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Topping PA5 Review (Amplifier)

KSTR

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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?
So you are saying it would make a difference if you had a perfect amp by this definition (with some 1MHz++ bandwidth) and then put a, say, 50kHz 2nd order lowpass in front of it, on both channels? No way! Actually the group delay when using the LP only on one channel is inaudible.
You need several 10's of microseconds to even notice a microscopic center image shift to one side (with headphones, with speaker again: no way) and that effect is completely benign, no change of soundstage or imaging

You need to put up some serious evidence to your claim.
 

Nikola Tesla

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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.
Agree. Also, their site says the inputs are TRS, not TS which is what those adapters are.
Hoping that something like this will work nicely: https://www.ghentaudio.com/part/c02.html
 

KSTR

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Agree. Also, their site says the inputs are TRS, not TS which is what those adapters are.
Hoping that something like this will work nicely: https://www.ghentaudio.com/part/c02.html
a TS plug is a TRS with R connected to S.
Does not make any difference for a balanced input (it subtracts R from T, that's the whole idea of going balanced).

Please keep in mind: Balanced has NOTHING to do with signal symmetry or such. It's only about impedance balancing and keeping the common shield connection out of the signal path. The later is why it's recommended to go balanced at the source end by use of a proper cable or adapter.
 

Lambda

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So you are saying it would make a difference if you had a perfect amp by this definition (with some 1MHz++ bandwidth) and then put a, say, 50kHz 2nd order lowpass in front of it, on both channels? No way! Actually the group delay when using the LP only on one channel is inaudible.
sure if they have the same filter nothing would happen.
but what if one channel had 100kHz filter and the other channel a 20kHz filter?
Could you here the filter on one Channel if it gets turned on and off?
Could you hear if filters or channels get swapped?
 

KSTR

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sure if they have the same filter nothing would happen.
but what if one channel had 100kHz filter and the other channel a 20kHz filter?
Could you here the filter on one Channel if it gets turned on and off?
Could you hear if filters or channels get swapped?
Most likely, no. We're talking about a 5us delay difference, that's about 1.7mm distance difference ;-)
 

Kevinfc

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Maybe slightly OT, but here is goes anyway.
The argument between objective v subjective comes down to what the listener perceives versus what is actually being produced. But all recievers are different (our ears) so by virtue of that, objective measurements effect each subjective listener differently. To me that the future of fine audio will become tuning each system to the listeners hearing capabilities in order to recreate what is truest to the actual recording. We will think of systems as we do Hearing Aids, filling the gaps of our deficiencies.
 

voodooless

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objective measurements effect each subjective listener differently.
You mean that looking at the measurements makes us feel differently about the sound? Sure, I’ll grant you that. As does how the amp looks, how the volume control feels etc. None of those however bring us any closer to what we objectively hear. Only controlled tests can properly do that. The results we can then try co correlate with the measurements.
 

Lambda

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Most likely, no. We're talking about a 5us delay difference, that's about 1.7mm distance difference ;-)
right at the border...
1638995471128.png

Subject 8 has golden ears and can here 4µs with over 75% confidence if i interpret this right

The average threshold ITD across nine trained listeners in a two-alternative forced choice task is 6.9 μs at the 75% correct level using the 20–1400 Hz band-pass filtered noise. The experimental accuracy of this value estimated from the 11.5% relative standard error of the mean is 0.8 μs. Note that a 6.9 μs threshold ITD here means discriminating a target ITD of +3.45 μs from a non-target ITD of −3.45 μs

We will think of systems as we do Hearing Aids, filling the gaps of our deficiencies.
An amplifier is not the device to do this... it shuld only amplify.

Great! I did this with my old amp and it just added insane noise to the signal.
Seems like you had a crappy noisy source or amplifier
 
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BoredErica

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Isn't a gain of 19.1db already on the lower side for an amp? AFAIK Pa5 has both low noise and low gain, so it should amplify the noise of your source less. Either way the pa5 should be an upgrade.
 

F1308

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Great! I did this with my old amp and it just added insane noise to the signal.
Time to upgrade...going old to new gives this ..

 

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F1308

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Because...


"Only have rca output on DAC. Is it possible to DIY a rca to TRS balanced cable? Will this work?
It should but you won't get maximum power unless the DAC can produce 2.5 volts (some can, most cannot)."
 

F1308

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Isn't a gain of 19.1db already on the lower side for an amp? AFAIK Pa5 has both low noise and low gain, so it should amplify the noise of your source less. Either way the pa5 should be an upgrade.
Yes, it is...and yes it will...

Topping D90SE noise < 1.1µVrms

With Topping PA5, [email protected] and noise < 16µVrms...

((1.1×10^(19.1/20))^2+16^2)^.5=18.82 µVrms or 107.5 dB dynamic range.

And with AHB2 in stereo, [email protected] and [email protected]...

((1.1×10^(9.2/20))^2+7.1^2)^.5=7.77 µVrms or 115.2 dB dynamic range.

 
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Kevinfc

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You mean that looking at the measurements makes us feel differently about the sound? Sure, I’ll grant you that. As does how the amp looks, how the volume control feels etc. None of those however bring us any closer to what we objectively hear. Only controlled tests can properly do that. The results we can then try co correlate with the measurements.
No, I mean what we hear (frequencies) is different. It’s obviously more pronounced as we get older, but there are still measurable differences at every age. So something which may sound “bright” to a 30 year old, will sound perfect to a 60 year old. The point is; that although objective measurements may be scientifically accurate, it’s elevating the receivers experience (the human), each with unique and flawed listening capabilities, that should be the endpoint.

In the future, the emphasis of audio systems will be their configurability to the listeners actual hearing. Accuracy to the source will be measured by what the listener actually hears and systems will be judged by their precision in meeting those needs

Like I said before, a bit OT.
 

the_hamster 2

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Before someone starts complaining that this is not a "real" amplifier as it does not have enough power at 50w into 8 ohms and 80w into 4 ohms, I'd just like to point out a few things:
  • For almost any office or other near/mid field listening, this is plenty of power even for inefficient speakers.
  • If used with speakers with high but not extreme sensitivity of 89 dB SPL / 1W@1m, it will be the equivalent of a 200/320 watt amp when used with low sensitivity speakers of 83 dB SPL / 1W@1m.
  • Similarly, if used at a listening distance of 6', this will be the equivalent of a 200/320 watt amp when used at a distance of 12' to the speakers. Living rooms in many parts of the world are a lot smaller than those in America. This will be fine in them.
  • Even in a typically sized living room for someone in America who would be likely to consider an amp in this price range, this will be plenty of power for average sensitivity stand mount speakers being used with a subwoofer.
  • It has a decent amount of reserve power for peaks, similar to class AB amps, and it has no problem controlling the moderately difficult to drive Infinity R153s.
If you need a phono input or multiple RCA inputs, this probably is not the amp for you unless you are willing to use a preamp.

While it is totally unnecessary for desktop use, with such low noise and low distortion even at low power, I can't help wishing this came with a remote. However, that might push the cost up another $25-$50.


Yes, this would be great for the JBL Stage A130, in my opinion, although I personally might be inclined to go with a somewhat less expensive amp and somewhat better speakers (Wharfedale Diamond 12.1, maybe?) for the same price.


That is my favorite feature, appearance-wise!
 

rebbiputzmaker

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I was not an audiophile, but an engineer who used to design professional equipment at a Japanese manufacturer. So if you have such a symptom, you'll know right away.
PA5 speculates that it uses the TPA3255 chip in my research. AIYIMA A07 also uses TPA3255. But there is a clear big difference in the sound of the two amps. I have purchased and tested a number of amplifiers using the TPA3255, but simply using a PFFB and high-end inductors and capacitors does not provide these characteristics. It's a mystery how Topping acquired this kind of technology.
At the same time I am very interested in the latest TPA3255 amps that have adopted your company's PFFB.
It’s really not a mystery at all. Do you really believe that there is some secret brand new magic chip that they are using that nobody else has? When does a chip manufacturer not announce a new super product? Not have eval boards for manufacturers to try and build? Fact that it has not been announced to anybody in the world? More than likely it is the exact same chip with some good engineering to get the quality specs they are getting. Head over to DIY look at the engineers over there and what are you doing to get the last drop performance from the chip. Also people don’t pot or hide the super chip, they hide the generic parts that they are using in order to create their product. More than likely this is $100 amp with enough good design and tuning to make it into the $350 amp.
 

xrk971

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So you are saying it would make a difference if you had a perfect amp by this definition (with some 1MHz++ bandwidth) and then put a, say, 50kHz 2nd order lowpass in front of it, on both channels? No way! Actually the group delay when using the LP only on one channel is inaudible.
You need several 10's of microseconds to even notice a microscopic center image shift to one side (with headphones, with speaker again: no way) and that effect is completely benign, no change of soundstage or imaging

You need to put up some serious evidence to your claim.
To be clear, I am talking about amplifiers needing to have phase accuracy in one channel. I am just saying a recording should have a time base accuracy equivalent to a bandwidth of 300kHz (or 0.3MHz). Not a hard thing to ask for given that DAC clocks typically have a time base originating from a 12MHz Xtal oscillator. An amp should be able to reproduce a time series signal with phase accuracy relative to itself of at least 2usec. This can be confirmed with an auto correlation function.

It is a well known fact that people totally deaf in one ear can spatially locate sound sources in 3D space with their remaining ear. There have also been experiments where the pinna (external ear lobes) was taped over with a smooth funnel and the subject lost their ability to locate the directionally with one ear. (Perhaps try this experiment yourself). There are a lot of scientific papers on this. Just search “Human Pinna Sound Localization”. It’s no accident that the pinna is asymmetric so that directionality of the sound wave can be resolved through the phase differences imparted by the pinna, and the the brain applies real-time “bio-DSP” aka psychoacoustic processing, to determine the spatial location.

A 1mm path difference in the pinna can impart about a 3usec shift to a wave traveling at 342m/sec (speed of sound).

If you look at the paper here:

According to section V in the paper, the time domain of the pinna is 2usec to 300usec (0.3ms).

Look at Fig. 4 which shows the transformation of a sound pulse from a source from the side by a cast mold of a human pinna fitted with a microphone. We can see that it imparts a transformation of the pulse in the time domain.

3240319B-47AB-485F-BA59-7A3AB0A4A385.jpeg

More recently, there have been papers discussing the microsecond resolution of the human hearing:

Krumbholz K, Patterson RD, Nobbe A, Fastl H. Microsecond temporal resolution in monaural hearing without spectral cues? J Acoust Soc Am. 2003 May;113(5):2790-800. doi: 10.1121/1.1547438. PMID: 12765396.

Here is a very good review paper on sound localization by the human ear. Tons of references in there for those interested.


You can look for many more scientific publications discussing this.

This is why I think it is important for an amp to be able to reproduce sound without imparting too much phase shifts below 300kHz. When I design a discrete Class A or Class AB amp, I look at the phase shift and optimize the design in LTSpice to minimize phase shifts below 300kHz. In listening tests, this seems to improve the amplifier’s ability to provide better imaging and soundstage (all subjective measures).
 
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