Fosi Audio BT30D Pro review

[Austrian Printer]

@Fosi Audio Would it be possible if you were to also tell me the internal DAC model or specs of the bt30d pro?

 

[Graham849]

[QUOTE="Austrian Printer, post: 1580268, member: 61417"]
[USER=36817]@Fosi Audio Would it be possible if you were to also tell me the internal DAC model or specs of the bt30d pro?

No DAC as such, its a TPA3255 amplifier, capable of decoding a bluetooth signal using a ATS2853 chip c.f. https://www.i-lexia.com/productinfo/1031204.html regards g

 

[Fosi Audio]

@Fosi Audio Would it be possible if you were to also tell me the internal DAC model or specs of the bt30d pro?

There is no extra DAC of BT30D PRO.

 

[GrayA]

I put thicker gauge speaker wire and this thing is really powerful! I'm using Pioneer SP-BS22-LR and Infinity 12" Beta sealed sub and it plays loud! These are approximately my settings currently:

PC volume: 80
Sub Freq: 2pm
Sub Vol: 11am
Treble: 4pm
Bass: 1pm
Main volume: 10am

 

[GrayA]

Measurements with stock power supply (32V 5A) and upgraded power supply (36V 15A)

 

[AddamR]

Hello fellow desktop amp lovers. New here, just purchased a BT30D Pro and paired with an SMSL D6 DAC. I can honestly say, I'm totally blown away.

I've got a couple a vintage amps (JVC VR5515 Quadraphonic and a 4ch CE6000 - not much info on this 60s 15w/ch amp, except it was an OEM Solution and this one was branded as Cactus Electronics 6000, assuming 60w total power output, paired with a set of brown box 60s speakers, this amp sounds incredibly good)

The JVC I was using with a pair of JVC SK15 4 ways and these are the speakers I'll be using with the BT30D Pro - but they need restoration - new boxes to be built and modernised. As yet unpaired/tested.

Pic of SK15 from the web

Speakers tested so far

The Sony SS-F4000P are rubbish, decent bass though, way too harsh top end and a lacklustre midrange.

The Brionic (80L 12" 3 way dual ported), we're the first to get the treatment. They played well, loud, due to thier sensitivity, but lack that dynamism, probably because the DAC wasn't installed at the time. I'll save these for my DIY custom BT only TPA3221 amp project (pictured next). These boxes contain Magnavox drivers and I've replaced the tweeters with Vifa D25s, as one original tweeter was blown.

Anyway, it's Fosi time. I bought the BT30D Pro, primarily for the preout, as I want to play around with adding a 4ch (DIY TPA3118 mono x4) and an ADAU1701 for SigmaStudio active crossovers into the 4 amps (2 ceiling and 2 rear stereo).

The Fosi is currently being evaluated using a pair of Krix Brix K35s and a pair of Cisco transmission line subs from a $80000 MX700 Teleconferencing system (picked up almost an entire setup for $40 - was missing cameras and tablet interface, but everything else worked as intended, to power on stage. This Dual 55" screens come with a 2.1 amp built in, ones been repurposed as a PC Monitor, stripping most of the frame and covers, saving about 40kg in weight.

Cisco subs (currently on eBay for $500 a single)

They contain within, 2 x push-pull 4" woofers and with the Fosi sub controls set to both 11am, they produce nice bass, any higher and they become muddy and start to clip - probably a limitation of the 4" drivers and the fact these were designed for teleconferencing voice reproduction, not HiFi use. They are wired in parallel, which sounded better than in series. But you can't call 4x4" drivers in 2 x enclosures, a proper subwoofer, not in my books anyway.

I've also got an active 300w 8" sub, a vintage 'Singer' (yes, the sewing machine company, but probably not), not currently in use.

All in all, I am happy with these two products, the Fosi ticks all boxes. No issues with Bluetooth, it's quality isn't as good as the SMSL D6, so the aerial is removed. It never auto connected, like I've read elsewhere.

Looks like I'll be using the Krix Brix as the mains, until the JVC SK15s are rebuilt. The imaging, sound stage and all range of frequency, is just ear candy and I'm high from the experience. The Cisco subs, add just that required low frequency to match just fine.

I have 4 x Vifa P17WJ 6.5" drivers, which will eventually find a new box to become the passive subs. Another ported or sealed box project slated.

There's not enough time in this life....

Nice job @Fosiaudio. AUD$115 well spent. Highly recommend this amplifier.

 

[AddamR]

Quick question - is the preout TRS or TRRS (3 or 4 sleeve?).

 

[GrayA]

Fosi told me this about the Sub Frequency knob:

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

 

[GrayA]

I have been using this with my PC volume at 80% and BT30D Pro volume at 8am. Does lowering my PC volume say 40% and raising the BT30D Pro volume to 11am allow more power to go to the sub (and the mains)?

Another question; how do I find the optimal PC vs. BT30D Pro volume level?

 

[AddamR]

BT30D Pro main volume is set to 95%, sub 75% and volume is either controlled by phone or SMSL D6 DAC, either or is at 95-full volume.

I've also added a second BT30D Pro, for a 4.2 system, making full use of those pre-outs. It's also cranked to 95/60%

Speakers make all the difference. Optimal is user defined experience.

I have been using this with my PC volume at 80% and BT30D Pro volume at 8am. Does lowering my PC volume say 40% and raising the BT30D Pro volume to 11am allow more power to go to the sub (and the mains)?

Another question; how do I find the optimal PC vs. BT30D Pro volume level?

 

[GrayA]

BT30D Pro main volume is set to 95%, sub 75% and volume is either controlled by phone or SMSL D6 DAC, either or is at 95-full volume.

I've also added a second BT30D Pro, for a 4.2 system, making full use of those pre-outs. It's also cranked to 95/60%

Speakers make all the difference. Optimal is user defined experience.

BT30D Pro 95% and phone/DAC 95-full isn't too loud? If I cranked both my PC and BT30D Pro, I'd go deaf; probably because it's a near field desktop setup

I was wondering whether it was better to crank one or the other. My thinking was to crank up the source (Desktop PC) to have a stronger signal rather than using a weak signal and cranking up the BT30D Pro.

 

[AddamR]

BT30D Pro 95% and phone/DAC 95-full isn't too loud? If I cranked both my PC and BT30D Pro, I'd go deaf; probably because it's a near field desktop setup

I was wondering whether it was better to crank one or the other. My thinking was to crank up the source (Desktop PC) to have a stronger signal rather than using a weak signal and cranking up the BT30D Pro.

Phone can't go past 50% without hurting your ears, vice versa with the D6 DAC. If I leave the amps at ~70%, I've got more wiggle room. I'm in a 4x4 lounge that open plans into the kitchen dining area. I'm using (as I posted), Krix Brix as mains, I had a pair of 28L vented boxes (from an old 60s Pye4 surround sound), so not only did the Vifa PJ-W17 speakers fit nicely, the port is actually correct too. Vifas are in dual mono setup. Brown box Brionics are the 2nd amp speakers and I've got an 8" powered sub behind me that I'll take the noisy amp out of that and run it from the BT30D Pro.

I'm loving these amps! Currently on box redesign plans for the 15" JVC 4 ways and retire the Brionics, which have served well for 3 years.

Have ordered a Fosi Box X4, to try it out with my Dual 1215 turntable. I had to buy an ADC to get the line output into the D6 coax/optical. I'll see how that goes.

 

[GrayA]

Ahh, I see. I thought you meant phone or DAC were at 95-full volume. So you decided that phone 50% BT30D Pro 95% sounds better than Phone 70% and PT30D Pro 75%, for example? Or does it sound the same and you like phone volume to be low since you control volume on your phone?

I love the amp too!

 

[AddamR]

If, for example, DAC and both amps at full, the phone can't go past 25% (piss off neighbours before ears explode...)

Controlling volume by phone seems to work for me better, as the amps are putting out near full power, the phone is a pre-pre-amp.

More than enough juice. I'm yet to setup a mini pc for USB audio testing, but BT on the D6 is far better than the amp. Suggest a DAC if you haven't already, the Fosi will love what it does, even more.

 

[AddamR]

@Fosi Audio - using 2 x BT30D Pro, 2nd unit has an active sub attached to pre-out and when amps are powered down, the active sub gives an audible 'thoop'.

It's an old unit, 300w AC Powered amplifier, which will be removed to take the Fosi second .1 channel instead. Will see if it goes away, which I suspect it will, as the 2nd amp connected to the first, doesn't 'thoop' on a set of vintage 12" 3 ways.

 

[AddamR]

That shouldn't happen unless you've got a full frequency line in, into the sub

Source--> BT30D Pro --> pre-out--> active sub
--> L Ch
--> R Ch
--> passive sub

Have you got your audio source going into the active sub line in first, then out to the Fosi? That'll reproduce what you described.

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?

 

[AddamR]

Ahh, I see. I thought you meant phone or DAC were at 95-full volume. So you decided that phone 50% BT30D Pro 95% sounds better than Phone 70% and PT30D Pro 75%, for example? Or does it sound the same and you like phone volume to be low since you control volume on your phone?

I love the amp too!

I've just added a Box X4 after the DAC. And wow.

PC or BT --> SMSL D-6 --> Fosi X4 --> BT30D Pro --> BT30D Pro

first amp running Krix Brix monitors, 2 x Vifa 6.5" subs@120hz, sub volume set at 75%
second amp running vintage 12" 3 ways with pre-out to an active sub going down to 40hz, volume around 80%

As for volume/tone settings, ive found if i have phone/X4/amps at 100%, volume controlled by the DAC remote, the soundstage is far better. I don't fine a need for tone controls, so they're set flat, with the X4 treble just a tad past 12 o'clock.

I've got a big job to service my turntable now, so I can test out some analog audio

 

[AddamR]

Just popping in to give an update on the BT30D PRO.

I've simplified the setup to only one unit, still running through the SMSL D6 DAC and Box X4 tube preamp, using the pre-out to a dedicated active sub.

Speakers are the vintage Krix Brix 4" ported, (sub .1) woofers are a dual (split) Vifa PJ-W17 6.5" in a ~28L ported boxes. Frequency wise, the Fosi is rolling off at around 120hz, where the active sub takes over down to 35hz, with room placement, I'm measuring it down to 25hz using an app on my Android phone. It all seems to gel nicely to my ears and produces deep bass and crisp mids and highs. The S23, however only displays its EQ to 16000khz. But I'm in my early 50s, so ears may not register those higher frequencies anyway? I am HFA and sound is one of my sensory issues, so I do hear things others don't. Need some real test gear to determine what's being produced.

Usage is primarily been Samsung S23 Ultra bluetooth through LDAC (with Dolby Atmos enabled) to the SMSL D6, so getting better than CD quality and a nice expanded sound stage with most music.

Have not had time to setup the Dell 7040M mini PC, where I plan on streaming through USB to D6 and experience higher fidelity than LDAC.

Volume control wise, S23 Ultra, BT30D PRO and Box X4 are set to 100% (max volume), with the D6 controlling the main volume, using the remote for convenience.

I'm using OCC silver plated copper interconnects to link it all together, but still just basic OFC copper to the speakers. Amp is still running the default 32v PSU and I intend, oneday, on trying out a 36V input and see if that makes a difference.

Overall, this little amp and peripherals attached, produce a distortion and completely noise free listening experience (Speakers are 86db sensitive). I've had the D6 up to 60, which is max volume, with no issues at all (not even neighbours), but its freaking loud (too much for consistent or persistent human hearing in such a confined area where it's setup).

Highly recommend Fosi BT30D PRO and I'm considering getting the Fosi V3, just to do away with the extra tone controls, which aren't needed (BT30D Pro, Box x4 and S23 Ultra are set to flat) and use the BT30D Pro as a desktop PC amplifier elsewhere.

Also in planning stages of a DIY, DSP enabled active speaker project, using 8 x TPA3255 amps and ADAU1701s, with new speakers designed around the Vifa 6.5s and D25 tweeters, which ive got lying around, but that's a long term thing.

 

[ethanhallbeyer]

Ok, I'm interested in getting either Fosi BT30D Pro or BT20A Pro. I want to use bluetooth, but don't like the idea of any random neighbor connecting to it and playing stuff through my speakers. Is there now a new model that gives you the option of having to press a button to pair?

Also, I plan to connect a powered subwoofer. Read that some models cause a popping sound when using the connector meant for sub out. Are the models with pre-out the ones affected and not the ones marked sub out? Or both make that popping noise?

Lastly, read somewhere that for the BT20A Pro the RCA signal passes on even if the device is powered off, so if you have an active subwoofer the signal gets sent on to it. Does the BT30D series do the same?

Thanks!

 

[richardm]

Owned a BT30D Pro for a few weeks. Adding my thoughts here.

Summary: It's OK, I guess. I do not love it.

Pros:

• The line-out is a true "pre-out" with output controlled by the volume knob. I understand with many similar amps the pre-out is technically a line-out.
• No hiss. It's silent at any volume level. Above 9 there's a faint buzz from my signal source that disappears if I disconnect the input.
• No turn-on or turn-off thumps.

Cons:

• No high-pass filter.
• The subwoofer controls affect only the speaker-level (passive) sub output. They do not affect the pre-out (i.e. the pre-out is full range).
• Bluetooth SBC/AAC only. No LDAC, Apt-X, etc.
• No Bluetooth authentication.

Some thoughts:

• Why is the case not ventilated? I understand it can drive any reasonable load at any reasonable output level without shutdown from overheat. But heat is the enemy of longevity and I just don't see this thing surviving to "vintage" status without some circulation.
• Repeating what others have said: why use the TPA3255 then save 50 cents on capacitors that can't handle a 48v supply?
• It needs a high-pass filter. I can't find a way to fully leverage this amp! Using it with a passive sub I can't keep LFE out of my L&R. I could drive my active sub from pre-out which grants me one master volume knob -- but this forces me to send LFE to the Fosi where, again, I can't keep it out of my L&R. Instead I'm driving my active sub via C/SUB on my PC (where I can implement effective/flexible bass management). The BT30D 3rd channel is a useless paperweight that I cannot put to work!

Simple features to add... $1-2 things that would make this product far more flexible and useful:

• A true main-in that bypasses everything on the front panel. Make it three channel so I can access the 3rd channel directly for whatever I see fit. Make sure the 3rd channel is full-range, same gain as L&R, etc.
• Line-in for all three channels, not just L+R, and perhaps a two-position switch that selects LFE source (e.g. sourced from L+R or sourced from line-in - I'd need to ponder this a bit).
• Pre-outs for all three channels. Make them true pre-outs, downstream from all front panel controls/filters.
• High-pass filtration.
• I'll admit this is getting into "Daddy can we buy a Pony?" territory: Variable and defeatable loudness contour, defeatable tone controls, defeatable sub controls.

Bottom line, it's my first mini class-D amp and I'm enjoying it. But it'll never serve as anything more than a basic, nearly featureless two-channel amp in my system. The volume control is useful as a gain control but every other feature this thing has lies just out of reach.