Topping PA5 Review (Amplifier)

[pkane]

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)

I was sure I tried it yesterday, but now that you mentioned it, I went back to try again. TRS connection on PA5 side: T=hot, R=gnd, S=gnd. Again, into 8Ω and 5W output:

 

[pjug]

I was sure I tried it yesterday, but now that you mentioned it, I went back to try again. TRS connection on PA5 side: T=hot, R=gnd, S=gnd. Again, into 8Ω and 5W output:

View attachment 206045

Interesting. So the noise issue you were having goes away if you ground the ring?

What about + and - speaker voltage amplitudes? Are they the same when you ground R. Because the point made surrounding the scope shots showing otherwise is that the amp does not give full power because of the + and - amplitude difference.

 

[pkane]

Interesting. So the noise issue you were having goes away if you ground the ring?

What about + and - speaker voltage amplitudes? Are they the same when you ground R. Because the point made surrounding the scope shots showing otherwise is that the amp does not give full power because of the + and - amplitude difference.

The output was half (6dB lower) than with the balanced connection, @ same DAC output.

 

[pjug]

The output was half (6dB lower) than with the balanced connection, @ same DAC output.

What I am wondering is what each of the + and - P-P or RMS magnitude is, with R=NC vs R=gnd.

If you look at the 6th scope shot (ring grounded), the + magnitude is about 5.3Vrms and the - is about 3.9Vrms (or vice-versa). Normally in a bridged amp these would be the same. Because they are unequal the amp cannot put out as much power as it can with balanced input.

 

[pkane]

What I am wondering is what each of the + and - P-P or RMS magnitude is, with R=NC vs R=gnd.

If you look at the 6th scope shot (ring grounded), the + magnitude is about 5.3Vrms and the - is about 3.9Vrms (or vice-versa). Normally in a bridged amp these would be the same. Because they are unequal the amp cannot put out as much power as it can with balanced input.

Ring grounded or not doesn't make a difference in the output level for me. Ring disconnected adds the noise/distortions I posted earlier. Output level remains the same.

 

[pjug]

I think I am not good at asking the question. I am not wondering so much if the voltage across the terminals changes (although useful to know it doesn't). At 5W or what level you prefer, if you:

Measure AC component of + terminal voltage, relative to ground
Measure AC component of - terminal voltage, relative to ground

Are these measurements both the same, or are they somewhat different? In the scope shot they are different. Does it matter if the ring is grounded?

Sorry that I must I seem like a pest by now!

 

[pkane]

I think I am not good at asking the question. I am not wondering so much if the voltage across the terminals changes (although useful to know it doesn't). At 5W or what level you prefer, if you:

Measure AC component of + terminal voltage, relative to ground
Measure AC component of - terminal voltage, relative to ground

Are these measurements both the same, or are they somewhat different? In the scope shot they are different. Does it matter if the ring is grounded?

Sorry that I must I seem like a pest by now!

Relative to what ground? Sorry, maybe I'm missing something. You're asking for measurements at the speaker terminals, no?

 

[terrys999]

Little guy has arrive. It sounds super but can’t really comment too much as I’m using it with a new set of speakers I’m not too familiar with. Also don’t have anything to AB test it with as my other systems are active. Definitely no complaints from me in the short time I’ve had it going.

Sound great in general and for a desktop setup I’m using it in, it’s awesome.

View attachment 174107

Ohhhh I have same setup, do you keep adi at 0.0? And use pa volume.

 

[pjug]

Relative to what ground? Sorry, maybe I'm missing something. You're asking for measurements at the speaker terminals, no?

Yes, speaker terminals. It is bridged so I assume each will have the audio signal riding on half the power supply voltage. But I think measuring at 100Hz using AC on a meter, relative to ground, will work. If you don't want to use a scope.

 

[pkane]

Yes, speaker terminals. It is bridged so I assume each will have the audio signal riding on half the power supply voltage. But I think measuring at 100Hz using AC on a meter, relative to ground, will work. If you don't want to use a scope.

I don't know that the two output terminals are referenced to the same ground that I'm using to measure. But, the two speaker terminals are 1.363v rms on one, and 1.824v on the other. When both + and - are connected in balanced configuration, the output is 3.189v on both terminals.

 

[pjug]

OK this seems consistent with the other scope measurement. You get the same results whether the ring is grounded or not?

Thanks for doing this!

 

[pkane]

OK this seems consistent with the other scope measurement. You get the same results whether the ring is grounded or not?

Thanks for doing this!

Yes, doesn't matter if ring is grounded or not.

 

[pjug]

Yes, doesn't matter if ring is grounded or not.

That's good to know. So then for using this amp unbalanced one should ground the ring, or use mono 1/4/" TS plug to ground the ring. This to avoid having the noise issue you came up against. But the amp will not go quite up to rated power with an unbalanced input (this point I'm not sure has been verified by someone measuring?)

 

[pkane]

But the amp will not go quite up to rated power with an unbalanced input (this point I'm not sure has been verified by someone measuring?)

PA5 power vs THD+N sweep. Single-ended input, ring grounded. At 50W THD+N is 0.1%:

 

[restorer-john]

PA5 power vs THD+N sweep. Single-ended input, ring grounded. At 50W THD+N is 0.1%:

2 channels driven or just 1?

 

[pkane]

2 channels driven or just 1?

Just one.

 

[pjug]

PA5 power vs THD+N sweep. Single-ended input, ring grounded. At 50W THD+N is 0.1%:

View attachment 206136

So less than Amir measured int 8 ohms with balanced, right? I think it should be about 75% to 80% of balanced power based on your unequal voltage measurements. Not a big deal, but something that would dig at me if I wanted to use it unbalanced.

 

[antcollinet]

So less than Amir measured int 8 ohms with balanced, right? I think it should be about 75% to 80% of balanced power based on your unequal voltage measurements. Not a big deal, but something that would dig at me if I wanted to use it unbalanced.

Amir's plot shows about 70W at -40dB (0.1%), so in this case about 71% (-1.5dB) of balanced power. More or less in line with the earlier measurements I referenced above.

 

[nagster]

Amir's plot shows about 70W at -40dB (0.1%), so in this case about 71% (-1.5dB) of balanced power. More or less in line with the earlier measurements I referenced above.

Doesn't it look like about 60W at 0.1% on amirm's THD + N vs 8ohm output plot?

 

[pjug]

Doesn't it look like about 60W at 0.1% on amirm's THD + N vs 8ohm output plot?

Maybe a hair or two above that, to get all engineerish about it.