This is a review and detailed measurements of the Audio Research Corporation (ARC) 100.2 stereo power amplifier. It is on kind loan from a member. The 100.2 came out in year 1998 at a cost of US $2,995. It was later raised to US $3,495. If I remember correctly, the owner told me this the last solid state amplifier ARC produces before going to all tube route.The 100.2 is as solid as a rock:The back panel is as you expect with the exception of (custom?) speaker binding posts:In use the 100.2 cooked and cooked good. I measured 45 to 47 degrees C on the heatsinks. The internal temps are likely much higher. I read that it uses unobtanium output MOSFET transistors so if they go, you likely have a giant door stop.In use though the 100.2 did not complain one bit and ran through all of my tests.Strangely when you power the unit down, it takes it a while to do that. What it is doing, I don't know.The design of the unit is based on low feedback factor of just 6 dB. Based on that alone I can tell you it is not going to perform well.We have huge power supply peaks, like due to poor power supply rejection ratio of low feedback design. Secondthird harmonic dominate the distortion profile resulting in lackluster SINAD of just 65 dB. That lands the ARC 100.2 near the bottom of some 72 amplifiers tested so far:Frequency response is excellent:Response changes some with a simulated 2-way speaker load but nothing to cry over:Multitone test shows the high distortion products of the power supply:And rather high noise floor which we can directly measure using signal to noise ratio:Crosstalk shape is odd but not an audible concern:The sins of low feedback factor stare at you in the face with our 4 ohm load:Yes, distortion gradually increases but then it clips anyway. So why not have clean power until clipping???Same deal into 8 ohms:At least it slightly exceeds its power specifications.Strangely burst power (momentary peaks) doesn't generate much more power:Keeping THD+N constant at 0.1% gives us incredibly low and strange amount of power:There is so much distortion and noise in the output of this amp that you don't get much power if you set your goal at 0.1% THD (likely threshold of audibility for some people). FYI I ran the above at 0.2% THD+N (not shown) and it produced about 80 watts with a straight line. Anyway, who says only class D amps have trouble with this test?I powered the unit cold and let it run nearly half hour while recording distortion and noise. This is what I got:That is very high degree of improvement. Again, low feedback means that it is more sensitive to operating temperature. Given the high heat dissipation, it is a tough deal to have to also keep the unit on for a while to get the best performance.Sigh. The best analogy I can think of here is if car owners said, "you know, a car should have more square tires" and manufacturers running to build cars that way. Yes, audio folklore says feedback is a bad thing. Well, I have news for you: distortion is really, really bad thing. As is noise. It surely doesn't give you "blacker background" if it has higher noise, does it?I read some place that it has less feedback so it can deliver less phase shift. Do folks not know that you have reflections in your room, every one of which arrives at your ears with a different delay and hence phase? That they all mix up and as a result, the brain discards that info? If it did not, we would go crazy trying to make sense of people talking to us in indoor situations. Anyway, we digress.Needless to say,Serviceability will be poor and so will the performance.------------As always, questions, comments, recommendations, etc. are welcome.Been working on a project morning to evening every day and spending the last two hours before midnight on reviews. Even the panthers are feeling sorry for me. If you do too, pleaseusing