This is a review and detailed measurements of the Niles SI-275 stereo power amplifier. It is on kind loan from a member. The SI-275 is discontinued. But since it is sold to the custom integration channel, they come up used and in working orders (companies pull out gear wholesale to redo homes). I am told it can be picked up as low as US $100 to $150. I see one on Amazon for US $230. But there is a used one on ebay for $100.The look is fine:I like the tall feet on amplifiers to allow for more air flow. A massive heatsink goes the full width of the unit with beefy transistors. Love the fact that it has two trim resistors to balance the gain in both channels. So annoying that these days balance controls are impossible to find yet amplifiers routinely have gain that is different in each channel (causing slightly shift in imaging).Back panel is simplicity in itself:In use, the SI-275 was solid as a rock. Never shut down. Never complained even when fully clipped. The top of the unit barely got warm despite using traditional class AB amplification. That large and heavy heatsink does a great job of spreading the heat load. Nothing remotely like flimsy heatsinks in mass market stereo amplifiers or audio/video receivers.Here is our dashboard:Notice the perfectly matched channels. SINAD is middling but is actually better because distortion is near -100 dB. It is pulled down by power supply noise which due to being low frequency is not very audible. Using what we have, performance is slightly above average:Noise performance follows the same standard:Frequency response is dead flat in audible band and extends way up:The wider the bandwidth, the more challenging the design (if not done well, the amp can oscillate).Power into 4 ohm is healthy:Allowing for 1% THD+N, we get even more:8- Ohm power is:Response with bot loads is very controlled with no oddities.Amplifier was stable as soon as powered on and performance did not change much after running for a few minutes (not shown).The Niles SI-275 is made for abuses of custom integration channel which routinely stuffs amplifiers in places they don't belong (i.e. lack of circulation/cool air). Its construction is well beyond today's mass market product. Measured performance is just above average. Combine these with prices as low as just $100 and you have a great deal.I am happy to recommend used Niles SI-275. Bargain shoppers rejoice!------------As always, questions, comments, recommendations, etc. are welcome.I know... You think because no one goes out to eat dinner that my cost of living has gone down. But it has not! Plenty of expensive things to buy online. So please don't be stingy andwhat you can using