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When I got into speaker building, the main reason is the pursuit of the best affordable sound possible and to learn about what factors influence that and can be controlled. As a result, I have set up a lot of sound systems for myself and others - and have integrated amplifiers into projects such as boomboxes and soundbars. For some amplifiers, detailed measurements have been published. Unfortunately, for many other products specifications are not standardized or don't exist at all in any meaningful way, so it is difficult to make decisions on how a system might be set up or improved. When looking for high-value products, one frequently has to rely on subjective reviews and hearsay.
I've found value in measurements for speaker design, so a natural next step is to add the capability to measure other equipment. The industry standard for such measurements is Audio Precision, but their newer products have a 5 figure price tag, which is out of range for many hobbyists. It's possible to cobble together some reasonably priced, high performing D/A and A/D converters along with a few additional accessories and software to do the job, but the learning curve is rather steep. I wanted to find something reasonably accessible from a cost and usability perspective. Fortunately, there is a small business Quantasylum that is focused on that goal.
The Amplifier Test setup is built around the Quantasylum QA403 audio analyzer and QA451B Programmable Load, which should be sufficient for handling approximately 200W according to their ratings and with the capability of using external load resistors for higher power capability.
Low Budget Amps
Amplifier testing requires pushing equipment to its limits. As I am getting my process figured out, it seems prudent to start with small, cheap amplifiers. These fit the bill.
TPA3116 Amplifiers
When these class D amplifiers came out in the mid 2010's, they were touted as step up from small, low power T-amps and other chip amps. The advertised power output capability of the TPA3116 chip was 30W into 8 ohms and 50W into 4 ohms. My first experience with these amplifier was when I set up a friend with a pair of my Lithium speakers and a T-amp, which wasn't particularly happy running at 4 ohms and subsequently failed. Rather than trying the same thing and hoping for a different result, I bought a TPA3116 amp board, found a case that would fit, and assembled a TPA3116 amp that we ran off of a 19V laptop computer power supply. I think it is still running almost 10 years later. Back then, there weren't a lot of commercial examples, but a couple of years later I received a Dayton version as a door prize courtesy of Parts Express at a DIY speaker event. Here, I will compare that Dayton Amp to a couple of other early TPA3116 amplifier boards (including the "red board" I used for my initial build) from Chinese supplier Yuan Jing.
Vintage Receivers and Amplifiers
Over the years, I have been fortunate enough to have owned or listened to a variety of interesting Receivers and Amplifiers. Having grown up in the Monster Receiver era, I have fond memories of those big Sansui, Pioneer, Yamaha, Kenwood, and Technics receivers and hanging out at audio shops to listen to those. In my teenage years, I bought a silver-faced Pioneer receiver as the centerpiece of my first "real" audio system. Over my years in the audio hobby, I have owned most of the others on the list at one time or another and still own a couple of solid state Scott Receivers from that late 1970's era.
Many people still look at products from that period (and before) and lament that they don't make 'em like that anymore. In some ways, that's true. I don't really think about it that way though. The market just changed. The familiar brands from that era did go more "mass market" with more digital displays, more plastic, less overbuilt. There were also more options that entered the market at various price and quality points to fill that void. Brands like Marantz, Harmon Kardon, NAD, Carver, Luxman, Adcom, Rotel, and Parasound made equipment that generally was positioned above that mass market tier, but still not completely beyond the reach of middle class audio enthusiasts. High end brands such as Krell and Mark Levinson started to emerge as well.
That long-winded explanation at least partially serves the purpose of explaining what I will be considering within this category. In addition to the analog, silver faced receivers and amplifiers from the 70's, I will also include equipment from the 80's through early 2000's as I find the evolution interesting and potentially relatable for others that lived through that era as audio enthusiasts.
1970's and earlier Amplifiers and Receivers
Scott 375R
1980's and 1990's Amplifiers and Receivers
Harman Kardon HK3250
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