Topping Mini 300 Amplifier Review

[wwenze]

I think most people overestimate the typical average power output of their amps. If you listen at 75 dB with a speaker offering an efficiency of 86 dB/(m*W) and sit 3 m away from your speaker, you need 0.11 W of power. In that region, amp effieciency is garbage for all classes and is dominated by idle power consumption. So in the end, that is what counts for the majority of people: Idle consumption.

Mathematically, this is of course also the reason efficiency drops towards zero for small power outputs.

TPA3251 power dissipation due to idle losses: 1W
TDA7294: around 5W

Makes sense since class AB still has quiescent current (bias current) even when output is 0V, while class D only has switching loss.

One thing to be careful about is comparing total system efficiency to amplifier efficiency. Every practical home amp in the world consists of an AC/DC converter and a DC powered amplifier section. The TPA datasheet and the wikipedia pic above are only amplifier stage efficiency with no assumptions about PSU. That ICE power chart is total system efficiency.

Most class D amps are just shy of 90% efficient and sit behind PSUs that are also just shy of 90%. The total system result is thus typically 75-80% at full load. Class B (& AB) have a 78.5% theoretical maximum (falling to mid-60s with real-world PSU), so most real world class D including PSU are just at or above the theoretical max for linear amps.

Instead of looking at % efficiency at low loads, I would proposed that the most useful metric is “on but idle” power draw measured in watts. Every amp has falling efficency at low loads, but what is really happening is the power usage tends towards idle and isn’t correlated with load at low levels. Then also show amplifier power burn in watts at 50 watts into 4 ohms (wall power - 50) to show loaded behavior.

Yea... about that...

If we are already this deep into the rabbit hole regarding "amps only operate at 1% of the max output power all the time hence efficiency is mathematically bad", I should mention that the same applies with PSUs. The discussion is endless.

I would proposed that the most useful metric is “on but idle” power draw measured in watts

I remember witnessing a semantics war on the meaning of idle.

The solution is simple - Power at 1mW output

 

[delta76]

We also see this with devices from major brands that have been established for decades: irreparable breakdowns, products not supported, bugs not fixed, endless updates to correct what was damaged in a previous update... and so on and so forth...

Yes and those should be avoided. Established brands do not mean reliable!

 

[TurtlePaul]

I remember witnessing a semantics war on the meaning of idle.

The solution is simple - Power at 1mW output

One idea to look for idle shenanigans and present the data well would be a chart like that BeQuiet chart but with power wastage (input - output) on the y-axis and have the x-axis be power output plotted log scale.

 

[capslock]

This is the same type of graphs for Mini 300 in solid colors vs. PA5 II in pale colors. Basicall the same picture as vs. PA5. For 15 / 10 / 5 kHz THD+N, the Mini 300 comes in about 5 dB better. For multi tone IMD, the difference is less clear than for Mini vs PA5, but there is still a bit of pale grass hiding if you look closely. We now can also compare two tone IMD which was missing in the review of the original PA5. While first order products are the same between Mini and II, the Mini does a lot better on higher order products:

 

[gvl]

Glad to own one, anyway rear I/O should be arranged like:

Perhaps, especially if channel separation was a distance.

 

[Kevinfc]

Wow. They just keep “topping” themselves.

 

[PristineSound]

I guess maybe some of you Fosi fans are jumping ships now?

 

[capslock]

And finally, let's compare the Mini to the 3e audio A5 (which is a bit of an unfair comparison because the A5 uses two chips in PBTL configuration). The picture is a little different from the two previous comparisons but the Mini seems to come out as a winner. This surprises me because from the spreadsheet I keep, the A5 comes out slightly ahead of the PA5 II in ASR testing and a bit more in archimago's. I will have to do a comparison of the A5 vs. PA5 II to get to the bottom of this.

In THD+N testing, the Mini clearly leads by about 7 dB up to about 5 W. At higher power, the gap narrows, which might be owed to more current capable coils in the A5 or the PBTL configuration, and the A5 clearly has a higher power before it clips.

Multitone is much like the first two comparisons with a few dB higher grass in the A5.

Finally, two tone testing really surprised me, as the Mini is a lot cleaner in basically all products except those supersonic products that might be amplified by the peaking of the output filter.

 

[TurtlePaul]

This is the same type of graphs for Mini 300 in solid colors vs. PA5 II in pale colors.

Nice analysis. I had assumed the Mini300 was a cost optimized PA5. It looks like they found more performance but how?

Are these inductors better than the PA5/A5 competitors? Has the LC filter been moved high in frequency to reduce in-band inductor distortion? Has an LC filter peak been tuned to the top of the audible range to give more gain for the PFFB to use? Did they find more gain somewhere else?

Topping remains at the top of the PFFB game and also is now price competitive again and in fact a price leader. Lets hope the TPA3255 48V version comes soon.

 

[capslock]

Nice analysis. I had assumed the Mini300 was a cost optimized PA5. It looks like they found more performance but how?

Are these inductors better than the PA5/A5 competitors? Has the LC filter been moved high in frequency to reduce in-band inductor distortion? Has an LC filter peak been tuned to the top of the audible range to give more gain for the PFFB to use? Did they find more gain somewhere else?

Topping remains at the top of the PFFB game and also is now price competitive again and in fact a price leader. Lets hope the TPA3255 48V version comes soon.

The PA5 II and Mini 300 have very similar peaks. The A5 has a slightly drooping response and not much of a peak at 8 R load. So yes, the Mini has a higher frequency of the peak (48 vs 39 kHz), and its peak is more pronounced. This is what causes the higher IMD products around the sum of the two tones (The PA5 II is actually worse in this respect because it combines a similar peak with higher order distortion).

Is this relevant? Probably not. You'd have to have a tweeter with a resonance up there (that can be true for metal domes) and then some mechanism that allows this ringing to modulate into the audio band. Can happen, but it will likely be small in magnitude.

 

[amirm]

I wish you would have chosen to extend the chart one more step to the left, i.e. include zero to 1k, as 1k is a very interesting frequency for the difference tone and as it presented now, its just on the edge of maybe visibility. Why create a possibility for a doubt?

//

The test is without value as it doesn't represent anything remotely realistic. The reason I added it was to have at least one measurement you could compare to stereophile. To that end, I emulated their presentation and parameters: https://www.stereophile.com/content/ch-precision-m11-power-amplifier-measurements

 

[TurtlePaul]

The PA5 II and Mini 300 have very similar peaks. The A5 has a slightly drooping response and not much of a peak at 8 R load. So yes, the Mini has a higher frequency of the peak (48 vs 39 kHz), and its peak is more pronounced. This is what causes the higher IMD products around the sum of the two tones (The PA5 II is actually worse in this respect because it combines a similar peak with higher order distortion).

I guess my question/suspicion with the higher peak is maybe Topping swapped out to a lower value inductor to trade less in-band distortion at power in exchange for less carrier wave suppression. The ASR test for class D amps no longer includes carrier wave spectrums (because it confused so many people?).

 

[TNT]

you could compare to stereophile.

I see. Maybe it can be improved and be better but still comparable. Personally I think it has merits as it really stresses the amps linearity even if I do agree on that something like this will never be present on a music recoding. But, this is science - and in the name of science, we might, and should perhaps, want to go forensic - right?

Edit:
And now I see that I'm wrong - the left most line represents 0Hz - right!
Please excuse my sloppiness.

//

 

[TNT]

The chart goes all the way down to DC? You can count the spikes at 5k, 4k, 3k, 2k, 1k and DC.

Indeed... https://www.audiosciencereview.com/...00-amplifier-review.68581/page-8#post-2485340

//

 

[Jimster480]

Looks alright, but it seems to have some low frequency issues?

 

[BillH]

Looks alright, but it seems to have some low frequency issues?

Like what?

 

[JSmith]

Like what?

It was difficult to measure power at 40 Hz as the amp would go into some intermediate protection mode where it would distort but not shut down. Eventually I got a single measurement:

JSmith

 

[pichu]

Looking at the performance and the internals of this amp, I could see a boutique audio company charging an arm and a leg for this. I'm so glad im alive to experience audio another year

It keeps getting better and better! Happy New Year everyone!

 

[martin900]

Also, note that the TI TPA signal paths are not DC coupled. Any significant DC at the output will be due to a fault in the amplifier.

View attachment 501429

Bingo, so it has no DC output protection in case of a output FET failure? The caps are just input coupling and filtering the DC offset.
To me the absolute most important feature an amplifier should have (fire hazard, especially if you run full range speakers with no crossover).
Unless it is able to monitor it and shut off the supply voltage.

 

[PJR918BMW]

Just don't really see how anybody can realistically criticize this amps performance at pretty much any price.. never mind $200. It's nuts what they are managing to do ....