Topping B200 Monoblock Amplifier Review

[antcollinet]

Thanks for the advice. That’s very helpful.

To be honest, I wouldn’t worry much about speakers that drop even as low as three ohms.

It’s only going to be an issue if you are trying to push close to full power at it, and then only if a large proportion of that energy is specifically at that frequency where the impedance dips.

 

[pma]

SOA trajectory with complex impedance is important together with design of protection circuits. Rather than impedance magnitude at a given frequency.

 

[antcollinet]

SOA trajectory

Not a term I am familiar with.

 

[terryforsythe]

SOA trajectory with complex impedance is important together with design of protection circuits. Rather than impedance magnitude at a given frequency.

Yes, I agree. But, but I did not see a published SOA trajectory for the B200. If I missed it and you have a link to it that you can post, that would be great.

From Amir's complex load testing, we can see that the B200 was stable at 4 ohms with capacitive and inductive loads (30 and 60 deg. phase angles), but triggered the protection circuit at 2 ohms with +30 and +60 degrees of impedance phase angle (inductive load).

 

[jmdesignz2]

Yes, I agree. But, but I did not see a published SOA trajectory for the B200. If I missed it and you have a link to it that you can post, that would be great.

From Amir's complex load testing, we can see that the B200 was stable at 4 ohms with capacitive and inductive loads (30 and 60 deg. phase angles), but triggered the protection circuit at 2 ohms with +30 and +60 degrees of impedance phase angle (inductive load).

The Fosi monoblocks are stable into 2 ohms. They are fractions of the cost of the B200

I think it’s reasonable to hold the B200 to being stable into 2 ohms and maintaining if not increasing the power

 

[terryforsythe]

The Fosi monoblocks are stable into 2 ohms. They are fractions of the cost of the B200

I have not heard them. They seem like a very good value. According to Amir's measurements, there is a 1.5dB difference at 20kHz between a 4 ohm load and an 8 ohm load. I suspect most of us in the forum don't hear that high of frequency anymore, so that may be a moot issue. I would be curious to see their response with a complex impedance representing a more realistic speaker load. I did a quick search but did not find it for the monoblocks, but here is a chart showing it for the Fosi ZA3 amplifier, courtesy of Erin's Audio Corner:

I think it’s reasonable to hold the B200 to being stable into 2 ohms and maintaining if not increasing the power

For some people that is an important feature, and the B200 is not for them. For other people (e.g., with 8 ohm speakers, or 4 ohm speakers where the designer(s) paid attention to not let the impedance drop too far below that, which includes most 4 ohm speakers to which I have paid attention), it may not be a feature that they care about. For instance, I have a pair of B100s and I am very happy with them; they have presented zero issues for my use case.

I'm not sure how you can hold the B200 to be stable into 2 ohms. Perhaps you can ask Topping to put out a revision that meets your expectations. If enough people ask maybe they will do so. Nonetheless, you can vote with your wallet. If you don't like them, don't buy them. But, that does not mean nobody should buy them - that is up to individual needs and desires.

 

[antcollinet]

I have not heard them. They seem like a very good value. According to Amir's measurements, there is a 1.5dB difference at 20kHz between a 4 ohm load and an 8 ohm load. I suspect most of us in the forum don't hear that high of frequency anymore, so that may be a moot issue. I would be curious to see their response with a complex impedance representing a more realistic speaker load. I did a quick search but did not find it for the monoblocks, but here is a chart showing it for the Fosi ZA3 amplifier, courtesy of Erin's Audio Corner:

View attachment 482492


For some people that is an important feature, and the B200 is not for them. For other people (e.g., with 8 ohm speakers, or 4 ohm speakers where the designer(s) paid attention to not let the impedance drop too far below that, which includes most 4 ohm speakers to which I have paid attention), it may not be a feature that they care about. For instance, I have a pair of B100s and I am very happy with them; they have presented zero issues for my use case.

I'm not sure how you can hold the B200 to be stable into 2 ohms. Perhaps you can ask Topping to put out a revision that meets your expectations. If enough people ask maybe they will do so. Nonetheless, you can vote with your wallet. If you don't like them, don't buy them. But, that does not mean nobody should buy them - that is up to individual needs and desires.

I think @jmdesignz2 was referring to the Fosi V3 mono which has post filter feedback and doesn't suffer from that load dependent frequency response you are showing from the ZA3. Amir's measurement shows +0.5dB at 20kHz - which will not be audible with music.

Further, the feedback has been improved further since the measurement and doesn't even suffer from that now. See post No 14 in the review thread.

 

[joeg26er]

I have not heard them. They seem like a very good value. According to Amir's measurements, there is a 1.5dB difference at 20kHz between a 4 ohm load and an 8 ohm load. I suspect most of us in the forum don't hear that high of frequency anymore, so that may be a moot issue. I would be curious to see their response with a complex impedance representing a more realistic speaker load. I did a quick search but did not find it for the monoblocks, but here is a chart showing it for the Fosi ZA3 amplifier, courtesy of Erin's Audio Corner:

View attachment 482492


For some people that is an important feature, and the B200 is not for them. For other people (e.g., with 8 ohm speakers, or 4 ohm speakers where the designer(s) paid attention to not let the impedance drop too far below that, which includes most 4 ohm speakers to which I have paid attention), it may not be a feature that they care about. For instance, I have a pair of B100s and I am very happy with them; they have presented zero issues for my use case.

I'm not sure how you can hold the B200 to be stable into 2 ohms. Perhaps you can ask Topping to put out a revision that meets your expectations. If enough people ask maybe they will do so. Nonetheless, you can vote with your wallet. If you don't like them, don't buy them. But, that does not mean nobody should buy them - that is up to individual needs and desires.

Please don't cut out my quotes selectively - the whole point was the B200 collapsing when faced with a 2ohm load, being nearly 5X the cost of the Fosi MONO Block that handles 2ohms quite well.

"The Fosi monoblocks are stable into 2 ohms. They are fractions of the cost of the B200
I think it’s reasonable to hold the B200 to being stable into 2 ohms and maintaining if not increasing the power"

I did NOT buy the B200s mainly due to them failing into 2ohms. For me, the Buckeye NCX500 monoblocks had far more power per dollar and fantastic SNR/THD

 

[terryforsythe]

Please don't cut out my quotes selectively - the whole point was the B200 collapsing when faced with a 2ohm load, being nearly 5X the cost of the Fosi MONO Block that handles 2ohms quite well.

"The Fosi monoblocks are stable into 2 ohms. They are fractions of the cost of the B200
I think it’s reasonable to hold the B200 to being stable into 2 ohms and maintaining if not increasing the power"

I did NOT buy the B200s mainly due to them failing into 2ohms. For me, the Buckeye NCX500 monoblocks had far more power per dollar and fantastic SNR/THD

I quoted everything you wrote, but separated the statements so that you can easily see to which statements my responses are applicable. But, I'll quote it they way you want it done.

I would not call the B200 going into protection mode with a 2 ohm inductive load "collapsing". It just isn't designed for that type of load, and the protection circuit did its job. The B200 is a class A/B amplifier, where the Fosi MONO Block and NCX500 monoblocks are class D amplifiers. They are different technologies. From what I have seen, on average, class D amplifiers usually handle low impedance loads better than class A/B amplifiers, though there are some exceptions. But, the class A/B amplifiers that do handle well a 2 ohm load, at least that I have seen, tend to be even more expensive than the B200.

With advances made in class D technology in recent years, I do think class D amplifers deserve serious consideration and provide a very good performance/dollar ratio. Indeed, I also own a Hypex Nilai stereo amplifier, which is class D, with which I am very happy. But at this point in time that amplifier costs more than two B200s, though it is stable into 2 ohms, not that I care that it is.

I have not seen data showing the frequency response of the Fosi MONO and B200 amplifiers with realistic speaker loads, which are far from being purely resistive. But, based on what data I have seen, I expect the B200 will be extremely flat and the Fosi MONO will look similar to the Fosi ZA3. For some people that is not an issue, but for some people it is an issue. Also, the B200 has one-tenth of the combined noise/THD of the Fosi Mono, -120dB vs -100dB. For some people it is worth spending the extra money to have such levels of performance. Indeed, Amir has stated that it is around -115dB where noise and distortion are totally inaudible, whereas some people claim they can't hear any noise/distortion higher than -80dB. Who is correct, I don't know, but I do to take seriously Amir's statements with regard to measurements and their applicabilty to audio.

 

[antcollinet]

Fosi MONO will look similar to the Fosi ZA3

Why? It has flat load independent frequency response, just like the B200 - it will look nothing like the ZA3.

 

[jmdesignz2]

Why? It has flat load independent frequency response, just like the B200 - it will look nothing like the ZA3.

I quoted everything you wrote, but separated the statements so that you can easily see to which statements my responses are applicable. But, I'll quote it they way you want it done.

I would not call the B200 going into protection mode with a 2 ohm inductive load "collapsing". It just isn't designed for that type of load, and the protection circuit did its job. The B200 is a class A/B amplifier, where the Fosi MONO Block and NCX500 monoblocks are class D amplifiers. They are different technologies. From what I have seen, on average, class D amplifiers usually handle low impedance loads better than class A/B amplifiers, though there are some exceptions. But, the class A/B amplifiers that do handle well a 2 ohm load, at least that I have seen, tend to be even more expensive than the B200.

With advances made in class D technology in recent years, I do think class D amplifers deserve serious consideration and provide a very good performance/dollar ratio. Indeed, I also own a Hypex Nilai stereo amplifier, which is class D, with which I am very happy. But at this point in time that amplifier costs more than two B200s, though it is stable into 2 ohms, not that I care that it is.

I have not seen data showing the frequency response of the Fosi MONO and B200 amplifiers with realistic speaker loads, which are far from being purely resistive. But, based on what data I have seen, I expect the B200 will be extremely flat and the Fosi MONO will look similar to the Fosi ZA3. For some people that is not an issue, but for some people it is an issue. Also, the B200 has one-tenth of the combined noise/THD of the Fosi Mono, -120dB vs -100dB. For some people it is worth spending the extra money to have such levels of performance. Indeed, Amir has stated that it is around -115dB where noise and distortion are totally inaudible, whereas some people claim they can't hear any noise/distortion higher than -80dB. Who is correct, I don't know, but I do to take seriously Amir's statements with regard to measurements and their applicabilty to audio.

Tery - Please don’t create disinformation

The Fosi Mono blocks are very resistant to load impedance

 

[terryforsythe]

Tery - Please don’t create disinformation

The Fosi Mono blocks are very resistant to load impedance

I am not creating disinformation. That accusation itself is disinformation. If you disagree, please identify what I stated that is disinformation.

I looked for a frequency response graph of the Fosi MONO with a complex load impedance, but did not find one. Perhaps I missed it, which absolutely is possible. If so, please provide a link that shows that the Fosi MONO frequency response with a complex load impedance supporting your contention that "[t]he Fosi Mono blocks are very resistant to load impedance."

Now, I did say "I expect the B200 will be extremely flat and the Fosi MONO will look similar to the Fosi ZA3." (Emphasis added). I truly do expect that. My expectation for the performance of the Fosi MONO is based on the similarity of the MONO to the ZA3 with respect to the frequency response divergence comparing the 4 ohm and 8 ohm resistive load tests, indicative of an increase in output impedance vs frequency, which is not uncommon in budget class D amplifiers. The B200 does not exhibit nearly as much divergence, indicating a lower output impedance in the upper frequency range, and it has a specified output impedance of <0.005ohm. Thus, the B200 should exhibit less fluctuation with a real speaker load. EDIT: I did expect that, but I just now saw the link by antcollinet where Fosi posted an improvement to the MONO after Amir released his test data.

For reference:

 

[terryforsythe]

I think @jmdesignz2 was referring to the Fosi V3 mono which has post filter feedback and doesn't suffer from that load dependent frequency response you are showing from the ZA3. Amir's measurement shows +0.5dB at 20kHz - which will not be audible with music.

Further, the feedback has been improved further since the measurement and doesn't even suffer from that now. See post No 14 in the review thread.

Thank you for the link. I just now saw it. It looks like they did further optimizations with PFFB after Amir's review.

For reference, I was looking at this chart posted in Amir's review of the Fosi v3 Mono, which apparently was measured before the optimizations. Specifically, I was looking at the divergence of the 4 and 8 ohm plots, which is indicative of a rise in output impedance. But, apparently Fosi fixed that, which is very good to see.

 

[antcollinet]

Thank you for the link. I just now saw it. It looks like they did further optimizations with PFFB after Amir's review.

For reference, I was looking at this chart posted in Amir's review of the Fosi v3 Mono, which apparently was measured before the optimizations. Specifically, I was looking at the divergence of the 4 and 8 ohm plots, which is indicative of a rise in output impedance. But, apparently Fosi fixed that, which is very good to see.

View attachment 482547

That is the V3, not the V3 mono, it is there, written on the chart. Amir included it in the mono review to demonstrate how post filter feedback improves the situation - to show how much worse the V3 is than the V3 mono.

Please stop using measurements for a different amp to try to say what the V3 mono will do. At best it is simply muddying the waters - at worst ... well, it looks deliberate.

Neither the V3, nor the ZD3 have post filter feedback - this makes them completely different beasts from the V3 Mono.

Even in Amir's original measurement, the divergence (between 4 and 8) was almost non existent, so no load dependency. The frequency dependence (independent of load) was only +0.5dB at 20K. Here with the V3, you have a load dependence (divergence 4 to 8) of 1.5dB at 20K, and an absolute divergence at 8ohm, of 1dB. This makes a massive deifference to Erin's measurement you have posted above.

This is the V3 mono chart - from BEFORE Fosi improved it to remove the peaking at 20kHz.

See the difference?

 

[terryforsythe]

That is the V3, not the V3 mono, it is there, written on the chart. Amir included it in the mono review to demonstrate how post filter feedback improves the situation - to show how much worse the V3 is than the V3 mono.

Please stop using measurements for a different amp to try to say what the V3 mono will do. At best it is simply muddying the waters - at worst ... well, it looks deliberate.

Neither the V3, nor the ZD3 have post filter feedback - this makes them completely different beasts from the V3 Mono.

Even in Amir's original measurement, the divergence (between 4 and 8) was almost non existent, so no load dependency. The frequency dependence (independent of load) was only +0.5dB at 20K. Here with the V3, you have a load dependence (divergence 4 to 8) of 1.5dB at 20K, and an absolute divergence at 8ohm, of 1dB. This makes a massive deifference to Erin's measurement you have posted above.

This is the V3 mono chart - from BEFORE Fosi improved it to remove the peaking at 20kHz.

View attachment 482596

See the difference?

You are correct that I grabbed the wrong chart from the review. My bad, but unintentional.

Still, in that earlier design there likely would have been frequency response ripples in the audio range with a real complex speaker load, but probably not audible. Nonethless, as you pointed out, Fosi has addressed that with PFFB optimization, so the point is now moot.

 

[antcollinet]

frequency response ripples in the audio range

Almost certainly not, because there is no load dependence (same curve for both 4ohm, and 8ohm). What there would have been would be that 20kHz peaking up to about half a dB. Inaudible for anyone - including - I suspect - bats.

 

[globadyne]

I currently have a pair of PMC Twenty5 22I
Rotel 1570 Preamp Running Balanced to a Rotel 1582MKII
Sources are HQPlayer( I like DSD) to Roon to Zen Stream to Gustard X16 Running Balanced to PreamP
and my Phono Stage running over RCA( Lehmann Black Cube SE)

These toppings are kind of a appealing and the idea of MonoBlocks

Would you say moving to something like this would be a sonic upgrade - I hear good things , Detail and Black Background but curiuous peoples thoughts

Cheers from Canada

 

[abrcdbra]

If your loudspeakers require power down below 4 Ohm, then these amps are not for you, however that doesn't mean that they are somehow lacking for all use cases.

I think so too.

AMPs with significant feedback (the B200 uses very large feedback, according to its distortion coefficient) aren't stable enough, especially at the extremes of the operating frequency range. And my main listening system has JBL4429 speakers, whose impedance drops below 4 ohms at 20 kHz.

Therefore, the B200 is out of the running.

 

[jmdesignz2]

I currently have a pair of PMC Twenty5 22I
Rotel 1570 Preamp Running Balanced to a Rotel 1582MKII
Sources are HQPlayer( I like DSD) to Roon to Zen Stream to Gustard X16 Running Balanced to PreamP
and my Phono Stage running over RCA( Lehmann Black Cube SE)

These toppings are kind of a appealing and the idea of MonoBlocks

Would you say moving to something like this would be a sonic upgrade - I hear good things , Detail and Black Background but curiuous peoples thoughts

Cheers from Canada

wow your speakers are bit more $ than I expected

The way it sounds depends on how it interacts with the amp- not sure if impedance dips enough to make a difference as yours are rated at 8ohms so should be fine

interesting article

PMC twenty5 22i Bookshelf (Stand-mount) Speakers with Built-in Power Amplifiers Upgrade Review - BONUS: HOW TO IMPLEMENT AN ARYLIC BLUETOOTH S50 PRO+ RECEIVER - HomeTheaterHifi.com

PMC is one of the few speaker companies that have been awarded an Emmy® for their contribution to the recording industry.

hometheaterhifi.com

 

[Marc v E]

I currently have a pair of PMC Twenty5 22I
Rotel 1570 Preamp Running Balanced to a Rotel 1582MKII
Sources are HQPlayer( I like DSD) to Roon to Zen Stream to Gustard X16 Running Balanced to PreamP
and my Phono Stage running over RCA( Lehmann Black Cube SE)

These toppings are kind of a appealing and the idea of MonoBlocks

Would you say moving to something like this would be a sonic upgrade - I hear good things , Detail and Black Background but curiuous peoples thoughts

Cheers from Canada

Probably not.
If I would want a sonic upgrade, I would look at adding a subwoofer.
Measuring your current system with rew and applying eq with roon is also an idea to try.