Can a 80 watt receiver put out more than 80 watt?

[M Code]

Several years ago, I was contacted by an off-shore, smaller, car audio factory who wanted to expand their business in the category of high-powered car amplifiers.. I assembled a team of capable engineers and we developed complete product plan including ID design. The design was a long/low/sleek profile titantium heat sink rather large as the (2) models were rated @ 250@ x 2, and @ 400W x 2 @ 0.5% THD into 4 Ohms. It took about 6 months to go from design, proto-types, tooling, sample validation and mass production. We rolled out the products @ CES and took some very large orders of >$1 million. Also I visited many key dealers to support the product launch, sales started fine and the feedback was positive. About 10 months later, certain dealers started contacting me about having some reliability issues....
Being somewhat puzzled, I visited 1 of the dealers I knew well and asked him to return a couple of the amplifiers that failed.... In examining the amplifiers loosely, I discovered that the basic output stage topology had been changed by eliminating a couple of pairs of output devices...
Which significantly decreased the safe operating area for the amplifier.. Raising its temperature significantly and destroying its reliability..

It turns out the back @ the Far-East factory 1 of higher managment decided to revise the design of the output stage... Eliminating some output devices.. Also he changed the etched brand logo to be silkscreened.. All done to save some $$... Suffice it to say that U just can't trust certain brands..

Just my $0.02...

 

[Irvrobinson]

It turns out the back @ the Far-East factory 1 of higher managment decided to revise the design of the output stage... Eliminating some output devices.

Disgusting.

Just curious, but...

Was adherence to your design specified in the production contract?

Did you inspect any of the manufacturing samples?

 

[M Code]

Disgusting.

Just curious, but...

Was adherence to your design specified in the production contract?

Once the development is completed and mass production started, we are paid in full for our participation. The tooling, electrical design, software is owned by the client. We do provide a 6 month for technical support if needed. But the mentioned change was done 10 months after mass production had started. Once we discovered the design changes the client was responsible, however we did provide our analysis about the change, but by then the client was well aware of the negative impact of his changes..

Did you inspect any of the manufacturing samples?

Our development cycle requires inspection & testing of 5 production samples that were pulled from mass production after it started and sent by air to our USA team for inspection, testing and specification/design validation. Shipments into North America were not permitted until we validated/approved the mass production samples, releasing the product for shipment to the market.

Conclusions..
This is a common happening in certain Far East factories, typically the client is always pushing for cost-downs and pressuring their subcontractors for lower pricing. In the end, corners are cut and lower grade internal components are supplied. Thats why many brands have had significant technical and resulting shipment delays as the product design and/or specifications have been revised to save $, sometime too late as marginal products have already been shipped into the market. In my organization, we have always had our own independent technical/QA staff in the Orient that would visit the subcontractors and audit their actions. But in the above example, was done for a very popular car audio brand that has its own production, procurement and QA teams so what goes on inside is always kept secret. They came to me as we had the design/technical expertise that could expedite the product much faster than what they could do internally...

Just my $0.02...

 

[mtrycrafts]

Agreed, that's why in my earlier response to you (Post#38), I state: "clipping should simply mean as soon as the sine wave cannot reach it's theoretical peak, and that could be low enough that it cannot be seen visually on a scope, without looking at the displayed value.", in trying to make the point ski made later, just differently.



I thought you were serious until I noticed the emoticon lol..

You are right though, I was aware of the 2 W at the low end, but I thought everyone would know I was referring to the high end where it shows >150 W.

As we all (or most of us) know by now, class AB amps typically has their THD trending a little higher towards the low end, some would go much higher due to crossover distortions. At very low output level, it should behave much more class A, but even though the XOD is lower, as % it could get much higher due to the low output (the fundamental).

Thanks. Was just making sure I understood correctly.

 

[mtrycrafts]

... But the mentioned change was done 10 months after mass production had started. Once we discovered the design changes the client was responsible, however we did provide our analysis about the change, but by then the client was well aware of the negative impact of his changes...

Just my $0.02...

So, the production had good amps for 10 month , then changed the design and issues became known. Just wow.

 

[lovinthehd]

Gotta love the bean counters, eh?

 

[M Code]

So, the production had good amps for 10 month , then changed the design and issues became known. Just wow.

For the 9 months or so, sales were strong and reported field failures were nil.. And then the bomb hit, a major customer had multiple failures. When this happens the 1st action is to get the failed samples and do a failure analysis. When checking the returned failed units this is when we spotted the decreased # of
output devices..
Up until that time we had no idea why the failures, during mass production anything can happen component failure, workmanship issues.. But finding the trimmed down count of output devices it was apparent what had happened. At 1st the client danced around but behind closed doors we presented out failure analysis report and then the client conceded about what happened...
These car audio amplifiers are often bridged driving multiple subwoofers @ 2 Ohms.. And thats why we designed with additional output devices in parallel to handle the increased current demands and higher temperatures....

Just my $0.02...

 

[Irvrobinson]

Gotta love the bean counters, eh?

A bean counter wouldn't have known about reducing the output transistor pairs. That was an engineer. He may have been ordered to identify opportunities for cost reduction by a manager, but the opportunity (ha!) was identified by an engineer.

 

[lovinthehd]

A bean counter wouldn't have known about reducing the output transistor pairs. That was an engineer. He may have been ordered to identify opportunities for cost reduction by a manager, but the opportunity (ha!) was identified by an engineer.

Bean counters often don't know the details of how things work, true.

 

[PENG]

I use my Denon AVR as prepro, but was curious after seeing M Code's post. The output transistors were rated 15 A, that's pretty good, but it is cheap insurance to put a fan or two on top, for people who do use the internal amps.

 

[Irvrobinson]

I use my Denon AVR as prepro, but was curious after seeing M Code's post. The output transistors were rated 15 A, that's pretty good, but it is cheap insurance to put a fan or two on top, for people who do use the internal amps.

My Marantz in pre-pro mode is throwing off enough heat after my wife has been binge-watching for three or four hours that I'm thinking of putting a fan on top.

 

[mtrycrafts]

Gotta love the bean counters, eh?

Yep, you don't want to eat too many calories.

 

[M Code]

A bean counter wouldn't have known about reducing the output transistor pairs. That was an engineer. He may have been ordered to identify opportunities for cost reduction by a manager, but the opportunity (ha!) was identified by an engineer.

Irv Robinson was right on...
In this instance the executive ordering the cost reduction was the Overseas Managing Director, he was responsible for his own profit margin that was poor and wanted to increase this so he looked for high cost products selling @ high volume rates.. The ironic thing is that always looking for improving profit margin is fine... But before ordering the actual technical product revision, modified units should have been built and put through the same rigorous QA/life testing process as a new product. A short time later the Managing Director was fired, as the USA brand tanked, and eventually pulled back from the USA market. Note that today the factory survives building home & auto products for some of the major audio brands....
To most outsiders very few realize what goes on inside some of these off-shore Far East audio corporations. I have actually been approached to write a book about some of my experiences over the last 40 years and someday I just might..

Just my $0.02...

 

[lovinthehd]

LOL call it a bean counting decision....what was more profitable in the end after all the failures/loss of faith cost?

 

[PENG]

Irv Robinson was right on...
In this instance the executive ordering the cost reduction was the Overseas Managing Director, he was responsible for his own profit margin that was poor and wanted to increase this so he looked for high cost products selling @ high volume rates.. The ironic thing is that always looking for improving profit margin is fine... But before ordering the actual technical product revision, modified units should have been built and put through the same rigorous QA/life testing process as a new product. A short time later the Managing Director was fired, as the USA brand tanked, and eventually pulled back from the USA market. Note that today the factory survives building home & auto products for some of the major audio brands....
To most outsiders very few realize what goes on inside some of these off-shore Far East audio corporations. I have actually been approached to write a book about some of my experiences over the last 40 years and someday I just might..

Just my $0.02...

I have been reading many schematics that are publicly available on the net lately and noticed that manufacturers such as D&M, Yamaha and others use obsolete chips and transistor output devices in their products as recent as their 2017 models. It does not always mean that is bad, except it is frustrating when in many cases I couldn't even find their datasheets. Do you have insight into the reasons behind their decision to use obsolete parts, other than I guess due to volume discount they might have acquired huge inventory over the years, or it is just another cost cutting measure so they could scoop up old inventory from suppliers? Thank you in advance.

 

[M Code]

I have been reading many schematics that are publicly available on the net lately and noticed that manufacturers such as D&M, Yamaha and others use obsolete chips and transistor output devices in their products as recent as their 2017 models. It does not always mean that is bad, except it is frustrating when in many cases I couldn't even find their datasheets. Do you have insight into the reasons behind their decision to use obsolete parts, other than I guess due to volume discount they might have acquired huge inventory over the years, or it is just another cost cutting measure so they could scoop up old inventory from suppliers? Thank you in advance.

Hmmm....
Don't know the exact reasons but my thinking is...
1. For certain ICs, HDMI, audio DSPs, controllers, DACs, connectivity... New standards & later technologies that requires later ICs have been introduced making the previous generations obsolete... But the technologies are likely to be backward compatible with the later, newer iCs but the new ICs are a thinner micron and less expensive to produce..
2. As long as the purchase qtys' are significant the semiconductor factory will continue to supply, typically @ lower cost..

Just my $0.02...