Kenwood KA-1000 vintage super-integrated- The Age Of Plastic...

At around the same time as The Buggles brought their weirdly-bleak view of the future to our ears, some new and slightly unorthodox-looking amplifiers were emerging from Japan. They would have very much seemed at home sitting in the background of the Video Killed The Radio Star video, on top of Hans Zimmer's keyboard rig. A visual reminder and statement that the 70s were over, with promises of a sleeker, more technological future to come.



Almost 4 decades later, I became aware of these unusual amplifiers.

During the covid shitshow, I finally managed to get hold of one, which, typically, wasn't working.


People would be shocked if they picked up the main portion of the KA-1000 as it is extremely light, due to the largely plastic construction. This was done as Kenwood chased a philosophy of low magnetic interference- hence as little metal as possible. Plastic sides and front with a thick glass panel embossed with logos for the controls hidden behind it.
Some might raise a cynical eyebrow at this point and ask whether it was really about the rather more ignoble concept of cost-cutting. However, Kenwood produced plenty of amplifiers with plenty of solid metal long after this, so I'm inclined to believe the reasons given.

The main reason for the lack of weight, however, is due to the three transformers for the amp being housed in a separate (and very heavy) box with its own small glass front, connected to the main unit by an prodigiously thick umbilical cord. Having opened this box (couldn't resist), you can see the big transformers for the left and right channels, stamped L-01.

This must refer to the "big brother" L-01 amp- very similar concept but on the ultra high-end level. At least I know the transformers are shared!

Freon gas heat pipe for cooling, as was all the rage in the hi-fi world of 1980.

The figures were fairly typical for a big Japanese integrated at the time- 100w/ch at 8Ω, accompanied by an unusual feature that, used correctly, could extend the feedback loop of the amplifier to include the speakers themselves- resulting in a massive damping factor which today's manufacturers like Hegel would be proud of. Kenwoods new futurist oeuvre had a fitting name for this wizardry- Sigma Drive.

Yet more unusual was that despite the conservative manufacturers rating of a 4Ω, independent tests revealed that this odd-looking thing could drive a 2Ω load without expiring in a heap of smoke.

The next step- well, there wasn't much of a next step as we sat locked in our homes. I had to get the amp working.

More to follow....

 

The L-01 transformers inside their seperate housing:

 

Lovely to see one of these! I remember lusting after one, along with the matching FM tuner back in the day. I recall reading a comparative review (IIRC by Chris Thomas?) of three £1,000 system, of which one had the Trio amp + PS fronted by a Sony PSX-600. The Trio amp took up much the lion's share of the £1k budget. IIRC he quite liked the amp but hated the rest of that system, particularly the turntable, feeling things improved greatly first with a Planar 3 and then with a Linn Sondek up front. I look forward to seeing more pictures and hearing more about the restoration.

 

Thanks for sharing. Very Space:1999. Isn’t there a British hifi manufacturer that embraced non-metallic enclosures. I recall a write up in the Listener. Boxes made from plexiglass. The name escapes me, but I think it’s three initials.

 

DNM
Dennis Moorcroft ?

 

NVA

 

Yes, that’s the one I was referring to.

 

Wasn’t Dennis Moorcroft somewhat controversial with some of his thoughts on audio amplifiers ?

 

Looking forward to seeing you restore this. It does look a bit like a mains consumer unit though!

 

Me, restore? I can just about manage a speaker crossover- wouldn't dare work on anything that plugs into the mains!

I've been very busy with clearing out my storage unit and getting ready to move into our new home- but I shall continue the tale as soon as I can.

 

And besides other goodies it sports volume knob memory after power off, in 1980!

 

It may look like the future then, but that feature was achieved with a piece of string and a rotary wheel (no, I am not joking!)

 

I know but that doesn't matter how it was implemented if it works )))

 

So, I now had the amp of mystery in my clutches, but of course, it wasn't working.

Having considered the issue for a while, I decided to kill 2 birds with one stone. At the time my gorgeous (and now gone) Sony TA-F7 Vfet integrated needed some looking over and I had tracked down the chap who had originally restored it, Chris Reddish.

After speaking to him, he agreed that I could bring both amps down to him in Manchester to be looked at.

After an initial inspection in my presence, he said that there were 2 options- simply get it working, or fix it properly replacing any out-of-spec components as well as the obvious dead ones. The latter option seemed the only sensible one.

After what seemed like an interminable wait (and it was many months), I heard from Chris that both amps were ready to collect..

The Kenwood had had a recap with Nichicon Golds where needed, and I believe the main issue had been some dead transistors- the ultra-high-speed originals are no longer available and substitutes have to be used. The cable-driven mute switching had also been repaired.

I took both amps back with me to Scotland, but it would be a long time before the Kenwood would ever be fired up, caused by the small matter of not having my own home for a 2 year period....

 

Freon heat pipe cooling system clearly visible:




(For those wondering about the stacked power supplies, I had, incredibly, managed to pick up a spare 240v power supply for the amp, fully working - but bearing the alternative Trio branding).








We are now at a point around. 2-ish months back- our new home being close to ready, bur definitely not yet ready for prime time, as the saying goes.

I set the refreshed Kenwood on top of an as-yet unpainted window ledge, amd connected it up to some other old survivors--a pair of low sensitivity Griffin APE 27 3-ways from the 70s. Obscure but considered by some (including those who sold them back in the day) to be a dangerous competitor to the Spendor BC1.

Tentatively pressing the power button, I waited, then started playback from my tablet.

At low volume, everything was sounding very pleasant. After a couple of minutes, I pushed the volume fader to somewhere that should be marked "enjoyable".

I was surprised by the clarity and definition. The duration and design of reverb tails and other fx were plainly noticeable. Bass seemed strong but not overwhelming. Although a mere test run,, I liked what I heard. I tend to enjoy a presentation unadulterated by he equipment itself to any great degree.
Sweet colouration, enhancements etc, are fun, but not my thing.

The KA 1000 sounded precIse, fast, ACCURATE.

I hadn't even tried out the Sigma Drive yet.

 

When you search for information on the KA1000, this article is the first one that comes up:

https://www.hifi-classic.net/review/kenwood-ka-1000-263.html

Fortunately, it is a no-nonsense review from those days of yore- when we were neither slaves to android-like "only measurements are useful, why bother listening to choose" paradigm, nor wallowing in a subjectivist's paradise where "the lower mids exhibited a chocolate-like voluptuousness- gateaux rather than meringue, if you will."

Anyway, (post mini-rant), examining the review above gives a good idea of the amp's capabilities.

The Sigma Drive was tested and found to have a minimal yet discernable impact, more apparent through measurement than listening. ASR heaven.

In this test, a pair Kef 105.2. were used for the Sigma Drive test.
I know someone who owns a pair- currently making up some narrow-gauge cables for Sigma Drive use- he has agreed to let me test the amp with them soon.

Will definitely try not to drink too much during the test. Honest.

 

Not too much but also not too little. I found myself when I'm getting a little tipsy (but little, and you must use specific bewerages, not all works) sound perception improves drastically.

 

In the days of, ahem, "good quality" substances, I found that a small intake would increase sound perception of things buried in the mix! It wasn't just imagination, as those newly-uncovered parts would remain audible when heard again "straight"....

 

I've always said this as well,though it's been a while!
And acid even more so......

 

But those bodge wires in last pic... I wouldn't want to work on one. And now I can see where Aiwa got inspiration for themselves and have done on another level.