BerryBak BVS2300 2-channel TPA3255 power amp module

[BossBunos]

Thanks for this review/work!
Good to see a measurement of these diy boards. Was wondering about them for some time now. I agree it's quite a nice deal for diy. 3E sells the pffb and much better measuring modules for roughly twice the price. Nice to have options!

 

[MCH]

This question is to be addressed to the designer of the module.

My thoughts:

• older implementations of TPA3255 (and this is probably one of them, though the manual is dated year 2023) did not use PFFB and there is still a plenty of modules without PFFB on the market,
• design cost reason, just take the TI EVM board design (published July 2016), and you are done, without further R&D costs,
• PFFB design with TPA3255 is not without possible stability issues (depending on complex load impedance) and again you need time to tune it.

All and all, successful PFFB design (if you do not do a mere unscrupulous copy of another existing design) reflects in higher price (see here) and probably is not requested for a mass budget product.

Interestingly, Texas Instruments speaks about PFFB as a way to reduce costs, by achieving decent results when using lesser inductors (which carry a good chunk of the cost of the original suggested designs)

 

[pma]

PFFB design with TPA3255 is not without possible stability issues (depending on complex load impedance) and again you need time to tune it.

This is a note from TI SLAA788A Application Report (March 2018):

 

[pma]

Interestingly, Texas Instruments speaks about PFFB as a way to reduce costs, by achieving decent results when using lesser inductors (which carry a good chunk of the cost of the original suggested designs)

But they say nothing about R&D costs to make it properly. Like including ESR, Q, etc. into the PFFB design. Another coil manufacturer, another parameters.

Without R&D, you can make it all in one person together with putting it into production. You can do it in one person all, but then you probably end up with a small-lot production.

 

[MCH]

But they say nothing about R&D costs to make it properly. Like including ESR, Q, etc. into the PFFB design. Another coil manufacturer, another parameters.

Sure, they just show what is possible. Then, I guess, above a certain volume, all those costs might be easy to offset....

 

[pma]

Then, I guess, above a certain volume, all those costs might be easy to offset....

.... if it is considered to be necessary. It is just business.

Anyway, stability is probably the strongest point of the non-PFFB design. A non-PFFB design will always be more stable into load with very high capacitive impedance, by nature of feedback. This is proven when testing TPA3255, Ncore and Purifi with 8ohm//2uF load.

 

[daniboun]

For almost the same price I would get this Tpa3255 PFFB module full balanced

New Dual TPA3255 Module + PFFB / Fully differential / OP amps DIP8 @ Great price

Hi amigos, As usual, I'm sharing my little discoveries from the web. I made a good find, so I'm sharing it. I found a TPA3255 dual chip module with PFFB and DIP8 op amps at a pretty good price! SPEC : Dual Chip TPA3255 (PBTL) Version A : Fully Balanced Version B : SE inputs Power : 150W / 8R...

www.audiosciencereview.com

See attached file for measurements

 

[NTTY]

Thanks for the review and all associated hard work Pavel! Very interesting.

I’m thinking of reviewing amplifiers so I’m learning here

I see the SINAD is calculated with 20dB headroom at the input of the ADC. You might want to toggle the "Apply ENOB calculation" in RTA distorsion window so it shows the real value using the carrier as the reference of max amplitude, not the one of the ADC.
Also, what FFT size do you use, 64k, right?

With -20dB from max of the 1kHz carrier, it means the ADC Cosmos has a SINAD reduced by the same, not an issue looking at the profile of the noise coming from this amplifier, but would it be worth thinking of a buffer to increase the gain before entering the ADC, like the cosmos scaler (but not enough voltage input for this one of course)?

Thank you again!

 

[pma]

With -20dB from max of the 1kHz carrier, it means the ADC Cosmos has a SINAD reduced by the same, not an issue looking at the profile of the noise coming

All true, but as you have said, in case of this specific amplifier the Cosmos dynamic range reduction is no issue, still we are more than 20dB better than the DUT. In case of better amplifiers I change input dividers to get maximum range. I am limited at about 118 - 120 dB SINAD measurement of amplifiers.

It is the output impedance measurement of the BTL amp with CMV = Vdd/2 that has been a challenge (solved already). Everything must be floating then.

 

[pma]

To demonstrate output impedance effect to frequency response with the real speaker, I am posting a result with my CNO-T25 speaker.

 

[torgeirs]

The LF distortion (0.3% at 20Hz) would be in any case inaudible and masked by speaker.

One problem with using it in a sub is the LF eqing often done at 20Hz.
The sub may give low output at 20Hz but 40hz and 60hz distortion components from caps gets full output from speaker element.
So distortion is not masked by fundemantal

 

[DonH56]

Hello Don and thanks for your comments. Some time ago I posted here LF distortion from various types of capacitors, including high K ceramics. And also a review of PRE-TC10, which is a nice product, unfortunately degraded by use of ceramics in the EQ circuit, as also described in the publications posted by @sam_adams .

Thanks again! I did a little digging and it jogged my memory. LF noise, and LF phase noise for things like RF mixers and PLL circuits, is a huge problem with unbiased (or improperly biased) electrolytics and tantalums, and voltage nonlinearity/piezo effect in ceramics kills LF performance. Memory be slipping in my old age... Trust you to have taken the measurements!

I also agree with your comments about PFFB; given an unknown and widely varying load (the speaker), maintaining amplifier stability is key especially for an inexpensive product. Can't afford a lot of returns, let alone a reputation for blown amplifiers and speakers, and the cost of added components adds up over many units.

 

[ObjectiveSubjectivist]

For the price it seems to be nice.

 

[pma]

To demonstrate output impedance effect to frequency response with the real speaker, I am posting a result with my CNO-T25 speaker.

For the reference and better view, below is the measured complex impedance of the CNO-T25 speaker:


Above 5kHz (critical range considering BVS2300 inductive output impedance rising with frequency), the CNO-T25 impedance is almost resistive with abs(Z) = 11 ohm approx. As such it does not affect frequency response of the BVS2300 much up to 20kHz (+0.6dB/20kHz). Above 20kHz, the rise of FR plot is evident (+3.5dB/40kHz), however I do not know if it may have any audible effect. Output impedance of the BVS2300 module is shown in the post #1 of this thread.

I also measured THD vs. frequency at amplifier output terminals with the CNO-T25 speaker, at 2.5V output voltage level and 45kHz bandwidth, and compared it to the plot measured with 4.7 ohm resistor. They almost overlap.

 

[pma]

Finally, I did some listening during weekend days, with Marantz SA7001 as a source, optical to DX5 and then to BerryBak, and CNO-T25. Listening to jazz, rock and classical music. I have no objections. There is more than enough power, bass is tight, the sound is transparent. No clicks during turn-on and turn-off, at least in my implementation.

 

[eric00886]

Berrybak/Sure/Wondom make several TPA3255 models based on this board. In the US, I see the BDM-8 with Bluetooth and DSP/PC interface for $39 on Amazon. Also the BDM-8a, with no Bluetooth or DSP for $21 (after 40% coupon on page). There may well be other differences.

The Amazon offerings have a fan which I understand seldom fires up at all except under high load and may not be necessary in most applications.

Wondom is about to ship a model JAB6 dual TPA3255 PFFB board with docking/replaceable DSP and Bluetooth modules that looks interesting.

Spot on! Wondom's been in the Class-D game for ages. I’ve picked up a few of their boards, and honestly, they actually design their stuff properly—not like those cheap Taobao randoms that just sell whatever makes a sound. That said, I did get one from them where the BT and RCA channels were swapped L/R, so there's that lol.

If they actually drop a TPA3244 PFFB, I’m definitely hyped for it!

 

[pma]

This one (the DUT) is also apparently Wondom (post #1), and advertised as sure-electronics. The original BerryBak manual is from Malaysia and they say they do not provide any services for sales, shipping, or manufacturing from other regions. The manual is attached. There are some contradictions, like they declare 300W/4W power and "Specifications typical @ +25°C, Powered by 36V DC, unless otherwise noted", which is impossible, to get 300W/4R from 36V supply in BTL. It is also impossible to get it from 48Vdc (module maximum) supply, even if they specify the power at 10% THD. Manuals of such manufacturers are full of incorrect data.

 

[daniboun]

Spot on! Wondom's been in the Class-D game for ages. I’ve picked up a few of their boards, and honestly, they actually design their stuff properly—not like those cheap Taobao randoms that just sell whatever makes a sound. That said, I did get one from them where the BT and RCA channels were swapped L/R, so there's that lol.

If they actually drop a TPA3244 PFFB, I’m definitely hyped for it!

I thought this might interest you... the BRU5 amp based on the TPA3244 has a DSP inside (but no PFFB design)
I've read a good things about this little amp...

https://www.ebay.com/itm/354744405729

 

[eric00886]

I thought this might interest you... the BRU5 amp based on the TPA3244 has a DSP inside (but no PFFB design)
I've read a good things about this little amp...

https://www.ebay.com/itm/354744405729

Haha, that's the one! The RCA and Bluetooth channels are flipped on this. I wonder if they ever fixed it in later revisions.

As for the 'DSP' feature—it’s basically just fancy EQ adjustments.

 

[GGroch]

As for the 'DSP' feature—it’s basically just fancy EQ adjustments.

I suppose, that's kind of what DSP is.
There is a substantial thread on the TPA3255 version here for those who have not seen it.

The supplied ACPWorkbench PC software allows for stereo parametric EQ, plus adjustments for dither noise, noise cancelling etc. Owned two and was able to set them up as active crossovers for a stereo pair of speakers. They are limited as the DSP processing ( ADAU1701) is not sophisticated.

Like most Wondom stuff, they were not not designed for optimal measurements. I could hear hiss 6" from the speaker. But still they sounded great to me in normal use. Not distinguishable from other TPA3255 amps. Except of course that with REW or other Room EQ software you can better match your speakers to the room. For $50 (plus the cost of a power supply) it gives a hobbyist who does not want to solder a lot of tweaking fun.

On the other hand, my ears are old and I cannot hear the difference between High End DACs fed through a comparator box