Topping B100 Amplifier Review

[terryforsythe]

PURIFI 1ET400A 4Ω, 1%THD+N = 425 W

It is a very good amplifier. But, at 425W the THD+N is higher than 1% according to Amir's test results. It hits 1% at less then 400W:

Review and Measurements of Purifi 1ET400A Amplifier

This is a review and detailed measurements of the Purifi 1ET400A Class-D amplifier module. Company was kind enough to send me a complete, assembled kit consisting of two modules, power supply and case, ready to go. They have not disclosed the cost of the unit. Modules will be available to DIY...

www.audiosciencereview.com

If you want less than 1% THD+N at 425W, sell your 1ET400A and get the 1ET9040BA. Also, be sure you have 8V to drive it, or use in I/O module to increase the gain.

 

[Egoist]

That external power supply for the monoblocks, which are supposed to be near the speakers, are a absurd design choice.

 

[vkvedam]

Thanks for the review @amirm, excellent little amp. As others wished, I wish it had an internal PSU at least. Using two of these with two speakers and then a DAC and a Streamer would result in a bit of a cable vomit behind the scenes. I shall wait for an integrated with PSU inside.

 

[rongon]

There seems to be a circuit misunderstanding. Power supply output impedance is not equivalent to amplifier output impedance. An amplifier with high feedback factor may have very low output impedance even if its power supply has output impedance in units of Ohms. The result of higher power supply impedance is decreased maximum output power of the amplifier.

Correct. The output impedance of the amplifier is not the same thing as the impedance the power supply presents to the audio circuits it feeds.

The result of higher power supply impedance is decreased maximum output power of the amplifier....differing with frequency too.

But I don't want to get too obsessed with this point. Since voltage regulators provide a stiff power supply with low impedance to the audio circuits, using well designed supplies solves these issues for the most part.

 

[terryforsythe]

That external power supply for the monoblocks, which are supposed to be near the speakers, are a absurd design choice.

Put them in a cabinet, or behind the cabinet. If you can't do that, then buy something else.

 

[rongon]

Topping Facebook
View attachment 392872

My goodness. Typos, confusion.

I'll say it again. If this is actually a class B output stage, color me impressed!

How does it sound in use? Indistinguishable from a well designed class A or class D amp within their limitations, e.g., at 1 watt output into a good speaker with reasonably sensitivity of maybe 85dB/1W/1m?

 

[Deleted member 72219]

My goodness. Typos, confusion.

I'll say it again. If this is actually a class B output stage, color me impressed!

How does it sound in use? Indistinguishable from a well designed class A or class D amp within their limitations, e.g., at 1 watt output into a good speaker with reasonably sensitivity of maybe 85dB/1W/1m?

I’ve owned a pair for a week now. They sound great and yes, I likely cannot consistently pick them in an ABX against V3 Monos (I’ve owned both as well as a pair of ZA3s). Pushing a pair of KEF LS50 Metas (supplemented by an SVS SB-3000).

-Ed

 

[ReinhardS]

I miss an option in the rating:
[x] confused.

For an analog amplifier design the heat sink and air ventilation is much too small.
I would expect it to overheat within minutes when you drive this amp at 1/3 of rated power.

 

[rongon]

Well, if it really is running in class B, the output devices will be shut off half the time in normal operation, so they won't require the giant heatsinks warm biased class AB output stages need.

 

[rongon]

Not sure what you don't agree with. Firstly, your comment "The power supply is 100% in the signal path in almost all audio amplifier designs" is completely wrong at all levels.

Now you are saying something different. You are now alluding to different things.

OK, please show. Without an actual example, this is an anecdote.

Again, please show.

Well, let's read some posts about psu design for amplifiers.

The Truth About HiFi Amplifier Power Supplies

In any well designed HiFi amplifier, there will be a power supply whose job is to convert the AC mains supply voltage to a DC voltage. The power supply must also be able to provide a reserve of power to cope with any sharp transients in current demand without suffering a decrease in voltage...

www.audiosciencereview.com

https://www.eetimes.com/audio-amplifier-power-supply-design-part-1-power-supply-types-transformer-considerations/

In the EETimes article, by using a regulated voltage supply instead of an unregulated voltage supply "Clipping behavior will be cleaner, as the clipped peaks of the output waveform are not modulated by the ripple on the supply rails. Having said that, if your amplifier is clipping regularly you might consider turning it down a bit."

That right there is a change in sound quality.
And a clue: "...the clipped peaks of the output waveform are not modulated by the ripple on the supply rails."
Power supply ripple modulates the audio output waveform.

[I know this is an engineering problem that has been solved, but the point I made was that the power supply is part of the signal path and has influence on the audio output, meaning that if you hobble even the best audio amplifier circuit with a poorly designed, noisy, high impedance power supply, the sound quality from that 'best' audio amplifier will definitely suffer, first objectively (measurements) and if bad enough, subjectively too.]

I once had a simple push-pull 300B tube amp rigged up, with an external power supply. I made a giant regulated supply using a 6336 pass tube and a 12AX7 differential stage as the error amplifier, along with an 0D3 as a voltage reference. It changed the sound of the amplifier in subtle ways, but bass was tighter with the midrange sounding less 'tubey' and more like a very good solid state amplifier. I could jumper out a few things and switch it back to an unregulated 'passive' power supply, which absolutely increased the power supply impedance. The resulting sound was more in line with what you'd expect from a vintage tube amplifier, with that more ill-defined, slightly woolly bass and what I thought was a more tubey sounding midrange (although I admit that was probably my own biased opinion, not based on real differences I'd stand by now).

At one point I tried to lower the B+ voltage by adding a high power/low value resistor in series from the power transformer center tap to ground, which did lower the B+ voltage but also really raised the power supply impedance. I could really hear that! The bass got all bloated and loose.

All that's just anecdotal, I know. But it was an experiment I ran for myself to prove/disprove effects of power supply impedance on a simple push-pull triode output stage.

Anyway, the articles I linked to answer the question. Please read them and quote whatever you like to disprove any points I've made or prove any points you've made. The whole point is to try to be 'scientific' here on Audio Science Review. Right?

 

[Vigovsky]

If you want less than 1% THD+N at 425W, sell your 1ET400A ....

The PURIFI 1ET400A has more than enough power and no distortion on the peaks. It's enough for any tasks for home audio

 

[martin900]

The problem is that NFB destroys the sound, hence why the THX AAA Benchmark AHB2 and the likes sound dead and closed in, a cold sterile tool with no enjoyment.

 

[terryforsythe]

The PURIFI 1ET400A has more than enough power and no distortion on the peaks. It's enough for any tasks for home audio

I was just messing with you.

 

[Deleted member 72219]

The problem is that NFB destroys the sound, hence why the THX AAA Benchmark AHB2 and the likes sound dead and closed in, a cold sterile tool with no enjoyment.

At the risk of once again being derided for subjective input, I will tell you my pair of B100s do not sound sterile or closed in at all—I got that sensation when I auditioned an SMSL SA400, which I purchased used and immediately sold right back off because of that dead, lifeless sound despite its wonderful measurements. The Fosi Class-D amps and the B100s sound wonderful in comparison, so I politely disagree with your blanket statement in spite of the B100’s triple nested feedback design.

-Ed

 

[terryforsythe]

The problem is that NFB destroys the sound, hence why the THX AAA Benchmark AHB2 and the likes sound dead and closed in, a cold sterile tool with no enjoyment.

I have a pair of Topping LA90D amplifiers and a Hypex Nilai Stereo amplifier, and they all sound fantastic. I assume they are using negative feedback, but that may or may not be the case.

 

[oleg87]

The problem is that NFB destroys the sound, hence why the THX AAA Benchmark AHB2 and the likes sound dead and closed in, a cold sterile tool with no enjoyment.

Oh god, one of these people

 

[oleg87]

I have a pair of Topping LA90D amplifiers and a Hypex Nilai Stereo amplifier, and they all sound fantastic. I assume they are using negative feedback, but that may or may not be the case.

I doubt there's an amp on the market that doesn't use negative feedback in some capacity (though manufacturers will often play word games like "no overall loop feedback!" to satisfy audiophile ignoramuses like the one you quoted - what qualifies as acceptable use of feedback and not, and more importantly why, is not really articulated). It's kind of hard to avoid if you want to design something approaching high fidelity.

Moreover, pretty much every recording has gone through all sorts of NFB-employing circuits and converters on its way to your ears, but as usual in the land of audiophile old wives’ tales, the last bit magically "destroys the sound".

 

[Deleted member 72219]

Oh god, one of these people

Hah…and y’all thought I was bad!

-Ed

 

[dfuller]

The problem is that NFB destroys the sound, hence why the THX AAA Benchmark AHB2 and the likes sound dead and closed in, a cold sterile tool with no enjoyment.

Uh huh.

 

[rongon]

At the risk of once again being derided for subjective input, I will tell you my pair of B100s do not sound sterile or closed in at all—I got that sensation when I auditioned an SMSL SA400, which I purchased used and immediately sold right back off because of that sound despite its wonderful measurements. The Fosi Class-D amps and the B100s sound wonderful in comparison, so I politely disagree with your blanket statement in spite of the B100’s triple nested feedback design.

-Ed

That's great to hear about the Fosi and this B100 amp. I know what that 'closed in' sound is like, and it bothers me. I remember hearing it from an NAD power amp from the 1990s, as well as Crown power amps from the 1980s. 'Dull but harsh' is what I'd call it. But I have also heard solid state amps that sound smooth and don't bother me. I have this weird aversion to reproduction that calls attention to its being electronic. I want to be fooled into thinking I'm hearing something like live people making sounds. I'm really intrigued by this B100 amp because it's 1) apparently using a class B output stage, which is unusual, and 2) not expensive, so I could actually afford a pair if I get serious about it.

The two class D amps I've owned so far are a small TPA3116 thingie made by Breeze Audiothat sounds a bit loose in the bass, murky in the midrange, and loads down easily driving difficult bookshelf speakers, and a Behringer A800 which is plenty powerful but has a bit of an electronic 'edge' to its high frequencies (I can't explain it better than that) perhaps a result of more intermodulation at higher frequencies (as measured in the ASR review) than measured in the Fosi V3, for example. Right now I'm suffering with an old Hafler P1000 amp, which drives my speakers well enough for my small space and is relatively smooth sounding. I'd love to be able to improve on that, but I can't afford a Benchmark, Bryston, etc. I'm hoping Topping has made a smooth sounding, just powerful enough, affordable amp that fills the bill, even if it is running its output stage in class B linearized by great gobs of negative feedback!