My initial impressions switching from Parasound Halo to an ATI AT524nc

[AcuDefTechGuy]

You're the authorized dealer, can't you get a demo model?!

Alright. I had that coming.

 

[AcuDefTechGuy]

Interesting. My old Classe CP50 and CA200 were silent. My Crown XLS amp has some hiss, but you have to be close.

Pretty much all pro-amps are gonna have hiss noise.

I think the CA200 from the 1990’s had THD+N 1kHz 1W of about 0.005%. But the one I heard from around 2012 probably didn’t have the same low noise. The hiss noise that I heard from that Classe amp was louder than both the Crown XLS 2500 and Yamaha PX3 pro amps.

 

[PENG]

I just tested my Yamaha MX-A5000 amp. All the tweeters on my RBH SX-T2R are dead silent with my ear pressed against those tweeters.

That means my Yamaha MX-A5000 is SOTA, while the ripoff Macs are not SOTA.

Alright, now who has some Legacy Audio amps to test?

I don't know, not doubting you or anything but I remember you also said something like your ATI amp's huge toroidal transformers were silent, again not doubting you but I am 1000% sure such transformers would hum and I have never heard one (including those priced well above my pay grade) that was even near silent with ears inches from one. Iirc RichB would agree with me, but again as I said some people are more sensitive to transformer hum noise and perhaps the same apply to hiss.. Just like I am not, or at least no longer sensitive to >12,000 Hz.

 

[PENG]

It seems the Parasound, Macs, Classe have the hiss. What measured noise level do you think will predict this hiss noise?

If you refer to AH and ASR bench measurements, it would be SNR measured at 1 W unweighted, or at higher level but convert it to 1 W level, or less such as 0.5W if you are like me, who typical listen to spl that requires much less than 1 W, like 0.2W. Hiss could be source contents related too, from the recording process.

Found an article on the topic, author unknown:
3.3-Removing-Hiss-Hum-and-Noise.pdf (cusjc.ca)

 

[AcuDefTechGuy]

I don't know, not doubting you or anything but I remember you also said something like your ATI amp's huge toroidal transformers were silent, again not doubting you but I am 1000% sure such transformers would hum and I have never heard one (including those priced well above my pay grade) that was even near silent with ears inches from one. Iirc RichB would agree with me, but again as I said some people are more sensitive to transformer hum noise and perhaps the same apply to hiss.. Just like I am not, or at least no longer sensitive to >12,000 Hz.

I heard absolutely NO HUM whatsoever on any of the ATI amps I've owned (AT3005, AT3002, AT2005, AT6012).

But let's see if others can share their experiences here.

 

[PENG]

Pretty much all pro-amps are gonna have hiss noise.

I think the CA200 from the 1990’s had THD+N 1kHz 1W of about 0.005%. But the one I heard from around 2012 probably didn’t have the same low noise. The hiss noise that I heard from that Classe amp was louder than both the Crown XLS 2500 and Yamaha PX3 pro amps.

I think you are right. To make sure your amp don't hiss or hum on their own you pretty much have to consider the Amir's level of SOTA SNR, SINAD, that is 120 dB, or at least 115 dB, otherwise you may hear the noise if your room is anechoic quiet like, and you typically listen to music, movies that have a lot of quiet passages/moments. More so with highly sensitive speaker obviously.

Someone like @RichB, if hiss were heard, he would have the authority to blame it on something else, not his amps.. He has, or had an AT5XXNC too, I would love to know if he heard any noise. But then his Salon2, like yours, are not very sensitive at all.

 

[PENG]

To be clear, transformer hum (the mechanical type) that is audible with ears touching the chassis is normal unless the transformer is dead or not energized. It the hum is audible from a few inches away, however quiet, may or may not be normal and may or may not be fixable with external devices/gadgets and there are many available including the usual suspects like PS Audio. As always, some may work better than others. Also, some transformers are more susceptible to imperfections in the incoming ac line.

 

[DigitalDawn]

My clients have been very, very happy with the Class D ATI amps. Plenty of power and dead silent.

 

[Out-Of-Phase]

Pretty much all pro-amps are gonna have hiss noise.

I think the CA200 from the 1990’s had THD+N 1kHz 1W of about 0.005%. But the one I heard from around 2012 probably didn’t have the same low noise. The hiss noise that I heard from that Classe amp was louder than both the Crown XLS 2500 and Yamaha PX3 pro amps.

Classé CA-200 Power Amp:
S/N ratio: 135dBr
THD+Noise: 0.004%

Over time, I learned to take those numbers with a grain of salt.

 

[Irvrobinson]

I heard absolutely NO HUM whatsoever on any of the ATI amps I've owned (AT3005, AT3002, AT2005, AT6012).

But let's see if others can share their experiences here.

I agree. I have two ATI amps, an AT3005 (now configured as a 3004) and an AT602. Neither has any audible hum or tweeter hiss. I expected a touch of tweeter hiss with the AT602, because it's powering relatively efficient Klipsch RF62ii speakers and the amp is driven by an inexpensive Marantz AVR operating as a pre-pro. The complete silence of the AT3005 is also a little surprising, because it sits on an amp stand out in the listening room, not in a cabinet or closet, and it has two huge toroid transformers (of different sizes).

 

[PENG]

I agree. I have two ATI amps, an AT3005 (now configured as a 3004) and an AT602. Neither has any audible hum or tweeter hiss. I expected a touch of tweeter hiss with the AT602, because it's powering relatively efficient Klipsch RF62ii speakers and the amp is driven by an inexpensive Marantz AVR operating as a pre-pro. The complete silence of the AT3005 is also a little surprising, because it sits on an amp stand out in the listening room, not in a cabinet or closet, and it has two huge toroid transformers (of different sizes).

I would agree as well based on other's feedback including yours. My comments about all transformer hum were about near silent kind of hum that can only be heard with ears touching chassis and assuming near perfect incoming line quality. If there were excessive dc., harmonics etc. in the line, then transformer hum/noise may be audible from even a few inches and again it depends on one's sensitivity to the related frequencies. There are definitely ATI amps and McIntosh amps owners reporting transformer hum, and I suspect those are made worse by the line power quality (dc offset, harmonics etc.). It could be complicated for a lot of users because some amps would hum, or rattle in reaction to the amount of dc and/or harmonics. I have at least a dozen of power amps and the one that is most susceptible is the Halo A21, the Bryston, NAd and all Denon AVRs seem immune, like virtually "silent", even when plugged into the same outlet as the Halo amp. The A21 could be near silent too if nothing else in the house is running.

Hiss, of course is a different animal, and that should be predictable by bench measurements results on noise.

If one can only hear the transformer hum with ears touching the chassis, then I would agree that it is practically silent, even in a very quiet room.

 

[Irvrobinson]

There are definitely ATI amps and McIntosh amps owners reporting transformer hum, and I suspect those are made worse by the line power quality (dc offset, harmonics etc.).

Agreed about DC offset on AC mains. Several years ago a friend had a humming Sony amp. He was going to just replace it, so I told him to call the power company and have them assess the power quality in his house. He thought I was being silly. It took a $20 bet to convince him to do it. Two days later the power company was out, and found an unacceptable level of DC offset in his house. As a result they apparently replaced a transformer (or whatever, I never got a detailed story) in his neighborhood. The interesting thing was that he said he noticed some electrical motors were now running quieter, which I thought would be due to sine wave distortion more than DC offset, but whatever. The audible humming was gone. I let him keep the $20.

 

[AcuDefTechGuy]

Classé CA-200 Power Amp:
S/N ratio: 135dBr
THD+Noise: 0.004%

Over time, I learned to take those numbers with a grain of salt.

Somehow I don't think any amp with a THD+N of less than 0.01% or maybe 0.009% is going to have any hiss noise.

 

[AcuDefTechGuy]

I think you are right. To make sure your amp don't hiss or hum on their own you pretty much have to consider the Amir's level of SOTA SNR, SINAD, that is 120 dB, or at least 115 dB, otherwise you may hear the noise if your room is anechoic quiet like, and you typically listen to music, movies that have a lot of quiet passages/moments. More so with highly sensitive speaker obviously.

Someone like @RichB, if hiss were heard, he would have the authority to blame it on something else, not his amps.. He has, or had an AT5XXNC too, I would love to know if he heard any noise. But then his Salon2, like yours, are not very sensitive at all.

What about your Anthem and Bryston amps? Do they produce any hiss noise?

 

[Out-Of-Phase]

Somehow I don't think any amp with a THD+N of less than 0.01% or maybe 0.009% is going to have any hiss noise.

Yes, they were both quiet. But they didn't sound any better than my old Yamaha integrated amplifier. But that's a different topic for a different thread.

 

[PENG]

What about your Anthem and Bryston amps? Do they produce any hiss noise?

I haven't checked for a few years but I just did some quick experiments for you. The results were roughly the following:

Denon AVR-X4400H pre out + Anthem MCA20 (the earlier gen. of the MCA225, very similar specs):
No hiss heard with volume below -10, not audible even with volume at +18 from MLP or even a few feet away.

Denon pre out + Marantz MM8003, volume had to be in the + before I could hear the hiss, but it was powering the surround speakers that are probably a couple dB less sensitive than the main towers.

Marantz AV8801 + Parasound Halo A21:
About the same as the Denon + Anthem MCA20, but was hooked up to the BMR that are about 2 dB less sensitive so I would say the AV8801, despite all those copper shielding, toroidal transformers etc., did not do any better, if not worse, or it could be the Halo amp a little noisier than the Anthem.

Now, to my big surprise, I went back to the HT room upstairs to check the combo using the Denon internal amps and hooked them up to the more sensitive Focal 1028Be. Guess what, it was the quietest of all the tests! Hiss was practical not audible until volume > 0, more like +6 or higher. Not sure if separates could actually do worse because of the extra connections/interconnects. It is not a scientific way the way I did it because to compare apples to apples I would have to do a lot more work, including the use of the shortest possible runs and most direct route of the interconnects cables.

In any of the tests above, I had my ears pressed on the grille of the mid range domes or tweeters of the speakers to hear the hiss. Otherwise the hiss was not audible from even a few inches, at any volume. There was always a very faint (constant level) power supply noise, likely due to the ripples on the rectifier bridge and that was there in every test, but again only audible with ears pressed on the grilles (except the BMRs that don't have a grille yet so I have to be careful to avoid damaging the speaker diaphragm, sort of funny because its normally the speaker that damages the ears.

In summary, even just using the AVR, there's absolutely no audible transformer hum unless ears are touching the chassis, no hiss from MLP from several inches away, and no hiss even with ears on mid/tweet grilles unless volume is > +6 to +7. Its not scientific and should not be taken as facts because those were quick tests, the room wasn't silent though I did turn off the HVAC, and its just my ears that I know are super sensitive to transformer hum any power supply noise, but are likely much less sensitive to the hiss frequencies.

Edit:
- Forgot to include the combination with the Cambridge Audio preamp paired with the Halo A21, it was definitely quieter than with the AV8801, I would say at least a few dB difference on the volume.
- I also did the same (by ears only) with just the power amps on, the faint noise was constant, obviously.

 

[RichB]

Transformer Noise
I had two ATI AT6002 and an ATI AT6002 with custom wound transformer. There were installed in a open credenza about 2 feet from the rear sheetrock wall. I could easily hear these transformers from be seated position about 11' from the wall and 8 feet from the amps. The AT6002s used the normal transformers and the At6006 was quieter with the handbound transformers from ATI. The AT6006 had greater sensitivity to something external that would cause the hum to come and go that was easily heard at night. Drove me nuts. I removed the DC fans from the cabinet and that seemed to improve it. This was my number 1 issue with ATI.

The Parasound amps (A21, A31) had less transformer noise that was not audible from my seating position.

Hiss and Buzz
Some hiss was definitely coming from the AV8801. One day it got bad when after installing a different component and finally found that jiggling the power cord got rid of it. When shipped for the second fried trigger, Marantz also replaced the power receptacle.

The ATI AT2000, ATU AT3000, Parasound A31 all buzzed from the center and rear channels. This was likely environmental.
The AT6000s and Benchmark AHB2 are completely silent.

The Benchmark AHB2 are mechanically silent and produce no buzz or hum. My daughter can detect some hiss with ears up against the tweeter but that goes away if I turn of the Emotiva RMC-1 (100 dB SINAD).

Everybody has their own experiences and may be a combination of the environment and product variance.
These issues are completely solved. BTW, Emotiva (like all these 16+ channels) has issues.
Dirac has issues, just look that the software release count.

One thing I can say for sure, is used with just Bass Management the Emotiva 2.0 Dolby Upmixer implementation is astoundingly good.
We watch many shows, especially foreign, that have 2.0 sound tracks and the center channel is clear, and surround are used and the bass, unlike previous up-mixers, remains intact.

I installed a Denon 3700H and the upmixer sounds like PL-II. Since this system was using the 20+ year old Sunfire, Ill try it again in may when I install the ATI AT522NC.

- Rich

 

[RichB]

To be clear, transformer hum (the mechanical type) that is audible with ears touching the chassis is normal unless the transformer is dead or not energized. It the hum is audible from a few inches away, however quiet, may or may not be normal and may or may not be fixable with external devices/gadgets and there are many available including the usual suspects like PS Audio. As always, some may work better than others. Also, some transformers are more susceptible to imperfections in the incoming ac line.

I can hear hum from the ATI AT522NC but only within a foot.
The AT522C had less hum than the ATI AT4002, likely due to the size of the transformers, but could also be unit to unit variance.

From my experience (in my environment) Parasound had less transformer hum than ATI.

- Rich

 

[RichB]

Here is some ATI AT522NC porn.

- Rich

 

[PENG]

Here is some ATI AT522NC porn.

View attachment 46129View attachment 46130View attachment 46131View attachment 46132

- Rich

Wow, thank you so much for those adult only photos. Any chance for something to show the VA rating of the power tranny? I supposed I could try searching for the part number.