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Topping PA5 Review (Amplifier)

Holmz

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this is not how it works... but ok.
You would still need 112dB to get 82dBA at 50Hz
And with a crest factor of 12dB this would be 124dB peak need to give you distortion free music at 82dBA RMS from 50-20000Hz

I am of the opinion that bass might not be ideal to talk about in terms of crest factor(?)
It is more like “It draws what it draws” and the “The draw is intermittent on/off”.
At least that is how I think about it.

But that is more of a concept I apply to say rap or some hip-hoppy music, and not to say an upright bass.


And in a related way…
How can a "38V/4A=152W" PSU power a 2x125W amp? Even if it's custom made for music playing purpose, this seems a bit low. The PA3s has a "26V/5.75A=149W" PSU which is basically the same output in watts, but the PA3 is not nearly as powerful.
If it is playing music with a crest factor of say 13 dB, then that is 20x. So the peaks would be at say 100W and the RMS power would be at 5W.
Since the 5W < 150W, then all is fine.
If it is being channeled to a subwoofer which trying to send 40 or 50 Hz out then it could do 100W for a while, and gradually the capacitors would start sagging in voltage, and the output starts dropping to the 76W leve… or lower.
 

Holmz

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That's what I was saying current deliverability for certain power is function of internal resistance( output impedance ) say you have a 1kw amp with output impedance of 1ohm and you attach a 8ohm speaker and use 20w power and now you attach same speaker to a 50w amp with output impedance of 0.1ohm

Why do we care about the output impedance of the amplifier?


… Obviously an amp with output impedance of 0.1ohm will be able to supply more current for the transient when speaker impedance dips to say 2ohm than 1kw amp having 1ohm output impedance because out impedance of amp is something which is fixed irrespective of how much power you draw.

The output current will be determined almost entirely by the load that the output sees…
Which in your case was stated as an 8 ohm speaker.

A better way to consider the output impedance is to hook up the head phones to an unpowered subwoofer and aim it at something making noise.
The sub‘s cone will be jiggling back-n-forth imperceptibly, creating minute currents from the motor, which we now reclassify by calling it a generator.
And it will damn near blow the ear buds out of your ear canal.

The 0.1 output impedance amplifier will be fighting that back EMF like Arnold Schwarzenegger holding the cone.
Whereas the amplifier with 1 ohm impedance will be more like Pee Wee Herman or Mr Rodgers trying to more gently coax the back EMF in a sifter push.

Does it matter?
Some say, “yes a high damping factor is great”.
Others say, “Low damping factor amplifiers are way more musical”

I dunno whether there is a right answer… Just that both amps at 20W, are supplying the same exact current to the 8 ohm speaker. Which is 2.5 amperes and can be done with a pair of 20V rails. There is not large “burst of current” happening anywhere that are like the floodgates of hell were unleashed.
 

dshreter

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Y'all are very helpful and I am thankful for that, but you and the others keep missing the point: multiple people would love (and would PAY) to have this feature in a ready-to-purchase product. There are plenty of DIY and paid hack-y (miniDSP, inline filters) solutions out there, yet it would be GREAT if there were a high resolution DAC with a digital crossover option so you could set a frequency to high pass your speakers and low pass your subwoofer. (There's some SMSL DACs with sub-out but doesn't appear to filter anything).

Apologies for the tangent that really doesn't have much to do with this amplifier so let me end by saying this amplifier looks fantastic, performs well above expectations, and is very reasonably priced. Well done to Topping!
That functionality is built into Sonos Amp, and it is trivially easy to use. And you’re right, the product stays sold out and they keep raising the price.
 
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aj625

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Why do we care about the output impedance of the amplifier?



The output current will be determined almost entirely by the load that the output sees…
Which in your case was stated as an 8 ohm speaker.

A better way to consider the output impedance is to hook up the head phones to an unpowered subwoofer and aim it at something making noise.
The sub‘s cone will be jiggling back-n-forth imperceptibly, creating minute currents from the motor, which we now reclassify by calling it a generator.
And it will damn near blow the ear buds out of your ear canal.

The 0.1 output impedance amplifier will be fighting that back EMF like Arnold Schwarzenegger holding the cone.
Whereas the amplifier with 1 ohm impedance will be more like Pee Wee Herman or Mr Rodgers trying to more gently coax the back EMF in a sifter push.

Does it matter?
Some say, “yes a high damping factor is great”.
Others say, “Low damping factor amplifiers are way more musical”

I dunno whether there is a right answer… Just that both amps at 20W, are supplying the same exact current to the 8 ohm speaker. Which is 2.5 amperes and can be done with a pair of 20V rails. There is not large “burst of current” happening anywhere that are like the floodgates of hell were unleashed.
E= i (R+r) =iR+ir where R is akin to load and r is akin to output impedance. If r is more it eats the available output. Even if we assume that you compensate by cranking up the volume even then high 'r' causes shortage of current during the frequency passages for which the impedance of speaker dips very low. So in a way control of driver or damping factor is about availability of current. If a high power amp has high output impedance it will cause less availability of current for certain frequencies ( for which impedance dips) at "all power outputs". Assuming most people use 20 to 40w power most of the time, there is no point in using 500w or 1kw amp if it does not deliver current due to not enough low output impedance. On the other hand even a 50w amp will beat that 1kw amp if that 50w amp has low enough output impedance to supply enough current for passages when impedance of speaker dips low. Remember even 1kw amp will supply only the required 20 to 40 watts for your listening preference depending upon the volume pot position. There is nothing special which a high power amp can provide which a low power amp with good current capability can't provide, as long as you don't clip for your listening levels. In fact high power amps need higher gain stages for the same input sensitivity. That high gain is "fixed" so if you listen 20 to 40w on a 1kw amp, the input signal has to be attenuated too drastically due to very high gain. Both high gain and high attenuation are bad for "low level details". That's why benchmark ahb2 with variable gain is a win win situation. I use ahb2 in low gain as my dac has very high ultra clean output. So why to attenuate that ultra clean output unnecessarily.
 

daniboun

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I wish the first of you that get the PA5 could share the pictures with the opened case so we we can see the beast from inside ) Hope to get mine within 10 days...fingers X )))
 

DanielT

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Now I became curious, I may have missed but has Topping PA5 for example by Amir been tested , measured THD at 20 kHz and half power?:)

What is the bandwidth of the measurement? Common question asked when measuring class D. :)
This is how I got it (but I may be wrong): If not enough bandwidth is used in the measurement, say up to 80 kHz, it is difficult to determine levels of distortion from 6 kHz. The measurement does not say much about it then.

No, I'm not an expert in the field of measurements, PMA, Amir, for example, can clarify and explain it much better
or someone else knowledgeable may explain how it works. Measurements according to what I mentioned and how to interpret the results.

Edit:
Or has the boat only been tested putting forward in a few knots in and weather-protected harbor, so to speak, and not in harsh conditions? :)
 
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Koeitje

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Music, what else?
Music doesn't use full power. It only uses full power at certain moment, i.e. peaks in the content.

John Yang said, "In 100W both channel condition, the amplifier would shut down before the SMPS at around 1 minute mark. The SMPS is more than adequate for this amplifier." So I guess the answer is one minute with music.
No, the answer is not one minute. The answer is that it most likely will never shut down with music content. 100W average output is absolutely batshit insane, because that means the output is 10000W for 20dB peaks.

This is called a power amplifier. What do you mean Full power “rms” is a useles spec? What else matter more and do you know what rms mean?
In case you haven't noticed, music is not a constant test signal sine wave. What you need in an amplifier is enough power above the RMS of the signal to handle the peaks. A class D amplifier can handle those just fine and shed all the heat in the time between those peaks so it will never run into a thermal overload with music.
 

Dennis_FL

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Really wish for a stereo amp with sub output and DSP: high pass for stereo, low pass for sub. I don't see one yet, at least from Chinese companies.
The amp is last in the chain, and I for one want it to be taking the analog output of my expensive DAC and not messing with it. Why fool around with DSPs at this stage? That requires AD and DA chips. Better to do DSP upstream IMHO.
 
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africanus

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The input voltage Amir fed for the 5W@4R test would have been ~500mV. For rated output, I believe 2.5V (2500mV) is needed.

Thanks for the reply. Since I know nothing about audio measurements, I am a bit disconcerted. Both @amirm and @WolfX-700 used 0.5V input voltage in their reports. However, it seems that dacs' standard output is roughly 2V in single-ended and 4V in balanced outputs. So my question is, if this assumption is correct and the amplifier is fed with 2V single-ended or 4V balanced, how would measurements change? More power before clipping? Same power before clipping but more distortion?
 

Bruce Morgen

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In case you haven't noticed, music is not a constant test signal sine wave. What you need in an amplifier is enough power above the RMS of the signal to handle the peaks. A class D amplifier can handle those just fine and shed all the heat in the time between those peaks so it will never run into a thermal overload with music.

Even the bargain basement Aiyima A07, with its notoriously poor thermal management, won't shut down while playing music at any but downright deafening levels -- music is not a steady sine wave from a piece of test gear!
 

Dennis_FL

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Most DACs these days also have integrated preamps and can be connected to power amps directly.
I was thinking of doing just that. I'm currently using unbalanced RCA output to a preamp and then to an AB amp. I have some XLR cables and I would love to eliminate the preamp (my amp and DAC both have balanced connections). My sub has high level inputs so maybe I'll test that today. I have a USB mike and can use REW for room correction if I can figure out how to do that. I can use either the DAC or Roon for volume control. But I'm not sure of the impedance mismatch. Indeed someone here on another thread reported the sound wasn't very good and went back to a preamp.
 

restorer-john

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Thanks for the reply. Since I know nothing about audio measurements, I am a bit disconcerted. Both @amirm and @WolfX-700 used 0.5V input voltage in their reports. However, it seems that dacs' standard output is roughly 2V in single-ended and 4V in balanced outputs. So my question is, if this assumption is correct and the amplifier is fed with 2V single-ended or 4V balanced, how would measurements change? More power before clipping? Same power before clipping but more distortion?

The 5W@4R figure is a nominal low power figure Amir uses to test all amplifiers and compare them against each other in a level playing field.

It's a reasonably representative figure for normal to loud-ish domestic playback. Obviously the more voltage you feed the amplifier, the more it swings on the output- up until the point it clips (or hits the PSU rails).

The amplifier can output close to 140W@4R at 1% THD (-40dB) if you look at the AP plot, so that equates to something around 23.7V or so. That ties in with the 2.5V sensitivity for full power and the gain in dB that Amir measured.

Those rough eyeball figures translate to 19.5dB gain and he measured 19.1dB. Don't you love maths? :)
 

PeteL

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In case you haven't noticed, music is not a constant test signal sine wave. What you need in an amplifier is enough power above the RMS of the signal to handle the peaks. A class D amplifier can handle those just fine and shed all the heat in the time between those peaks so it will never run into a thermal overload with music.
I agree, but that's not what you said. You said full power at RMS is a useless spec. Output power of an amp is a RMS metric. And that's the main spec of a power amplifier.
 

FeliZ

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Hey there,
Can anyone Tell me where you ordered the PA5 for 300€ from netherlands?
Want to get a pa5 too

Thanks
 

pma

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I agree, but that's not what you said. You said full power at RMS is a useless spec. Output power of an amp is a RMS metric. And that's the main spec of a power amplifier.

I agree with you. And I have to add that I am unhappy with something that I would call a "selective parameters test method". I will explain, it has been usual for decades to measure not only THD+N vs. level and vs. frequency, but also SMPTE IMD, DIN IMD, CCIF IMD, frequency response into both resistive loads and complex dummy load, maximum power, input impedance and output impedance vs. frequency. And as a rule the same set of parameters for any tested products in the same category, amplifiers here. It was unusual for the reviewer (like J.A.) to modify the parameter set to the "selected ones" according to those that would make a specific product look better and to hide some shortcomings. Objective test is then converted to something a bit subjective supported by reviewer's subjective opinion which parameters he considers important, based purely on his subjective view.
 
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anphex

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Wow, congrats to anyone who doesn't own AHB2, Purifi or NC400 already and doesn't need a lot of power. This thing is an awesome deal. Looks like it should work perfectly with a Denon AVR without ground loop issues if I see correctly.
 

Koeitje

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I agree, but that's not what you said. You said full power at RMS is a useless spec. Output power of an amp is a RMS metric. And that's the main spec of a power amplifier.
I'd argue that peak output at some low distortion level (less than 1% for sure) is more important. You will never run an amplifier at its RMS level with music because it wont be able to handle the peaks. It wont even come close to handling the peaks. RMS gives some indication of what an amplifier is capable of, but it doesn't really describe the real world potential of an amplifier.
 
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