Review and Measurements of IRS2092 IRAUD350 Class D Amplifier

[Headphonaholic]

Thank you for this eye opening review Amir! This is basically a public service announcement. I've seen dozens of amp kits on Ebay just like this one. Never bought em myself due to quality concerns but it didn't occur to me they would be a major safety hazard (makes sense though). The fact that it arrived falling apart is appalling.

 

[VintageFlanker]

@sbsj, I think you have the honor of having identified a new testing metric on ASR: the "Pink-Panther-O-Meter". I think it's safe to say that if the PPM (the widely accepted acronym for the Pink-Panther-O-Meter) is showing 180 degrees off its center point (said feline's nose), then we have a stinker of a test subject. My sincere congratulations!

Sure. In that case, PPM probably didn't exist some weeks earlier when the R2R-11 has been reviewed!

 

[Jimster480]

Thank you for this eye opening review Amir! This is basically a public service announcement. I've seen dozens of amp kits on Ebay just like this one. Never bought em myself due to quality concerns but it didn't occur to me they would be a major safety hazard (makes sense though). The fact that it arrived falling apart is appalling.

its amazing to me that so many products are for sale which are inherently unsafe!

 

[Headphonaholic]

its amazing to me that so many products are for sale which are inherently unsafe!

Right? On one hand I'm sure it's all about the quick buck but on the other shouldn't the fear of legal repercussions due to such shoddy work be a concern? I guess because most of these are made in China the creators don't really care...

 

[Jimster480]

Right? On one hand I'm sure it's all about the quick buck but on the other shouldn't the fear of legal repercussions due to such shoddy work be a concern? I guess because most of these are made in China the creators don't really care...

Yes especially because there is unlikely any real repercussions.

 

[restorer-john]

FWIWFM, HTH, IME, IMO, YMMV, etc. - Don

That's one hell of a disclaimer Don.

 

[andreasmaaan]

That's one hell of a disclaimer Don.

Google confirms that @DonH56 is the only person on the internet using this one:

 

[DonH56]

That's one hell of a disclaimer Don.

I usually add "my 0.000001 cent (microcent)", can't believe I missed one... I got tired of getting asked to provide proof and references for every engineering/science reference back to grade school and decided to just qualify everything and let other people look it up and prove me wrong if they wish. I am certainly not correct all the time, and my audio expertise is pretty limited, but if I have to explain why RF skin effect at 20 Hz is not a problem for your 12 AWG speaker wire one more time...

 

[restorer-john]

I usually add "my 0.000001 cent (microcent)", can't believe I missed one...

Just put them all in your signature line with:

"this post must be read in its entirety, according to the terms and conditions in the disclaimer below"

 

[HammerSandwich]

Another way to look at this is that the filter is a network which includes the speaker. All the values (i.e. the values of the components of the filter as well as the loudspeaker crossover components and transducers) interact to produce a low pass filter at a specific frequency and with specific properties.

Excellent point.

In addition, many class-D amps source their feedback loops before the filter. One of UcD's big improvements was allowing post-filter feedback, meaning that the amp is able to correct the signal at the speaker terminals. This provides a much flatter FR, because the filter/speaker interaction is fed back for correction.

More recently, I've read of post-filter designs from other suppliers, not just Hypex, but I don't remember which right now.

 

[DonH56]

^^^ I don't know which manufacturers either, but there have been a number of papers in various IEEE Journals describing the use of feed-forward and multi-loop feedback circuits with modified transfer functions that, along with higher switching rates, allow the design to close the loop after the output filter. So I'd hope a great many... I think ICE and IR are using such designs now? Again, I do not really know... Feedback theory has been around a long time and none of this is really new.

 

[restorer-john]

In addition, many class-D amps source their feedback loops before the filter. One of UcD's big improvements was allowing post-filter feedback, meaning that the amp is able to correct the signal at the speaker terminals. This provides a much flatter FR, because the filter/speaker interaction is fed back for correction.

More recently, I've read of post-filter designs from other suppliers, not just Hypex, but I don't remember which right now.

It's not like any of this is rocket science. It's been done for generations, people are going on like Hypex re-invented the wheel. I find it hilarious and just like that movie- Groundhog Day, or Back to the Future. Trouble is, unlike the movie, this endless re-hashing of existing ideas never seems to end.

Suddenly excessive amounts of NFB are cool again after decades of being vilified by the low NFB crowd, or worse, the complete lack of feedback crowd. Oh, and wait for it, let's 'invent' feed-forward correction again and extol its virtues. Let's 're-imagine' (I hate that term) Peter Walker's current dumping and call it THX or something. It's all been done, bigger, better, and a whole lot cheaper, several decades ago.

Go have a look a Kenwood's Sigma Drive in the early 1980s. They took additional feedback from the speaker terminals themselves to cancel the effects of the speaker cable, giving damping factors of over 1000 @ 8ohms at all frequencies. Plenty of amplifiers have used post Zobel combination feedback and negative impedance drive situations by lifting the 0v return via a low value resistor (Yamaha AST). Feedforward was one of Sansui and Denon's babies and it looks like enjoying a renaissance under someone else's dubious patents.

Here's a nice 'Class D' from 1977.

Powered by, wait for it, an SMPS.

 

[Hugo9000]

I wonder if this unit subjectively induces extreme anxiety in its users.
IRS2092 IRAUD350

Internal Revenue Service is right in the name! Followed by Internal Revenue Audit!

 

[MattG]

Infrared camera shows the regulator transistors (?) to be the hottest component as I noted earlier:

I believe those are the actual output transistors. My understanding of the IRS2092 chip is that the chip itself is really just a driver of some other output device(s). Compared to a "monolithic" design, where the switching logic is combined with the output device into one chip (TI tpa311x for example).

So I think it is technically possible to make a 700W amp with the IRS2092, as the limit won't be the IRS chip, but whatever output MOSFETs are used. Proper heatsinking will of course be very important. Not sure what kind of efficiency you get with IR2092 based designs, but 90% is not uncommon for class D amps. At 700W output, that's still 70W of heat to get rid of. That needs either a fairly large heatsink or active cooling.

FWIW, the CDA and SDS series amps from Class D Audio are based on the IRS2092 chip.

IIRC (big if!), the IRAUD reference design amps suffer from low input impedance. So if you're not driving them with some kind of buffer (preamp), you're likely to have a suboptimal experience. And also IIRC, that's the main upgrade between the CDA and SDS series amps from Class D Audio, the latter adds a (I think) THAT1200 (or similar) front-end.

With regards to post-filter feedback: one interesting example of this, with the IRS2092 chip, is ChocoHolic's SystemD LiteAmp. This was long on my "want to build" list, but I never got around to it. I'd be really curious to see how this measured.

In general, I would caution against using this review as a proxy for all IRS2092-based amps. As with DAC chips, I think the performance is overwhelmingly defined by the implementation, rather than the chip itself.

 

[amirm]

I believe those are the actual output transistors.

The output transistors are the ones mounted on the heatsink. I am referring there to the surface mount transistors.

You can see the real output transistors (barely) on top of left. The one that got the hottest was the one I have indicated as "replaced transistor."

I considered whether they are driver transistors but they don't seem to be and is not consistent with the recommended design from IRF.

 

[MattG]

Ahh, my bad, I mis-understood, I thought you were referring to the heatsink-mounted devices.

 

[RayDunzl]

<--- *tries to make sense of this:

 

[amirm]

It is a re-worked resistor in the middle.

 

[RayDunzl]

Fugly...

 

[trl]

What do you think of using such a unit as a pure subwoofer amp?

My Mackie sub is just fine with this IRS2092 chip: https://www.audiosciencereview.com/...nside-pics-personal-thoughts.4360/#post-99406. I think it's a decent amp for a sub after all.

However, under 32Hz is completely dead...I think it's not related to amp itself, but to the high-pass filter inside, because the diaphragm is not moving even at max. power; it also cuts the bass from the Mackie monitors too.