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Reliability Science in Audio Equipment

EERecordist

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Some time ago I worked in semiconductor reliability for a Fortune 50 company. I have worked on software reliability.

Here is a simplified discussion of quality and reliability for audio equipment. I would term quality as ship and pre-ship quality and reliability as quality over time.

The short version is:

1 Buy equipment with the longest warranty you can find.
2 Buy equipment that can be returned for a money back guarantee within a minimum of a month.
3 When you get the equipment, run it for one week straight 168 hours at 110% of the supply voltage and 140 degrees F. Most people are not set up at home to test the equipment for a few days at high pressure and humidity, or on a shake device.
4 If it fails, return it and get your money back, then buy a different manufacturer's product.
5 Extended software-firmware reliability is essentially impossible

Hardware reliability

Electronics are made from all the resistors, capacitors, inductors, discrete semiconductors, chips, etc. which the audio system maker buys from component vendors.

They are assembled on a PCB with solder. Wires and connectors are added. It is put in a chassis.

Every manufacturer would do some kind of test on the PCB and on the finished product. It is much cheaper to throw out the bad PCB before it becomes a system.

Every part of the above would have one or more failure modes - reason for a failure. Statistically failures are high at the beginning of life, low in the middle of life, and high at the end of life. That is called the Weibull Curve or the bathtub curve.

So how do you build electronics that will last, for say 20 years, without testing them for 20 years?

For that reliability engineers use statistics to calculate acceleration factors for failure modes. The math allows calculation of long term failure probability from accelerated testing.

The accelerated testing could include greater than normal temperature, humidity, voltage, current, vibration, radiation, etc.

The chip vendors (are supposed to) do all of that and produce data sheet variations at different prices. Regular grade will be priced lower than military, automotive, aviation, or space grade.

Since the component vendor has used reliability engineering, the system buyer should not need to test the incoming components. Usually the test equipment is not cheap.

Today the PCB assembly is contracted out. The assembly vendor or systems vendor would test the PCB. That will hopefully uncover soldering problems. The final assembly and testing would likely be contracted out, with testing. Packaging usually would be contracted out.

So you want your audio system equipment maker to choose good quality component vendors.

Japanese, American, Taiwanese, Korean, and German chip makers, foundries, and systems makers have been doing quality and reliability for some time. Where they do a step in another country, they are capable of, and responsible for, managing that quality.

There are many chip failure modes: material impurities/contamination, chip layer defects, electromigration - where the current flow moves metal atoms creating a narrow spot - accelerating to an open circuit, moisture getting to the chip and corroding it, inadequate heat removal through the package, bonding opens and shorts, design flaws resulting in inadequate electrical margins, and more.

A favorite, that a friend of mine discovered, is radioisotopes in the packaging emitting alpha particles which cause bit changes in some memory circuits. That problem was solved; you wouldn't encounter it in audio gear.

Different capacitor technologies have different failure modes. So it is common when restoring old audio equipment to replace capacitors with better specified current day capacitors.

Electronic components have a manufacturing economic lifecycle. So getting drop-in replacements becomes harder over time. This also intersects with the right-to-repair movement and regulation.

Warranty

Equipment makers (should) know their calculated failure rates over time. So they set the purchase price to include the cost of replacements over the warranty period. Usually the labor cost of customer communications, receiving, and shipping, is much greater than the replacement hardware cost.

If the company goes out of business there is no way to support the warranty. If they are acquired, the fate of the warranty will vary.

Software Reliability

This brings us to software reliability, the short version. Most software is designed to only get through the release outgoing testing.

The software is only as good as the testing. Another time I was an engineering manager for an Internet backbone company. It is expected to get every bit through unaltered every time for years. One of my employees in our vendor qualification lab was known as Dr Death. They were very good at finding issues the equipment maker never designed for in software, but could happen with the operations staff. An analogy in audio equipment would be if the device had 4 input selector buttons. What happens if you push all 4 at the same time? Another friend is an academic in provably-correct software for radiation therapy machines.

The software development is made through a tool chain of other software.

The software target is the audio equipment. The brains of digital audio equipment is very often a small computer: microprocessor, microcontroller, etc. The computer runs a real time (enough) operating system and a stack(s) of network communication software. In modern microkernal operating systems, the operating system would have all kinds of libraries, and code to couple to the external world - drivers in Windows-speak. The operating system, network stacks, and libraries have their own parts of the toolchain.

Then hackers will try to penetrate the entire software system. Usually they would use the Internet to get to the equipment. That has resulted in botnets of home routers and security cameras. Anyone in the profession knows there is no air-gap, witness Stuxnet. Hackers can find new flaws, and old flaws in the libraries. Theoretically if your device is not networked it can run reliably for years on its original software.

Very few system companies have the resources to maintain the security of their systems for any amount of time against hackers which also requires maintaining all the associated toolchains, and a way to remotely update the customer software throughout the world.

All of the above is represented in the end-of-life or end-of-support date set by the equipment maker to the customer.

The Philosophy of Quality

Finally, there are many good books written on quality, many readable by non-engineers. There is a contrast in philosophy between the six-sigma approach and the Toyota Way, and the idea that you just take the factory output and bin it out from high to low quality at corresponding price.
 

pseudoid

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Great summary... I think the thread discussion is about "Reliability Engineering", not 'science' per se!

MIL-HDBK-217, MIL-STD-756 and MIL-HDBK-810 have set the original standards for Hardware 'reliability' engineering.
MIL-STD-497 and DOD-STD-216x are the basic standards for software 'quality' assurance programs.
Notice that even the notion of "software reliability" does not deserve a single military standard, or a handbook or even regulation.;)

Subjectively speaking, software sucks... the life out of audio hardware and music. And hoping the next (umpteenth) update is going to make software good-enough is like watching the same movie over and over again with the hopes that the ending does not bring tears to your eyes.
 
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OP
E

EERecordist

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Great summary... I think the thread discussion is about "Reliability Engineering", not 'science' per se!
Agree. I just used science in the title because of ASR. Useful, readable, short, and entertaining was my objective.
Notice that even the notion of "software reliability" does not deserve a single military standard, or a handbook or even regulation.;)
Many friends and colleagues worked on the Ada programming language, a spectacular program failure.

We do have aviation and medical software standards, even so they have had spectacular life safety failures. But I shudder to think what would happen in those fields without those standards.

Thanks for reading it!
 
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SSS

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Some time ago I worked in semiconductor reliability for a Fortune 50 company. I have worked on software reliability.

Here is a simplified discussion of quality and reliability for audio equipment. I would term quality as ship and pre-ship quality and reliability as quality over time.

The short version is:

1 Buy equipment with the longest warranty you can find.
2 Buy equipment that can be returned for a money back guarantee within a minimum of a month.
3 When you get the equipment, run it for one week straight 168 hours at 110% of the supply voltage and 140 degrees F. Most people are not set up at home to test the equipment for a few days at high pressure and humidity, or on a shake device.
4 If it fails, return it and get your money back, then buy a different manufacturer's product.
5 Extended software-firmware reliability is essentially impossible

Hardware reliability

Electronics are made from all the resistors, capacitors, inductors, discrete semiconductors, chips, etc. which the audio system maker buys from component vendors.

They are assembled on a PCB with solder. Wires and connectors are added. It is put in a chassis.

Every manufacturer would do some kind of test on the PCB and on the finished product. It is much cheaper to throw out the bad PCB before it becomes a system.

Every part of the above would have one or more failure modes - reason for a failure. Statistically failures are high at the beginning of life, low in the middle of life, and high at the end of life. That is called the Weibull Curve or the bathtub curve.

So how do you build electronics that will last, for say 20 years, without testing them for 20 years?

For that reliability engineers use statistics to calculate acceleration factors for failure modes. The math allows calculation of long term failure probability from accelerated testing.

The accelerated testing could include greater than normal temperature, humidity, voltage, current, vibration, radiation, etc.

The chip vendors (are supposed to) do all of that and produce data sheet variations at different prices. Regular grade will be priced lower than military, automotive, aviation, or space grade.

Since the component vendor has used reliability engineering, the system buyer should not need to test the incoming components. Usually the test equipment is not cheap.

Today the PCB assembly is contracted out. The assembly vendor or systems vendor would test the PCB. That will hopefully uncover soldering problems. The final assembly and testing would likely be contracted out, with testing. Packaging usually would be contracted out.

So you want your audio system equipment maker to choose good quality component vendors.

Japanese, American, Taiwanese, Korean, and German chip makers, foundries, and systems makers have been doing quality and reliability for some time. Where they do a step in another country, they are capable of, and responsible for, managing that quality.

There are many chip failure modes: material impurities/contamination, chip layer defects, electromigration - where the current flow moves metal atoms creating a narrow spot - accelerating to an open circuit, moisture getting to the chip and corroding it, inadequate heat removal through the package, bonding opens and shorts, design flaws resulting in inadequate electrical margins, and more.

A favorite, that a friend of mine discovered, is radioisotopes in the packaging emitting alpha particles which cause bit changes in some memory circuits. That problem was solved; you wouldn't encounter it in audio gear.

Different capacitor technologies have different failure modes. So it is common when restoring old audio equipment to replace capacitors with better specified current day capacitors.

Electronic components have a manufacturing economic lifecycle. So getting drop-in replacements becomes harder over time. This also intersects with the right-to-repair movement and regulation.

Warranty

Equipment makers (should) know their calculated failure rates over time. So they set the purchase price to include the cost of replacements over the warranty period. Usually the labor cost of customer communications, receiving, and shipping, is much greater than the replacement hardware cost.

If the company goes out of business there is no way to support the warranty. If they are acquired, the fate of the warranty will vary.

Software Reliability

This brings us to software reliability, the short version. Most software is designed to only get through the release outgoing testing.

The software is only as good as the testing. Another time I was an engineering manager for an Internet backbone company. It is expected to get every bit through unaltered every time for years. One of my employees in our vendor qualification lab was known as Dr Death. They were very good at finding issues the equipment maker never designed for in software, but could happen with the operations staff. An analogy in audio equipment would be if the device had 4 input selector buttons. What happens if you push all 4 at the same time? Another friend is an academic in provably-correct software for radiation therapy machines.

The software development is made through a tool chain of other software.

The software target is the audio equipment. The brains of digital audio equipment is very often a small computer: microprocessor, microcontroller, etc. The computer runs a real time (enough) operating system and a stack(s) of network communication software. In modern microkernal operating systems, the operating system would have all kinds of libraries, and code to couple to the external world - drivers in Windows-speak. The operating system, network stacks, and libraries have their own parts of the toolchain.

Then hackers will try to penetrate the entire software system. Usually they would use the Internet to get to the equipment. That has resulted in botnets of home routers and security cameras. Anyone in the profession knows there is no air-gap, witness Stuxnet. Hackers can find new flaws, and old flaws in the libraries. Theoretically if your device is not networked it can run reliably for years on its original software.

Very few system companies have the resources to maintain the security of their systems for any amount of time against hackers which also requires maintaining all the associated toolchains, and a way to remotely update the customer software throughout the world.

All of the above is represented in the end-of-life or end-of-support date set by the equipment maker to the customer.

The Philosophy of Quality

Finally, there are many good books written on quality, many readable by non-engineers. There is a contrast in philosophy between the six-sigma approach and the Toyota Way, and the idea that you just take the factory output and bin it out from high to low quality at corresponding price.
Well done presentation on qualitiy. Decades ago working for hp there were components and hardware quality control standards which maintained the hp renowned long life instruments usage without problems. But times had changed and there is no need to build equipment which will last for 50 years because of fast technology changes. My old 40 years old oscilloscopes, voltmeters, signal generators still work like at the first day. At those days more and more was software controlled. Programming software reliably is hard work with clever architectural design needed. Complex big software programs with dependance on software libraries can be an nightmare. Myself I best use audio hardware without microprocessor. But modern DACs have software in it, so I live with this.
 

Audiofire

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3 When you get the equipment, run it for one week straight 168 hours at 110% of the supply voltage and 140 degrees F. Most people are not set up at home to test the equipment for a few days at high pressure and humidity, or on a shake device.
Well, that is certainly a rigorous accelerated stress test. In reality, specifications of audio equipment are not necessarily that high (then you're deliberately damaging it).

4 If it fails, return it and get your money back, then buy a different manufacturer's product.
I would return it if it does not fail too (money-back guarantee), then get another (of the same) one.
 
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