Fosi Audio BT30D PRO TPA3255 "Subjective review"

[Soulsounds]

Somebody notice that the bt30d pro on Bluetooth mode sounds very low compared to the rca input or its normal?

how can I fix that? That remind me the A04 problem that was fixed removing 2 electric resistance to the board.

 

[Ultratek]

Gracias por mencionar que Fosi Audio BT30D PRO es un amplificador TPA3255, adopta 2 piezas de TPA3255, aquí está el último manual .

Y gracias por la sugerencia de nuestros clientes, ahora estamos desarrollando la versión de 48V de BT30D PRO.

Te agradecería si pudieras enviar fotos en alta resolución de la placa completa Hi-Fi Fosi Audio BT30D PRO TPA3255 al foro
Sería interesante ver los componentes internos.

 

[tktran303]

What is the slope of the filter on the subwoofer channel? 1st order or 2nd order or 4th order? Linkwitz Riley?

 

[SWSL]

Te agradecería si pudieras enviar fotos en alta resolución de la placa completa Hi-Fi Fosi Audio BT30D PRO TPA3255 al foro
Sería interesante ver los componentes internos.

Found on this site posted by another. I also had ours apart to drill out ventilation holes. The large black capacitors are rated 50V.
Lo encontre aqui en el foro. Tambien dearmamos nuestro para poner huecos de ventilacion. Las capacitores negras grandes son de 50V.

 

[Ultratek]

View attachment 278814
Encontrado en este sitio publicado por otro. También tuve el nuestro aparte para perforar agujeros de ventilación. Los condensadores negros grandes tienen una clasificación de 50 V.
Lo encontre aqui en el foro. Tambien dearmamos nuestro para poner huecos de ventilacion. Las capacitores negras grandes son de 50V.

SWSL gracias por la imagen, pensé que ya nadie contestaría.
A veces me pregunto porque este tipo de Amp Clase D basados en TPA3255 x2 son tan limitados ya que soportan fácilmente 48V hasta 53v de operación con picos de 63V según documentos de Texas Instruments; ¿Será que las distorsiones, las temperaturas extremas, las pérdidas, etc. empiezan por encima de esos 36V, o simplemente se reservan para futuros productos de mayor potencia y más caros?
No puedo ver la marca/calidad de los condensadores de 50v, ni el opa que calculo debe ser el NE5532 sin enchufe dip8 para jugar con algun LM4562 u otro, una verguenza.

¿Existe una lista de cambios/bricolage/actualizaciones recomendadas para mejorar esta placa amplificadora?

 

[SWSL]

SWSL gracias por la imagen, pensé que ya nadie contestaría.
A veces me pregunto porque este tipo de Amp Clase D basados en TPA3255 x2 son tan limitados ya que soportan fácilmente 48V hasta 53v de operación con picos de 63V según documentos de Texas Instruments; ¿Será que las distorsiones, las temperaturas extremas, las pérdidas, etc. empiezan por encima de esos 36V, o simplemente se reservan para futuros productos de mayor potencia y más caros?
No puedo ver la marca/calidad de los condensadores de 50v, ni el opa que calculo debe ser el NE5532 sin enchufe dip8 para jugar con algun LM4562 u otro, una verguenza.

¿Existe una lista de cambios/bricolage/actualizaciones recomendadas para mejorar esta placa amplificadora?

Es una pregunta porque no 48v. Ya hice y me contestaron x los capacitores pero no parece. Yo sigo con la idea que la verdad es porque los estan vendiendo con 3251 y no 3255. O tal vez estoy equivocado. Hubo fotos de adentro sin "heatsink" pero no los puedo ver. De todos modos es chip de calidad y con una fuente de 36 v x 10 a va a rendir muy muy bien. Rinde bastante bien con su fuente de 32v x5 a que tengo ahora. Tambien puedo comentar que si quiere ventilacion extra si lo vas utilizar con volumen alto.

 

[Ausmith]

I'm adding my experience here with this amplifier. The 2 channel portion of the amp does seem to do a good job. Very low noise floor, plenty of power for my application, and the fit/finish is good.

The .1 , or subwoofer, implementation seems suspect to me. I'm not sure if I have a bad unit or if they just missed the boat on their low pass filter implementation. Attached here is a frequency response graph (nearfield measurements) of a small sealed subwoofer. One measurement is using the Fosi amp with the "sub freq" knob turned to the middle position.... which should provide a low pass filter around 80Hz. The other measurement is of the same subwoofer using a different 2.1 class d amp and the shape of that curve is what I would expect. The Fosi amp seems to implement a ~10dB gain from 15Hz - 50hz. Depending on your set-up you could cause damage the woofer

I've written to Fosi asking for an explanation.

 

[GrayA]

I'm adding my experience here with this amplifier. The 2 channel portion of the amp does seem to do a good job. Very low noise floor, plenty of power for my application, and the fit/finish is good.

The .1 , or subwoofer, implementation seems suspect to me. I'm not sure if I have a bad unit or if they just missed the boat on their low pass filter implementation. Attached here is a frequency response graph (nearfield measurements) of a small sealed subwoofer. One measurement is using the Fosi amp with the "sub freq" knob turned to the middle position.... which should provide a low pass filter around 80Hz. The other measurement is of the same subwoofer using a different 2.1 class d amp and the shape of that curve is what I would expect. The Fosi amp seems to implement a ~10dB gain from 15Hz - 50hz. Depending on your set-up you could cause damage the woofer

I've written to Fosi asking for an explanation.

Fosi told me sub frequency middle position is 150Hz. If you want to test 80Hz, you'd have to ask if that's 7am or 8am. They said:

9am: 100Hz
10am: 110Hz
11am: 130Hz
12pm: 150Hz
1pm: 170Hz
2pm: 190Hz

 

[SWSL]

I'm adding my experience here with this amplifier. The 2 channel portion of the amp does seem to do a good job. Very low noise floor, plenty of power for my application, and the fit/finish is good.

The .1 , or subwoofer, implementation seems suspect to me. I'm not sure if I have a bad unit or if they just missed the boat on their low pass filter implementation. Attached here is a frequency response graph (nearfield measurements) of a small sealed subwoofer. One measurement is using the Fosi amp with the "sub freq" knob turned to the middle position.... which should provide a low pass filter around 80Hz. The other measurement is of the same subwoofer using a different 2.1 class d amp and the shape of that curve is what I would expect. The Fosi amp seems to implement a ~10dB gain from 15Hz - 50hz. Depending on your set-up you could cause damage the woofer

I've written to Fosi asking for an explanation.

I have a couple of questions about the measurements. Probably my ignorance but anyway;

- why does the second amp show such a shallow drop in gain above the peak (crossover ) point? Is it not a low pass filter? Very low slope, right?
- how do you actually know what the crossover point is for the Fosi? or for either? - By measuring the peak, I would think. Wouldn't the graph be the best way to know?
- how do you know that the reference amp is flat?

So the primary difference is that the Fosi is set at a lower crossover point than the other? That is, the Fosi crossover point is at 70 hz and the other is at 112 or higher?
Would the best way to compare (in my admitted ignorance) be to set the peaks to align and then compare the curves?

I know that the idea that 12 o'clock might be 70 hz setting conflicts with what Fosi told Gray A., but it seems that the proof is in the measurement and that the knobs may not be calibrated nor the pots consistent anyway. Nor is Fosi's information necessarily correct.

 

[WinWiz]

We have plans to make a three channel amplifier indeed, but it is not the same as your idea.

Yours have just two channels out, right? The right channel goes to the right speaker, and the left channel goes to the left speaker, and then you connect both right and left channel to your center speaker. Am I correct?

This can be done too, but I think it is not friendly to users, I may make three channels out, right channel for speaker, left channel for left speaker and a center channel for center speaker.

I have ordered the BT20A pro. But have realized mono would probably fit my need better. Plan is to power 4 pcs markaudio 3" fullrange woofer ceiling installed in a small rectangular room.
So connecting both L+ and R+ to the positive connector on a speaker is possible without shorting and destroying the amp?
What is the minimum allowed impedance in such a configuration?

 

[chitodb]

Thank you for refering that, Fosi Audio BT30D PRO is a TPA3255 amplifier, it adopts 2 pcs of TPA3255, here is the lastest manual.

And thanks for our customers' suggestion, we are developping the 48V version of BT30D PRO now.

Hey Fosi,
When are you coming out with a TPA3255 amp with optical input and remote control?

 

[Fosi Audio]

Hey Fosi,
When are you coming out with a TPA3255 amp with optical input and remote control?

Thanks for your attention, we will release one with optical input but no remote control in about August, and with both optical input and remote control will be released in about October.

 

[grogi.giant]

I'm adding my experience here with this amplifier. The 2 channel portion of the amp does seem to do a good job. Very low noise floor, plenty of power for my application, and the fit/finish is good.

The .1 , or subwoofer, implementation seems suspect to me. I'm not sure if I have a bad unit or if they just missed the boat on their low pass filter implementation. Attached here is a frequency response graph (nearfield measurements) of a small sealed subwoofer. One measurement is using the Fosi amp with the "sub freq" knob turned to the middle position.... which should provide a low pass filter around 80Hz. The other measurement is of the same subwoofer using a different 2.1 class d amp and the shape of that curve is what I would expect. The Fosi amp seems to implement a ~10dB gain from 15Hz - 50hz. Depending on your set-up you could cause damage the woofer

I've written to Fosi asking for an explanation.

Crossover handling looks perfectly fine to me. There is -3dB at the crossover plus further ~18dB/octave (which is a bit high, typically it's 12dB, but maybe your subwoofer adds addition filtering here) attenuation above. It is the other amp looks that looks has no LPF applied at all.

There is however no HPF in bass channel nor over-excursion protection with this amp, that's for sure.

 

[johnlevmason]

Hi FOSI, I currently have a Klipsch Icon SB1, powered sound bar and wireless sub. I have this on my back screen porch with only a Auris Bluetooth receiver connected to the sound bar. I play music from my phone, sounds great. I want to add 2 speakers to the porch to this current set-up and use a FOSI amp to power the 2 additional speakers. Here is where my knowledge starts to decline, even after researching online. The Klipsch bar has the following inputs, Analog RCA input and a Digital Optical cable input. Can I use a RCA cable from the Klipsch and plug into the Line In RCA on the FOSI and add 2 wired speakers to the FOSI, and stream music with all of it working together? Or would the Klipsch need to go into an Output RCA on a FOSI amp and not Input? Or neither, and what I am trying to accomplish will not work? Looks like you have a great line of amps, looking forward to getting one. Thank you,

 

[WinWiz]

Hi FOSI, I currently have a Klipsch Icon SB1, powered sound bar and wireless sub. I have this on my back screen porch with only a Auris Bluetooth receiver connected to the sound bar. I play music from my phone, sounds great. I want to add 2 speakers to the porch to this current set-up and use a FOSI amp to power the 2 additional speakers. Here is where my knowledge starts to decline, even after researching online. The Klipsch bar has the following inputs, Analog RCA input and a Digital Optical cable input. Can I use a RCA cable from the Klipsch and plug into the Line In RCA on the FOSI and add 2 wired speakers to the FOSI, and stream music with all of it working together? Or would the Klipsch need to go into an Output RCA on a FOSI amp and not Input? Or neither, and what I am trying to accomplish will not work? Looks like you have a great line of amps, looking forward to getting one. Thank you,

Your soundbar probably does not have any outputs.
If the fosi amps line out is fullrange you could connect it like this:
From BT receiver output -> fosi amp input. Fosi amp output -> soundbar input.

If the fosi amp out line is not fullrange you could connect it like this:
BT receiver output -> rca Y cables -> fosiamp & soundbar.

Either way the soundbar probably adds some delay. So audio from fosi amp and soundbar might not be 100% in sync.
This could be problematic but really depends on the amount of delay and the distance from your listening position in relation to the various speakers. If you hear echo effect or uneven frequency response caused by soundwave cancelation you probably need a dsp to timealign soundbar and amp.

 

[johnlevmason]

Your soundbar probably does not have any outputs.
If the fosi amps line out is fullrange you could connect it like this:
From BT receiver output -> fosi amp input. Fosi amp output -> soundbar input.

If the fosi amp out line is not fullrange you could connect it like this:
BT receiver output -> rca Y cables -> fosiamp & soundbar.

Either way the soundbar probably adds some delay. So audio from fosi amp and soundbar might not be 100% in sync.
This could be problematic but really depends on the amount of delay and the distance from your listening position in relation to the various speakers. If you hear echo effect or uneven frequency response caused by soundwave cancelation you probably need a dsp to timealign soundbar and amp.

Thanks for your response and information, much appreciated. Correct, the Klipsch bar doesn't have an output, it's just labeled as RCA Input. I was just trying to use what I have and add a few more speakers to the experience sitting out there, but sounds like in order to do so, probably should entertain a different path. Thanks again.

 

[WinWiz]

Thanks for your response and information, much appreciated. Correct, the Klipsch bar doesn't have an output, it's just labeled as RCA Input. I was just trying to use what I have and add a few more speakers to the experience sitting out there, but sounds like in order to do so, probably should entertain a different path. Thanks again.

Thinking about it a soundbar developed to work with a TV should have minimal delay. So it will probably work fine together with an amp like the bt30d pro. The 3.5MM preout is fullrange so you should only need a 3.5mm -> rca cable for the connection.
But bt30d pro is a 2.1 amp. Your sub is active (internal amp) so you only need a 2.0 (regular stereo) amp -like the fosi v3 or bt20a pro (if you want tone controls)

 

[johnlevmason]

Awesome, thanks for the additional info. I am old school and just trying to create my own "wall of sound" of sorts from the 70's if you will. I love my music and have newer components from the last 5-10 years,.... Denon integrate amp, etc, etc, ( which the newer stuff doesn't compare to my 1977 mint condition Yamaha CR-1020, period) ...all this is not the kind of gear I want on the back porch, which is where the FOSI comes in and trying to combine the horn tweeter Klipsch sound bar with some additional speakers. I just don't know enough of the detailed newer tech and how it all flows together. So I really appreciate the follow-up and passing along some knowledge, big help and Grateful!

 

[Habiff753]

Thank you for your suggestion, we will consider it carefully and let you know when we have a decision.

For the specs, it's ±12dB for Bass control and ±6dB for Treble control.

Can I connect a passive speaker (to be used as center) to the passive subwoofer output terminal? Can I still hook up my active sub using the pre-out if I do this? I am trying to create a 3.1 set-up using the BT-30D Pro amp. Thanks!!

 

[grogi.giant]

Can I connect a passive speaker (to be used as center) to the passive subwoofer output terminal? Can I still hook up my active sub using the pre-out if I do this? I am trying to create a 3.1 set-up using the BT-30D Pro amp. Thanks!!

No, you can't do this.