Topping PA5 Review (Amplifier)

[Deleted member 46664]

You guys could probably talk each other into it being the soups fault that you are trying to eat it with a fork.

Spotting a serious technical flaw in a product, that could cause other problems or reduce it's lifetime isn't trivial.

 

[Vini darko]

I checked toppings website there is no mention of common mode rejection for this amp.
Also there is no mention of it for the A90 or pre90. So this may be the way all topping products are.

 

[Deleted member 46664]

I checked toppings website there is no mention of common mode rejection for this amp.
Also there is no mention of it for the A90 or pre90. So this may be the way all topping products are.

Sadly that's not surprising ...

 

[Vini darko]

Sadly that's not surprising ...

Untill this afternoon I had assumed balanced xlr/trs connection ment having cmr. I suspect the majority would think the same as its one of the main touted benifits of the connection type.
Maybe the apx555 can test for this?

 

[Deleted member 46664]

Untill this afternoon I had assumed balanced xlr/trs connection ment having cmr. I suspect the majority would think the same as its one of the main touted benifits of the connection type.
Maybe the apx555 can test for this?

Safe assumption, with pro equipment ... apparently not so safe with consumer stuff.

 

[KSTR]

Untill this afternoon I had assumed balanced xlr/trs connection ment having cmr. I suspect the majority would think the same as its one of the main touted benifits of the connection type.
Maybe the apx555 can test for this?

Well, the PA5 will have some**) common-mode rejection when measuring differentially at the speaker outputs but the common mode/noise signal is still present. The speaker does the subtraction in this case.
But, common-mode signals see the full amplification so any common mode signal large enough can easily clip the amp even when the payload signal is low.

**) maybe 20dB or so. The tracking properties of the 4-gang volume pot might be the limiting factor.

AP can easily test the CMRR as the test is very easy: simply short the input lines together and move them in unison. No signal should be present at the output.

 

[antcollinet]

Safe assumption, with pro equipment ... apparently not so safe with consumer stuff.

Common mode rejection has nothing to do with driving the thing unbalanced.

 

[pma]

Klaus, I agree, there is little to be expected in CMRR from the circuit with 4-gang pot input. We know that. @tonycollinet , it does not help if such circuit is driven balanced. It just does not have the CMRR. It cannot have, there is no way.

 

[antcollinet]

Klaus, I agree, there is little to be expected in CMRR from the circuit with 4-gang pot input. We know that. @tonycollinet , it does not help if such circuit is driven balanced. It just does not have the CMRR. It cannot have, there is no way.

Possibly gonna show my ignorance here:

But...

I realise CM signals will be amplified by both sides of the amplifier (for one channel) but will presumably both come out on the relevant speaker terminal, and will become amplifed CM signals on the speaker terminals - at which point they'll cancel out.

Won't they?

Admittedly - any gain mismatch between the two sides of the amp will reduce rejection.

 

[HansHolland]

I realise CM signals will be amplified by both sides of the amplifier (for one channel) but will presumably both come out on the relevant speaker terminal, and will become amplifed CM signals on the speaker terminals - at which point they'll cancel out.

Won't they?

Yes, they will cancel out. KSTR wrote it like: "The speaker does the subtraction in this case.", 3 posts back.

 

[JeffGB]

Possibly gonna show my ignorance here:

But...

I realise CM signals will be amplified by both sides of the amplifier (for one channel) but will presumably both come out on the relevant speaker terminal, and will become amplifed CM signals on the speaker terminals - at which point they'll cancel out.

Won't they?

Admittedly - any gain mismatch between the two sides of the amp will reduce rejection.

I agree. https://www.audiosciencereview.com/...-magnius-balanced-headphone-amp-review.15252/ the Schiit Magnius is designed in a similar manner to the PA5. It also uses a 4 gang pot at the input and no conversion but as we can see it still provides superb distortion and noise when used as designed. With a singe ended input it has sinad of 94 and with a balanced input a sinad of 120. This tells me the use of the 4 gang pot is not creating a major problem. Neither it nor the PA5 is designed for all around use with single ended and balanced equipment and the performance shows it.

For me, it is an advantage to not have any conversion because it eliminates multiple opamps and their noise and distortion but that only applies if it is driven by a balanced differential signal. I wouldn't call the PA5 "broken" because it was never intended to be used single ended.

 

[Deleted member 46664]

Possibly gonna show my ignorance here:

But...

I realise CM signals will be amplified by both sides of the amplifier (for one channel) but will presumably both come out on the relevant speaker terminal, and will become amplifed CM signals on the speaker terminals - at which point they'll cancel out.

Won't they?

Admittedly - any gain mismatch between the two sides of the amp will reduce rejection.

Yes that's the assumption ... however there is a risk doing it this late in the chain...

Lets say you have a huge noise spike (maybe from the local CBer) on your inputs... that will be a common mode signal. It will hit both sides of the amplifier in phase and thus produce no audible output ... BUT... it can still saturate the output stages and cause serious clipping and distortion ... even with quiet music.

 

[Deleted member 46664]

For me, it is an advantage to not have any conversion because it eliminates multiple opamps and their noise and distortion but that only applies if it is driven by a balanced differential signal. I wouldn't call the PA5 "broken" because it was never intended to be used single ended.

Done properly balanced audio converted to single ended, processed, then reconverted to balanced eliminates one full channel of circuitry from the device ... it also reduces heat production, lowers power consumption and reduces the risk of failure.

 

[777]

Lets say you have a huge noise spike (maybe from the local CBer) on your inputs...

What is it, "CBer" ?

 

[Deleted member 46664]

What is it, "CBer" ?

Someone you operates a two way Citizen's Band radio station. They were notorious for interfering with stereos and televisions in the 1970s and 80s.

 

[pma]

If we take into account a mismatch of a good Alps multi-gang pot, we get a CMRR of only some 20dB. With a proper design with an input differential amplifier and then the SE path volume control, we get 60 - 80 dB without special parts selection.

Multi-gang pot CMRR test

 

[Nonick]

Hi guys, I’ve been using my Denon AVC-X4700H as a stereo amp to power a set KEF Q350 speakers, feeding from Topping D90SE.

It does sound great but I’m wondering if it can be even better.

What is eveyone’s opinion if I swap the Denon with a Topping PA5 as the stereo amp? Would the smaller watt defeat the sound quality?

Thanks in advance. Cheers.

It wont ruin sound quality on low, medium-loud enough listening levels. If you plan to go extremely loud then expect distortion.
I have speakers with 90 dB sensitivity and PA5 can drive them perfectly to very loud levels (room size 35 m2, volume cca 100 m3).
With Denon i could drive them to extremely loud levels.

 

[antcollinet]

@pma , @Douglas Blake

Thanks for the clarifications (amplified CM spikes and gang pot)

Much appreciated.

I have always stated that a balanced amp should have a proper diffamp in the input if for no other reason than to cope with the ways people are likely to try to drive it. Good to fully understand the other reasons also.

 

[Deleted member 46664]

@pma , @Douglas Blake

Thanks for the clarifications (amplified CM spikes and gang pot)

Much appreciated.

I have always stated that a balanced amp should have a proper diffamp in the input if for no other reason than to cope with the ways people are likely to try to drive it. Good to fully understand the other reasons also.

My pleasure.

 

[oivavoi]

Hi guys, I’ve been using my Denon AVC-X4700H as a stereo amp to power a set KEF Q350 speakers, feeding from Topping D90SE.

It does sound great but I’m wondering if it can be even better.

What is eveyone’s opinion if I swap the Denon with a Topping PA5 as the stereo amp? Would the smaller watt defeat the sound quality?

Thanks in advance. Cheers.

If you put a blindfold on you will with 99% certainty not hear any difference at all. These two amps will sound exactly the same with all expectations removed. If you want to upgrade your sound the best choice is to either get even better speakers, work with your room acoustics, and/or apply EQ/DSP.

EDIT: As long as the PA5 works as it should. There are reports in this thread of the amp misbehaving and making noise etc, and there seems to be flaws in the engineering. Then you may hear a difference, but not in the PA5's favor. I would not buy it at this point