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, a 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:
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 than 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.Sansui
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 removed, we can see just how much time and effort Sansui engineers put into the design and layout of the AU-919.
Service & Other Considerations
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 always need service and this doesn’t mean just spraying a crappy contact cleaner at them. I’ve developed a deep-cleaning regimen involving chassis washing, which allows me to clean away decades of accumulated grease and grime from switches, rotary controls, boards and chassis parts.
I follow that up with a multi-step treatment process for switches and pots, and really bad parts just have to be opened and mechanically cleaned. The power switch in the most recent AU-919 I serviced was seized solid and needed some time and persuasion, to fix.
Then of course there are dry joints, relay problems, ‘black flag’ film caps, about which much has been written, much of it alarmist and not actually correct. These and other snippets are then amplified by people not actually working on these things day in, day out. Then there’s the infamous corrosive polychloroprene glue which really is a problem, and various other things to look out for, the worst of which is often poor previous work.
On the topic of polychloroprene glue, I’ve actually seen people call it hot glue and describe it as benign. I don’t know if what you see above looks benign to you, but as someone who took university chemistry, I can assure you it’s not. The problem in hi-fi is the sheer volume of misinformation. This compound literally eats through the legs of components given the right set of conditions and the damage it causes must be rectified.
If you value good advice, let me offer a little, from the perspective of having worked on thousands of pieces of classic hi-fi equipment like this AU-919: This isn’t an amplifier to fiddle with after a couple of beers, with a cheap multimeter, forum-fueled bravado and crossed fingers. No amplifier is, but especially not one like this.
People love fiddling, but there’s a time and a place. Fiddle with your garden sprinklers, but don’t fiddle with potentiometers in a circuit you don’t understand. Fiddling with complex stuff you don’t understand is generally not sensible, and sometimes even dangerous. The smallest slip, piece of bad advice or wrong decision can kill an amplifier like this, or YOU, so just be careful.
Working on your own equipment can be very rewarding and lots of fun, but keep in mind that reading a couple of articles doesn’t make you an expert. If you have the skill, tools, parts and access to informed technical assistance rather than opinion if you need it, by all means, have a go, but be mindful of the risks. If you are unsure or if this isn’t your thing, take it to a specialist who works on equipment like this instead and have the work done properly, and safely.
Something people complain about is that having work done properly can be expensive. Yes, of course, it can, it’s highly skilled work requiring extensive experience, training, costly tools, parts and highly specific techniques and procedures. It’s not much different to surgery, just on electronic equipment.
It’s actually no different than taking your mechanical wristwatch or Ferrari to be serviced. It has to cost something and the more challenging and specialised the work, the more it will cost. Still, a specialist will likely complete the work in a lot less time, do it better and attend to many other things that the home repairer isn’t even aware of.
Damaging or destroying your amplifier is by far the most costly option, so be wary of false economy. Check out what happened to this stunning Gryphon DM-100 for example. That was done to ‘save money’. It destroyed the amplifier. The replacement cost is upwards of $50,000.
But Mike, I want cheap, I don’t want to spend any money.
Honestly, if that’s your approach I can’t help you. I don’t work cheaply, I don’t cut corners, and I don’t support that approach, ever. If you want cheap, get a NAD 3020.
I generally cannot recommend most online sources of information/misinformation in relation to fixing an AU-919 or any other amplifier, because I have a different, professional perspective. For me, nothing comes down to chance. Most owners are ill-equipped to take on this sort of work and often do more harm than good, no matter how clued-in the person helping them is, and they rarely are.
Whilst there are a few very switched-on individuals who frequent an even smaller number of useful forums, the vast majority of conversations and advice I’ve witnessed are bad opinions and regurgitated “I’ve heard that xyz…” nonsense. Some of these folks get annoyed with me about this and leave comments about how great the forums are, yet the fact remains that I’ve seen more damage caused to hi-fi gear because of forums than any other cause.
Half the bad repairers whose work I regularly come across get their advice from forums. Check out this failed repair on an AU-317 for example. A shotgun repair attempt that fixed nothing and greatly devalued the amplifier. What a waste of time and money.
For the record, and I don’t care who doesn’t like it: I’m not interested in debating randoms about what other randoms heard, said, read, or repeated via Chinese whispers, which was never correct in the first place.
Remember: it’s all just speculation until someone with a clue actually puts their hands on a piece of equipment. Take this away even if you take nothing else.
I offer an advisory service BTW, for those who want factual information, from a trusted source. It’s accessible via the contact page.
Kits & ‘The Shotgun’
People often ask me about selling kits, what kits I use etc. I don’t sell, use or recommend kits. The ‘replace everything’ approach, otherwise known as shotgunning, is often responsible for ruining gear and, ironically, rarely fixes anything, nor teaches you anything along the way.
People seem to love the idea of kits, yet kits don’t repair faults. Re-capping is often mistakenly viewed as a cure-all, yet no re-cap or kit will resolve a noisy transistor or drifty differential pair and from a technical perspective, there’s enormous merit in tracing and resolving faults in equipment.
For most, installing a kit is also likely to do more harm than good, too. Good parts will be thrown away because the operator has no way to test them. Others will be damaged as they are removed and installed, boards and pads will be damaged and there will likely be even more problems afterwards. I have seen this so often that I expect it now.
“Mike, are you saying overhauls are a waste of money?”Someone…
No, quite the opposite, overhauls, done well, are an absolute must for older equipment. I can’t personally assist most readers, but my advice is to find the right person to look after one of these amplifiers for you, including taking care of any overhaul work that might be required.
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 using premium parts, the right semiconductors where necessary and a conservative, technically informed approach. I cannot over-emphasise this.
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. This is often unnecessary, especially with large filter capacitors, 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 an AU-919 offers.
Sure, the AS-3000 is pretty, but $9K buys a lot of premium, vintage hi-fi gear doesn’t it? The AS-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 figure. 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 all this in mind, if you can find a Sansui AU-919 for the right price, have access to a technician who can inspect/service/overhaul it for you and don’t mind the almost certain need to spend a little money, GO FOR IT! These are stunning amplifiers, definitely one of the greats.
On the point of maintenance, deciding on whether to have your amplifier overhauled for example should be relatively simple. If it’s not or if you are worried about the idea of having to invest some money into a piece like this after 40 years, this probably isn’t the right amplifier for you.
As always, thanks for visiting and I hope you found this article useful. If you own an AU-919 and would like me to carefully go over everything for you here in our Perth workshop, get in touch.