Come with me this time as I repair a Sansui AU-317 integrated amplifier and discuss problems associated with the wrong approach to caring for old beauties like this.

This isn’t really a rant of course, we leave that to others, but it is a chance for me to express my thoughts, to hopefully educate, inform and help readers make better decisions. Welcome back, everyone!

I’ve just repaired this lovely Sansui AU-317, a classic integrated amplifier from the late ’70s that we will chat more about as we go. This case presents a useful learning opportunity and provides pause for owners of such equipment to carefully evaluate who they entrust it with.

By the way, I’ve been busy updating the FAQs and the Hall of Shame, in particular case #16, featuring one of the worst-made hi-fi products I’ve seen in a while, and a business owner who threatened me with legal action for making people aware of it. But I digress… Time to geek out a little bit at one of the best budget amplifiers ever made. Let’s go 😉

For more about this story and a nice little video summary that has gone viral, by my YouTube channel standards at least, check this out:

The Sansui AU-317

Many of you will have seen my own Sansui AU-317 in the workshop over the years. I love these amplifiers, their baby brothers the AU-117 and AU-217 and the bigger brother AU-517 and AU-717, AU-D707/AU-819 and AU-919. I repaired an AU-217 only last week and there is a lot to love about the slightly more capable AU-317. The rest of the range is of course legendary and I love these stylish, serviceable and great-sounding amplifiers.

The Sansui AU-317 is a fully discrete component, full-featured design that can form the heart of a nice little system. With 50 Watts per channel and a solid 10kg build, these babies from 1977 – 1980 make modern $1000 amplifiers look like the toys they are. The AU-317 has a really good discrete phono preamplifier containing some very nice parts built in, a headphone ‘amplifier’ (really just a socket, but you know what I mean), and bypassable tone controls.

These amplifiers are completely repairable even now, more than 40 years on. Virtually nothing would render an AU-317 unrepairable unless it caught fire maybe, so there’s a lot to love here. Try repairing a Cambridge Audio CXA61 in ten years and you’ll appreciate my enthusiasm for equipment like the AU-317.

Sansui AU-317 Specifications

Courtesy of HiFi Engine (absolute legends, BTW!)

• Power output: 50 watts per channel into 8Ω (stereo)
• Frequency response: 5Hz to 70kHz
• Total harmonic distortion: 0.03%
• Damping factor: 70
• Input sensitivity: 20mV (mic), 2.5mV (MM), 150mV (line)
• Signal-to-noise ratio: 77dB (MM), 100dB (line)
• Channel separation: 65dB (MM), 73dB (line)
• Output: 150mV (line), 1V (Pre out)
• Speaker load impedance: 8Ω (minimum)
• Semiconductors: 51 x transistors, 25 x diodes, 2 x FET
• Dimensions: 430 x 110 x 340mm
• Weight: 9.5kg
• Year: 1978

The Right Approach

I focus on preserving and rejuvenating classic hi-fi equipment, so I don’t want to waste too much time discussing what not to do, but there’s no avoiding it in cases like this. Most regulars will know I have a particular dislike of poor workmanship, unnecessary work and especially the ‘recappers’, so no surprises here.

There’s a ton of Sansui AU-317s around and they fail occasionally, in different ways, but repairing an AU-217, AU-317, AU-517, AU-717 etc., should be no big deal. Seriously. Successfully repairing equipment like this is heavily dependent on a technician’s approach. Can there be right and wrong approaches? There ARE right and wrong approaches, not just my opinion, demonstrably incorrect ways to do things.

The wrong approach, so often applied to lovely pieces like this hinges around:

• Individuals being unable to technically assess equipment in front of them, so they continuously resort to…
• Shotgun parts replacement suggested by third parties and ‘improvements’ typically found in forums and based on what people often with little experience or knowledge ‘reckon’ should be done instead of knowing/determining what needs to be done based on a skilled assessment.
• Removing perfectly good original parts and replacing them with junk like we see in this example.
• Not testing components and circuits due to a generally non-technical, unskilled approach that has no place in a technical troubleshooting environment.

This approach is predictable wasteful, ineffectual and prone to damaging and devaluing equipment. Sadly, this is by far the most common because it requires the least knowledge and technical proficiency. And because of the internet.

The right approach is quite different because:

• It is a conservative, technically focused one that assesses and cares for the equipment in front of a technician, rather than in a forum somewhere!
• Parts are replaced where necessary to improve the performance of equipment, with components equal to or better than the original.
• It focuses on repairing faults and restoring perfect operation, whilst keeping to the original design intent with careful, measured technically skilled work.
• It is informed by a technician’s experience, knowledge and skill, and the condition and faults of equipment in front of that technician based on hands-on assessment.

This approach is sadly far less common because it requires an unusual level of experience, skill, technical knowledge, and the ability to find and solve problems without external assistance. Everything about this approach is better though and the upside is that it adds value and performance to hi-fi equipment, making it more collectible, more desirable and more enjoyable to use.

“She Needs a New Flux Capacitor, Sir…”

So, this Sansui AU-317 went to a local repairer, via her previous owner. Like some others, this business has borrowed from my approach, content and style without acknowledgement. Where this business differs from other copycats is that they’ve changed their business name at least three times in just a few years.

Why? Probably because of accumulating some very bad reviews and losing a significant case in Joondalup Magistrates Court in 2024. Does any of this matter? Readers can make up their minds but I would want these details before deciding where to take my cherished hi-fi equipment. I won’t name the business unless it becomes necessary, but they are skating on thin ice…

The amp went in for presumably the same issues she came to me for: unlistenable levels of distortion and DC offset that rendered the amplifier completely unusable. She was sent back with those same problems but minus all of her original high-quality capacitors and with a new set of crappy ‘Suntan’ brand caps, driver devices and trimmer potentiometers installed, at the owner’s expense.

That owner finally gave up on her after reading the diagnosis I’m about to show you and listed her for sale. The current owner, my customer, purchased her for next to nothing. The seller kindly suggested the amplifier should come to me. Thank you to the previous owner.

What caught my attention though was the diagnosis provided by the previous repairer:

“The transformer related to the power section is on its way out” and “the JFET ICs need to be replaced.”

Previous repairer

Complete and utter nonsense.

This is gold, to be honest, and while the customer might not understand what this ‘means’, any competent technician reading this will think “Hang on a minute..!”.

Why? Well, unfortunately, none of that ‘diagnosis’ is accurate, nor even possible in this amplifier. He might as well have said, “She needs a new flux capacitor!”

Nonsense Breakdown

Let’s dig into this as it might be informative for some. What does “The transformer related to the power section is on its way out” mean, exactly? Is there a transformer party somewhere that this transformer needs to attend? Transformers – more than meets the eye!

Note that there is only one transformer, so why qualify this with “the power section”? Why not just say the transformer is on the way out? This cannot happen by the way, transformers either work or they don’t. And what is “the power section” apart from a great band name, potentially..?!

As for the “JFET ICs”, there are no integrated circuits or ICs in an AU-317, it’s one of the lovely things about the design. The service manual refers to the input differential JFET pairs as ICs, but that’s a translation thing, they are simple dual JFET packages, not integrated circuits.

These JEFT packages work perfectly, a fact confirmed by simple testing, or even a quick test of the amplifier. Even if these packages were “on the way out”, replacement is straightforward for a competent technician, so why not test them? Why blame them for the amplifier’s issues? And why replace all the trimmer potentiometers and driver devices?

A Better Way

Again, some may wonder: “Mike, why does any of this matter!” It matters because this amplifier was someone’s pride and joy. They no longer own it because of this nonsense diagnosis and whilst I’ve fixed the amp, it now contains a ton of junk parts, and that sucks. If this doesn’t matter to all hi-fi equipment owners, there is something wrong!

This diagnosis was given because the person giving it needed to tell the owner something useful or fix the amp and they couldn’t, so they simply made it up. This work can be challenging, but sending equipment back with false, misleading or made-up fault descriptions is dishonest and unethical.

It would be infinitely better to say “I spent an hour trying to locate the fault and I couldn’t”. Sending equipment back unrepaired, having done one’s best within a certain time frame, is occasionally part of tackling complex technical repair work. Many repairs are not possible within an hour or two. As long as this is carefully explained, it’s sometimes part of the job and part of being human.

Ultimately, people doing work like this need to do better. If you did this or something like it and you want to copy what I do, I challenge you to copy my ethical, honest approach, rather than my layout, style and content. You might find it helps business.

Service & Repair

The path to repairing this lovely classic AU-317 was to isolate, diagnose and repair the faults, of which there were two. That took six electronic components and some time.

Fault 1 – Distortion. The distortion was caused by blown current limit resistors in the bias/drive circuit that turned this amplifier into a class-B design with no driver stage. That means that huge signals would be needed to drive the output stage at all, and what you get would be badly distorted. I replaced the current limit resistors, set the bias current and bingo, the distortion was gone.

Fault 2 – DC offset in the right channel of the phono preamp. DC offsets are typically caused by leaky or drifty small signal semiconductors and the obvious pair to check in the right channel of the phono preamp is the right channel input differential pair. Sure enough, one device was bad, so I replaced both with a new hand-matched pair with improved specs.

Some critical cleaning, service and adjustment completed the work here and is what had this AU-317 running perfectly again.

Results

This Sansui AU-317 repair was particularly rewarding because her owner is such a nice guy and he appreciates the approach I’ve described in this article. He owns many Sansui amplifiers including a Sansui AU-101, AU-217, AU-555A and AU-4900, all of which I’ve serviced and repaired for him but his favourites are the AU-217 and AU-317 I recently worked on. Here’s what he told me about the AU-317:

[The] 317 sounds spot on, you are the man, thanks again Mike. She sounds bloody awesome, I hate to admit its in a tight second spot for my favourite.

Michael B

In terms of overhaul and restoration, less is more, especially with pieces in generally good condition. Overhauls by the right people are worth having done, but as always, the devil is in the details. The right technician won’t be getting their information from forums, installing Suntan capacitors or charging $1500 AUD to overhaul a basic amplifier. They will already know what to do, based on the condition of the equipment in question. Keep this in mind.

If you want to spend that much on a vintage amplifier, I suggest you take the $1500, sell the AU-317 and put all of that money into a nice Sansui AU-717, AU-819 or AU-919. That’s going to give you a far better piece of gear and bang for your buck than going crazy with an AU-317 or AU-4900.

The Bottom Line

Want a beautiful-looking, great-sounding, affordable, reliable, repairable moderate-power integrated amplifier? I highly recommend you consider the Sansui AU-317 if so. These are solid, well-designed, well-made pieces of Japanese hi-fi history.

Nothing like this will be made again and at their current prices, you can’t go wrong. I’d take one of these over new plastic rubbish with Bluetooth integration every day of the week. Just take it to someone with the right approach when it needs service!

As always, thanks for reading and I hope you found this article informative. If you’d like me to look at your Sansui AU-317 or any other lovely Sansui amplifier, get in touch.

Sansui AU-317 Integrated Amplifier

$500 - $800 AUD

8.5

Build Quality

7.0/10

Features

8.5/10

Sound Quality

7.0/10

Servicability

10.0/10

Bang-Per-Buck

10.0/10

Pros

• Full-featured integrated amplifer
• Excellent phono preamplifier
• Tape and headphone functions
• Superbly servicable
• A great performer in its niche

Cons

• Lacks slam, air, refinement etc. of course, given what it is.