Topping B100 Amplifier Review

[Maciekw]

I just checked voltage on speaker terminals during playing 200Hz sine tone using the RCA input on the B100.
Between "ground" on the power connector and both "+" and "-" is X volts. And between "+" and "-" there is 2X volts.

The RCA input certainly goes into the differential amplifier from which you get a balanced signal.
Therefore, the measurement from the RCA input explains nothing.

 

[miero]

Non-BTL amplifiers use to have the negative output tied to the "ground".

Using the balanced input I'm able to driver either only the "+" output or only the "-" output of the amplifier, depending on which hot/cold pin of XLR is (unbalanced) source signal connected.

Also there are two output coils...

 

[pma]

It seems to be definitely the case. However, if there was a true differential input, the function of only one half would not happen with the RCA-XLR cable.
It also explains why a single-ended RCA input has +6dB gain compared to XLR (26dB RCA, 20dB XLR). They must have a non-inverting opamp input and the further unity gain inverting opamp, to drive two halves of the bridge. This, of course, doubles the gain, thus 6dB more. And they switch it by a rear panel toggle switch. We should re-measure the amp, @miero .

 

[capslock]

Well, I had two B100 units that I ordered in early October from amazon.de marketplace. One of the cartons arrived crushed, so I was going to send them back anyway. I tested the "uncrushed" unit today, using a Motu M4 set to 2 V RMS symmetrical signal. I set the frequency to 110 Hz to be sure that my true RMS multimeter would measure the voltage correctly. I used three 12 R Isabellenhütte manganine resistors in cases like large power transistors in parallel, so 4 R test load, glued to a pretty massive heat sink. The B100 was set to medium gain, and of course, I used a TRS to TRS cable from the M4 to the B100.

I started out a little too agressively because, out of habit, I divided U² by twice the load impedance, so I was assuming I was still at 10 W when I really was at 20 W. Voltages around 13 - 15 V RMS triggered the protection (it may have been code 1 - 3, forgot to count the pulses). At voltages around or slightly above 10 V, it was running fine for a few minutes, with the load resistors on the heat sink getting noticably warm. Assuming 10 V RMS output voltage, that was 25 W output into 4 R! I then increased the input voltage 1 dB at a time, and after setting 11.6 V, the protection triggered within about 3 seconds.

I disconnected input and load and cycled power but all I got was the 1 - 1 code (negative and positive voltage abnormal). The case was warm by that time, so I waited for about 15 minutes, still the same problem. I came back after two hours, during which the B100 had been sitting on the 20 °C floor without power applied, and the problem persisted. Packed them up and posted them (it was the last day I could return them).

So my unit did not have as touchy a protection as Miero's (or was it because I drove it from a symmetrical source?) but the protection failed to protect the amplifier when it was asked to output 33 W after being already slightly warm to the touch.

So on the plus side, it should be able to play music with peaks up to 80 or 100 W. On the other hand, it is not exactly confidence inspiring that one can break it by running 1/3 of rated power for a few seconds on an already somewhat warm unit.

@ RestorerJohn, a few pages ago, you posted about the FTC rule. Warm-up at 1/8 rated power and then full power at any frequency into 8 R for 5 minutes. What about units rated for 4 R, are they tested at full power into 4 R?

 

[Sokel]

They shoud swap these Nichicons with ordinary caps and transfer the cost to heatshinks
If I get the size right and this tiny heatshink is all there is,it's a miracle that does 25 W.

Edit:Is that a bimetallic switch attacked to heatshink?Cause if it is,that's low DIY kind of protection and a rather brutal one.

 

[pma]

(or was it because I drove it from a symmetrical source

It may be a better scenario, the load of both BTL halves is symmetrical. But your results also confirm that the amp has issues with the rated sine power and shuts down quite early.

 

[ban25]

They shoud swap these Nichicons with ordinary caps and transfer the cost to heatshinks
If I get the size right and this tiny heatshink is all there is,it's a miracle that does 25 W.

A couple oz of aluminum, six fins, air-gapped, sealed in a metal box.

 

[capslock]

They shoud swap these Nichicons with ordinary caps and transfer the cost to heatshinks
If I get the size right and this tiny heatshink is all there is,it's a miracle that does 25 W.

Edit:Is that a bimetallic switch attacked to heatshink?Cause if it is,that's low DIY kind of protection and a rather brutal one.

I would assume it is an NTC temperature sensor. I agree that the heat sink seems woefully undersized.

What is that little PCB riding askew on those small electrolytics? It seems to pass through the power from the external brick.

Did anyone notice that there are no serious supply capacitors on the board? Those six caps that PCB rides on are probably something like 220 µF / 50 V.

 

[Sokel]

I would assume it is an NTC temperature sensor. I agree that the heat sink seems woefully undersized.

What is that little PCB riding askew on those small electrolytics? It seems to pass through the power from the external brick.

Did anyone notice that there are no serious supply capacitors on the board? Those six caps that PCB rides on are probably something like 220 µF / 50 V.

Can't see the size right but those seem to be Nichicon KA series and judging by the XLR connector size they must be 25 or the most 35V.
If someone can measure them we will be sure.

 

[Sokel]

What is that little PCB riding askew on those small electrolytics? It seems to pass through the power from the external brick.

It seems like a power Mosfet,if I get the writing correct,this one:

https://www.irf.com/product-info/datasheets/data/irfi5210.pdf

 

[pma]

@ RestorerJohn, a few pages ago, you posted about the FTC rule. Warm-up at 1/8 rated power and then full power at any frequency into 8 R for 5 minutes. What about units rated for 4 R, are they tested at full power into 4 R?

The document speaks about rated power, in the test conditions section. And about impedance to which the amplifier is primarily designed. Here it is 4ohm and 8ohm for which are the B100 specifications listed.

https://pmacura.cz/FCT/FTC_Part432_as_of_7-05-2024.pdf

 

[capslock]

The document speaks about rated power, in the test conditions section. And about impedance to which the amplifier is primarily designed. Here it is 4ohm and 8ohm for which are the B100 specifications listed.

View attachment 409855

https://pmacura.cz/FCT/FTC_Part432_as_of_7-05-2024.pdf

I guess this is the pertinent paragraph.

No doubt the B100 does not live up to this standard. I suppose this becomes a problem only if it is sold via US based dealers, so as long as individuals mail order from China, they become the importers. Do we have a similar rule in the EU?

Now, I don't think the rule is relevant for music - there is no way I will be needing a continous power of more than 10 W. That the amp self-destructs after about 2 seconds at 33 W into 4 R is a bummer, though. I ordered two more from Hong Kong a few weeks ago that have not yet shipped. Apparently, they are waiting for new stock from Topping. Not sure if they will have ironed the faults in new production. Those that I had were the last pair in stock in a German Amazon warehouse at the beginning of October, so they may have been from the first run.

I have half a mind to ask the seller to cancel the order because shipping the amps back to China after any peak load does not sound fun.

 

[pma]

Do we have a similar rule in the EU?

Yes, of course, with same or more strict requirements. I proposed it here some time ago.

(Suggestion on) Testing power amplifiers according to IEC 60268-3 standard

(Suggestion on) Testing power amplifiers according to IEC 60268-3 standard I would like to start the debate on ASR power amplifier testing and suggest some degree of conformance with current standards. --------------------------------------------------- The part 3 of IEC 60268 applies to...

www.audiosciencereview.com

Now, I don't think the rule is relevant for music - there is no way I will be needing a continous power of more than 10 W.

I find this remark irrelevant. As many people, as many opinions. And we need standards. The amplifier did shut down with music and speaker, as I did describe earlier in the thread. From now on, I will stay strictly on the side of standards and definitions and end up with passed/failed.

so as long as individuals mail order from China

then the responsibility is on individuals. However, even @Audiophonics should not be happy with selling the product that fails to pass EU standards.

 

[capslock]

Yes, of course, with same or more strict requirements. I proposed it here some time ago.

(Suggestion on) Testing power amplifiers according to IEC 60268-3 standard

(Suggestion on) Testing power amplifiers according to IEC 60268-3 standard I would like to start the debate on ASR power amplifier testing and suggest some degree of conformance with current standards. --------------------------------------------------- The part 3 of IEC 60268 applies to...

www.audiosciencereview.com

I find this remark irrelevant. As many people, as many opinions. And we need standards. The amplifier did shut down with music and speaker, as I did describe earlier in the thread. From now on, I will stay strictly on the side of standards and definitions and end up with passed/failed.


then the responsibility is on individuals. However, even @Audiophonics should not be happy with selling the product that fails to pass EU standards.

Mine came from a Chinese seller (Hifi college store or something like that) on amazon.de, so easy to evade responsibility. I believe there was also a a company somewhere in Belgium listed on the wrapping foil (I believe this is required by EU product liability and recycling rules, though most Chinese companies list no designated representative), which is probably no more than a letterbox in a nondescript office building.

I didn't realize audiophonics already sell them, but I had already gotten the impression that they are a bit lax with EU rules, selling new products almost as quickly as they appear on aliexpress.

If it is true that you were driving only one half of the bridge, and the total continious output power is limited at about 25 W, then it is no surprise you were seeing problems at about 10 W.

What I meant to say is that a continuous output power of 25 W is probably enough for home listening, no matter what the FTC rules are. In fact, the FTC rules can probably be considered wasteful, resulting in larger transformers and heat sinks than strictly needed and resulting in a higher idle power consumption. When it was written in the 70s, it was meant to ward off "unfair" Japanese marketing. Ressources and electricity were cheap. Similar rules were written for cars, and you can still buy cars and trucks with V8 gasoline engines that go back to the 1940s. The cumulative effect is significant.

 

[Sokel]

When it was written in the 70s, it was meant to ward off "unfair" Japanese marketing. Ressources and electricity were cheap. Similar rules were written for cars, and you can still buy cars and trucks with V8 gasoline engines that go back to the 1940s. The cumulative effect is significant.

The FTC rule is brand new and less brutal than the 70's one (1/8 of rated power instead of 1/3 for preconditioning,etc) and there was a long time they gathered info and suggestions from all parties involved.
No one forces the companies to change trafos of thermals,all it does is that makes them state the true power figures following the test.
I understand that big numbers were a good selling point but it was getting ridiculous with all the competition pushing them to some astronomical specs for amps with heatshinks that would otherwise cool a couple of 7815's .

 

[antcollinet]

a continuous output power of 25 W is probably enough for home listening,

That is very very much dependent on the setup.

It will be true only when listening at "desktop" distances with sensitive speakers at moderate or lower levels and with not very dynamic music.

 

[Sokel]

That is very very much dependent on the setup.

It will be true only when listening at "desktop" distances with sensitive speakers at moderate or lower levels and with not very dynamic music.

..and most importantly no room correction,specially (wrongly) filling dips.

 

[antcollinet]

..and most importantly no room correction,specially (wrongly) filling dips.

Here is an example calculator output for my specific use case. (86dB efficient speakers, 2m distance, 85dBa "average" listening level (not always, but sometimes) but wanting to listen to music with 15db of dynamics without clipping. 100W needed. (First screenshot)

If listening distance were to increase by just 1m to 3m then that power requirement would more than double to 226W (Second screenshot)

At a desktop distance of 1m, only then would I be down at 25W. (no screenshot for this)

(non of these with allowance for DSP)

 

[Old_School_Brad]

What I meant to say is that a continuous output power of 25 W is probably enough for home listening, no matter what the FTC rules are. In fact, the FTC rules can probably be considered wasteful, resulting in larger transformers and heat sinks than strictly needed and resulting in a higher idle power consumption.

Alternatively, the manufacturer could rate the amplifier at 25 W rather than designing it with a larger power supply and heatsink. This approach doesn't force any redesign -it simply means the reported power figures wouldn't be as exaggerated for a given amplifier design.

Regarding power requirements, you can't simply claim that a certain wattage is sufficient without considering the many factors that influence it, such as listening distance, speaker frequency response, impedance, phase characteristics, program material, desired listening SPL, room acoustics, DSP settings, EQ adjustments, or room correction methods.

 

[Esprit]

Ouch, I wonder if PA5 II behaves in any similar manner

Are there any answers?