Topping B100 Amplifier Review

[capslock]

No, I cannot measure that low. Just down to -130dB. Anyway, I find such race pointless, bringing nothing but issues we can see here. But it sells, the SINAD sells to certain group of customers, regardless other parameters.

If you didn't see any harmonics in a -130 dB noise floor, that is also an excellent result. My question was not about chasing SINAD but trying to understand if there is a weak spot in their design. I still doubt that it is really full class B, though.

 

[miero]

It is IEC 60268-3 here in the EU.

OK, thanks. I replied them with a request for a clarification on the actual power output capabilities.

 

[pma]

If you didn't see any harmonics in a -130 dB noise floor, that is also an excellent result.

My limit looks like this:

The noise floor is lower, however the distortion peaks do attack -130dB. B100 does not make it worse.
It may be class B with nested feedback composite amplifier and proper frequency compensation method.

 

[jan.didden]

Late to the party, but it seems to me Topping is squarely aiming at the 50-100W class D offerings from the usual sustects.
Similar size and cost, yet hugely better performance.

Jan

 

[KSTR]

So also at -140 dB? I really wonder how they do that with no or a very small idle current. No amount of feedback should be able to iron out heavy crossover distortion.

Idle consumption indicates a small standing current, so not pure class-B which would not reliably work.

 

[LKA]

A loop probe (for an oscilloscope or spectrum analyzer) can help detect whether it is class-d or not.

 

[pma]

Idle consumption indicates a small standing current,

idle consumption of the output stage in isolation remains unknown, IMO.

A loop probe (for an oscilloscope or spectrum analyzer) can help detect whether it is class-d or not.

It is no class D. I measured spectrum up to 10MHz, no trace of switching frequency. No rise of THD+N with frequency.

Digital "square" 1k spectrum

Sine measured with 25MS/s, no switching frequency

 

[jan.didden]

The only way I know to get such low distortion in a linear amp is a combined-loop with an opamp and a power output section like a number of // '3886 or similar.
Something like neurochrome.com does, he gets similar performance specs.
This is the modulus-286.

Jan

 

[KSTR]

idle consumption of the output stage in isolation remains unknown, IMO.

Well, we have some 9W of total consumption with zero signal and I would assume at least some of this is burned up in the output stage because there isn't much else that could dissipate significant power. But yes, speculation as of yet, maybe someone could open it and check the temperature on that measly heatsink. If it gets warm then standing current would be the most likely reason.

 

[KSTR]

The only way I know to get such low distortion in a linear amp is a combined-loop with an opamp and a power output section like a number of // '3886 or similar.
Something like neurochrome.com does, he gets similar performance specs.

Jan

Yep, it is pretty much certain that this is a design with tons and tons of feedback, so likely a composite with an OpAmp as master and some discrete output stage (with a bit of gain perhaps).

 

[pma]

9W including power supply consumption or not? Me, I do not have enough info on this.

 

[misterdog]

The only way I know to get such low distortion in a linear amp is a combined-loop with an opamp and a power output section like a number of // '3886 or similar.
Something like neurochrome.com does, he gets similar performance specs.
This is the modulus-286.

Jan

I suspected similarly, the Neurochrome amps are an excellent product, though DIY is not for everyone.
Good to see a familiar face on here Jan.

 

[LKA]

B100 has much flatter THDvsFreq graph than Modulus

 

[Sokel]

B100 has much flatter THDvsFreq graph than Modulus

Look at the scale.
Also,Amir's measurement is with 10dB gain,is it comparable to modulus? (I ask,I have no idea)

 

[LKA]

The B100 has lower 10k-20k distortion than the Modulus. I have no idea how such low 10k-20k distortion can be achieved with a true class B topology.

 

[jan.didden]

Do we know the output voltage of that outboard supply?

Jan

 

[Old_School_Brad]

The B100 has lower 10k-20k distortion than the Modulus. I have no idea how such low 10k-20k distortion can be achieved with a true class B topology.

This is the thread where the design was discussed:

Class B amplifier with SINAD of 120, how is that possible?

I thought that class B based amplifiers advantage were a lot of power in combination with the disadvantage of high distortion. To solve the negative aspect class A design was integrated, creating the classic combination: Class AB amplifier. BUT why bother with this AB combination if it can be...

www.audiosciencereview.com

 

[EddNog]

Do we know the output voltage of that outboard supply?

Jan

38volts, 4amps.

-Ed

 

[pma]

Do we know the output voltage of that outboard supply?

Jan

Jan, you will find the info in the 1st post of the thread. And output is a BTL, so 38V is enough. However, 4A is not enough. It may lead to those 4ohm stepped sine shut downs.

 

[jan.didden]

That is probably bipolar, like +/-38V?
That would give it something like 35V peak output, tops, or 25Vrms, or close to 80W in 8 ohms. Makes sense.
And with those graphs, it definitely is not class B. Even a small bias current will make a huge difference, and puts it in AB.

Edit: if BTL yes 38V unipolar is enough for 80W/8, yes.
Does anyone have a pic of what is under that heatsink?

Jan