Topping PA5 II Stereo Amplifier Review

[antcollinet]

Please report on your findings.
Perhaps if you use the stock psu with a regulator this may help, with sufficient capacitance to prevent voltage sag at high volumes

1 - what makes you think there is voltage sag?
2 - The stock PSU is probably already regulated.
3 - Even if there were voltage sag, an external regulator would require a voltage difference across the regulator at no load as big as the voltage sag at full load. IOW you would run permanently at the reduced voltage.

 

[welwynnick]

Please report on your findings.
Perhaps if you use the stock psu with a regulator this may help, with sufficient capacitance to prevent voltage sag at high volumes

Does your linear PSU have a voltage regulator?

Can you show us a picture of it?

Cheers, Nick

 

[DSJR]

You know, the performance of amps like this is incredible as long as they can last many years doing it. Reading through numerous HiFi Choice review books from the 70's and 80's, an estimated sinad in the 60's was judged acceptable and over the 70's excellent, the 'best sounding' amps, usually expensive US made ones by ARC, CJ and so on, had estimated sinad in the 30's and 40's and Krell's room heaters weren't that wonderful apart from their load driving abilities.

On a more graphic level, the earliest 'Choice books had plots of distortion with frequency (I forget the level but will trawl again to confirm). They even measured IMD up to 100kHz which many amps (including my old Crown) weren't always happy with, but the base audio-frequency level in most 'recommended' amps was never much below the upper -70dB region. This little box seems to be several orders of magnitude better than that - as long as it stays the course of the tests of time.

 

[Killingbeans]

Please report on your findings.

Please only do that if they are being verified by measurements.

There's no limit to the "findings" people can report purely from their imagination.

 

[villason]

View attachment 342081View attachment 342082
Only difference.


The Plus can play 7% louder at 4Ω. At 8Ω, there's no difference.

Do you know if the V- is connected to the AC ground? Having GPU noise thanks to that at the moment with another amp.

 

[welwynnick]

I happen to have the batteries, they have a few mOhm of resistance. I can charge them with solar panels. I'll have no ground loops. What is not to like?

Please do report on your findings if you DON'T have any measurements!

 

[staticV3]

Do you know if the V- is connected to the AC ground? Having GPU noise thanks to that at the moment with another amp.

I don't, sorry.

Are PC and Amp connected only via Mains, or also via USB->DAC->Amp?

 

[welwynnick]

You know, the performance of amps like this is incredible as long as they can last many years doing it. Reading through numerous HiFi Choice review books from the 70's and 80's, an estimated sinad in the 60's was judged acceptable and over the 70's excellent, the 'best sounding' amps, usually expensive US made ones by ARC, CJ and so on, had estimated sinad in the 30's and 40's and Krell's room heaters weren't that wonderful apart from their load driving abilities.

I have similar recollections. I really got into HiFi at university (EE) in the '80s when HiFiChoice were publishing those half size magazines with blind testing and lots of measurements that we poured over endlessly. We tried to figure out which measurements correlated with sound quality, and I've been trying to do just that ever since.

People are always asking why subjective and objective assessments don't correlate. being rooted in science and engineering, this was very frustrating. All my life, I've taken measurements with a pinch of salt, and always trusted listening. However in the last year I've (again) been pouring over Amir's and others measurements, and seem to find some reconciliation.

I think the answer is that figures like THD+N of 0.01% - which were often held up as exemplary - are actually not very good after all. For something to sound really good, I think it needs to measure really good, too, and better than that.

 

[restorer-john]

I think the answer is that figures like THD+N of 0.01% - which were often held up as exemplary - are actually not very good after all. For something to sound really good, I think it needs to measure really good, too, and better than that.

Are you serious?

0.01% is 80dB below, yes BELOW your reference. That is THD+N at 1 ten thousandths (yes 1 divided by ten thousand). And you think that's audible? No chance.

-60dB is just audible and only on single pure tones.

 

[welwynnick]

Yes that's exactly what I'm saying

 

[Julf]

Yes that's exactly what I'm saying

Just being curious - what do you base that claim on?

 

[DSJR]

I still think it's great that modern amps can perform so bloomin' well as they do, attention to load immunity and low impedance drive without melting (this one shuts down if severely abused it seems) making them basically an amplifying 'appliance' which really is all they need to be.

I know, you don't get the adrenaline going with a dinky black box as you do with a huge far eastern knob-laden confection from the 70's or 80's that were only priced acceptably due to high volume manufacture I suspect (few of these flagships ever came to the UK in the 80's and almost none in the 90's I fear apart from low range models), but these days, a discrete little amp all but hidden away, or a passive speaker system set up on a workstation desk with one of these little amps alongside does have appeal you know

 

[Yorkshire Mouth]

Yes that's exactly what I'm saying

Ah! Just spotted that it’s welwynnick from AVForums.

It’s been a while.

 

[welwynnick]

The very same

 

[capslock]

I have similar recollections. I really got into HiFi at university (EE) in the '80s when HiFiChoice were publishing those half size magazines with blind testing and lots of measurements that we poured over endlessly. We tried to figure out which measurements correlated with sound quality, and I've been trying to do just that ever since.

People are always asking why subjective and objective assessments don't correlate. being rooted in science and engineering, this was very frustrating. All my life, I've taken measurements with a pinch of salt, and always trusted listening. However in the last year I've (again) been pouring over Amir's and others measurements, and seem to find some reconciliation.

I think the answer is that figures like THD+N of 0.01% - which were often held up as exemplary - are actually not very good after all. For something to sound really good, I think it needs to measure really good, too, and better than that.

My experience, too. Sources or amps measuring in the -80ish territory tend to sound stale, uninvolved, blurry.

 

[Julf]

My experience, too. Sources or amps measuring in the -80ish territory tend to sound stale, uninvolved, blurry.

If I was an amp, I would feel stale and uninvolved too. You need at least 1% THD before you feel the amp is fully involved.

 

[welwynnick]

We need to set our sights higher, not lower.

 

[DSJR]

The very same

Welwyn as in Herts?

 

[welwynnick]

Yup

 

[MAB]

My experience, too. Sources or amps measuring in the -80ish territory tend to sound stale, uninvolved, blurry.

Perhaps take this test (for instance), it will help calibrate what level of distortion is audible.

Listening Test

www.klippel.de

Regarding noise, even the most silent amplifiers have measurable noise if connected to a speaker with sufficiently high efficiency:

Is the entire audio industry a fraud?

What? Why would professionals not care about hiss? They usually will be seated closer than home listeners. I'm sure it is a cost saving measure and good enough, but barely. In more expensive monitors it really is unforgivable or at least quite unnecessary. People complaining about hiss in...

www.audiosciencereview.com

But that is an absurdly high efficiency driver, and padded it is silent with the PuriFi amp. I took a look at some other amps for noise comparison.

I set up the D2 driver, put a mic in the mouth of the lens, and hooked up a bunch of different amps, with and without the crossover filter.
PuriFi 1ET400A
Hypex NC400
Two Marantz MA500, just refurbished
Bryston 3B, original >20 years old
Aiwa A22 micro integrated amp from the late '70s, refurbished ~5 years ago

First, I compare a PuriFi 1ET400A and Hypex NC400 amp to the ambient noise in my test setup with and without the passive filter:

Run to run differences are mostly environmental/background noise, especially below 600Hz (traffic, and chain saws still going here in Portland), and high frequency (it's windy again today). I did time these captures when noise was minimum and not bias one run vs. another. The passive filter is key in noise reduction, and as shown in the other thread mostly due to the capacitor. I cannot hear either of these amps' noise with the passive filter in place, I can just barely hear the noise without the filter, but just barely. I'll compare the rest of the amps with the filter in place, focusing on 600Hz and above. An aside, I think the resonances are due to cavity dimensions, much like putting your ear against a sea shell.

Comparing all of the amps with the passive filter, along with the Purifi and Hypex with no filter and the baseline:

The Marantz are very quiet, only ~2dB noisier than the PuriFi and Hypex leaders. The Bryston 3B is another +7dB noisier. Perhaps 25 years of near continuous service is catching up, this is one of my oldest daily use amps. And the Aiwa is +15dB noisier than the PuriFi.

This 110dB driver is going to show noise differences when you use an amplifier like an Aiwa A22. While it is working properly since I rebuilt it (power supply capacitors that had aged out of spec), it does produce audible noise at distances less than ~5cm. The Bryston needs me to place my ear close to the surface of the lens to hear. The Marantz are inaudible, I just recently serviced both of these, and am really surprised by the performance.

I am sure the PA5 would have been right along side of the PuriFi and Hypex. But since these test close to 10dB lower than what I can hear at a few cm, on a driver that close to 20dB more sensitive than most. The Aiwa works great on most speakers (for instance).

Aside from noise, I am sure I would never be able to distinguish my PA5 from the myriad other amps I own due to distortion (again, take the tests above!), except for an old tube amp and a few other anachronisms and corner cases...