Topping B100 Amplifier Review

[pma]

Well, maybe PMA received a unit without thermally conductive grease.

It is not mine. I was asked by a colleague to test it. It arrived yesterday as a new unit.

Amir wrote:

The analyzer will drive the amplifier long enough to get a stable reading. Likely tens of milliseconds at most. It will then drive it at higher and higher levels though. The gaps will be small. It will even push it into limiting as you see in the clipped portion of the graph. So the amplifier is being stressed.

Here: https://www.audiosciencereview.com/...-output-power-measurements.55602/post-2023130

So his tests are much less severe than mine.

I cannot imagine too small a heatsink will result in thermal shutdown within seconds.

I do. If the SOA is controlled by a uC.

However, who cares? The SINAD 5W number is excellent and I do confirm. This seems to be the only parameter that common readers are looking at here. I can decode it from the posts.

 

[antcollinet]

It is poor performance for sure. But if it is a real limitation for music listening depends on for how long it can sustain rated power

If it can manage rated power for (lets say) 30s or a minute, and average power at 25% (-6dB) of rated power continuously, then it will probably work Ok with typical music dynamic range.

 

[Old_School_Brad]

It is poor performance for sure. But if it is a real limitation for music listening depends on for how long it can sustain rated power

If it can manage rated power for (lets say) 30s or a minute, and average power at 25% (-6dB) of rated power continuously, then it will probably work Ok with typical music dynamic range.

PMA's measurements are 300 ms burst and 100 ms idling.

 

[pma]

If it can manage rated power for (lets say) 30s or a minute,

Rated power is 100W/4R.

I could not get even 20W/4ohm on the scope screen as an instantaneous measurement for about 1s. It was shut down right after the DAC generator has started.

 

[totti1965]

It is poor performance for sure. But if it is a real limitation for music listening depends on for how long it can sustain rated power

If it can manage rated power for (lets say) 30s or a minute, and average power at 25% (-6dB) of rated power continuously, then it will probably work Ok with typical music dynamic range.

Well let’s say rated power is 80 Watts (Amir’s measurements at 8 Ohms with many different frequencies between 20 Hz and 15 kHz):
That means that we can expect at least 20 Watt of continuous power at any frequency and not an immediately breakdown with 5 Watts at 50 Hz or so.

My first thought was also that they have forgotten the thermally conductive grease, because they have to build so many items within a few weeks after @amirm ´s test and a resulting lush quality control.

I can only shout, like Otto in A FISH CALLED WANDA: „I ´ m dissapointed!“ (at least the German Synchronisation was: „Ich bin enttäuscht!“)

 

[FERCSA]

A70 Pro uses similar (same?) T’ang-ku-la Module which has (officially) 17W@16Ohm power output. Pma's measurement was 19-20W@4Ohm. Is it a big surprise after all? No.
Although it would be nice to be confirmed by someone else as well.

That 100W is obviously bs.

 

[Bleib]

My first thought was also that they have forgotten the thermally conductive grease

Well, I think the cooler is too small in the first place. I mean, it's not even class D

 

[totti1965]

Well, I think the cooler is too small in the first place. I mean, it's not even class D

I thought for myself after reading the @amirm ´s test and watching the pictures: „Well, seems they have taken the whole case for cooling purposes - as they did with the Class D Fosi V3 - Genius!“

This was wishfull thinking.

 

[MAB]

Well, maybe PMA received a unit without thermally conductive grease. I cannot imagine too small a heatsink will result in thermal shutdown within seconds. It takes like a minute or more for the fins of the heat sink to reach thermal equilibrium. I am also pretty sure that in Amir's testing, loads above 5 W were applied for extended periods of time.

So let's wait and see.

If so, manufacturer has a significant quality issue. I'm not sure what is worse, marginal thermal design or failure to have a quality manufacturing process.

 

[totti1965]

If so, manufacturer has a significant quality issue. I'm not sure what is worse, marginal thermal design or failure to have a quality manufacturing process.

Maybe it is an issue with a microcontroller / a chip that controls the parameters / an electronic fuse / the parameters settings of one of this…….
We will see.

 

[misterdog]

Amir wrote:

Here: https://www.audiosciencereview.com/...-output-power-measurements.55602/post-2023130

So his tests are much less severe than mine.

Amir followed with.

I could just drive it continuously with a sine wave but that can damage the amplifier and possibly my dummy load.

Keep in mind that the crest factor of sine wave is also lower than what you get in music or even effects. What you perceive as bass lasting a while does not translate into continuous max power.

 

[pma]

Strictly practically - with the Telarc CD 83393

https://www.discogs.com/release/15955317-Ray-Brown-With-John-Clayton-Christian-McBride-SuperBass-Recorded-Live-At-Scullers

track 6, Mack the Knife, the amplifier turned off itself when playing very loud (however within specs). The speaker was

CNO-T25_Pavel

The same happened with Telarc CD 80238

https://www.discogs.com/release/16256951-Dvo%C5%99%C3%A1k-Andr%C3%A9-Previn-Los-Angeles-Philharmonic-Orchestra-Symphony-No-9-In-E-Minor-Op-95-From-The-Ne

Adagio: Allegro molto, drums in 1st 2 minutes.

So, as an amp for a PC speakers, I find it very good. As an amp for the main home hifi system - never.

 

[terryforsythe]

I have the B100 on my test bench. When measuring THD vs. level at 1kHz/4ohm, the amplifier repeatedly shuts down at 8.8V, i.e. 19.36W.

Measured with STEPS with 300ms bursts followed by 100ms pause. Thus, I am voting poor. There is no wonder, it is a linear amplifier and physics rules, there is no chance to dissipate heat from such a miniature box. Again, a toy, not an adult amplifier.

I wish I had seen this yesterday, before I ordered a pair after they went on sale at Apos. I'm hoping you just got a bad unit. Since I already have them on order, I'll try them out. They will be pushing my tweeters in an all active system, so it is less likely I will run into any issues.

 

[misterdog]

the amplifier turned off itself when playing very loud (however within specs)

the amplifier repeatedly shuts down at 8.8V, i.e. 19.36W.

I will test more. FYI - 50 Hz stepped sine and the amp shuts down at 5W

 

[pma]

BTW, I have the complete info of the moment where the B100 shut down with music. See the sample, see the speaker impedance. The bass frequency is 100 Hz. Vrms was 14.8V.



We are at the scientific forum, so we have to bring scientific reasoning and evidence .

 

[restorer-john]

Someone send me a random example (I'll send it back after testing) and I'll confirm Pavel's findings. I'm not wasting my money on one just to test.

I've been extremely vocal for many years about continuous ratings and how important they are for performance and reliability.

Amir steadfastly refuses to test amplifiers in accordance with how they are required to be advertised and marketed. That is a continuous (5 minutes) test. Not doing so and not disclosing ANY continuous ratings is a gross misrepresentation of any amplifier's fitness for purpose. It makes for situations like this.

And using an excuse like this, is mind-numbingly hilarious:
"I could just drive it continuously with a sine wave but that can damage the amplifier and possibly my dummy load."

Get some low cost, high power dummy loads. The FTC continuous rating is at 1% THD, so you don't need to care about the VCR of the load resistors. Some cheap Chinese resistors are fine. I use them and they are awesome for that purpose.

If the amplifier fails, shuts down or blows up- so what? If it does, it's a POS and that's what a review is for- letting people know something doesn't meet it advertised ratings.

Why would any of these Chinese (used deliberately) manufacturers spend actual money engineering, designing and producing products that can meet their lofty (read: inflated) ratings if nobody is actually testing them properly? (think VW emission scandal).

No, they focus on the ridiculous 5W@4R SINAD chart which anyone with half a brain knows is absolute BS. (think VW clean-diesel, high mpg etc).

I've had enough fights over this and my advice is simple- do not buy cheap amplifiers with dubious power ratings from Chinese manufacturers until they start being honest in those power ratings.

And @pma, we can always start HHR (Honest HiFi Review) if you want.

 

[restorer-john]

It won't be long till the new FTC rule will be in effect.20 days or so.

It's been in effect for a while now. 60 days after being inserted in the Federal Register.

§ 432.3 Standard test conditions.
* * * * *
(e) Any power level from 250 mW to the rated power shall be obtainable at all frequencies within the rated power band of 20 Hz to 20 kHz without exceeding 1.0% of total harmonic distortion plus noise (THD+N) at an impedance of 8 ohms after input signals at said frequencies have been continuously applied at full rated power for not less than five (5) minutes at the amplifier’s auxiliary input, or if not provided, at the phono input.

If you advertise and sell an amplifier in the US, as having any power over 2 watts, it is a legal requirement to specify in accordance with the FTC's rating. It's not a choice or optional.

 

[restorer-john]

The same happened with Telarc CD 80238

That's a fantastic CD too.

 

[miero]

Thanks to @pma for the insightful measurements of the B100 amplifier I brought to him.

I have already emailed my dealer to see if these unspecified amp protection shutdowns are design intent.

So, as an amp for a PC speakers, I find it very good. As an amp for the main home hifi system - never.

I bought this amp to drive the high frequency driver of a horn speaker directly, so the 5W limit is fine for me.

Also I tried to directly drive the 12" Dayton DSA315-8 (sensitivity 90.3 dB @ 2.83V/1m) which I use in my active speakers with a crossover point approx 800Hz and there was no protection shutdown on tracks we tested previously.

It is not an universal amplifier, however for moderate listening levels in smaller rooms with higher sensitivity and higher impedance speakers, this amplifier could do a great job.

 

[Sir Sanders Zingmore]

Do you have a sense of how quickly it would go into protection in a real-world scenario?
Like would it take a single dynamic whack of a kettle drum or would it need to be a sustained cranking-up of Black Sabbath?

40 pages later we have an answer.
Thank you @pma