HISTORY:
While my wife has an eye for "the arts" in all it's forms, she is not so keen on all the electronic gear that I used to acquire for later investigation ... my wife now says (after it having been in the spare room for 15 odd years) "for goodness sake, get rid of that mountain of gear" so them's my orders (and she is always right!) ... out goes all the equipment, some working fine and others are sick or dead!
This is an "interesting" amplifier from Sansui, a later model and quite a departure from their earlier "most magnificent" equipment. I am not saying that this amplifier is "bad" but just quite different to Sansui's earlier products (such as the AU-7700 I used to have) and obviously made with production cost savings in mind. Well laid out inside (although I do not like amps with the power transformer sitting to one side, making the amplifier lop-sided when lifting) Extensive use of discrete transistors but more noticeable is the abundance of integrated circuits. Many of these IC's are for the analog audio switching (inputs etc) using the 4066 and I notice the Phono stage uses a low noise dual Op Amp, 5218A
Instead of using discrete transistors for the driver-power output stages, Sansui have opted to use a two channel block amplifier, the STK4191II
The case construction is pretty "plasticky" with the two "click n lock" side panels and the front panel being all plastic. Fortunately the top cover, under plate and rear panel are all metal so this provides the rigidity to the case.
I have been "all over" this amplifier to both get rid of the 40 years of dust (those dreaded ventilation slots in the top cover always let lots of dust get inside) and just to have a general look around.
I have tested the amplifier and it does have an issue, pretty easy to service and repair but I have no desire to work further on this amplifier as I still have a lot of other gear to sort through ...
So let's get down to the nitty gritty (no dirt band though!) ...
SANSUI (ELECTRIC CO. LTD) - Stereo Amplifier
Country of origin: not specified on the rear panel labeling
Model: A2000
Released to the marketplace 1989
Basic specifications:
Inputs: Phono (MM), Tuner, Tape, DAT-VCR
There is also an input-output loop for the insertion of a processor such as an external EQ system
High Filter ON-OFF
Loudness control - variable instead of a switch (nice)
The usual Bass, Treble and Balance controls
Power Output: 45W + 45W into an 8 Ohm load - best to not use 4 Ohm systems as this may stress the STK4191II just a bit much
Remote controllable (IR)
Front lit Volume control knob using a Red LED (great when the listening room is dark!)
Front panel indications of STANDBY, ON and the selected INPUT using LED's
Rear panel is quite "stock standard" but also has a 10 way socket for the SANSUI interconnect system and 3x two parallel pin AC outlets (NOT earthed) for other equipment in the sound system.
Speaker terminals are the click n lock lever type.
DIMENSIONS:
A mid sized amplifier with the whole top cover being designed for ventilation, which means you need to be careful what other equipment is placed on top of this amplifier while ensuring free air flow for heat to escape the case.
I would describe this amplifier as being "mid sized"
430mm Wide x 210mm Depth x 130mm Height
WEIGHT: 5.2Kg
LOOKING AROUND INSIDE AND TESTING:
Although quite sturdy when the top, bottom and sides are in place, this amplifier becomes quite flimsy once the support sides in particular are removed. Just one screw and then you need to release the front mounted lock and away come the side panels. Actually getting around inside this amplifier is a breeze, it is well laid out and easy to access most areas for servicing.
I looked over the boards and components for any signs of past operational stress, nothing obvious at all. It appears to me that no-one has serviced this equipment since 1989! That's a good thing because I have seen some real botch jobs when someone tries to fix their own amplifier but don't know what they are doing.
Next, let's fire up this baby!
On comes the Red STANDBY LED, great. Next I turned the amplifier ON and the LED changes to ORANGE and also an input LED lights up. The Volume control knob indicator also lights up - note that the Volume control does not automatically reset to zero at turn on, that would have been a nice touch.
I took at look at the power supply rails and am measuring +/- 47.7V across the ELNA filter caps. Although this is just within specs for the STK4191II, it is pretty close to the recommended maximum supply rails of +/- 50V
This is not a fault but does indicate that the STK4191II normally would run quite "borderline" to the maximum supply rails.
Up until this point there are no loudspeakers or input signals connected. I always check the loudspeaker outputs for DC voltages, if present this would spell disaster for the loudspeakers.
Ah! here is a problem ... Channel A is "not quite right" but Channel B is shorted to the supply rail, 47.7V would have been shot up to the loudspeakers - Ouch!
The DC voltage on Channel A is significant too but not too bad, sitting at around 3 - 5V (it keeps changing) so I connected a test loudspeaker (with inline fuse) to see what is happening on Channel A.
All good actually, the audio was sharp and clean plus plenty of it! I took this moment to check the tone controls, loudness (I love that rotary control for loudness) and of course the Volume. Everything is working as it should except for this low level "noise" (which becomes buried by the signal source) and this noise is of a constant level so it is not being caused by the preamp/input stages. I only made these tests on Channel A for around 3 minutes because I did not wish to risk damaging the test loudspeaker system but it was enough time to show me that the audio stages (at least on one channel) BEFORE the STK4191II appear to be running fine but that STK4191II is shot! The output should never have such a high voltage and it would seem to have shorted to the supply rail, actually I believe the other channel is going the same way too because of all the noise on that channel which does correspond with an ever increasing amount of DC present on that output as well i.e initially I was reading 3V then 3.5V then it jumped to 9V then back down to 3.5V - you get the idea.
I believe the servicing of this amplifier will centre around replacing the STK4191II - once a new one is fitted, I am confident the amp will fire away on both channels without any problems. I have taken a quick look around online and it seems those block amplifiers are readily available and the asking prices seem to range from A$10 ~ A$15 each - not too steep.
Accessing the PCB and STK4191II is not difficult, it is tucked away underneath the Aluminium heatsink in the centre, 18 pins to desolder from the single sided PCB.
I have also been able to check out the remote control side of things using a Tevion universal remote and this amplifier responded fine, changing inputs and the volume level remotely - love that volume control knob rotating "all by itself" (small things amuse me!) I am not offering a remote but the remote control system is working.
Alternatively, I guess the amplifier could be used as an "organ donor" for another A2000 but, well that is up to the buyer. The AC transformer is part number A2720XX and of course all of those front panel knobs are reuseable, as is the front panel (very good condition)
COSMETIC CONDITION:
Overall, very nice condition
Clean
NO damage to any of the controls, no missing controls.
ALL front panel push buttons work as they should and the front display panel is clear and unmarked.
NO labelling is worn off, even slightly
Top cover has no damage and with no discolouration or scratching
Rear panel is clean and again, all labelling is clear and easy to read
Right side panel is unmarked however the Left side panel does have some scratch marks, this is often caused by the amplifier being difficult to carry around - this is the side which has the heavy power transformer.
Power lead (2 wire - this is not an "earthed" piece of equipment) and standard Australian 2 pin plug are in very good condition - no lead sheath damage etc
PLEASE PLEASE take heed of my test results above and NEVER connect your own wonderful loudspeakers to Channel B in particular - you WILL cook them! Instead, get a replacement STK4191II and you are laughing ....
I am fine shipping this amplifier anywhere in Australia (International too but that seems unlikely due to the weight) packed very carefully and for just $9 shipping cost.
