Kenwood L-02A

May
1 9 8 2 may 1982
1 9 8 5 1985

Kenwood's masterpiece, becoming an instant hit in Japan - consumer and reviewer-wise.
Unfortunately remaining largely unobtainable elsewhere.

This was however very different than the earlier L-01A or KA-1000 : no Heat-Pipes and a "normal" metal & aluminium chassis.
The 01A and 02A were just two years apart from each other but they were completely different. And the L-08C / L-08M combo, standing in between, was again a different story - Kenwood was searching and searching more for the right high-end formula...


The L-02A is a large two-piece arrangement : inputs, outputs and controls in the big box, power-supply in the L-02A-PS rear-attached box.
The latter holds three transformers : two big (enormous) EI, plus a smaller one for the control, LEDs and motorized tray. That box can be either attached directly to the back of the L-02A or separated from it as far as four meters by way of (thick) multi-pin cables.

Nine power-supply routes and seven windings separately feed the EQ stage, the voltage amp and, separately, the high rail / low rail of the L and R channels' pre-driver and output stages.

DLD (Dynamic Linear Drive) is a dual-rail circuit operating in parallel to the normal power stage ; its switching speed reaches the Ghz.
Whenever superior power output needs are sensed between the pre-driver and the driver stages, the signal is assigned to the high-power rail which "glady obliges by delivering the brief energy peak needed'.


In the same vein, the Sigma Drive circuit allows a super-high damping factor by linking the loudspeakers' returning electrical energy and the overall NFB loop. Super-high damping factor here means 10,000 at 55Hz !
The link is made with a supplementary set of cables and terminals on both sides. The Sigma Drive circuit doesn't like mishaps : make a mistake in the 8-wire hookup and you'll end up with an expensive set of four big black fried french fries !

An internal Sigma Drive circuit is also used between the pre and power stages to compensate for signal loss and keep a low internal impedance.

There are only two NFB loops in the 02A, one of which is for the MM/MC stage, the other for the amplification's overall circuit (and the Sigma Drive loop).


The chassis of the L-02A is made of metal but all strategic circuit areas use non-magnetic materials to avoid stray currents and magnetic inteference.

Besides the external PS, the various stages in the main chassis are physically shielded from the others.
The two enormous 90V / 10,000µF ELNA main caps and their 50V / 8000µF auxiliaries are horizontally on one side of the chassis (left), the volume and MM/MC stage on the opposite side (right), output stages center, the heatsink forming a central venting area between the top and bottom of the chassis.

All inputs/output switching is done by "microprocessor-controlled" sealed solenoid relays for shortest signal paths.
The output transistors are Toshiba's 2SA1095A / 2SC2565A bipolars, two complementary pairs per channel ; ICs inside are mostly Toshiba, too.


The belt-motorized tray hides input switching, rec out selection, speaker on/off and other basic controls, all with blue pads scripted in... green !
The belt drives an endless screw like the tray of the Sony TC-K88B ; there is a locking screw at the bottom of the 02A to keep the tray safe when in shipping - don't forget it !

The variable loudness / bass boost was inherited from the L-08C and allows a continuous 30Hz...100Hz center frequency with +3, +6 or +9 boost.
As on the L-01A or L-08C, one can only select off the front "tape, "phono" or "others", where "others" means the source selected on/in the 'hidden" tray which therefore acts as a sort of preset... A bit awkward.

The technical blurb scripted left of the faceplate is typical of the times... and the specs quoted there differ from those of the service manual :)
There are unused areas for another RCA input (CD ?) and a DIN i/o on the circuit boards, too.
The AUX input is located at the bottom of the front, under the tray (awkward again), alongwith headphones.


Looks-wise... let's face it, this was a bit blunt. Make that quite blunt.
Impressive for sure but not too fine regarding finish and texturing. The reason why L-02As visually age poorly : black is black is black never did age very well, whatever the brand or timeframe... We were there far from the Supreme series. Horribly difficult to photograph, too, as visible from 90% of the literature published for it.


The last test and measurement were done at Kenwood during november and december 1981 and actual production was rushed shortly afterward ; this may explain some of the awkward details noted above.
The same happened to the 01s and the 08s : production-wise, Kenwood seems to never have really recovered from the sadly aborted LX 1978/1979 project.

But the L-02A was made to be mated with Kenwood's L-02T tuner masterpiece and the L-07D turntable masterpiece. And also the LS-1000 sleeper - searching everywhere made very good for Kenwood in those days.



This extensive post was originally made possible thanks to Patrick Matucci, Kenwood enthusiast.
Thanks to Jason, too, for the literature originally uploaded on the Kenwood Yahoo discussion group.

Since posting this page on the old TVK in august 2005 (!), I have found a lot more, here posted - and I still have more to come !

A wealth of detailed internal views can be seen at the indispensable amp8.com : here or here or here.

Kenwood L-02A, image 1 Kenwood L-02A, image 2 Kenwood L-02A, image 3
Kenwood L-02A specifications
Title Value
Power : 2x 170W (20Hz...20Khz, 8 Ohm, 0,003% THD)
THD : 0,03% (rated power, 8 Ohm)
0,003% (1/2 rated power, 8 Ohm)
0,003% (1W, 8Ohm)
0,003% (phono IN to speaker OUT, -20dB volume)
IMD : 0,03% (rated power, 8 Ohm)
Rise time : 0,9µs
Slew rate : ± 150V / µs
Frequency response : DC...350Khz (-3dB)
Damping factor : 10,000 (55Hz, 8 Ohm)
Speaker Impedance : 4...16 Ohm
Inputs : 2,5mV at 33 / 47 / 100kOhm (MM)
0,1mV at 100 Ohm (MC)
150mV at 30kOhm (tuner, aux, tape 1 & 2)
MM max input level : 350mV (RMS, THD 0,007% at 1Khz)
MC max input level : 15mV (RMS, THD 0,007% at 1Khz)
S/N ratio (IHF-A) : 91dB (MM, 2,5mV input)
97dB (MM, 5,0mV input)
103dB (MM, 10mV input)
73dB (MC, 0,1mV input)
110dB (line inputs)
Tape output : 150mV at 430 Ohm
RIAA : ± 0,2dB (20Hz...20Khz)
Loudness control : +3 / +6 / +9dB, variable from 30Hz to 100Hz
Subsonic filter : 18Hz (6dB/oct.)
Dimensions : 48 x 18,3 x 48,2cm (with PS unit)
Weight : 34,5kg.
List price : 550,000¥ (1982)
Kenwood L-02A : 0 topic
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page online since : august 2005
page updated : july 2010
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