Topping PA5 Review (Amplifier)

[maty]

Got a PA5 for desktop use and for measurements

Please, can you measure the phase curve as a function of frequency? How much phase shift at 20 kHz?

 

[pkane]

Please, can you measure the phase curve as a function of frequency? How much phase shift at 20 kHz?

Phase shift at 20kHz??? Are you sure you're going to hear something there?

 

[maty]

I can not hear nothing at 20 kHz now but it is a important paramenter to me, the phase curve. With Class A and A/B it is never a problem (< 6º at 20 kHz, usually).

 

[pkane]

Below -120db

-thoughtful-

Noise is a little higher than this (about 3dB higher) due to the way Cosmos ADC sums the two channels. Still pretty good, I'd say!

 

[daniboun]

Audiophonics has shared some pictures from the PA5, nothing has changed )
The pictures are consistent with the one that has already been shared, the caps are the same as the rest.

 

[pma]

Paul @pkane , could you make your measurements calibrated?? It is so easy with REW, and comparisons are easier then, especially noise. Please take into account that not everyone here can make it in his head.

 

[staticV3]

Paul @pkane , could you make your measurements calibrated?? It is so easy with REW, and comparisons are easier then, especially noise. Please take into account that not everyone here can make it in his head.

Noise shown in FFT measurements will be false regardless of whether you calibrate the software or not. That's the nature of FFT gain.

WolfX-700 measured the PA5's noise floor at 20µVrms and 14µVrms A-weighted

 

[pkane]

Paul @pkane , could you make your measurements calibrated?? It is so easy with REW, and comparisons are easier then, especially noise. Please take into account that not everyone here can make it in his head.

Pavel, it was calibrated, I just posted the plot in dBFS. I plan to do more testing and will post the results then.

 

[pkane]

Paul @pkane , could you make your measurements calibrated?? It is so easy with REW, and comparisons are easier then, especially noise. Please take into account that not everyone here can make it in his head.

Is this better?

 

[pma]

Is this better?

View attachment 175586

Sure, thank you! Noise itself is best to measure in V and then switch scale to dBV. The result in V will remain in top right corner .

 

[pkane]

Sure, thank you! Noise itself is best to measure in V and then switch scale to dBV. The result in V will remain in top right corner .

Quickly reconnected everything to remeasure. This is with ADC in stereo mode, so no 3dB noise floor reduction

 

[pma]

Quickly reconnected everything to remeasure. This is with ADC in stereo mode, so no 3dB noise floor reduction

View attachment 175599View attachment 175600View attachment 175601View attachment 175602

Interesting, I measure 36uV noise (20Hz-22kHz unw.) at the output of my NC252MP amp, with input terminated by 100 ohm.
If your noise measurement is not influenced by the ADC noise, then the PA5 has higher noise than expected.

 

[pkane]

Interesting, I measure 36uV noise (20Hz-22kHz unw.) at the output of my NC252MP amp, with input terminated by 100 ohm.
If your noise measurement is not influenced by the ADC noise, then the PA5 has higher noise than expected.

Likely internal and external noise sources, this was just a quick wiring job with makeshift connections and loose wiring. Had to resolve some ground issues earlier today with @IVX’s help, too.

 

[staticV3]

Interesting, I measure 36uV noise (20Hz-22kHz unw.) at the output of my NC252MP amp, with input terminated by 100 ohm.
If your noise measurement is not influenced by the ADC noise, then the PA5 has higher noise than expected.

Here are reliable noise measurements for the PA5: https://www.l7audiolab.com/f/topping-pa5-poweramp/

 

[nhs]

Hi @pkane, thank you for your measurements. Is it possible for you to measure the PA5 when reducing the level by -10db using the volume knob of the PA5?

 

[pkane]

Hi @pkane, thank you for your measurements. Is it possible for you to measure the PA5 when reducing the level by -10db using the volume knob of the PA5?

Volume control at max, 5W out:


Volume control at -10dB, 0.55W out:


Volume control at -10dB, 5W out:

 

[Solveit]

@pkane if you measure at 1W wich is my normal volume what do you get?

 

[pkane]

@pkane if you measure at 1W wich is my normal volume what do you get?

You can see above that 0.55W it's nearly the same as 5W, so seems pretty consistent. I'll run some sweeps later.

 

[nhs]

Keep the same power out (5W), but lower volume knob by 10dB, is that what you're looking for? Or lower output by 10dB?

I mean same 5w power output but lower volume knob by 10db. I know, that only possible if you have 4ohm load. If not, you could measure at any meaningful lower power output. Thank you

 

[pkane]

I mean same 5w power output but lower volume knob by 10db. I know, that only possible if you have 4ohm load. If not, you could measure at any meaningful lower power output. Thank you

Already measured. Please see above.