Sony TC-K81

It’s hard to understate just how important Compact Cassette was as a format in 1979. The Long Playing record was now in the late autumn of its life – or so we thought – with ever more people buying pre-recorded cassettes instead of vinyl. The quality of LP pressings seemed to be falling off a cliff at that precise time – with thin, recycled vinyl that warped easily becoming the norm. Simultaneously, both cassette hardware and software were taking a sudden turn for the better, and now offered far superior performance to just five years earlier.

For example, Sony’s foray into high end cassette begun in 1974 with the TC-177SD. A top loading, dual-capstan, three-head design, it was one of the most sophisticated machines around at the time – yet couldn’t hold a candle to the Sony flagship of just half a decade later in terms of sound quality, features or performance. At the same time, tape formulations had vastly improved since the mid nineteen seventies, with IEC standardisation of all recording media making getting good sound from Compact Cassette far less hit and miss.

In 1979 Sony dramatically refreshed its range, getting rid of the machines it had been running for several years and which now looked and felt antiquated. Top of the new line was the TC-K81, and it couldn’t have looked more different to the company’s previous high end decks. Its immediate predecessor – the TC-229SD – had been a large, chunky and heavy front-loader with two heads and big analogue VU meters. Here now though, was a new slimmed down product measuring 430x130x290mm and weighing 6.3kg, that had three heads, dual capstan drive and sophisticated bar-graph LED metering, complete with peak-hold facility – plus much more…

Selling for a not inconsiderable £399 in 1980 – that’s £1,989 in today’s money – the TC-K81 was a high end machine that normal people could at least dream of owning, unlike top end Nakamichis which cost as much as a new car. By this time however, the Japanese Yen had begun its long rise in value, and manufacturers had begun to cut costs – so the new Sony was less hefty than the company’s flagship decks of yore. It was still very well made though, and unlike its forebears had a delicate, high precision feel to the way it worked. It sported a satin silver pressed steel case and a matt-finish diecast aluminium front panel – unlike the lesser decks in the new range which had a sheet of aluminium clipped over a plastic frame.

Central to the TC-K81 was a miniature version of Sony’s BSL (Brushless and SlotLess) direct drive motor, driving the flywheel via a ground flat rubber belt. Coincidentally, this same motor was also found in the company’s top PS-X800 Biotracer turntable’s tonearm servo drive, so was a true quality item that worked smoothly and silently. Also fitted were Sony’s new Sendust & Ferrite heads, completely separated for recording and playback but aligned with one another to prevent azimuth error issues. Sony’s whole new cassette deck range had a crisper and sleeker look than what had come before, with a large, non-tinted cassette door with backlit tape window, plus precise logic controlled transport buttons. The result was a utilitarian looking yet still ergonomically excellent fascia that was pretty self-explanatory to use. The excellent tape calibration system – engaged via the ‘Cal’ knob – worked with the LED level meters to offer fine adjustment of the deck’s recording level calibration and bias.

The other big ‘wow factor’ was metal tape compatibility. This had arrived barely a year before the Sony deck was launched so was an early implementation – yet was still done perfectly. The TC-K81’s new Sendust & Ferrite heads were able to record higher levels than the Ferrite & Ferrite types fitted to previous models, as well as resisting the inherently more abrasive nature of this new tape formulation. Using a Sendust core set into a Ferrite guard block, the record/replay heads work as well today in my example as they did when new, forty years ago.

If you knew what to look for, you could see how serious this machine’s recording credentials were just by the inscriptions in the metering section. At that time most Japanese manufacturers put the Dolby level reference – which is an absolute signal magnitude referenced by a calibrated mater tape – at around +3dB. Sony however, put it at -2dB on the TC-K81, proving that the deck had far more headroom than most cassette decks. Able to record much higher than the Dolby reference level without distorting, this was an impressive party trick that made for great recordings.

Compact, sleek and stuffed with ‘hi tech’ features, you could argue that this was one of the first of the modern era of hi-fi stereo cassette recorders. Metal tape, peak meters, fine bias and record calibration all seemed very impressive at the time. Yet in many ways, you could view it as the last gasp of the older generation. By the late eighties for example, most budget cassette decks were quieter, measured better and had clever features undreamed of by Sony when the TC-K81 was born. For example, there is no Dolby C or S noise reduction, nor does it have a built-in DAC like some of the last Aiwas, nor is there a powered cassette door. Metering is good but it got better still and was matched with digital tape counters that showed real time – unlike the Sony’s old mechanical affair.

For its time, it measured superbly – there were few decks that did better at any price. Claimed frequency response was 20Hz to 20kHz with Type IV (Metal) tape; with Type I (Ferric) it was a very respectable 20Hz to 16kHz. Signal to Noise Ratio was quoted at 65dB (with Dolby B in) and wow and flutter was said to be 0.04%. The line level output was a paltry 0.435V (compared to a nominal 2V line out from a modern CD player today). These are all excellent figures for the day, but by the mid-nineties an entry level Sony cassette deck did better. Such was the relentless march forward of progress…

This said, there’s little that’s vintage about its performance – indeed it makes superb recordings for a deck of its day. In my view, it’s head and shoulders above earlier generations of high end Sonys, thanks in no small part to the excellent dual capstan transport and the calibration functionality. It means that you can feed it with a humble TDK D ferric tape and be amazed at how clean and open things sound. Better still, you can punch high levels onto the tape – up to +4dB without any appreciable distortion. It’s not quite high end Nakamichi territory, but it’s still really good for a deck that reached British dealers’ shelves in 1980.

How does this translate into sound quality? Well it means that you can take a budget tape and squeeze the living daylights out of it, so to speak. The classic budget formulation of the nineteen eighties, TDK D sounds slightly opaque and a little loose in the bass and smooth in the treble, but flicking between source and tape monitor as it records still shows that there isn’t that much of a difference. Move to TDK SA Type II tape, reset the bias and record calibration, and suddenly you’re listening to quite a different sound. Now you can tell why so many people bought this tape; it cost twice as much as D but was more than twice as good sounding. There’s a good amount of air and space in the upper mid and treble that wasn’t there before, and TDK D’s slight vagueness on, say, hi-hat cymbals has been replaced by a much more precisely defined metallic sheen. In the bass, things tighten up a lot too, and the music just sounds far better resolved and vibrant.

Try Sony Ferrichrome – the company’s top tape formulation before Metal came along – and after resetting the calibrations, again one is most pleasantly surprised. The midband cleans up further and there’s a superior sense of detail everywhere, alongside better three dimensional scale to the soundstage. Bass is tauter still and treble sounds less tinselly and more finely etched. Move to TDK MA – a Type IV Metal formulation – and the deck soars ahead. You can really push the recording levels up with this, and the sound is much more dynamic; there’s more energy to the music as things get much closer to open reel. Bass gains real power, the midband is clearer and with better definition, and treble is brighter, better etched and more sparkly. You can see why Metal tape was such a revelation at the time, even if at around £10 a go it was beyond most people’s means.

Although this deck has excellent transport and heads, my only criticism is that the electronics aren’t quite as good – it’s quiet enough but things sound just a little too dry and lacking in real low level detail. Later cassette decks from all brands improved noticeably here; for example I found that this issue even befell top end Nakamichis. The electronics of the ZX9 of this period were obviously less warm and open sounding than the mid eighties CR7, for example.

Although not the finest cassette deck in the world then or now, the Sony TC-K81 was a real class act at a time of flux in both hi-fi and cassette technology in general. It offered meaningful audiophile features alongside almost no gimmicks whatsoever, and a really good performance that let users squeeze excellent results out of any tape – budget or high end – capable of it. Strange then that it has slipped down the memory hole simply because its brand name isn’t trendy enough for some, because it deserves so much better.


  1. Hugo

    Nice review.

    I never had a Sony from that era.

    A year ago I sold my TC-K770ES (1991).
    Great deck to be honest.

    But my other decks perform better.
    (Nak 582, Aiwa AD-F770 and a Denon DR-M44HX)

    But.. I have two Sony decks in good condition,
    for the looks. Their perfect design.

    A TC-K88B and a TC-K7B II.
    Yes older (Pre-Esprit era), 2 heads, no dual capstan.

    My Alpine AL-90 is still under repair.
    How will I find the time… ?? Oh well.

    Thnx for the time you have put in this review.


  2. Gumer

    3 years ago I bought a TC-K81 together with a TA-F55 and an ST-J55 for a few euros and I was hooked with this brand and that period. I’m waiting a pair of APM-77W from repair …
    Thank you very much for all your reviews, always interesting and enjoyable.
    Greetings from Barcelona

  3. Heinz Anderle

    The predecessor of the international version of the TC-K81 was the TC-K75 with plain ferrite heads, but the same features for tape calibration and level monitoring. Introduced in 1979 and available only for about a year, it was marketed at the same time as the highly appraised Eumig FL-1000 – but for one of the Austrian “luxury saloon decks”, you could buy about two and a half Japanese fully equipped “slim sedans”.

    The Eumig as well as the Austro-Dutch Philips N4522 2-track reel to reel tape recorder of the same year may then have given a richer and more voluminous sound, but the Sony did not record worse on the TDK SA tape generation of that year with Dolby B NR, if the cassette was played back on a suitable deck.

    I would regard the TC-K75/TC-K81 as quite ahead of its time, uncovering the real potential of the cassette before the advent of the studio-grade decks such as the TC-K777ES or the Revox B710.

    (I am from Austria and could acquire the vintage testimonies from the past – but I was not surprised to hear the Sony deck and the TDK tape as equal and equivalent.)

  4. Garic Nosvidad

    I remember seeing this cassette on display in London in or around q980…it was sitting with its sisters, the k55, 61, 65, 71 and 75. I hD just been given my first “Pye” mono player…and went to buy some tapes (agfa c60’s)…the Sony display just made my jW drop… I wanted one of those decks….didn’t care which one…but any would do…. well only had to wait 40 years.. I have the k22, 33, 44, (not 45 or 51 yet) 55, 61, 71, 75 and my holy grail 81 should be here within a week….they say you should never meet your hero….but I think on this occasion I could take the chance. The TC-K51 is more of a challenge…..but I am ready to finish my quest.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: