Fosi v3 Mono | TPA3255 PFFB | Balanced | [First Look from Fosi FB]

[Doodski]

But... but... my car can go 180 MPH! (not really) That would be a capability that you cannot take advantage of. Cool to have, but useless.

I know all this and am simply having fun poking fun... I barely walk fast now never mind drive fast.

Do you have a 2 Ohm load to drive with this amplifier? If the answer is YES, then buy it! If not, there seems to be no real good reason to do that...

Yeah, yes and no I think sometimes but not always. To have a low Z drive is great because of improved dynamic range and having power for transients due to a low source impedance evan if 2 Ohms is not part of the load's Z. I am splitting hairs of course but if me I like to have that.

 

[charlielaub]

I would not worry about the source impedance in this case. It's not stated explicitly but if it were not very small there would be more of a difference in the low and mid frequencies between the output level for 4 and 8 Ohm loads due to the amplifier output impedance being in series with the load.

Dynamic range and power for transients has nothing to do with "low Z drive" or low source impedance. Maybe you are thinking about some amplifier (e.g. like a tube or SET amp) with a relatively large output impedance. This is a solid state class-D amp and output impedance is very low.

 

[Doodski]

I would not worry about the source impedance in this case. It's not stated explicitly but if it were not very small there would be more of a difference in the low and mid frequencies between the output level for 4 and 8 Ohm loads due to the amplifier output impedance being in series with the load.

Dynamic range and power for transients has nothing to do with "low Z drive" or low source impedance. Maybe you are thinking about some amplifier (e.g. like a tube or SET amp) with a relatively large output impedance. This is a solid state class-D amp and output impedance is very low.

Hmmz. I like this kind of information because #1 - My imagination is in full use trying to put all the technical theory together into a systematic approach that makes sense and #2- I really need to bounce details and ideas off other experts and advanced experts so I get better fundamentals of theory knowledge.

I would not worry about the source impedance in this case. It's not stated explicitly but if it were not very small there would be more of a difference in the low and mid frequencies between the output level for 4 and 8 Ohm loads due to the amplifier output impedance being in series with the load.

I understand the divider effect when in series and if I dig deep after a few moments I get how the frequency response can change but here's the clincher for me... Why the low and mid frequencies? Does that depend on the reactance and how do we know if it's capacitive or inductive reactance?

 

[ban25]

We may be months away from formal purchase/release date at this point.

If you don’t mind me asking, aren’t you happy with ZA3?

I only bought the ZA3 to toy with. Perhaps I'll find a use-case for it down the line.

 

[charlielaub]

I understand the divider effect when in series and if I dig deep after a few moments I get how the frequency response can change but here's the clincher for me... Why the low and mid frequencies? Does that depend on the reactance and how do we know if it's capacitive or inductive reactance?

There is a different effect that causes these class-D amplifiers to have different high frequency responses under different load conditions, eg. above 5k Hz for 8 Ohms there is sometimes a rising response that is peaking around 20kHz at up to 3 dB, and that is why I left out high frequencies. The TPA3255 amps that use PFFB will not have this problem either.

Neither of these things are related to the load reactance. Load reactance (capacitive or inductive) influences the max power delivery a bit but not the frequency response.

 

[charlielaub]

Don't get me wrong, this seems like it will be a great amplifier. It's just that to me it seems many people do not understand what extra capabilities it offers over the stereo TPA3255 with PFFB and why it might not make sense to get this particular amp. I build my own loudspeakers and it would be great to have a low cost amp like this that can deliver a lot of power into 2 Ohms. This gives me the option to use some paralleled woofers, for example, that would be a challenging load for many other amps. For a 4 Ohm or 8 Ohm load this amp would work great, but not all that much better than a stereo amp (for example the AYIMA A70 that was recently reviewed on this site) that might cost about the same as one mono amp but give you twice as many channels of amplification.

 

[Doodski]

There is a different effect that causes these class-D amplifiers to have different high frequency responses under different load conditions, eg. above 5k Hz for 8 Ohms there is sometimes a rising response that is peaking around 20kHz at up to 3 dB, and that is why I left out high frequencies. The TPA3255 amps that use PFFB will not have this problem either.

Neither of these things are related to the load reactance. Load reactance (capacitive or inductive) influences the max power delivery a bit but not the frequency response.

OK. Thanks. That makes sense and explains the void in my working knowledge. Thanks for taking the time to explain that stuff.

 

[TonyJZX]

these guys need to show us the matching analog preamp

also people are waiting for the companion stereo XLR pffb model

i feel like a monoblocks may be a step too far when an 75w or so stereo pffb model would be enough

 

[Sokel]

As a side note all these specs listed above are affected by the thermal design.
You can have a look at the TI forum for guides but is easy to calc losses based on specs and efficiency.

As power goes up needs are different.

 

[sejarzo]

For a 4 Ohm or 8 Ohm load this amp would work great, but not all that much better than a stereo amp (for example the AYIMA A70 that was recently reviewed on this site) that might cost about the same as one mono amp but give you twice as many channels of amplification.

That was another consideration for me. I'm an engineer so value always factors in my purchases...which also explains why I find it hard to believe he number of pricey DACs I see folks run through in the classifieds on other audio sites.

 

[daniboun]

i feel like a monoblocks may be a step too far when an 75w or so stereo pffb model would be enough

This new Fosi is operating in PBTL. (Mono). That only brings about 30% more power under 4R and more or less 10% under 8R vs BTL (Stereo).
So the main interest here it is drive 2R loads...

I would wait for the Stereo version instead... This new Mono PFFB has a limited interest....
You can read the review between the 3E Audio Mono PFFB vs the Stereo PFFB to understand this point.

 

[ban25]

This new Fosi is operating in PBTL. (Mono). That only brings about 30% more power under 4R and more or less 10% under 8R vs BTL (Stereo).
So the main interest here it is drive 2R loads...

I would wait for the Stereo version instead... This new Mono PFFB has a limited interest....
You can read the review between the 3E Audio Mono PFFB vs the Stereo PFFB to understand this point.

One of my ideas for this monoblock is to use it to drive a center channel in the case where I already have another 2-channel amp driving FR/FL.

 

[Tangband]

Here's another analogy about the mono TPA3255 mode: It's like asking the question of whether you should put a big spoiler on your car. Sure, a spoiler will indeed help with downpressure and traction and will look COOL! But not really until you reach 100 mph, and since you can never really drive that fast (at least where I live) it's not going to actually provide much tangible benefit. In the same sort of way, the mono mode TPA3255 is not going to make a difference compared to the same (e.g. PFFB enabled) TPA3255 stereo amp for almost all conditions and most all home audio speakers.

Apart from the advantage of infinite channel separation with a mono poweramp ….The mono power amp will have separate power supplies for the two stereo channels - in an ordinary stereo tpa3255 the powersupply at 32V 5A will be shared by two channels, having only 2.5A per channel at full blast, both channels.

So there is a real benefit with mono poweramps in this case because the current capability is in reality doubled.

 

[lewdish]

i wanna just be able to join them together some how in 1 box

 

[TonyJZX]

i think having a combined XLR + RCA 'mix' function would be nice but its a kind of niche feature and would possibly have some nasty effects if not done right

 

[charlielaub]

Apart from the advantage of infinite channel separation with a mono poweramp ….The mono power amp will have separate power supplies for the two stereo channels - in an ordinary stereo tpa3255 the powersupply at 32V 5A will be shared by two channels, having only 2.5A per channel at full blast, both channels.

So there is a real benefit with mono poweramps in this case because the current capability is in reality doubled.

Who would use such a weak power supply for a stereo TPA3255 amp??? Voltage is far below what the chip can handle and current capability is also very anemic. I use a 48V, 500W or 1kW SMPS!

 

[Fleuch]

I have become uneasy with Topping's reliability record as of late, so their products are off my list of potential buys.

There are also Topping products "missing in action"; it is confidence in Topping as a company that has become a problem, as well as product reliability.

Quoting from the ASR review by Amirm (https://www.audiosciencereview.com/forum/index.php?threads/tp-ra3-rackmount-amplifier-review.46085/) of the TP RA3 Rackmount Amplifier suppliedby the company, "This line of products, at least for now, will be sold by Topping direct. Alas, it is not yet on the website so you may have to wait a bit to order it." The Topping Audio Store on AliExpress note "Sorry, this item is no longer available!" (https://www.aliexpress.com/item/1005005787838746.html), although it still offers the Topping RD3 Rackmount DAC (https://www.aliexpress.com/item/1005005791366431.html), also reviewed by Amirm (https://www.audiosciencereview.com/forum/index.php?threads/topping-rd3-tp-balanced-dac-review.47196/).

Up till now, neither product has appeared on any of the Topping websites (https://www.toppingaudio.com/, https://www.tpdz.net/index, https://topping.pro/, etc), meaning there is no technical support available.

Both products were "announced", but not on Topping's own websites, with only a small number of products available on AliExpress, which fails to generate any degree of confidence for a prospective purchaser - of any Topping product!!

 

[Fleuch]

I don't need a new amp immediately, and if two of these cost under $350 with equal performance to the $440 or so alternatives, they are in the mix.

It is reasonable to suggest that a V3 mono with PFFB should not cost appreciably more than the current stereo V3.

The Texas Instruments Application Report on Post Filter Feedback (for the TPA324x and TPA325x series) shows a total of nine components (five resistors and four capacitors) forming the feedback network.

Given that this is a Mono product there will be fewer components required than for the existing stereo V3.

It is difficult to understand why there should be a price hike from the existing $90 / $110 for the stereo V3 to the $175 mentioned above.

The elevated price of the Ayima A70 is unacceptable in comparison with the Ayima A07MAX.

 

[Guddu]

It is reasonable to suggest that a V3 mono with PFFB should not cost appreciably more than the current stereo V3.

The Texas Instruments Application Report on Post Filter Feedback (for the TPA324x and TPA325x series) shows a total of nine components (five resistors and four capacitors) forming the feedback network.

Given that this is a Mono product there will be fewer components required than for the existing stereo V3.

It is difficult to understand why there should be a price hike from the existing $90 / $110 for the stereo V3 to the $175 mentioned above.

The elevated price of the Ayima A70 is unacceptable in comparison with the Ayima A07MAX.

*** I am not suggesting if the said price is justifiable or not.

Additional components isn't the only factor, there are many other factors as well in the mix and engineering/investigation efforts add up to the cost.
Having said that, pls don't get me wrong, I am in the same boat as you or another enthusiastic and would love a product (that I need) for lowest price possible.
But then I am an engineer and understand the money/profit is one big factor deriving improvements or developments.

 

[312elements]

It is reasonable to suggest that a V3 mono with PFFB should not cost appreciably more than the current stereo V3.

The Texas Instruments Application Report on Post Filter Feedback (for the TPA324x and TPA325x series) shows a total of nine components (five resistors and four capacitors) forming the feedback network.

Given that this is a Mono product there will be fewer components required than for the existing stereo V3.

It is difficult to understand why there should be a price hike from the existing $90 / $110 for the stereo V3 to the $175 mentioned above.

The elevated price of the Ayima A70 is unacceptable in comparison with the Ayima A07MAX.

The actual cost of the parts is only one variable in determining the sell price of product or service. A smart company will charge what the market will bear. You get to influence that by choosing to buy or not buy, but the market as a whole will dictate the price.