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 and virtually nothing would render an AU-317 unrepairable, 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 here, 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 readers will know I have a particular dislike of poor workmanship, unnecessary work and ‘recappers’, so there are no surprises here.

There’s a ton of Sansui AU-317s around. They fail occasionally, in different ways, but repairing an AU-217, AU-317, AU-517, AU-717 etc., should be no big deal. Successfully repairing equipment like this is heavily dependent on a technician’s approach. Can there be right and wrong approaches? Absolutely.

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

• Individuals not properly assessing the unit sitting in front of them
• Shotgun parts replacement
• Looking for ‘Improvements’ found online that are the last thing one should be focussed on
• Removing perfectly good original parts and replacing them with junk new parts
• Not testing components and circuits and a generally non-technical, un-skilled approach
• What people ‘reckon’ should be done rather than what needs to be done with the unit in question

This approach is wasteful, generally ineffectual, devalues equipment and yet sadly, is the most common, as it requires the least knowledge and technical proficiency.

The right approach:

• Is a conservative, technically focused one that assesses and cares for the equipment
• Sees parts replaced where necessary or to improve the performance of the equipment, with components equal to or better than original.
• Focuses on repairing faults and restoring perfect operation, whilst keeping to the original design intent with careful, technical work.
• It is informed by the unit in question and an individual’s skill and experience
• Is, sadly, far less common as it requires an unusual level of experience, skill and technical knowledge

“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 they differ is that they’ve changed their business name at least three times in recent years. This is probably because of bad reviews and losing a case in Joondalup Magistrates Court in 2024.

Does any of this matter? Readers can make up their minds but I would certainly want these details before deciding where to take my cherished hi-fi equipment. I won’t name the business, hopefully it won’t become necessary to do so.

The amp went in for presumably the same issues she came to me for – unlistenable 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 then 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 given 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

Yeah… Now, the customer might not understand what this means but any competent technician reading this is going to think “Hang on a minute..!”. Unfortunately, none of that ‘diagnosis’ is even remotely accurate, nor is it possible in this amplifier. He might as well have said, “She needs a new flux capacitor!”

What does “The transformer related to the power section is on its way out” mean, anyway? Is there a transformer party somewhere that this transformer needs to attend?! Transformers – more than meets the eye! And there is only one transformer, so why qualify this with “The power ‘section'”? What IS the power section anyway..?

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

Anyway, what really bothers me is that these JEFT packages work perfectly, simple testing confirms that. Even if they didn’t, replacement is straightforward. So why not test them?

Some reading this may again be wondering: “Mike, why does any of this matter!” It matters because this was someone’s pride and joy and they no longer own it because of this. Surely that matters, or it should.

This diagnosis was given because the person giving it needed to tell the owner something, and they didn’t know what to tell them, so they made it up. That’s terrible practice.

We’ve all had tricky repairs, and this work can be challenging, but sending equipment back with false, misleading or even made-up fault descriptions is unethical. Why not simply say I’ve spent an hour trying to locate the fault and I can’t? You do your best and then just be honest, for goodness sake!

Sending something back unrepaired having done one’s best within a particular time frame is absolutely acceptable. We are not miracle workers and many repairs are simply not possible within an hour or two. One must clearly state that though, not make up some imaginary reason why the equipment CANNOT be repaired and risk an owner junking it.

Ultimately, the people doing this need to do better. If you did this or something like it and want to copy more of what I do, copy that approach!

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 parts 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.