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Ultra-Rare Sansui AU-X11 Master Integrated Amplifier

It’s not often you see one of these ultra-rare beauties, the other Sansui AU-X1. The Sansui AU-X11 is a Japan-only integrated amp. My customer bought one and it was damaged during shipping. Let’s take a look.

That’s right, the Sansui AU-X11 integrated amplifier is the AU-X1 nobody knows about. That’s because it was only sold in Japan, as far as I can tell. This one is definitely a Japanese market 100V only version. My customer purchased the unit you see here, against my advice, but that’s OK, not everyone takes my advice!

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I worked on this amplifier in late 2018 and it’s taken me a while to write about it, sorry about that! I uploaded a video at the time and have just made it public, so take a look:

Specifications, Courtesy HiFi Engine

It’s worth pointing out here that the AU-X11 specs are very similar to those of the AU-X1. Similar power output, weight etc.

Power output: 160 watts per channel into 8Ω (stereo)
Frequency response: 1Hz to 300kHz
Total harmonic distortion: 0.004%
Damping factor: 100
Input sensitivity: 0.27mV (MC), 2.5mV (MM), 200mV (line)
Signal to noise ratio: 77dB (MC), 91dB (MM), 110dB (line)
Output: 200mV (line), 1V (Pre out)
Load impedance: 4Ω to 16Ω
Dimensions: 515 x 197 x 450mm
Weight: 28kg – jeepers!
Year: 1981

Features

Sansui incorporated a bunch of marketing-driven buzz-terms and features into the AU-X11 and other amplifiers in the series like the AU-919. These include ‘Straight DC Stereo Amplifier‘, DD/DC Power/Phono Amps‘, and others I forget…

DC indicates that the AU-X11 amplifies everything from DC – 0 Hz – through to 300 kHz in this case. This is achieved using very fast transistors, no capacitors in the signal path and servos. Direct Coupled circuits are more complex but technically better. Servo circuits keep DC offset voltages to a minimum.

DD stands for diamond differential, referring to the circuit topology that utilises transistors in a particular symmetrical configuration. Symmetrical, differential configurations are expensive because they use many parts. They also deliver excellent technical performance.

Like the AU-919, there is an advanced, low-noise FET-based phono preamp that can almost certainly not be repaired if it fails. Thankfully they generally don’t fail. Unlike the AU-919, there are no tone controls in this more purist amplifier or in the AU-X1. The AU-X11 is also much more powerful than the AU-919, on a par with the AU-X1.

AU-X11
The super neat and tidy layout is typical of Sansui. Note the covers over each circuit block. Note also the twin transformers and capacitor banks. The smaller EI transformer and two capacitors form the power supply for the preamps. The larger toroidal transformer and eight capacitors feed the power amplifiers. That’s the way to do it!
AU-X11
With the covers removed we can see the main amplifier, phono, tone and line amplifier circuits. The layout is almost identical to that of the AU-X1, the only obvious difference being that the eight power supply capacitors in the middle are on the outside of the heatsinks in the AU-X1.

Problems

This particular AU-X11 came from Japan and was purchased after many hours of discussion with the soon-to-be owner. I advised him against buying this amplifier and for those wondering why I keep saying this, it’s for three main reasons.

Reason 1: Shipping anything involves risk. The heavier, rarer and further away something is the bigger the risk. This isn’t a theory, I’ve assessed the damage, many times. Sadly, the risks were proven very real by this shipping-damaged example.

Reason 2: A bigger potential issue with rare equipment like the AU-X11 is the complete absence of service data. The term ‘service data’ refers to factory schematics, engineering drawings, procedures and so on. This information is especially important with a complex piece of gear that doesn’t work properly.

The lack of service data means that owners must rely heavily on the skills and experience of technicians willing to assist, where this critical information is missing. Whilst the AU-X11 is very similar to the AU-X1, there are differences.

Reason 3: This is a 100V only model. That means you must use a step-down transformer, even where the local voltage is 120V. This is an additional cost and with amplifiers, performance is generally better where additional transformers are not involved.

Damage

This AU-X11 was very poorly packed for something so heavy and rare. With just bubble wrap and cardboard protecting it, even one drop would likely be catastrophic, sheer stupidity on the part of whoever packed it.

The chassis damage was obvious as soon as I pulled the lid off. This unit was dropped, twice I reckon, on its left front and left rear. It may have toppled out of the back of a truck or just been dead dropped. Either way, the sort of chassis damage it sustained cannot easily be repaired.

AU-X11
Here we see the first signs of severe front left side impact damage. Ouch.
AU-X11
That damage is mirrored almost perfectly on the right side. A severe blow to the front caused this.
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The rear panel is also damaged. This appears to have come from another drop as this impact was to the left rear, from behind.
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More damage, more disappointment…
AU-X11
I’m not sure how easy this is to see, but the impact was so great that it deformed the aluminium alloy heatsink and bent it like a banana. It’s lucky this amp worked at all after all this. Just imagine the forces needed to do this. This AU-X likely endured at least one or two dead drops from at least 1m. This is why I dread shipping.

The drop event/s that caused this chassis damage also caused another, potentially solvable problem. I discovered a break in the signal path, despite all the circuits working nominally after service and adjustment. This meant that signals would not pass through the amp. Mechanical damage correlates strongly with these sorts of issues.

Service

Thankfully, I’ve worked on a lot of Sansui amplifiers and so I was able to put together a service procedure for this AU-X11. Like the AU-919, this amplifier is complex and has many adjustment points, mostly for DC servos. From memory, there are at least 10 in the AU-X11. I spent around three hours with this amplifier on the bench, carefully measuring and adjusting everything.

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Here she is, the AU-X11 on the 2018 workbench.
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Here’s the underside of the amplifier. I had to repair the inrush current limiting resistor. It had broken loose from the impact, its the white rectangular object, to the right-rear.
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Some work had been done here previously. I didn’t get to the point of working out why, but it’s likely to bypass the speaker protection relays.
AU-X11
Here the AU-X11 is metered up for setting of critical electronic adjustments. There are many inside this amplifier, at least 10 from memory.

Future Repairs

The signal integrity problem with this AU-X11 is no doubt fixable. Ideally, this whole amp should be disassembled and carefully reassembled, repairing and replacing bits and pieces as needed. That’s a big job. My customer is a lovely fellow but he didn’t want to spend much more on this amplifier.

The owner also struggled with the idea of not knowing exactly what was wrong and therefore exactly how much this AU-X11 would cost to repair. There is no doubt that to do this job properly, many hours of additional work are needed. Last I heard, he was pondering what to do with this lovely old beauty.

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Such is the nature of rare, old equipment, there’s a bit to be learned from this story. If you own or play with old gear like this, you have to accept the risks involved with shipping and that some issues are not viable to repair.

In this case, with an irreplaceable rare AU-X11, it’s fair to say that even repairs up to several thousand dollars are both viable and very worth doing. You’d pay $10,000 AUD for something like this now and I guarantee it wouldn’t be as good.

Should You Buy One?

Should you buy a Sansui AU-X11? Sure, if you can live with the 100V problem, but only from a reputable seller, fully insured and impeccably packed.

In terms of its comparisons, something like an Accuphase E-480 has similar power. It likely won’t perform as well, having only two power supply capacitors and therefore higher power supply impedance. Yamaha’s AS-3200 is way less powerful, lighter and costs $10K. The new Luxman L-505uXII looks nice but is also lighter and less powerful. That great old gear hey..?!

In terms of its compatibility with local voltages, this is an issue. It’s never ideal running a big amplifier from a step-down transformer and that’s certainly what you’ll have to do with one of these. You’ll need a large one too, something like the 1000W version of this Tortech transformer, in Australia.

Don’t forget that there are more accessible Sansui amplifiers like the AU-717 and AU-919 which will get you a sizable chunk of Sansui vintage goodness, for much less money and risk. Whatever you end up with, let me know if you’d like assistance with your Sansui amplifier.

Liquid Mike

As a kid, I cherished my Tandy 200-in-1 electronics project lab, Dick Smith electronics kits, my Dad's hi-fi and my own first proper system. Later, I created Liquid Audio to help keep classic hi-fi gear alive and well. Our mission: to deliver TLC for classic Japanese, American and European hi-fi stereo equipment.

This Post Has 4 Comments

  1. Bryan

    What do you think of the Sony Str V7 reciever ?

  2. Merwyn Machado

    Nice write-up, came across your website and love it. I am in Brisbane and have a Sansui AUX-711 that I lugged from the Middle East paired to Infinity Ren 80’s. The amp has not been touched since I owned it for 20 years. It has a bit of crackle on the left channel and cuts out. I am dreading giving it for repair, probably needs capping and a good deoxit

    1. Liquid Mike

      Hi Merwyn, glad you enjoyed the article and yes, make sure you take this to someone who knows their stuff!

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