Come with me as I repair a Sansui AU-317 integrated amplifier and discuss problems associated with the wrong approach to caring for 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? Of course, there clearly are right and wrong approaches, and it’s something worth looking at so people better understand it.

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

• Individuals unable to technically assess equipment in front of them, so they 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, think 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.
• Plenty of guesswork

This approach is wasteful, ineffectual, and prone to causing damage, introducing new faults and generally devaluing equipment. This is the most common approach because it requires the least knowledge and technical proficiency.

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.
• 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.
• Guesswork plays no part in this approach.

This approach is 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. The upside is that caring for equipment in this way adds value and improves performance, making it more collectible and 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 ’emulated’ (i.e. copied) my approach, content, and style without acknowledgement. Where this business differs from other copycats is that it has changed its business name at least three times in just a few years.

Why? Probably because they accumulated some very bad reviews and lost a significant case in Joondalup Magistrates Court in 2024. Does any of this matter? That’s an individual decision, but I’m certain most would want these details before deciding where to take their cherished hi-fi equipment. I won’t name the business unless it becomes necessary to do so, but they are certainly not helping their case by ripping me off and destroying people’s hi-fi gear. Warning given.

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 be brought 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

This is complete and utter nonsense. 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 because nobody else is going to. 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!

There is only one transformer in this amplifier, not a separate one for “the power section”, so why not just say the transformer is on the way out? Transformers either work or they don’t, by the way, so a transformer of this type cannot be “on the way out”. And what is “the power section” anyway, 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 issue; they are dual JFET packages, not integrated circuits.

The JEFT packages work perfectly, a fact confirmed by simple testing and a quick functional test of the amplifier. Even if these packages “Need to be replaced”, the replacement is straightforward. Why not test them and determine categorically whether they need to be replaced or not? And why replace all the trimmer potentiometers and driver devices when these were perfect and did not need to be replaced?

A Better Way

This diagnosis was given because the person giving it couldn’t fix the amp but needed to tell the owner something useful and couldn’t do that either, so they made it up. That’s not good enough.

This work can be challenging, but sending equipment back with false, misleading or made-up fault descriptions is dishonest and unethical, and not something any reputable business would ever do. It would be far 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. Repairs may not be possible within an hour or two, and that’s OK, as long as this is carefully explained, with options provided. It’s part of working with complex equipment.

For anyone still wondering why any of this matters, I see two reasons:

• This amplifier was someone’s pride and joy. They no longer own it now, because of what happened to it.
• This unethical behaviour and general ruination of equipment is widespread. That’s a terrible thing that people need to know about.

I’ve fixed the amp, but it still contains a the junk parts this guy fitted to it and they will need to be replaced. Worse still, the business that did this changed their name yet again and still doing work like this. If this doesn’t matter to every hi-fi equipment owner and lover out there, there is something wrong.

My challenge to this business and others like it though, is this: Rather than copying my style and content, which is easy, let’s be honest, try tackling the harder stuff like my approach, focussing on technical precision and ethical behaviour. Yes, this will be much harder for the business featured here for example, but the benefits for all will be far greater if they can pull it off. And if they cannot, what does that really tell us about this 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.