View Full Version : ATI AT5xxNC Class D Amps

07-27-2018, 01:35 PM
Has anyone auditioned (or own) an ATI AT5xx class D amp with Sierra 2's or RAAL towers?
If so, thoughts?

07-27-2018, 02:18 PM
I haven’t, but sure would like to. They are supposed to be excellent.

07-28-2018, 04:43 AM
thanks, Curtis. I've heard the same. Need to find a dealer nearby to compare with ATI's class AB. The Monoprice Monolith (made by ATI, class AB) also looks to be great, as well

08-31-2018, 08:03 PM
Has anyone auditioned (or own) an ATI AT5xx class D amp with Sierra 2's or RAAL towers?
If so, thoughts?

I have an ATI AT 1802 (AB class) so not a class D. I think it sounds great! never breaks a sweat. I think the only amp I would consider over it is a belles audio. Those are a lot pricier though.

09-01-2018, 09:45 PM
Siegfried Linkwitz has had good experiences with ATI amps for many, many years. I think his work and his web-site are great (I built his Orion speakers, with active crossovers and 10 Emotiva amp channels). On his web-site, he has IM test plots for the AT528NC at 100mW and 1W, both of which look great. Read the page and look for the plots under "Other Power Amplifiers", towards the bottom:

I have no personal experience of them. I'm Jonesing for a Benchmark AHB2. :eek:

Note: I own and use Sierra 2 and Luna, regularly - their just not my "big" system.

09-01-2018, 09:54 PM
I thought I read that the switching of the power supplies in class D amps might be audible with sensitive/transparent/hi res tweeters.

I think the post mentioned that class D were originally invented to achieve high power levels for subs without having to finance the farm, without tripping 15A breakers and without melting down audio audio rack with excessive heat.

I like the ATI amps a lot but I've been looking at the ATI 1800 and 4000 AB's instead of the AT5xx D's because of the potential switching noise.

I'll definitely buy the AT5xx amps if my thoughts are incorrect so please do set me straight if I'm off the mark.

09-01-2018, 10:19 PM
Post #22 in thread "Preamp/Amp Suggestion for Sierra 2" in the loudspeakers forum looks to be a solid discussion on class D amps

I was wrong, not noise from the power supply, noise from the class D switching itself.

09-02-2018, 08:35 AM
... noise from the class D switching itself.

That doesn't appear to be present in that particular data, and it is a quite sensitive test. On the other hand, Dave did recommend against Class D amps with his products a year ago. Have you tried talking with ATI, directly, for any comments? Perhaps you'll only know by hearing one.

Meanwhile, I don't see how getting an 1800 or 4000 series amp could be a bad choice. Siegfried sold 1806 amps for his products for many years. How many channels are you looking for, just 2? Lots of choices... If you are looking for "clean" maybe the Benchmark AHB2 would be worth a listen - it is sold on a try at home basis. Whichever way you go, please let everyone know what you think.

09-02-2018, 03:43 PM
Class D runs at approx 90% efficiency because power semiconductors are switched off when not in use and they are switched on when in use. Early Class D amps used MOSFETs and their switch times are approx 25ns which does cause audible distortion. New power semiconductors such as eGaN FET's switch at about a 5ns rate and this somehow contributes less to distortion. You can read about this here if interested:


ATI has been an innovative quality amp designer for years and it just seems they wouldn't have GA'd the new amps without them working well well with all drivers, regardless of sensitivity, but that's just an opinion.

These new amps are cheaper, they consume less power plus they're smaller and lighter:

Two to four channel models: 17"W X 5 3/4"H X 10 5/8"D
Five to eight channel models: 17"W X 5 3/4"H x 15 1/2"D
39 to 62 1/2 lbs

So tempting ......

09-02-2018, 09:48 PM
All true. And the eGaN FET looks to improve performance in designs that use it. While that is nice, technically, you are interested in the highest audio performance (I think), and need to know about specific amp implementations, not just specs of a single electronic component.

I assume you have already read these:

The ATI design claims to use Hypex NCore output modules, which are in high end amps from several manufacturers. They are relatively new, and well regarded. Since the technology seems to interest you, you might want to read more about them.

But for many of us, two amps often sound different when we do not see why in the available measurements. In this case, I can't really see any 'switching noise' in the ATI amp and I would not expect to hear any. Period. But, depending on your own taste, associated equipment, etc, you still might not like how it sounds. Or, you might be very satisfied on every level.

Which brings you to your original question, has anyone used them on these RAAL equipped speakers?

09-03-2018, 04:34 AM
thanks for the additional comments.

Not 100% set on class D, although I like that they are more efficient, run cooler, and not as heavy as class a/b amps.

dfurry - ATI only use the Ncore modules for the amplification stage. Everything else is in-house design (input stage, output stage, power supply - which is their torroidal (not switching)... likely as they make them in house).

jimb -

did Dave recommend against Class D on this forum or elsewhere? in either case, will likely ask his input when I get closer to pulling the trigger.

I've communicated with ATI and one of their dealers. ATI says both are as neutral as they can make them. As I recall, the dealer indicated only one of his customers thought the class D was a bit bright.

I've read the two reviews (although I do take professional reviews with a grain of salt), as well as several forums. Several manufacturers use the Hypex NCore (Nord, Apollon, believe NAD). Found a couple of other US companies, although they use different modules (Class D Audio - ? module; D-Sonic - Pascal).

I did hear the D-Sonic -- their showroom is about 15 minutes from my office. In his system, the amp sounded fine - I didn't hear any distortion, brightness, or coloring. They also have a 30 day in-home trial.

Eventually, 9 channels of amplification, although front three are priority. So, either 3 + 6 or 9 channels in one chassis would be ultimate (one less box and power cord :-))

Like you mentioned, comes down to how they sound in my system and with the RAAL-equipped speakers.

09-03-2018, 12:03 PM
thanks for the additional comments.
jimb -

did Dave recommend against Class D on this forum or elsewhere? in either case, will likely ask his input when I get closer to pulling the trigger.

It was several posts up in the "Preamp/Amp Suggestion for Sierra 2" thread you referenced earlier, so I thought it was the basis for your concern. However, it was at a time that Dave might not have had a chance to hear the latest generation amps. He might have a different opinion today.

09-03-2018, 04:58 PM
thanks, JimB, for pointing out that thread (dfurry referenced it). My concern was that some forum posts suggested class D amps were harsh and/or bright, but this seems to be more related to earlier generations as don't see too many posts about this on current ncore or pascal amps.