Class D amp long term reliability

[restorer-john]

Inexpensive today? A little over ten years ago Yamaha produced their NS-1000 speakers for $1000 a pair, and sold many. Today their replacement for the NS-1000 is their NS-5000 for $15,000 a pair, which granted their replacement is quite higher performance, but it sure doesn't seem to me like prices are coming down, even in real dollars. Turntables? Technics has a $20,000 one today.

Your timeline and prices are incorrect.

The NS-1000 was expensive when it was released in 1974. In 1976 it cost US$1000 for a pair. It only became more expensive as time went on.

The speaker was discontinued very early in the 1990s, not "a little over 10 years ago". Nearly 30 years ago in fact.

I sold some of the very last pairs of NS-1000Ms and they had risen to AU$3999pr from $3499pr the year before. The replacement for the NS-1000 was the NS-1000X which co-existed for a few years and they cost AU$4999pr in 1991/1992.

Here are scans of my actual dealer price lists with the "new" NS-1000X series.

The NS-5000 cost AU$19,990 here in 2021.

 

[Doodski]

The NS-1000 was expensive when it was released in 1974. It only became more so as time went on. The speaker was discontinued very early in the 1990s, not "a little over 10 years ago". I sold some of the very last pairs and they had risen to AU$3999pr from $3499pr the year before. The replacement for the NS-1000 was the NS-1000X which co-existed for a few years and they cost AU$4999pr in 1991/1992.

The NS-5000 cost AU$19,990 here in 2021.

Which one had the screen over the woofer and which one had no screen? We sold the one without the screen. I was a Yamaha buff then but the speakers didn't ring in my memory as per the model number. They only lasted in stock for a couple of weeks and poof... gone, everything was sold and no more inventory available from Yamaha.

 

[antennaguru]

Hey, if it's beyond your skillz....but wtf cares after you're dead?

I have endeavored over my lengthy career to have done the right thing and bring along my people by sharing knowledge and placing my trust in them. When I’m gone I hope I have set the stage for those that worked for me and those I worked for to say that I was an upstanding trustworthy human being that cared deeply about his people and always tried to do the right thing. It’s about the legacy you leave behind when you’re gone.

 

[restorer-john]

Which one had the screen over the woofer and which one had no screen? We sold the one without the screen. I was a Yamaha buff then but the speakers didn't ring in my memory as per the model number. They only lasted in stock for a couple of weeks and poof... gone, everything was sold and no more inventory available from Yamaha.

The NS-1000 had the larger timber cabinet and no woofer screen. The NS-1000 Monitor (later to just become NS-1000M) had the woofer screen. In Japan they had the NS-1000M without grilles or grille clip holes. In 1984, they released a 10 year anniversary with special gold badging.

The NS-1000X came along in (IIRC) 1990. The NS-10000 was for Yamaha's centennary.

 

[antennaguru]

Your timeline and prices are incorrect.

The NS-1000 was expensive when it was released in 1974. In 1976 it cost US$1000 for a pair. It only became more expensive as time went on.

The speaker was discontinued very early in the 1990s, not "a little over 10 years ago". Nearly 30 years ago in fact.

I sold some of the very last pairs of NS-1000Ms and they had risen to AU$3999pr from $3499pr the year before. The replacement for the NS-1000 was the NS-1000X which co-existed for a few years and they cost AU$4999pr in 1991/1992.

Here are scans of my actual dealer price lists with the "new" NS-1000X series.
View attachment 147396
View attachment 147397
The NS-5000 cost AU$19,990 here in 2021.

stereophile was my source via google, and they said $1000 a pair in 2008. Guess that was a bad source. My point was that good gear is not getting less expensive in many cases. In actual fact it’s getting prohibitively expensive in many cases.

 

[Doodski]

The NS-1000 had the larger timber cabinet and no woofer screen. The NS-1000M had the woofer screen. In Japan they had the NS-1000M without grilles or grille clip holes. In 1984, they released a 10 year anniversary with special gold badging.

The NS-1000X came along in (IIRC) 1990. The NS-10000 was for Yamaha's centennary.

Well... they sounded so different that listening to them made other speakers sound bad. A very forward midrange and the top end was pretty strong too with a tight bass. I avoided them to be honest. I was so deep into selling KEF Uni-Q and Reference Series at the time that I dared not to push anything else for fear of looking like a hypocrite. I liked the Yamahas but the inventory levels where like 1 to show and 5 to go and I, "Don't live and die by the backorder." Backorders is the death of salespeople even the good ones

 

[Blumlein 88]

Have an early Tact amp now about 20 years old. Class D based upon the Tripath chips. Ran some electrostats for about a decade. Still have it as a spare amp in a bedroom system. Also have a Wyred4Sound ST500 IcePower which is about 12 years old. Runs the Soundlab ESL' s far better than anything else I've used. Pretty much never switched off.

So 10 years should be easy and maybe 20 years.

 

[restorer-john]

stereophile was my source via google, and they said $1000 a pair in 2008. Guess that was a bad source.

Yes, they confuse a bunch of people by re-publishing old reviews. Note the dates.

 

[Chrispy]

I have endeavored over my lengthy career to have done the right thing and bring along my people by sharing knowledge and placing my trust in them. When I’m gone I hope I have set the stage for those that worked for me and those I worked for to say that I was an upstanding trustworthy human being that cared deeply about his people and always tried to do the right thing. It’s about the legacy you leave behind when you’re gone.

Not that has a lot to do with the longevity of an untested reign of a particular technology but I like it!

 

[antennaguru]

Not that has a lot to do with the longevity of an untested reign of a particular technology but I like it!

A couple of years ago I was at an industry function and as I was walking past an Engineer that worked for me a few decades ago I said Hi to him by name, as I made it a point to know every employee’s name and a little about their family. A bit of a brain teaser running teams of upwards of a hundred engineers. Anyway when he realized it was me he ran up to me and hugged me as he told me teary eyed that he never had the opportunity to thank me for all I had taught him and the trust I placed in him over the years he worked for me, and he wanted me to know that his success in the industry came from working for me. That’s what I mean by the Legacy you leave behind as you move on to the next opportunity, whatever that may be. So yes, I do care about my Legacy after my eventual death as well.

 

[JJB70]

There is something to be said for the concept of"buy right, buy once", true quality isn't usually cheap but neither does it need to be particularly expensive. I have a Sony TA-F700ES amplifier I bought about 30 years ago and I plan on keeping it. I just gave it a major service and expect it to see me out. That wasn't cheap but nor was it ridiculously expensive, given the quality, the several decades of service and fact I would buy it again it has been a bargain. Build quality is outstanding, it is from that era when the Japanese were really serious about audio and when Sony wanted to they could embarrass most other companies with what they were capable of. I still have the matching CD player and tuner too with no desire to replace either.

 

[restorer-john]

There is something to be said for the concept of"buy right, buy once", true quality isn't usually cheap but neither does it need to be particularly expensive. I have a Sony TA-F700ES amplifier I bought about 30 years ago and I plan on keeping it. I just gave it a major service and expect it to see me out. That wasn't cheap but nor was it ridiculously expensive, given the quality, the several decades of service and fact I would buy it again it has been a bargain. Build quality is outstanding, it is from that era when the Japanese were really serious about audio and when Sony wanted to they could embarrass most other companies with what they were capable of. I still have the matching CD player and tuner too with no desire to replace either.

I have a Sony TAF-444esX in my ES amplifier collection which is essentially the same amplifier. They are a gorgeous product and I will never part with mine either.

 

[restorer-john]

But let's get back to the OP's question shall we? I have an 18 month old Hypex NC-252MP sitting here on my bench. Dead. Built 41st week of 2019. Sent to me by an ASR member to investigate why it failed as it had a very easy life in a multichannel amplifier. The brand and the member will stay anonymous as he was very happy with their customer service in rapidly rectifying the situation to his satisfaction.

Let's have a quick visual inspection to see if anything stands out.

I can immediately see some very dodgy hand soldering on the SMPS primary side switching transistors and some of the output MOSFETS, because these are the parts done by humans. Regardless, it should have never left the factory with soldering this poor. I think I am onto something:

Also, the board is clearly under a lot of strain (it bends) due to the screwing down of the PCB to the heat-spreader near the heat producing SMPS switchers:

The board bends enough to be 0.76mm out of alignment and the devices are no longer firmly pressed against the heat spreader:

The screws are also too far away from the devices and the impregnated heat transfer pad is too thick. (approx device package positions marked in red). They should not be using distantly mounted fixing/screw points and relying on the flexible PCB to maintain adequate device to heatsink contact. This is bad design 101.

First of all, let's dismantle the sucker and remove the heat-spreading aluminium plate and have a look-see:

Yes, you guessed it! It's gone fully Chernobyl!

Vaporised SMD components hanging off the primary side SMPS switching transistors. Basically, The board flexes under pressure (from the squishy "thermal" pad), so the transistors (FETs) are not adequately thermally coupled any longer to the aluminium spreader. They eventually fail from over heating (these particular devices are both internally shorted) and they take out some associated components around them:

A real mess. There's even a poor SMD transistor with its package cover blown right off. You can see the junction components! And a nice vaporized resistor or two, along with those poor MOSFETs that gave up due to their inability to get rid of heat.

All due to inadequately or properly mounting (you know, with screws, nuts and washers) and heatsinking the transistors. Hypex are simply squashing the devices against the aluminium plate, using plenty of PCBs screws and a foam heat pad, but not considering PCB material deforms under heat and pressure over a (short) period of time.

In my opinion, all the NC-252MPs will likely suffer the same fate in years to come, if this key section is not revised. Not remotely good engineering at all and certainly not likely to last the length of time customers deserve.

Apart from this glaring design fault, the rest of the board is of good quality. The components are adequate and very nicely laid out. I do not like TO220 heat producing devices squashed under pressure from PCBs. It doesn't work. It creates more problems than it saves money. And all the secondary rectifiers and output stage FETs are the same unfortunately.

Hypex can do a whole lot better if they are selling supposedly state of the art equipment. 18 months lifetime for an entire 250WPC module including PSU is just not remotely good enough.

 

[Snarfie]

But let's get back to the OP's question shall we? I have an 18 month old Hypex NC-252MP sitting here on my bench. Dead. Built 41st week of 2019. Sent to me by an ASR member to investigate why it failed as it had a very easy life in a multichannel amplifier. The brand and the member will stay anonymous as he was very happy with their customer service in rapidly rectifying the situation to his satisfaction.

Let's have a quick visual inspection to see if anything stands out.
View attachment 147422

I can immediately see some very dodgy hand soldering on the SMPS primary side switching transistors and some of the output MOSFETS, because these are the parts done by humans. Regardless, it should have never left the factory with soldering this poor. I think I am onto something:
View attachment 147423

Also, the board is clearly under a lot of strain (it bends) due to the screwing down of the PCB to the heat-spreader near the heat producing SMPS switchers:
View attachment 147425

The board bends enough to be 0.76mm out of alignment and the devices are no longer firmly pressed against the heat spreader:
View attachment 147426
The screws are also too far away from the devices and the impregnated heat transfer pad is too thick. (approx device package positions marked in red). They should not be using distantly mounted screw points and relying on the flexible PCB to maintain adequate device to heatsink contact. This is bad design 101.
View attachment 147424

First of all, let's dismantle the sucker and remove the heat-spreading aluminium plate and have a look-see:
View attachment 147427
Yes, you guessed it! It's gone fully Chernobyl!

Vaporised SMD components hanging off the primary side SMPS switching transistors. Basically, The board flexes under pressure (from the squishy "thermal" pad), so the transistors (FETs) are not adequately thermally coupled any longer to the aluminium spreader. They eventually fail from over heating (these particular devices are both are shorted) and they take out some associated components around them:
View attachment 147428

View attachment 147429

A real mess. There's even a poor SMD transistor with its package cover blown right off. You can see the junction components! And a nice vaporized resistor or two, along with those poor MOSFETs that gave up due to their inability to get rid of heat.

All due to inadequately or properly mounting (you know, with screws, nuts and washers) and heatsinking the transistors. Hypex are simply squashing the devices against the aluminium plate, using plenty of PCBs screws and a foam heat pad, but not considering PCB material deforms under heat and pressure over a (short) period of time.

In my opinion, all the NC-252MPs will likely suffer the same fate in years to come, if this key section is not revised. Not remotely good engineering at all and certainly not likely to last the length of time customers deserve.

Apart from this glaring design fault, the rest of the board is of good quality. The components are adequate and very nicely laid out. I do not like TO220 heat producing devices squashed under pressure from PCBs. It doesn't work. It creates more problems than it saves money. And all the secondary rectifiers and output stage FETs are the same unfortunately.

Hypex can do a whole lot better if they are selling state of the art. 18 months for an entire 250WPC module including PSU is just not remotely good enough.

Again you naild it John but this could also occur with ab amp's.

 

[restorer-john]

Again you naild it John but this could also occur with ab amp's.

Absolutely true, and well said.

But the thing is, those same poor design practices disappeared many decades ago in commercial A/B amplifier design. I spent years repairing equally bad f#$k ups. But the wonderful benefits available with collective hindsight, unfortunately, is it seems to be utterly ignored or forgotten by so-called "gun" designers or "paradigm shifters" intent on not listening to the past, learning from their predecessors mistakes, or acknowledging they don't know everything.

 

[JJB70]

Absolutely true, and well said.

But the thing is, those same poor design practices disappeared many decades ago in commercial A/B amplifier design. I spent years repairing equally bad f#$k ups. But the wonderful benefits available with collective hindsight, unfortunately, is it seems to be utterly ignored or forgotten by so-called "gun" designers or "paradigm shifters" intent on not listening to the past, learning from their predecessors mistakes, or ackowledging they don't know everything.

If it is any consolation, unfortunately this is not limited to audio.

 

[EJ3]

But let's get back to the OP's question shall we? I have an 18 month old Hypex NC-252MP sitting here on my bench. Dead. Built 41st week of 2019. Sent to me by an ASR member to investigate why it failed as it had a very easy life in a multichannel amplifier. The brand and the member will stay anonymous as he was very happy with their customer service in rapidly rectifying the situation to his satisfaction.

Let's have a quick visual inspection to see if anything stands out.
View attachment 147422

I can immediately see some very dodgy hand soldering on the SMPS primary side switching transistors and some of the output MOSFETS, because these are the parts done by humans. Regardless, it should have never left the factory with soldering this poor. I think I am onto something:
View attachment 147423

Also, the board is clearly under a lot of strain (it bends) due to the screwing down of the PCB to the heat-spreader near the heat producing SMPS switchers:
View attachment 147425

The board bends enough to be 0.76mm out of alignment and the devices are no longer firmly pressed against the heat spreader:
View attachment 147426
The screws are also too far away from the devices and the impregnated heat transfer pad is too thick. (approx device package positions marked in red). They should not be using distantly mounted screw points and relying on the flexible PCB to maintain adequate device to heatsink contact. This is bad design 101.
View attachment 147424

First of all, let's dismantle the sucker and remove the heat-spreading aluminium plate and have a look-see:
View attachment 147427
Yes, you guessed it! It's gone fully Chernobyl!

Vaporised SMD components hanging off the primary side SMPS switching transistors. Basically, The board flexes under pressure (from the squishy "thermal" pad), so the transistors (FETs) are not adequately thermally coupled any longer to the aluminium spreader. They eventually fail from over heating (these particular devices are both are shorted) and they take out some associated components around them:
View attachment 147428

View attachment 147429

A real mess. There's even a poor SMD transistor with its package cover blown right off. You can see the junction components! And a nice vaporized resistor or two, along with those poor MOSFETs that gave up due to their inability to get rid of heat.

All due to inadequately or properly mounting (you know, with screws, nuts and washers) and heatsinking the transistors. Hypex are simply squashing the devices against the aluminium plate, using plenty of PCBs screws and a foam heat pad, but not considering PCB material deforms under heat and pressure over a (short) period of time.

In my opinion, all the NC-252MPs will likely suffer the same fate in years to come, if this key section is not revised. Not remotely good engineering at all and certainly not likely to last the length of time customers deserve.

Apart from this glaring design fault, the rest of the board is of good quality. The components are adequate and very nicely laid out. I do not like TO220 heat producing devices squashed under pressure from PCBs. It doesn't work. It creates more problems than it saves money. And all the secondary rectifiers and output stage FETs are the same unfortunately.

Hypex can do a whole lot better if they are selling state of the art. 18 months for an entire 250WPC module including PSU is just not remotely good enough.

Yes. but they say: The efficiency will make up for it & you can replace it with something better in a couple of years.
You can, but as to me, it's a WASTE OF MY TIME to do other things in my life than spend TIME that I CANNOT get back researching new stuff (every few years) so that I can get something that works & stays working. For me, frequently getting NEW stuff is a waste of time, money, disposal space & more time & money (for others). All I want is good sound that stays good. It's not efficient at al. In the grand scheme of things, it's hugely wasteful for things to go bad because of bad design or trying to be cheaper than the others that make similar products. Basing things on "cheapness & "efficiency" can end up being hugely wasteful. Longevity needs to be part of the plan. Otherwise the products lifecycle is hugely wasteful.

 

[JJB70]

If people want to reduce their environmental impact then moving away from a throwaway short lifecycle attitude to the things we buy is a good step forward.

 

[Blumlein 88]

If people want to reduce their environmental impact then moving away from a throwaway short lifecycle attitude to the things we buy is a good step forward.

The opposite trend has held sway for decades and I don't see it changing.

 

[Blumlein 88]

Absolutely true, and well said.

But the thing is, those same poor design practices disappeared many decades ago in commercial A/B amplifier design. I spent years repairing equally bad f#$k ups. But the wonderful benefits available with collective hindsight, unfortunately, is it seems to be utterly ignored or forgotten by so-called "gun" designers or "paradigm shifters" intent on not listening to the past, learning from their predecessors mistakes, or acknowledging they don't know everything.

I bet those better designs were from a different country. So there is a break in institutional knowledge. Some of this knowledge will have to be learned anew. Doesn't have to be that way, but it is.