Fosi Audio BT30D Pro review

[john11]

Are the Op-Amps upgradable, e.g. with the Sparkos?

They are but sparkos run hot and need more current

 

[tramtrist]

Running fine with HMP100s.... Sounds surprising great with a turntable and the X1 preamp

 

[lucian]

unfortunately all pictures in this thread are broken and only links are visible. are these externally linked?

 

[Toku]

unfortunately all pictures in this thread are broken and only links are visible. are these externally linked?

Are you logged in to the forum?

 

[lucian]

Are you logged in to the forum?

yes - otherwise I could not write the remark !?

can see all other pics in other threads.

 

[SWSL]

I have a question about Impedance on this amp. Our ventilated amp cut the bass side out during an event. Almost surely overheating. Easy to reset toggling power but have to stop the music. Anyway, talking to my friend here who has the same amp (in a distant location) he has said that his idles cooler and operates (in use, not just idling) cooler. I mentioned that I am curious to see how his amp runs when he brings it next time and if it also cuts out ain the same tropical location. I suspect that my amp runs hotter than the average BT30D Pro. He said, "well, his runs cooler because, while he has the identical subwoofer (same driver model anyway, but different box) his is an 8 ohm whereas mine is in 4ohm, so he believes his BT30D pro will also have the same issue connected to a 4 Ohm sub.

Considering that this amp is rated for 2-8 ohms and comes with a somewhat low V power supply (for the 3255 chip), I had chosen a 4 ohm sub to allow for that and now am wondering if it was not wise. I had thought that an 8 ohm sub, all else being equal, would be less suited and have to draw harder on the voltage of the PS to get the same SPL., but now I wonder.

I have tried and tried to really sort out the impedence thing but again, the best I can tell, lower impedance, at same SPL will draw more current but less voltage than higher impedance. So that they will both use the same watts FOR A GIVEN SPL? Yes, 4 ohm is able to draw more power (watts) but it can also deliver a higher SPL so adjusting to same SPL compensates? In either case, we are going to turn up the sub to give a full sound and stop there. Basically on mine, we run the sub at 12-1 o'clock for both crossover and level.

Without asking for a full reiteration of the usual impedance explanations, does anybody have an opinion - did I optimize or not for THIS amp? What impedance sub are most people running on this?

 

[motleypixel]

I have been communicating with Fosi about ventilation for this unit as we had a scare during a party where the sound dropped way down and it had to rest before it would play again, which then repeated. I suspected it was actually a power brownout not the amp and it appears that was the problem as the amp has performed well at several more dance parties since. Though we now point a 6" fan onto the amp case to be sure. I am interested in finding out if some passive ventilation would be a good idea and also wanted to hear from Fosi what the limit for an improved power supply would be with some ventilation holes in the case. Fosi has been very helpful but at some point, the person helping me changed and became less so. They would not confirm if the 36V voltage limits were due to ventilation or components. Well, they sorta said, "both".

BUT, looking over the specifications, I found that while Fosiaudioshop.com (where I bought it) sells this as a TPA3255 amp, the manual for the amp lists it as a 3251 based product. I then found the TI marketing info for the 52xx series - TI New audio amplifiers - showing that the 3251 IS a lower output chip than the 3255 so now the 36V limit makes sense. It's the amp's limit because it's not using 3255s. The TPA3255 has an 18-53.5V PS range while the TPA3251 has a 12-36V PS range.

So, it's good to know what these amps are actually built with, especially since they are misrepresented on the product page. Still a great amp, but not what I thought I was buying. On the product page, they advertise a 5255 based amp with specifications of a 5255 but that seems to be false given the voltage limit and the chip specified in the user manual.
Product page - Claims dual TPA3255
User manual - Describes as TPA3251

Cheers

Yes this thing can get HOT! From experience, if you run it with a passive sub, 6ohm all-around and sensitivity 87db or lower, it will probably burn up in short time at long listening periods and/or high volume. Here's what I did to modify the case and it seemed to help a lot:

 

[motleypixel]

Where would this amp land on this line-up? https://www.audiosciencereview.com/...st-class-d-cheap-amplifier-review-png.348776/

Thank you,
Roy

 

[item]

+1 for matching high pass filter on this unit. Until then its utility is seriously compromised.

 

[Casubon]

I have a Fos BT30D Pro and a Wharfedale SW150 subwoofer. It has both high level speaker outputs and RCA low level input (see attached image)
. The subwoofer outputs on the BT30D are specced for passive subwoofers - could I safely connect these to the SW150 and would the SW150 still need power from its internal amp? Or, am I better off using the line out on the BT30D to the RCA input on the SW150? (I'm new to this kind of setup - not sure what would be best)

 

[IDXTREME]

Why not sell a version with all of the upgrades already installed?
Sparkos, 48 volt 10 amp power supply...

 

[early rejecter]

could I safely connect these to the SW150 and would the SW150 still need power from its internal amp? Or, am I better off using the line out on the BT30D to the RCA input on the SW150?

Your subwoofer will use its internal amp regardless of which input you use — if you use the high level input, the signal will pass through a circuit that reduces it before it’s amplified again. I’d use whichever is more convenient for you.