I don't really do reviews, but I want to discuss the popular Reisong A10 SET tube amplifier. It is available on Amazon for $450 or less. I first heard about this amp on Steve Guttenberg's YouTube channel. I was intrigued by it and decided to purchase one this past winter. I've been listening to it on and off since, and so far I'm impressed.
While I own around 15 different vintage tube amps, amps aren't the most important component as far as my listening enjoyment goes. Speaker selection is a lot more important. If you are into vinyl, I'd say the cartridge and stylus are the second most important components. I enjoy tube amps for the nostalgia of using vintage technology, and for the aesthetics. I've also come to enjoy the challenge of making 60 year old amps sound as good as new.
With that said, if you do what to try a tube amp the Reisong isn't a bad first choice. What do you get for $450? A handsome chrome, made in China, chassis, a 5 tube configuration (including two EL 34s output tubes), and a simple hand wired SET (Single-ended Triode) circuit. It has two line level inputs and a volume control which makes it work as a simple integrated amp.
Those are the good parts, so what's the compromise? It only has 6 watts per channel. 6 watts may sound like nothing by todays standards, but to put it in perspective I have a pair of 300B based SET mono-blocks which put out a minuscule 3 watts per channel. The Reisong doubles that output! And overall the Reisong is a bargain in today's market where quality vintage tube amps are selling in the $1000+ range.
While there are limitations with only 6 watts per channel, a lot of people are driving relatively inefficient speakers using this amp (myself included). I'd argue that most speakers really aren't that inefficient anyway. For instance my "inefficient" Sony SS-M3 may rate at 85db and the Klipschorn (a very sensitive horn speaker) has a rating of 105db. That is at one meter with one watt of input. While 20db may sound like a big difference, I'd argue they are basically in the same order of magnitude, and while it may take twice as much power to drive the Sony speakers to the same level as the Klipsch, it doesn't take 10 times as much.
While you can drive efficient speakers to higher volumes with the Reisong than inefficient, if your goal is listen to music at mirror shattering levels, a tube amp might not be the right choice. On the other hand, the Reisong at 6 watts can drive most speakers to room level listening volumes.
Where the Reisong shines, like a lot of tube amps, is in the midrange presentation. While it is subtle, it increases the soundstage. While the simple circuit (sans even a negative feedback loop) doesn't deliver a lot of power, there are far fewer components in the signal path than in more powerful amplifiers. It could be argued that helps improve the critical midrange performance.
The Reisong starts to fall apart when pushed to create a lot of bass with small speakers in small enclosures. With that type of load, you can drive it to clipping levels. But all amps more or less struggle at this task. When using the Reisong you are wringing all can out of the small amp at louder volumes, where more powerful amps leave tons of power in reserve that you will almost never use.
Further, it rolls of the top end off fairly significantly (as measured by a third-party and confirmed by my own listening). It gives it more of a warm "tubey" sound which may or may not like.
This amp works well combined with a powered subwoofer and active crossover, which is how I run it. My subwoofer handles the power intensive bass region and filters frequencies below 100hz from the Reisong and my main speakers. Then you kind of get the best of both worlds. Tube presentation and solid state grunt down low.
In conclusion if you are looking for a perfectly flat and powerful amp, this probably isn't the best choice. On the other hand you want to try the "tube sound" with out investing a small fortune or using vintage amps of questionable condition, then I think this is an excellent choice. Are there better tube amps out there? Absolutely, but they also don't cost less than $450.