Only recently did I learn that successive generations of the Chevrolet Corvette are referred to by the cognoscenti with two-character alpha-numeric identifiers: C1, C2, C3, and so on. I learned this while reading about the most recent version—C8, known to non-cognoscenti as the 2020 Corvette—which happens to be the first version since C2 that impresses me. (I say that as one who used to work for the owner of a C3, a then-middle-aged male who actually boasted, while under the influence, that he and two of his C3-owning friends drove them solely because their juvenile styling attracted juveniles. Rest assured I left his employ within days of that revelation.)
In most ways, the Shindo Cortese power amplifier ($13,500 with F2a output tubes) is as far from an audio Corvette as one can get. It is modestly powered, its build quality is in tune with its luxury-goods price tag, and its styling is the very soul of mature understatement. Yet it, too, has gone through a number of versions, evidence of which hides behind the amp’s modestly-sized casework.
The late Ken Shindo, who founded Shindo Laboratory in 1977 (footnote 1), was also known for his distinctive model designations—some are the names of rare wines, some are musical terms, at least one is a woman’s name—which he recycled from time to time. Thus Haut-Brion has been both a KT88-powered monoblock and a 6L6-powered stereo amp, Petrus has been both a two-box and a single-box preamplifier, and so forth. But as far as I know, Cortese has always been a stereo, single-ended amplifier priced near the budget end of the Shindo line.
The Cortese is known by most Shindo enthusiasts in the US—which is to say those who’ve come on board since 2003, when Tone Imports introduced the brand to North America—as a single-ended amplifier that uses one F2a power tetrode per side, offering about 10Wpc. (Indeed, if you do a search on the F2a tube, which is relatively unknown among audiophiles, photos of the Cortese will be among your first hits.) Throughout most of that time, the amp’s small-signal tube of choice has been the 6AW8A triode-pentode: Some versions of the amp used one of these per channel, others two—yet in either case, the Cortese is a three-stage design, like all Shindo amps I’m aware of. Most of those Corteses used solid-state rectification, yet an earlier, pre–Tone Imports version included a rectifier tube and used 300B directly heated triode output tubes instead of the F2a indirectly heated tetrodes.
In some ways, the most recent Shindo Cortese, designed by Takashi Shindo and available in the US since 2017, harkens back to older versions. This version, too, uses a rectifier tube (a 5U4GB), and the amp is available with either new-old-stock (NOS) F2a or newly manufactured 300B output tubes. I haven’t heard the 300B version ($12,995), nor do I know what technical changes were required for the amp’s use with that popular output triode—but field-swapping a four-pin tube and a nine-pin tube, the latter requiring an oddball, asymmetrical socket, is clearly not possible. (Note also that the new Cortese’s four-pin 300B sockets are mounted on a separate, recessed platform, presumably because those tubes are taller than F2a tubes. The tube cage could not otherwise clear them.)
Another twist: For the new Cortese, Shindo eschews the Philips 6AW8A—a tube whose prevalence in post-2010 Shindo amps and preamps was striking—in favor of an NOS Telefunken ECL82, also a pentode-triode. Here, Takashi Shindo uses a single ECL82 per channel—with the input signal from the volume pot appearing on the signal grid of the triode half, which is not how things were done in the earlier Corteses I’ve seen.
Internal changes abound. In addition to that rectifier tube, the Cortese’s power supply resembles that of the very earliest Shindo amps in its inclusion of a very large NOS 10.0 Mf [10µF], 600V oil capacitor (an NOS Micromold Radio cap, in this case) in the power supply’s pi circuit. (But unlike those early amps, including the whimsically named Sinhonia and the enduringly available Western Electric 300B, the new Cortese stows its oil cap underneath its transformer cover rather than letting it share real estate with the tubes.) And the use of a rectifier tube has made redundant the EY88 diode tube that’s used to slowly ramp up the B+ voltage in so many other Shindo amps.
The new amp’s circuit layout, which is tidy to the point of being unabashedly beautiful, also shows Takashi Shindo’s predilection for putting passive parts on tag boards—in this case, another beautifully finished steel plate. In his father’s later products, resistors and capacitors were fastened to seemingly random lengths of terminal strip, their physical positions dictated by their locations within the circuit.
Perhaps most striking is this Cortese’s use of auto-bias for its output tubes: The amp is designed and constructed without a bias-voltage supply. (The circuit contains only a single solid-state bridge rectifier, for the tubes’ heater voltages, and one solid-state regulator, apparently to maintain precise screen-grid voltages: The output tubes are operated as tetrodes, not triodes, and the pentode halves of the ECL82s are operated as pentodes.) The cathodes of the F2a tubes are raised above ground via 150 ohm, 30W Dale wirewound resistors. (On earlier, fixed-bias Corteses, cathodes were held only 1 ohm above ground—a boon to the math-challenged technician, since voltage measured across those resistors was the precise equivalent of bias current—and the negative bias charge was adjustable with potentiometers.) The new amp also has an output-tube plate voltage of 359.2V, which is lower than the 387 volts I noted in my first (2007) Cortese. (Screen grid voltage is held at 313.6V, vs the earlier Cortese’s 369.2V.) Between that and the fact that, in an auto-bias circuit, the tube “sees” only the voltage differential between the cathode and the plate, it’s a safe guess that the amp’s notably robust F2a tubes will enjoy very long lives relative to other audio-output tubes run in class-A.
One other change worth noting: Less-than-generously-sized though it may be, the newest Cortese is slightly larger and heavier than its predecessors. It measures 15″ wide × 8.85″ high × 11.6″ deep and weighs 32.4lb, compared to 13.75″ × 6.7″ × 10.25″ and 27.5lb for the earliest one.
Other things remain the same. The output transformer of choice in the latest Cortese, as in every other Cortese I’ve seen, is a Lundahl LL8820, a single-secondary design that appears to be a Shindo exclusive. Similarly, the mains transformer is a robust, copperwrapped Denki that’s at least outwardly similar to those in other Shindo amps. The dual-mono level pots are the same Japanese-made Cosmos I saw in the very first Shindo amp I encountered (the original EL84-equipped Montille), and which I’ve seen in no other audio gear. Its inputs are low-mass Switchcraft RCA jacks, which apparently offer desirable electrical and thus sonic qualities in compensation for what they lack in reliability. (As someone who breaks and makes signal connections far more often than the average enthusiast, I’m forced to keep spares on hand; for most users, that surely won’t be necessary.) And the steel enclosure and removable tube cage are of the same very high quality construction and finish as seen on all Shindo amps and preamps.
It almost goes without saying that the Cortese is a physically beautiful thing, in a Bauhaus sort of way. Company founder Ken Shindo felt that enclosures made of steel result in better-sounding electronics than those made of aluminum, but of course steel needs paint, and Shindo’s enclosures have almost always been painted—every surface, inside and out—in a trademark shade of green.
The amp’s published specifications are minimal (footnote 2). According to the supplied one-page info sheet, apart from its 10Wpc power rating, the new F2a Cortese exhibits an input impedance of 100k ohms, an input sensitivity of 1V, and a signal/noise ratio of 90dB.
Note to self
I pride myself on making and keeping extensive notes on the most interesting products that have come my way, and that includes almost every Shindo preamp and amp I’ve had in my home long enough that I could open them up and see what makes them tick. So you can imagine my frustration at not being able to find the notes I made in 2007 or ’08 when I brought the then-current Cortese to the test bench of my friend Neal Newman and we conducted some basic tests (footnote 3). I can’t quote the precise output power numbers we observed—but I can assure you that the amp proved most powerful when driving a 16 ohm load, confirming the assumption that the single secondary coils of the Cortese’s Lundahl output transformers were optimized for such high impedances. That’s unsurprising, given Ken Shindo’s obvious fondness for pre-1969 Altecs and similar vintage loudspeakers. (Jonathan Halpern of Tone Imports tells me that, during a long-ago visit to his sister’s home in Boston, the elder Shindo found, in a thrift store, a good-condition pair of Altec Flamencos, such as I own and enthusiastically use, and went to considerable trouble and expense to ship them back to his workshop in Tokyo, where he set about modifying them: a story for another day.) Also unsurprising: Although the Cortese sounded quite fine on my DeVore O/93 loudspeakers, it locked in better with my own Flamencos, and it is that pairing that forms the basis for the comments to follow.
Footnote 1: Shindo Laboratory, 20–9, Hongo 2 Chome Bunkyo-ku Tokyo 113–0033, Japan. Web: shindo-laboratory.co.jp. US distributor: Tone Imports. Web: toneimports.com Email: firstname.lastname@example.org.
Footnote 2: On Shindo’s website, one can see only the specs for the 300B version.
Footnote 3: One test Neal and I never performed on a Shindo amp was measuring the output tubes’ current draw under dynamic conditions, in an effort to determine the power envelope in which it is true class-A: That requires unsoldering and resoldering at least one connection, which I avoid doing to someone else’s property, especially something as meticulously built as a Shindo. In any event, a single-ended amp such as the Cortese always operates in class-A, by definition.