The beautiful Sansui AU-919 is a technical tour de force and an absolute stunner. Find out more about this legendary integrated amplifier in another of my COVID-19 series.
I work on a lot of Sansui gear and I always enjoy it. It’s well-engineered, well-made, great-sounding equipment, a pleasure to service. Sansui always injected their unique design aesthetic and DNA into their products, especially later ones, but really stepped up their game in the mid to late ’70s, releasing products stellar in their vision and execution. The AU-919 is one of these products.
The AU-919 is part of an elite group of integrated amplifiers we might call ‘the greats’. Other Sansui contenders include the incredible AU-20000, restoration article coming soon and the grand-master, the AU-X1, one of which is here for overhaul and pictured below. The legendary AU-717 definitely also deserves an honourable mention.
Sansui set the bar high with the AU-919 in terms of build quality, features and performance. It’s up there with models like the Accuphase E-202 and E-303 in many respects and other great integrated amplifiers like the Technics SU-V8, Sony TA-FA777, Kenwood KA-907 and a select few others.
By the way, check out the video overview I made of this stunning Sansui AU-919:
Specifications Courtesy HiFi Engine:
Power output: 100 watts per channel into 8Ω (stereo)
Frequency response: 20Hz to 20kHz
Total harmonic distortion: 0.008%
Slew rate: 200v/uS – seriously, this is insane!
Damping factor: 100
Input sensitivity: 0.1mV (MC), 2.5mV (MM), 150mV (line)
Signal to noise ratio: 74dB (MC), 90dB (MM), 100dB (line)
Channel separation: 75dB (MM), 70dB (MC), 80dB (line)
Output: 150mV (line), 1V (Pre out)
Speaker load impedance: 8Ω (minimum)
Dimensions: 430 x 168 x 428mm
Year: 1978 – 1981
Sansui incorporated a bunch of buzzwords into the marketing for this model and others in the series. These include ‘Straight DC Stereo Amplifier‘, ‘Exclusive DD/DC Power/Phono Amps‘. Let’s discuss these in turn.
DC stands for direct-coupled and direct current, with both terms applicable here. The AU-919 amplifies everything from DC – direct current – with a frequency of 0 Hz, through to 500 kHz. This is achieved with a design using very fast transistors and no capacitors in the signal path.
Circuits like this are also referred to as being directly coupled – DC. Servo circuits keep DC offset voltages to a minimum. Capacitors would normally block them but remember there are no capacitors in the signal path here.
Capacitors in the signal path always degrade sound quality, with no exceptions. Having no capacitors in the signal path is a great thing but servos are needed to remove any DC voltages and each one needs adjustment. Direct-coupled circuits are therefore always more complex that capacitor coupled ones.
The high speed and wide bandwidth of this amplifier give it a slightly unjustified reputation for unreliability. Yes, they can blow up, but it’s generally because people drive them with crappy gear or fiddle with them.
These circuits have such a wide bandwidth that they will amplify radio frequencies, given the chance. Use unshielded or badly made cables near a radio station for example and you might just see a puff of smoke from your 919 as it oscillates. Not entirely the amplifier’s fault, though the average user will assume it is.
The AU-919 has five power supplies. One, using an El-core transformer and constant voltage circuit, supplies the class-A preamp. Two others, using windings on the same El-core transformer, serve the class-A left and right pre-drivers.
The fourth and fifth use the big toroidal power transformer with separate windings feeding current to the driver and output devices. Four 15,000 uF oval-shaped capacitors provide the power reserve and that’s a lot for a 100 Watt stereo amp.
Sansui certainly felt proud of their achievements in the AU-919 circuits when they wrote this:
The Diamond Differential DC circuit in the power amp and phono equalizer offers one of the widest frequency ranges ever achieved in audio – extending from zero Hz (DC) to an amazing supersonic high of 500,000Hz – and you have some of the reasons the AU-919 delivers the purest musical performance you’ve ever heard.
The AU-919 isn’t the cheapest integrated amp on the market, and at a modest 100 watts per channel, it isn’t the most powerful. But we’re convinced that for the serious audiophile who really cares about sound quality, and who is willing to make an investment in truly state-of-the-art equipment designed for nothing less than straight, uncolored, dynamic audio performance, the AU-919 deserves the most superlative of all – The Finest.
Yep, it’s fair to say the Sanui marketing and design teams loved the AU-919 and why not, it would have cost them enough to design!
Like most Japanese amplifiers, the AU-919 has two sets of speaker terminals, tone controls, filters for turntables, loudness and tape controls. Most usefully, the phono preamp is superb by most standards, especially modern ones and caters for moving magnet and moving coil cartridges.
With the cover off, we can see just how much time and effort Sansui engineers put into the design and layout of the AU-919.
Properly servicing a Sansui AU-919 involves several hours, specialist equipment, chemicals and precision screwdriver twiddling. The screwdriver is for tweaking the – can you believe – 14 stages of trimming/adjustment! I’m not kidding and neither was Sansui.
Sansui designed the AU-919 with direct-coupled circuits end-to-end. That means DC servos at each stage and DC offset trimming everywhere, to prevent the amplifier from presenting DC voltages to the speakers. Can you believe there are six adjustments in the MC phono preamplifier alone? This is more than just about any amplifier I’ve ever seen, but thankfully, six became just two in the later revised AU-919 phono stage.
Some capacitors in the AU-919, AU-X1 and others don’t age well and can take out the output devices when they fail. Modern replacements for the caps and output devices are available but know that they WILL change the sound of the amplifier.
Switches and controls will all need service and this doesn’t mean just spraying a random contact cleaner at them. I often wash an amplifier chassis which allows me to deep clean switches, rotary controls, boards and chassis parts. I follow that up with a three-stage treatment process, a proprietary cleaning solution I’ve developed. The power switch in the most recent AU-919 I serviced was seized solid and needed some time, and gentle persuasion, to fix.
Then of course there are dry joints, relay problems, ‘black flag’ film caps, about which much has been written and rumoured, the infamous corrosive polychloroprene glue, and various other things to look out for, the worst of which can be previous poor quality work. I’ll often refuse to look at an amplifier that has been poorly worked on.
A few words of wisdom and a warning from someone who’s worked on a few of these: This isn’t an amplifier to fiddle with after a couple of beers, with a cheap multimeter, some forum guidance and crossed fingers. No amplifier is, this one especially.
I often come across the results of botched attempts to service or overhaul equipment like this. The reality is that not everyone can or should work on gear like an AU-919. If you have the skills, equipment, parts and access to the right technical assistance, by all means, have a go. But if you are even slightly unsure, take it to a specialist who works on equipment like this commercially and pay them to do the job properly. You’ll thank me later.
“But Mike, that will cost money…!”
Yes, it will. I know this isn’t what everyone wants to hear and make no apologies for that. I’m interested in preserving classic hi-fi gear, not egos! Actually, I’ll go further and state that many technicians have no business working on gear like this.
Seriously, trying to save a few dollars on servicing or overhauling a rare and irreplaceable amplifier like this is a fool’s errand. Too many working on electronics adopt a shotgun ‘replace everything’ approach, but lack the technical background and experience needed to troubleshoot and resolve faults. This approach can devalue or even ruin beautiful, otherwise untouched pieces. Electronics can be very challenging, one of the trickiest technical endeavours.
For perspective, Liquid Audio is an independent, specialist repairer. You won’t find me in public forums, nor am I interested in what someone read, that someone read, that someone, somewhere wrote about the 919 or anything else. When I need assistance, I speak to industry colleagues. Otherwise, I’m focused on what I’ve learned, seen, heard and measured actually working on thousands of pieces of hi-fi equipment like this beautiful Sansui AU-919. Everything else is just white noise.
This unusual approach is why we are busy and why people seek our advice. With this in mind, perhaps you’ll hopefully better understand why I say that the average owner has no business poking around inside an amplifier like this! It’s not about you, it’s about wanting to preserve your amplifier!
With this AU-919 freshly serviced, I was able to enjoy the sweet, sweet sound these amplifiers make. The AU-919 sounds powerful, clean, open and airy. These are fast amplifiers and fast amplifiers usually sound snappy and clean. Bass performance is strong, resolution of fine detail and nuance is excellent and 100 Watts per channel will drive most medium efficiency speakers without trouble.
Like many other Japanese amplifiers, the AU-919 won’t be entirely happy driving less sensitive, lower impedance loads though. Power-hungry, inefficient speakers are not best suited to the 919, but high-resolution monitors, bookshelves and floor-standers will work very well in most cases.
Watch out because many AU-919s have been worked on and messed with, often by owners who’ve fiddled and maybe not in any useful way. Output devices must be checked. Are they original? If not, are they appropriate, matched and graded parts? How about the driver transistors? Capacitors? Which ones have been replaced and with what? People love to replace the main filter caps for no good reason. An expert inspection is essential, even if the amplifier seems to work OK.
Service is mandatory because all 14 adjustments will almost certainly need ah… adjusting. An overhaul is also a very sensible consideration at this age. This really must be done by a specialist, using premium parts, the right semiconductors where necessary and a conservative approach.
Speaking of semiconductors, consideration must also be given to weird diode packages, blag flag capacitors, hard to find matched FETs (like the six grades in the MC phono preamp alone) and other unobtainable transistors that may require modern replacements.
Many people replace the unobtainable oval filter capacitors in the power supply because they read somewhere that all electrolytic capacitors must be replaced. Why? Well that part isn’t clear. This is almost always unnecessary, especially with large filter capacitors actually detracts from originality and sometimes performance. Amplifiers like this need appropriate care and many don’t receive it, so keep this in mind.
Bang per Buck
Prices for AU-919s vary quite a bit. These are very desirable amplifiers so you’ll pay a pretty penny for a good one, often over $2K AUD. They are highly collectible and appreciating in value as people realise that even $9000 for a Yamaha AS-3000 doesn’t get you the level of engineering, matched FETs, phono preamp quality, two transformers etc that the AU-919 provides.
Sure, the AS-3000 is pretty, but $9K buys a lot of premium, vintage hi-fi gear doesn’t it. The 3000 weighs about the same as the 919, has only one transformer, definitely doesn’t have the same high-speed circuitry and unhelpfully, Yamaha doesn’t provide a proper 8 Ohms RMS power output figures. I wonder why not..?
Seriously, the AS-3000 is lovely, but at $9000 AUD, they’ve gotta be dreaming. This is why I keep telling anyone who’ll listen that vintage hi-fi is where the real value lies. Gear like this sounds at least as good and is way cheaper for what you get. Once you form this understanding, you’ll find it very difficult to drop big money on modern high-end gear.
So with this in mind, if you can find a Sansui AU-919 for the right price, have access to an expert who can inspect/service/overhaul it for you and don’t mind the likely need to spend a little money, GO FOR IT!
These are stunning amplifiers, definitely one of the greats and deciding on whether to overhaul one of these is like deciding on whether to overhaul your classic Grand Seiko or Ferrari. In other words, the decision should be simple. If it’s not, this probably isn’t the right amplifier for you.
If you already own an AU-919, would like me to carefully go over everything for you and can get it to me here in Perth, Western Australia, get in touch.