distortion relative to our main tone). As it is, the 7140 lands below the average for all the amplifiers we have reviewed so far:
Frequency response is flat enough:
32-tone signal to resemble "music" shows the typical rise of distortion with frequency:
And rather high noise floor which could be caused by that power supply hum.
Here are the noise figures for 5 watt and full power:
We are not clearly more than 14 bits or so at 5 watts so not very quiet.
Here is our power versus distortion and noise at 8 ohm:
We see the elevated noise and distortion relative to our reference amplifier. Power produced is right on the money at 146 watts.
Here is the same at 4 ohm:
The above tests are at 1 kHz. Here is what happens when we sweep the frequencies, aiming to measure power at 1% THD+N
Quite a drop in power with both loads when we get down to 20 Hz. The power supply capacitors are likely too small to keep up with the slow rate of change at low frequencies.
We see a similar view when we look at sweeps at different frequencies:
Finally, some people like to see intermodulation distortion of 19 + 20 kHz tones so here it is at max power:
Conclusions
The Outlaw Model 7140 has a very sturdy build. It produces good power per specifications provided from manufacturer (at least in two channels). The down side is too much ground/mains leakage and distortion+noise that is slightly below average. Paying more (a lot more actually) will get you sharp reduction of such problems.
For typical home theater duty, the 7140 should do the job fine. It just isn't something to get excited about from pure performance point of view.
------------
As always, questions, comments, recommendations, etc. are welcome.
Folks, I was not kidding when I said this amp nearly killed my back to carry it upstairs to my lab. To keep testing these things, I need to get one of those staircase elevators old people put in. And that costs serious money. I appreciate you all donating to get me one of those things to save my back using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
The 7140 is a beast of an amplifier, nearly breaking my back carrying it up to my lab:
The design is highly modular with a massive toroidal transformer powering 7 independent amplifiers, each with their own power supply on board. The heatsinks are rather beefy with plenty of distance between them and top of the unit. The feet are also quite tall allowing better ventilation from bottom to top.
The back panel shows the inclusion of XLR inputs which I appreciate:
The inclusion of a grounding terminal was interesting. It did no good in my testing with XLR inputs as it should not.
During use, the 7140 was quite stable, never complaining, shutting down or anything as Audio/Video Receivers (AVRs) tend to do. Clearly then this is a more robust solution than internal amps in those units.
Power Amplifier Measurements
As usual we start with our dashboard view of 5 watts into 4 ohm load using a 1 kHz tone:
I was surprised to see such high mains hum at 60 Hz. A prior review of another unit with just RCAs complained about the same thing and recommended a ground terminal on the unit which they have added. But as I mentioned, it made no difference. I have to think this is magnetically coupled into the amplifiers.
Fortunately or unfortunately the distortion spike from 2nd harmonic is bit higher still so didn't impact measured SINAD (combination of noise and distortion relative to our main tone). As it is, the 7140 lands below the average for all the amplifiers we have reviewed so far:
Frequency response is flat enough:
32-tone signal to resemble "music" shows the typical rise of distortion with frequency:
And rather high noise floor which could be caused by that power supply hum.
Here are the noise figures for 5 watt and full power:
We are not clearly more than 14 bits or so at 5 watts so not very quiet.
Here is our power versus distortion and noise at 8 ohm:
We see the elevated noise and distortion relative to our reference amplifier. Power produced is right on the money at 146 watts.
Here is the same at 4 ohm:
The above tests are at 1 kHz. Here is what happens when we sweep the frequencies, aiming to measure power at 1% THD+N
Quite a drop in power with both loads when we get down to 20 Hz. The power supply capacitors are likely too small to keep up with the slow rate of change at low frequencies.
We see a similar view when we look at sweeps at different frequencies:
Finally, some people like to see intermodulation distortion of 19 + 20 kHz tones so here it is at max power:
Conclusions
The Outlaw Model 7140 has a very sturdy build. It produces good power per specifications provided from manufacturer (at least in two channels). The down side is too much ground/mains leakage and distortion+noise that is slightly below average. Paying more (a lot more actually) will get you sharp reduction of such problems.
For typical home theater duty, the 7140 should do the job fine. It just isn't something to get excited about from pure performance point of view.
------------
As always, questions, comments, recommendations, etc. are welcome.
Folks, I was not kidding when I said this amp nearly killed my back to carry it upstairs to my lab. To keep testing these things, I need to get one of those staircase elevators old people put in. And that costs serious money. I appreciate you all donating to get me one of those things to save my back using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/