Class D FAQ

[abdo123]

OP didn't offend anyone.

Did I offend you? I apologize then.

 

[voodooless]

OP didn't offend anyone.

That is a very bold statement in 2021.. Somewhere, somehow, someone is always offended .. and that offends me very much

 

[Matias]

I just listed common answers I have been writing throughout the years in different forums and groups. Haters gonna hate, offended people are going to be offended. Business as usual.

 

[pjug]

Did I offend you? I apologize then.

Thnks for the apology. No I was not really offended but I thought it was your intent to offend.

 

[pjug]

On the FTC 20-20K power question, I am wondering if this is really a big hurdle for Class D or if this is just a design decision not to care about meeting this. For example, the NAD C298 has a 20-20KHz power spec that is in line with the Purifi clipping levels. Is it just a matter of using an output filter that can survive the FTC test at high power?

 

[boXem]

On the FTC 20-20K power question, I am wondering if this is really a big hurdle for Class D or if this is just a design decision not to care about meeting this. For example, the NAD C298 has a 20-20KHz power spec that is in line with the Purifi clipping levels. Is it just a matter of using an output filter that can survive the FTC test at high power?

Yes

 

[Matias]

On the FTC 20-20K power question, I am wondering if this is really a big hurdle for Class D or if this is just a design decision not to care about meeting this. For example, the NAD C298 has a 20-20KHz power spec that is in line with the Purifi clipping levels. Is it just a matter of using an output filter that can survive the FTC test at high power?

I think you should be looking at this from another angle. Class D manufacturers chose to forgo heatsinks because they were not needed in real world use. If they wanted to ace the FTC tests, there is nothing preventing them from adding large heatsinks (and even a fan or two) like traditional class AB amps. And behold, there goes a zillion watts in 20 kHz, yay! Now what customer is willing to pay for that? It is a free market, if a manufacturer thinks customers value this, go ahead and good luck.

 

[somebodyelse]

I would just say I have more confidence in Class AB and linear power supplies. I have never had to throw out a Class AB amp. Class D just don't have much of a lifetime track record yet.

In other words the FUD has been successful, and/or you happen to have the skill to fix one but not the other. There's nothing inherently more reliable or repairable about Class AB than Class D, or linear PSUs vs. SMPS. If you have the diagnostic skills and/or service manuals, the necessary equipment, and the parts are available, then they can be fixed, but it may not be cost effective.

 

[pjug]

In other words the FUD has been successful, and/or you happen to have the skill to fix one but not the other. There's nothing inherently more reliable or repairable about Class AB than Class D, or linear PSUs vs. SMPS. If you have the diagnostic skills and/or service manuals, the necessary equipment, and the parts are available, then they can be fixed, but it may not be cost effective.

This may be true, but my initial point is that warranty is generally better with Class AB amplifiers. Are Class D manufacturers spreading FUD by offering shorter warranties?

 

[pma]

The parts that are subjected to high dV/dt like filter capacitors in Class D amplifiers and SMPS have considerably lower life time than the similar parts in linear circuits. There is no doubt.

 

[somebodyelse]

This may be true, but my initial point is that warranty is generally better with Class AB amplifiers. Are Class D manufacturers spreading FUD by offering shorter warranties?

I can probably find a few examples of manufacturers offering more than the mandatory warranty in Europe, but they're the exception rather than the rule.

 

[somebodyelse]

The parts that are subjected to high dV/dt like filter capacitors in Class D amplifiers and SMPS have considerably lower life time than the similar parts in linear circuits. There is no doubt.

You need to specify components suitable for the environment they'll be used in, and the design life. No doubt some will cut corners and have early failures, but that's not unique to Class D or SMPS.

 

[shal]

I don't understand . We are on a science site.
So we have to avoid using undefined concept and measurement

The power of an amplifier is one of this measurement.
If a manufacturer said my amp is XXXX Watt . The forum have to ask "what is the definition of the measurement method".

So :
- "250W on typical music programm " is OK for me , the consumer have the information of the power provided is not really a measure.
- "250W following the method XXX" is OK for me, too

But
"250W" is just a useless information or even can be understanding by the consumer

 

[Matias]

I don't understand . We are on a science site.
So we have to avoid using undefined concept and measurement

The power of an amplifier is one of this measurement.
If a manufacturer said my amp is XXXX Watt . The forum have to ask "what is the definition of the measurement method".

So :
- "250W on typical music programm " is OK for me , the consumer have the information of the power provided is not really a measure.
- "250W following the method XXX" is OK for me, too

But
"250W" is just a useless information or even can be understanding by the consumer

Read here for more info.
https://www.audiosciencereview.com/forum/index.php?threads/hypex-power-ratings.19302/

 

[ferongr]

We just haven't gotten to Yamaha S501 yet

I used to owna 501. I guess it would rank probably somewhat south of 90dB. Even noise by itself is not stellar.

 

[rony]

In the FAQ, can someone please update Hypex-nCore vs Purify differences objectively. Thanks!

 

[Matias]

In the FAQ, can someone please update Hypex-nCore vs Purify differences objectively. Thanks!

Honestly it is a tiny difference, like splitting hairs among the grand scheme of things. Both are way above average. Just check their datasheets.

 

[boXem]

Distortion and IMD levels are much lower for Purifi.
Another objective difference is only 10% of people seem to be able to correctly spell Purifi, while Hypex seems to be straightforward .

 

[restorer-john]

Another objective difference is only 10% of people seem to be able to correctly spell Purifi

Where are your measurements for that wild number of 90% who cannot spell Pewrefi?

 

[Matias]

Distortion and IMD levels are much lower for Purifi.

IMO the difference in SINAD from 94 to 102 of the Hypexes to 104 dB of the Purifi is small next to the average SINAD 80 of the overall amplifier market.

Same goes for IMD. Sure, the highest distortion of the Purifi is around -125 dB in 17 kHz, compared to around -110 dB of both a Hypex NC502MP or a Parasound Halo A21+ (example of a 80 SINAD amplifier around the same power). But this IMD is not much audible in the high treble (Fletcher Munson curves).

I am super curious to see if Bruno can build a higher power module like 1+ kW with the same low distortion as the 1ET400A. That would pull ahead of the high power NCores. Fingers crossed!