Printed version of the French audiophile magazine ON-mag (issue 6/24) includes a thorough review of CAD-300 SEI vacuum tube (valve) integrated amp, our most affordable single ended design, bearing 15W of mighty triode power. (Yes, those 300B triodes can give tremendous sense of power reserve and huge dynamics due to the very nature of pure Class A single ended operation). Written by Pierre Stemmelin, this review is not yet available online, but thanks to our French distributor, Roboli Design, we obtained a copy (download PDF, in French). Using AI-powered DeepL translation engine, we produced an English translation, which was edited and abridged for clarity. We encourage all francophones to read the original French PDF or, even better, purchase the ON-mag at your local news kiosk. It’s good to know that our Cary Audio CAD-300 SEI was awarded ‘Top Audio 2025’ by On-mag!
Here’s some excerpts from the original review in translation:
We previously reviewed Cary Audio’s excellent DMS-650 network player as well as SI-300.2d solid state amplifier. While these two devices show that the American brand knows how to diversify, this should not obscure the fact that its reputation is based on tube electronics above all. With the CAD-300 SEI stereo integrated that we’re testing here, we’re going back to the roots. This amp uses a Single Ended 300B triodes in a single-ended class A mode, probably the most emblematic of the tube genre.
Luxury, handcrafted hi-fi amp built locally in the USA
The appearance of the Cary CAD-300 SEI leaves no doubt as to its ultra-pure audiophile approach and pedigree. It is relatively compact in size, but also quite heavy and solid (almost 25 kg on the scales). […] It’s made in in Apex, North Carolina in the United States (not Cary or Raleigh, which are nearby).[…]
The tubes on top panel are of Russian origin: three 6SN7EHs from Electro-Harmonix, for input and driver stages; two PX300B Gold Lion Genalex for amplification. Behind them, on the right and left side are two encapsulated output transformers required for this type of schematics. They flank the EI-type power supply transformer transformer and its two filtering capacitors (1200µF/250V each). We took a peek inside, removing the bottom panel of the Cary CAD-300 SEI. Very impressive manual job: everything is wired point-to-point, no printed circuit boards, which is true quality solution for this type of product. It looks chaotic, but actually follows a very precise logic, and we appreciated the use of high-quality components (1% tolerance metal film resistors, polypropylene capacitors, including ones made by ClarityCap).
Tried-and-tested audiophile approach
Function-wise, the Cary CAD-300 SEI settles on minimalist features which are nevertheless practical: volume, source selector and L-R balance. The only bonuses are headphone socket and IR remote control. Because it operates in Class A, the Cary CAD-300 SEI consumes more idle than when playing music (around 100 watts). With all this electrical power it only provides 2 x 15 watts of audio amplification. All the rest is dissipated mainly in heat and a small part in light. When the device is switched on, you can hear soft clicks of the tubes as they heat up while their filaments gradually start glowing red.
After unpacking, you need to plug tubes in, and adjust the bias current to be between 150 and 160 mA DC. For that you use a flat blade screwdriver to rotate a small adjustment potentiometer hidden in a hole in the back. You would need a multimeter. To simplify measuring a test cable is included, with 6.35 mm jack plug for amp test point and alligator clips for multimeter connection.
The legendary musicality of the 300B triode triode without noise and hum
Because of its limited power, albeit quite generous for a 300B tube amp in Single Ended mode, it is recommended to use Cary CAD 300 SEI with high sensitivity loudspeakers. Our regular Kelinac KEL 714 MG speakers, with a sensitivity of 93 dB per W, did the job very well.
From the very start we were pleasantly surprised by how quiet the amp circuit is. Quite remarkable for a tube integrated. We didn’t had to turn off the WiFi, unplug the Internet box or keep smartphones and other wireless devices off to listen in peace. Only by turning the volume all the way up and sticking our ears to the speakers we were able to hear the slight hum. More good news came very soon after: although we are far from being big fans of vacuum tube electronics, we were quickly won over by the great engaging sound of this amp. No smeared highs or the woolly bass that often plague 300B triode circuits.
We were charmed by the gentle musicality of the Cary CAD-300 SEI, with the sound being very lively and supple at the same time. Articulation is excellent on electric bass and double bass, without becoming too warm. In the midrange voices are wonderfully materialized and embodied, at the front of the stage, in the very centre, solid and unwavering. The vocals are almost palpable.
The stereo image is particularly impressive. It has an almost holographic presentation, with lots of depth and layering. It moves out from the speaker boundaries. It gives envelopment without becoming ethereal or detracting from the legibility of the message, but on the contrary, it retains a superb resolution and beautiful substance. […]
In a nutshell
The Cary Audio CAD-300 SEI is a proud example of tube amp with 300B triodes in Single Ended Class A configuration done right. Manufactured and designed with undeniable expertise, it avoids the pitfalls sometimes found in designs of this type. Moderately powerful, with fairly minimalist controls, this is a true hi-fi amplifier for purist audiophiles, a pearl of musicality if paired with good speakers.
