Topping PA5 Review (Amplifier)

[ModDIY]

Serious question. Do you even listen to music?

Ha ha hummm...

 

[MarkWinston]

I don't have to i can uses measurements...

That must be most ignorant thing Ive heard all year.

 

[BDWoody]

So listening and asking for opinions are uncontrolled?

No. The 'reviews' given are almost universally based on uncontrolled listening sessions. A controlled test involves not knowing what is playing, making sure levels are matched, etc...

It isn't casual or trivial, and that's why most normal consumers don't bother. The reason professional reviewers don't bother is either because of genuine ignorance as to why it is necessary, or because it would reveal that the emperor has no clothes.

For those who haven't done one, it is worth the effort.

 

[pma]

Thanks for your wise inputs, @BDWoody .

 

[Mulder]

It is quite remarkable, in a forum dedicated to a scientific approach to audio, that such things as the need for the blind test must be repeatedly explained and justified. Strange also that it is not considered obvious to make IMD measurements based on two-tone tests, especially 18-19 khz.

 

[pma]

Strange also that it is not considered obvious to make IMD measurements based on two-tone tests, especially 18-19 khz.

... and also the step response, to have some idea about system stability

AIYIMA A07 TPA3255 Amplifier Measurements and Review - LM4562 (and OPA2134) option

Thank you very informative.

www.audiosciencereview.com

 

[Lambda]

... and also the step response, to have some idea about system stability

Sure nice to have!

I have never heard an scientist or engineer say they don't want some data and that they will just assume its fine.
usually it is a good thing to have redundant data from different test to get some confidence in the data.

Has the AP software an option to export a calculated impulse response?

 

[RndJeff]

In the work.

A lot of people are asking for more power, but I'd be happy with something like the PA5 with RCA connections, like a better PA3s.

 

[Lambda]

with RCA connections

 

[Mulder]

A lot of people are asking for more power, but I'd be happy with something like the PA5 with RCA connections, like a better PA3s.

So good for us to know

 

[xrk971]

Our ears hear sound to a frequency limit of 20kHz, but we hear phase information to the equivalent of about 300kHz. This is why it is important that an amp have as flat of a phase response up to at least 300kHz. This range corresponds to the very small microsecond phase shifts that the folds of our outer ear (pinna) impart to sound waves right before they enter our ear canal. Note that the pinna is asymmetric and it is this asymmetry that enables us to psychoacoustically locate a sound source in 3D even with only one ear. There are many research publications by the military that show the ability of the human ear to discern microsecond phase shifts for the purposes of localization of sound sources (audio imaging and sound stage as we like to call it). So an amp and speakers may not be asked to reproduce frequencies above 20kHz, but they should do so while preserving phase coherency up to 300kHz. Maybe this is why DAC clock jitter matters?

 

[pma]

Inter-aural, Sir. The difference between the channels is important, not one-channel phase.

 

[7jm]

I am not convinced that simply having an RCA phono to TS connection will work correctly, audiophonics have said that the cannot confirm this as they have no stock at the moment. I have one on order to use with an e30 but if I have to make up custom cables ( RCA to trs) then I may not bother and just get a pa3s instead.
It would be helpful if johnyang could confirm about connectivity as many people would probably be using single ended to connect to this.

 

[formdissolve]

Is it safe to turn this amp all the way up and just use the volume on my preamp? Or would that mess with gain matching? Wish there was a volume bypass on the amp!

 

[Lambda]

Is it safe to turn this amp all the way up

Yes

Wish there was a volume bypass on the amp!

just turn this amp all the way up.

I am not convinced that simply having an RCA phono to TS connection will work correctly,

Any reasoning or hypothesis why?

 

[KSTR]

I am not convinced that simply having an RCA phono to TS connection will work correctly, audiophonics have said that the cannot confirm this as they have no stock at the moment. I have one on order to use with an e30 but if I have to make up custom cables ( RCA to trs) then I may not bother and just get a pa3s instead.
It would be helpful if johnyang could confirm about connectivity as many people would probably be using single ended to connect to this.

Don't worry, it does work. It would need a totally screwed up design to make this not work. Any balanced input will and must always work with unbalanced by sheer definition.

 

[F1308]

Is it safe to turn this amp all the way up and just use the volume on my preamp? Or would that mess with gain matching? Wish there was a volume bypass on the amp!

It has been said: bypassing is achieved by setting volume at full.

 

[NTK]

... and also the step response, to have some idea about system stability

I would also like to see oscilloscope traces of clipping behavior. Example from the Purifi 1ET400A product page.

1ET400A - PURIFI

Single-channel, analog-input Class D amplifier module Negligible THD and IMD Extraordinary low noise Load-invariant response Exceptionally clean clipping Low losses & high efficiency Easy to integrate Designed in Denmark KEY SPECIFICATIONS

purifi-audio.com

 

[F1308]

Don't worry, it does work. It would need a totally screwed up design to make this not work. Any balanced input will and must always work with unbalanced by sheer definition.

Also been said: the only issue is a lower loudness will be achieved.

 

[Lambda]

Inter-aural, Sir. The difference between the channels is important, not one-channel phase.

Wait. he has an interesting point!
What if Phases shits with Load.
Or how mush dose phases shift with load.
If the current in one inductor/ channel is higher it is closer to saturation and therefore the inductance is lower. Causing a phases shift.
So IMD distortion causes phase shifts (in class d)?
Or non linear filter cause phases shifts but they also cause IMD...

Not sure but one more reason measure IMD and phase