Fosi Audio BT30D Pro review

[OllieHardy]

What is the difference between "SUB OUT" and "PRE OUT" of the two amps? Is it just about having / not having the low-pass filter? I mean, would it be a good idea to connect an active subwoofer to the PRE OUT port?

I bought both models and from what I can see so far , I can only control the volume and frequency of the active sub using the standard model's RCA out. The preout of the pro model isn't letting me control the active sub. I am using the same RCA but with a 3.5mm adapter. Any advice on controlling the sub directly from the fosi amp from anyone in the know would be appreciated @Fosi Audio

 

[Fosi Audio]

I bought both models and from what I can see so far , I can only control the volume and frequency of the active sub using the standard model's RCA out. The preout of the pro model isn't letting me control the active sub. I am using the same RCA but with a 3.5mm adapter. Any advice on controlling the sub directly from the fosi amp from anyone in the know would be appreciated @Fosi Audio

Yes, through the pre-out port, we can only control the subwoofer's volume from the amp. We've marked down your concern and we will consider modifying the design in the future.

 

[OllieHardy]

Thank you. So it is unfortunately not possible to utilise the 'Sub Vol' and'Sub Freq' Knobs on the pro, as this control must be done on the active sub? That is a shame. Are you able to advise on the returns process please? The original model is amazing, was hoping the pro could improve it if possible but if the above is correct i'd prefer the control that the original can offer over that of the pro, because those knobs then become a bit redundant and I don't like the idea of constantly having to touch the back of the subwoofer to adjust controls

 

[Kimbrough Xu]

I asked this in the other Fosi Pro thread and will delete which ever one doesn't receive a response first. ;-)

I've got a weird question. (3-Channel Setup)

I'm sure someone knows the answer to this. Could you make a three channel set up with this? Right channel goes to right speaker. Left channel goes to left speaker. And then the positive of left and right go to positive of a center channel positive, while you select either the left or right channel negative for the negative? I know in some amplifiers, connecting the positives of the amplifier can like, blow them up. I'm just curious if this could be done and have it not blow, up assuming you keep it within its volume limits.

Texas Instruments TPA3255EVM evaluation board

This link shows a TPA3255 evaluation board, and on page 18 they start showing schematics. May not be the exact same setup, but maybe this would show someone who knows what's going on, if that's possible.

Why not just make a 3 channel amplifier, the left channel goes to the left speaker, the right channel goes to the right speaker, and the center channel goes to the center speaker.

 

[Bohnster]

Why not just make a 3 channel amplifier, the left channel goes to the left speaker, the right channel goes to the right speaker, and the center channel goes to the center speaker.

What sources natively output a 3rd being the center? Almost everything is 2-channel stereo. I'm wanting make a quasi-center channel, like a phantom channel. I'm wanting to combine the left and right channels, but I just don't wanna blow up the amp.

 

[Kimbrough Xu]

What sources natively output a 3rd being the center? Almost everything is 2-channel stereo. I'm wanting make a quasi-center channel, like a phantom channel. I'm wanting to combine the left and right channels, but I just don't wanna blow up the amp.

There are 3.0 channel amps like the emotiva xpa 3, of course the center channel will transfer both the right and left channel to your center speaker.

 

[Nagrul]

I bought this amplifier and there was a problem. I connected an active sub to the pre-out output and it always plays, regardless of whether the amplifier itself is turned off by the toggle switch or turned on. What can be done about it?

 

[SWSL]

Yes, through the pre-out port, we can only control the subwoofer's volume from the amp. We've marked down your concern and we will consider modifying the design in the future.

The pre-out is very useful. The ideal would be to have both pre-out and Sub-out (line level). Otherwise your choice of pre-out is more flexible. I plan to use a separate subwoofer amplifier with it's own low pass eventually and the pre-out will be fine.

 

[SWSL]

Good to know.
There's also the stock power supply that's 32v 5A, so given the around 90% efficiency, the real power as shipped is somewhere in the 140W ballpark total.

It's still plenty enough for my needs, though that kind of advertising is lame...

Yep. With the 32v, 5A supply one can imagine it is getting around 30Wx2 + 80W for the sub... Though it depends on impedence. 3251 is rated for up to 78 watts x2 @ 8ohm. With the other one bridged mono one imagines around 200 watts @ 8ohms, more at 4. 1% THD. So, the BT30D pro should be able to use around 350 watts total at 1% THD at full power. A 36V 10A supply could do that. Ventilation might be in order.
I do think that the 3251 is really a good choice for this unit. Lower voltage keeps the power supply costs down and it's still very loud even with 140W. If it were sold with the 3255 and bundled with a 48V supply, I imagine it would be a $150 amp. 3251 is same sound as 3255 except for maximum wattage.

 

[SWSL]

I bought this amplifier and there was a problem. I connected an active sub to the pre-out output and it always plays, regardless of whether the amplifier itself is turned off by the toggle switch or turned on. What can be done about it?

Put an inline lamp switch on the power supply? Or run both through a power strip and use that switch?

 

[Soulsounds]

I would like to know if the bt30d PRO can manage a 48v power supply, because the tb10d can and it use the same tpa3255 chip,

Also I see in the @Fosi Audio web page that they are selling the 48v 5A power supply.. for tb10d and bt20A pro

 

[thonic]

I just registered to say that I bought the Fosi Audio BT30D and I am 100% happy with it. @Fosi Audio it's a great product.

Personally I find all the discussions about logarithms and this pot or that pot or, wait for it, the length ot the antenna !, a bit nonsensical. I turn the knob until I like the sound and could not care less how much I had to turn it. The antenna is of comparable length to thousands of bluetooth receivers, home routers, and other radio based electronics.

Leave it to audiophiles to overcomplicate things and take the fun out of a great value product!

 

[SWSL]

Yes, through the pre-out port, we can only control the subwoofer's volume from the amp. We've marked down your concern and we will consider modifying the design in the future.

I prefer having the pre-out. I bought a 2.1 for passive sub because I have a passive sub. If I wanted a 2.1 for active sub there are other Fosi models with a line level sub out. This is the only one that has pre-out. We use it for a second set of speakers. This is the only 325x amp that has this feature. Please keep it. We will buy another.

 

[GrayA]

I would like to know if the bt30d PRO can manage a 48v power supply, because the tb10d can and it use the same tpa3255 chip,

Also I see in the @Fosi Audio web page that they are selling the 48v 5A power supply.. for tb10d and bt20A pro

@Fosi Audio I would like to know if the BT30D Pro can take a 48v power supply as well, and if that is necessary to achieve 165Wx2 + 350W. Also, what is the power output with the supplied 32V power supply?

 

[SWSL]

@Fosi Audio I would like to know if the BT30D Pro can take a 48v power supply as well, and if that is necessary to achieve 165Wx2 + 350W. Also, what is the power output with the supplied 32V power supply?

This unit is rated to 36V.
The 32V supply it ships with is 5 amps. I don't know that much about how power supplies work but the simple math says that's 160 watts of supplied power. Evenly split that would be 80 watts supply for the sub chip and 40 per channel for the mains. Call it 70 + 35 x2. Probably the sub pulls more in that equation, especially as our sub is rated 4 ohm and the speakers 6.

What I've learned from use:
1) With just that 160 watt supply, it's very loud with our bookshelf (+ sub) speaker setup. Normal listening inside a house, it's powerful enough as sold.
2) You'd better upgrade the cooling on the amp if you are gonna pull all the watts in the provided power supply. The amp gets hot if turned up for long. Running it outside in warm weather, we drilled out the case and added a fan on top to be sure. Probably just ventilation holes are enough with the 160 watts of power supply running indoors at "room" temp. And it's probably fine as shipped if you are not playing loud for very long.

I plan to upgrade to a 36v 10 amp power supply at some point and that should be more than enough.

 

[Fosi Audio]

I would like to know if the bt30d PRO can manage a 48v power supply, because the tb10d can and it use the same tpa3255 chip,

Also I see in the @Fosi Audio web page that they are selling the 48v 5A power supply.. for tb10d and bt20A pro

Not right now.

 

[Fosi Audio]

I just registered to say that I bought the Fosi Audio BT30D and I am 100% happy with it. @Fosi Audio it's a great product.

Personally I find all the discussions about logarithms and this pot or that pot or, wait for it, the length ot the antenna !, a bit nonsensical. I turn the knob until I like the sound and could not care less how much I had to turn it. The antenna is of comparable length to thousands of bluetooth receivers, home routers, and other radio based electronics.

Leave it to audiophiles to overcomplicate things and take the fun out of a great value product!

Thank you for your feedback. If you have any suggestions about our products, you are welcome to share with us.

 

[GrayA]

This unit is rated to 36V.
The 32V supply it ships with is 5 amps. I don't know that much about how power supplies work but the simple math says that's 160 watts of supplied power. Evenly split that would be 80 watts supply for the sub chip and 40 per channel for the mains. Call it 70 + 35 x2. Probably the sub pulls more in that equation, especially as our sub is rated 4 ohm and the speakers 6.

What I've learned from use:
1) With just that 160 watt supply, it's very loud with our bookshelf (+ sub) speaker setup. Normal listening inside a house, it's powerful enough as sold.
2) You'd better upgrade the cooling on the amp if you are gonna pull all the watts in the provided power supply. The amp gets hot if turned up for long. Running it outside in warm weather, we drilled out the case and added a fan on top to be sure. Probably just ventilation holes are enough with the 160 watts of power supply running indoors at "room" temp. And it's probably fine as shipped if you are not playing loud for very long.

I plan to upgrade to a 36v 10 amp power supply at some point and that should be more than enough.

Do you have a link to the 36V 10A power supply you plan to buy? That will increase the power from 160W to 360W?

@Fosi Audio Will a 36V 10A power supply overheat the unit?

 

[SWSL]

Do you have a link to the 36V 10A power supply you plan to buy? That will increase the power from 160W to 360W?

@Fosi Audio Will a 36V 10A power supply overheat the unit?

https://www.amazon.com/MEAN-WELL-LRS-350-36-Enclosed-Switching/dp/B0131VAEEG/ref=sr_1_3?crid=357QLLLHKCBVB&keywords=meanwell+lrs+350+36&qid=1682895913&s=industrial&sprefix=meanwell+lrs+350+%2Cindustrial%2C1192&sr=1-3

 

[GrayA]

@Fosi Audio Can you tell us the sub frequency when the knob is at 10am, 11am, 12pm, 1pm, 2pm?

Everyone, I'm using this to power Pioneer SP-BS22-LR and Infinity Beta 12" sealed sub desktop PC setup and it sounds SO GOOD. I have the sub volume on max, sub frequency at 12:30pm, and main volume at 10am.