NEW BRZHifi PAD-30 : Dual TPA3255 +PFFB @ $99

[Sam_138]

Hello, I registered to leave this comment. I've been reading and, above all, learning from all of you for over a year.

I recently bought this amplifier after reading this thread, for €79 on AliExpress (without the power adapter). I'm delighted with it.
My listening environment is a 40 m² room, where a Wiim Ultra, this amplifier, and a Linton 85 Heritage speaker allow me to enjoy music every day, with my 58-year-old ears.

 

[ICIETDIYEUR]

People Hi

The PFFB circuit appears to be well-implemented on the PCB ->

It features the same number and type of components as a PFFB implementation by TOPPING, for example ->

It remains to be confirmed whether the component values were correctly selected; this will be objectively verified—or not—through measurements

 

[mhardy6647]

It remains to be confirmed whether the component values were correctly selected; this will be objectively verified—or not—through measurements

Why would they not be correctly selected? Some Muntz-grade engineering -- designers being instructed to use whatever leftover parts had been scavenged from an aborted project instead of the correct value parts, e.g.?

 

[harkpabst]

Why would they not be correctly selected? Some Muntz-grade engineering -- designers being instructed to use whatever leftover parts had been scavenged from an aborted project instead of the correct value parts, e.g.?

And: Who says that the values must be totally identical to the values chosen by Topping (or any other make) irrespective of the actual PCB layout?

 

[mhardy6647]

And: Who says that the values must be totally identical to the values chosen by Topping (or any other make) irrespective of the actual PCB layout?

Or the suggested values from the documentation of the amp chip's manufacturer?

 

[ICIETDIYEUR]

Hi.

Did anyone read me saying that the values had to be the same?
I simply said that the circuit was compliant, but that the values needed to be correctly selected (i.e., adapted to the circuit).
Please don't put words in my mouth—or else read my comments more carefully next time before weighing in

I am simply suggesting that the PFFB circuits in certain amplifiers are sometimes not optimized—or even 'inoperative'—a point that Amirm has clearly highlighted through his measurements

 

[harkpabst]

Or the suggested values from the documentation of the amp chip's manufacturer?

Sure. Amir never tested TI's reference board implementation. Still there seem to be measurable differences between 3rd party implementations and manufacturers like 3E AUDIO took the additional effort of covering the PFFB components with some sort of goo. Looking at the pretty perfect FR found for different loads they might (or might just not) have applied some optimization.

I simply said that the circuit was compliant, but that the values needed to be correctly selected (i.e., adapted to the circuit).
Please don't put words in my mouth—or else read my comments more carefully next time before weighing in

No, that's not what you said, but I'm glad you clarified your point.

I simply said that the circuit was compliant, but that the values needed to be correctly selected (i.e., adapted to the circuit).
Please don't put words in my mouth—or else read my comments more carefully next time before weighing in

No, that's not what you said, but I'm glad you clarified your point.

 

[ICIETDIYEUR]

For your information—recalling events from a few years ago and following up on numerous exchanges between myself and Lester (SYLPH Audio)—it certainly appears that 3eAudio originally copied the PFFB circuit created by Topping for their PA5 model (the first version). This happened back when they were still only manufacturing PCBs for the DIY market—that is, well before the release of their various A5 and A7 amplifier models.

 

[john61ct]

Nothing wrong with that, must have been a good template if true.

Has Topping created anything close to competitive with 3e's A7 line?

 

[Ruediger]

Has Topping created anything close to competitive with 3e's A7 line?

The PA series could have some candidates. F.e. the top model PA7 plus shows very good performance, but is in the Hypex 250 price range.

Topping PA7 Plus Amplifier Review

This is a review and detailed measurements of the Topping PA7 Plus stereo class D amplifier. It was sent to me by the company and costs US $549. The PA7 Plus is stylish with firm switches that have nice action. You can select power on/off or trigger input. In addition, you have a choice of...

www.audiosciencereview.com

 

[TonyJZX]

i think you guys are arguing amongst yourselves for no reason

we know TI publishes how to do this in a way where the designers at BRZ or whatever can just copy what they recommend... its well known now that in reality NO manufacturer needs to omit it given its addition is a few cents in parts and literally no additional work for their designers... it doesnt matter how prestigious the company claims to be if someone like Weilang manages to do it... there's no excuse for anyone NOT to do it at any price level

i really do not need another one of these but um yeah.... for the purposes of higher education

 

[harkpabst]

i think you guys are arguing amongst yourselves for no reason

we know TI publishes how to do this in a way where the designers at BRZ or whatever can just copy what they recommend... its well known now that in reality NO manufacturer needs to omit it given its addition is a few cents in parts and literally no additional work for their designers... it doesnt matter how prestigious the company claims to be if someone like Weilang manages to do it... there's no excuse for anyone NOT to do it at any price level

i really do not need another one of these but um yeah.... for the purposes of higher education

You certainly have a point here, but just to a certain degree. Different manufacturers' TPA3255 implementations do vary quite a bit in how well they manage load independency and distortion over frequency (where especially the latter also depends on other factors).

It's been years after TI published their white paper on PFFB before the first commercial implementations became available. And that's not just because nobody had noticed it. Manufacturers did have issues with e.g. louder on/off popping noise. The use of non-reference design output filters and simply different routing of PCB traces will require changes to component values, even if the topology stays the same.

 

[ICIETDIYEUR]

People hi

Video of the interior (PCB) here ->

https://www.douyin.com/video/7577322679720512774

Note: The volume potentiometer is detachable, allowing for easy replacement in the event of issues and enabling various potential modifications—such as bypassing it to use the amplifier as a simple power amp (retaining the on/off function while shunting the potentiometer's volume control section).
The device's 12-volt trigger function remains operational.

In this video, only four 82µF/100V capacitors (328µF total) are used for the PVVD, which seems far too few—hopefully, the final model includes more (even though the Rubycon ZLH capacitors are excellent).

It is clear that the op-amps each have two power rails (positive and negative), although their voltage cannot be determined visually from the video.

The decoupling for these rails appears adequate (a 47µF electrolytic capacitor in parallel with what is presumably a 0.1µF SMD capacitor).

I cannot read the values of the components surrounding the op-amps; knowing them would allow me to determine the input impedances and select the op-amp best suited to the circuit (schematic).

I could reverse-engineer it once I receive the unit...

The op-amp located near the volume potentiometer handles the pre-amplified output, routing the signal through a relay and then to the 3.5mm jack on the back of the device.

The unit shouldn't heat up when left on without a signal, as the power supply circuit includes an NTC thermistor.

Furthermore, the power supply design appears to have been carefully optimized to eliminate noise, judging by the filtering components used in the circuit.

Measurements are indeed the next step, but the unit looks promising

 

[ICIETDIYEUR]

"All other things being equal" (a term used in French; I’m not sure if it carries the same meaning in English-speaking countries)...

... it would be interesting to measure it using the same power supply as the 3eAudio unit (via the RCA inputs) for the sake of comparison—bearing in mind that the latter lacks a bypassable volume circuit, which acts as a "handicap" for measurements (as a reminder, every circuit component generates "noise," including the layout and the traces themselves, since it is a PCB).

At least this one might not suffer from gain mismatch issues at low volume levels

 

[ICIETDIYEUR]

People hi

I mentioned earlier the choice of an op-amp better suited to the circuit, so I am sharing my thoughts based on observations from the PCB images, the circuit schematic that can be inferred from them, and informative tables regarding op-amps.

Here is a fairly clear photo that confirms the input impedance applied to one of the op-amp inputs ->

Here, then, is the schematic that can be derived for this amplifier: it is used in most—if not all—Class D amplifiers employing one or more TPA3255 chips ->

Two things can already be observed:
- The input impedances at the inputs of the op-amp used are not equal.
- The input impedance is quite high (10 kΩ).

Here is a brief explanation from Texas Instruments regarding this matter, to clarify what follows concerning the choice of op-amp to use ->

In the case of this amplifier, it appears that Texas Instruments points us toward a JFET or FET-type op-amp rather than a bipolar one—as clearly demonstrated by their table—while also taking into account the applied input impedance.

Here, then, is a table showing the THD+N achieved based on input impedance and the op-amp model used ->

However, in Hi-Fi, frequency also comes into play, since we are listening to a frequency-modulated signal; therefore, to better determine which op-amp will respond best to this modulation, a higher impedance is deliberately applied to make the distortion stand out more clearly across different frequencies ->

Based on your observations, I will leave it to you to choose the op-amp that seems best suited for this circuit.

Note: This is a purely theoretical demonstration, as no measurements have been performed on the amplifier in question (the BRZHIFI PAD-30)—simply because I do not yet have it in my possession. However, by relying on sound theory and using known, proven models—that is, objective data—there is very little chance of obtaining poor results

 

[ICIETDIYEUR]

People hi

@ krisdeak :

Thank you for sharing your photos.

Could you let us know the values marked on the capacitors, as well as their diameter (in millimeters)?

Thank you in advance for your reply

 

[ICIETDIYEUR]

Would really like to see some measurements. If it's better than the Fosi v3 stereo in the same price region. Or closer to the 3e audio A7 amps.

I see the Brzhifi offer available to order on Ali atm.

Hi

So, will you be waiting for measurements to compare with the 3eAudio unit before making your choice?

I’ll go out on a limb here and say that the difference revealed by measurements will be completely inaudible when comparing the devices.

However, what you *will* certainly notice is the money left (or not) in your pocket depending on which one you choose—and you’ll see this very objectively, without needing to perform any complex measurements or calculations, even theoretical ones...

 

[Bleib]

Now, if we had arranged for one to be sent to Amir... we'd know
There was the idea before if 10 people contributed 10 USD each he could purchase it..

 

[john61ct]

Put me down as yes, pending reaching $90

 

[ICIETDIYEUR]

Do you honestly think Amirm is worried about a hundred dollars?

The same goes for BRZHIFI; they only need to send a single unit from their production run. They get publicity here at no cost to them, and "ASR" is quite influential when it comes to the sales volume of the devices tested