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Topping PA5 Review (Amplifier)

Grooved

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Drive unbalaced? not sure to what you mean, adi 2 dac fs balanced into trs? thats balanced yes?
Pictures 5 and 6 in attached pieces are named "05_thot_rgnd_sgnd" and "06_tgnd_rhot_sgnd"
These two tests are unbalanced (there is no cold signal), and I thought this what lead @HansHolland to say that there's a problem running the PA5 with unbalanced source, to which I answered that it should be tested with T=hot R=not connected and S=gnd (which is not done/shown in the post with these pictures).
 

terrys999

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Pictures 5 and 6 in attached pieces are named "05_thot_rgnd_sgnd" and "06_tgnd_rhot_sgnd"
These two tests are unbalanced (there is no cold signal), and I thought this what lead @HansHolland to say that there's a problem running the PA5 with unbalanced source, to which I answered that it should be tested with T=hot R=not connected and S=gnd (which is not done/shown in the post with these pictures).
okeydokey i understand
 

peng

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Thanks for reply, I might but it.
Do d class amps use less wattage than say cxa80 or 81?

Yes, class D amps are much more efficient than class AB amps so all else being equal, the PA5 should use much less power than the CXA amps, assuming those are class AB. By the way, 105 dB would be about as loud as what you would hear in a movie cinema.

You can play with different scenarios with an online calculator such as the following:

 

antcollinet

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Would this amp drive ma bronze 6?
Sensitivity 90db 8ohm

What are benefits of d class amp?
Yes.

Smaller - lower cost for the power, more efficient/less losses, so runs cooler.
 

pkane

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Thought I'd test the same PA5 I measured earlier in the year to see if there are any obvious changes. Seems to be doing OK to slightly worse, but perhaps I just didn't get it warmed up enough or connected it slightly differently... Still within a dB or two of previous results, so no major changes.

5W output into 8Ω, 1kHz from ADI-2 Pro FS, balanced:
1652220276808.png
 

terrys999

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dam. that looks good.
it seems that he first measurements were not a fluke.

i ordered the pa5, goin to hook itup to my adi 2 dac fs with balanced xlr to trs.
see how it sounds.

should the volume on this amp be left on full vol...?
and use adi volume? or would this screw up signal noise ect.
 

pkane

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dam. that looks good.
it seems that he first measurements were not a fluke.

i ordered the pa5, goin to hook itup to my adi 2 dac fs with balanced xlr to trs.
see how it sounds.

should the volume on this amp be left on full vol...?
and use adi volume? or would this screw up signal noise ect.

I measured it with the volume control set at maximum, and that’s how I use it for audio. DAC is the volume control in my set up.
 

terrys999

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I think the volume level will prevent you reaching clipping or distortion!

EDIT - or are you concerned about clipping at the input? Fear not, the PA5 has a balanced input which is rated to >4V. I fed mine 4.7 V the other evening and it wasn't clipping on the oscilloscope trace. I'll have to test it, but I think it unlikely that it would clip until it reaches somewhere nearer 7 or 8 V. Input sensitivity is simply the minimum voltage needed to reach full power. Going above it doesn't mean the input will clip. It just means the output will clip before the volume knob reaches maximum.

Hi there.
Could you give me some advice.
I just bought the pa5 I have it connected to my adi 2 dac fs xlr to trs , seems to sound fine.
My dilemma is I also own mdac plus the xlr voltage output is 4.5 xlr. Rca out of Mdac Plus is 2.2.5

Is it safe for Mdac Plus xlr to pa5? I noticed you used an higher voltage without clipping,
Any advice????
 

pkane

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Pictures 5 and 6 in attached pieces are named "05_thot_rgnd_sgnd" and "06_tgnd_rhot_sgnd"
These two tests are unbalanced (there is no cold signal), and I thought this what lead @HansHolland to say that there's a problem running the PA5 with unbalanced source, to which I answered that it should be tested with T=hot R=not connected and S=gnd (which is not done/shown in the post with these pictures).

While re-measuring my PA5, I tried to feed it single-ended input but couldn't get rid of some DAC-generated noise, so I didn't post these results. Some sort of ground loop, but nothing I tried seemed to help. The distortions were there even when the DAC wasn't playing anything.

EDIT: turns out I needed to ground the other input instead of leaving it disconnected, which I thought I tried :)

The DAC and the ADC power supplies were isolated from each other, the ADC running on a separate, battery-powered laptop. The ADC and PA5 grounds were connected by a thick wire (lots of mains noise otherwise), but no amount of connecting grounds or shields helped to eliminate the obvious distortions between the DAC and the PA5 when connected by a single leg of the balanced connection (ground and hot). Connecting the second leg of the balanced connection completely eliminated these, as did turning off the DAC. So it's definitely the interaction between the DAC and PA5. I tried...o_O

1652270868848.png
 
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peng

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While re-measuring my PA5, I tried to feed it single-ended input but couldn't get rid of some DAC-generated noise, so I didn't post these results. Some sort of ground loop, but nothing I tried seemed to help. The distortions were there even when the DAC wasn't playing anything.

The DAC and the ADC power supplies were isolated from each other, the ADC running on a separate, battery-powered laptop. The ADC and PA5 grounds were connected by a thick wire (lots of mains noise otherwise), but no amount of connecting grounds or shields helped to eliminate the obvious distortions between the DAC and the PA5 when connected by a single leg of the balanced connection (ground and hot). Connecting the second leg of the balanced connection completely eliminated these, as did turning off the DAC. So it's definitely the interaction between the DAC and PA5. I tried...o_O

View attachment 206011

Have you tried the alternative of using a RCA to XLR cable that is connected per Hypex's recommendations? I found in the past that if there is a ground hum, tying the two devices grounded chassis together never worked but every time when there is the option to use an RCA to XLR (power amp side) interconnect, it got rid of the hum.
 

pkane

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Have you tried the alternative of using a RCA to XLR cable that is connected per Hypex's recommendations? I found in the past that if there is a ground hum, tying the two devices grounded chassis together never worked but every time when there is the option to use an RCA to XLR (power amp side) interconnect, it got rid of the hum.
I used a balanced DAC output (XLR) and used a break-out cable to connect it partially to the TRS input of PA5. The break-out cable let me switch hot/cold legs, removing and adding grounds, shields, etc, in any combination. Nothing I tried helped, including adding a separate ground connection between DAC and PA5. Not sure what an RCA to XLR cable would do that I couldn't do with the break-out cable.
 

pjug

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I used a balanced DAC output (XLR) and used a break-out cable to connect it partially to the TRS input of PA5. The break-out cable let me switch hot/cold legs, removing and adding grounds, shields, etc, in any combination. Nothing I tried helped, including adding a separate ground connection between DAC and PA5. Not sure what an RCA to XLR cable would do that I couldn't do with the break-out cable.
Did you look at the output on a scope? Do any of the different unbalanced connections that you tried give + and - speaker waveforms of equal magnitude?

Edit: fixed error where I meant + and -
 
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pkane

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Did you look at the output on a scope? Do any of the different unbalanced connections that you tried give L and R speaker waveforms of equal magnitude?
Not on a scope, but using an FFT and an RMS voltmeter to match levels. Both, R and L legs produced the same distortions and levels at PA5 speaker terminals, and I adjusted output to match 5W I used to measure the balanced connection.
 

peng

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I used a balanced DAC output (XLR) and used a break-out cable to connect it partially to the TRS input of PA5. The break-out cable let me switch hot/cold legs, removing and adding grounds, shields, etc, in any combination. Nothing I tried helped, including adding a separate ground connection between DAC and PA5. Not sure what an RCA to XLR cable would do that I couldn't do with the break-out cable.

Thank you for the clarification, in that case it is not the kind of simple application I have in mind. I only use RCA to XLR cable when I had to use the RCA output from a DAC preamp to the XLR input of a power amp.
 

pjug

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Not on a scope, but using an FFT and an RMS voltmeter to match levels. Both, R and L legs produced the same distortions and levels at PA5 speaker terminals, and I adjusted output to match 5W I used to measure the balanced connection.
So then you have a different result compared to the scope shots that were shown? In that case, can you determine if the problem in the previous scope shot is because of the connection, or if you are just getting a different result with your PA5 compared to his PA5?
 

pkane

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So then you have a different result compared to the scope shots that were shown? In that case, can you determine if the problem in the previous scope shot is because of the connection, or if you are just getting a different result with your PA5 compared to his PA5?

Not really sure. What were the scope results and how are they different?
 

antcollinet

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So then you have a different result compared to the scope shots that were shown? In that case, can you determine if the problem in the previous scope shot is because of the connection, or if you are just getting a different result with your PA5 compared to his PA5?
Bear in mind that avoiding ground loop noise is much more difficult when feeding back the amp output to the PC via an ADC, compared with the usual one direction of signal flow.
 

pkane

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pjug

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I didn't see any imbalance at the output of PA5 between + and - input legs fed in individually.
Did you also try this with two of the TRS lines connected to ground in the unbalanced connection, like the scope shots indicate?

Because the convenient way to connect unbalanced would be 2X mono RCA to 1/4" TS which will ground the ring connection. So if the ring needs to be NC for best unbalanced operation it would be good to know. (@Grooved initially asked about this in post #4441 above)
 
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