Fosi Nailed It / NEW BT20A Pro Amp Review 

Are those polk 705s o5 703s? What has been your favorite pairing for them? I have the 705s with aperion super tweerers

I actually own the LSIM 705 703 and 706 center. I am using the 703 and 706 in a 3.1 in one room and the 705 is idle at the moment. They like a bit of power, really a well built beautiful speaker series though. They are a warm sounding relaxed speaker, pair well with amps that tend to liven things up a bit. I am sure I will find a way to get the 705's back in the rotation, always enjoyed them.

@@MattCoykendall1 I'm currently using a Cambridge cxr200 on the top and crown xls 2502 for the bottom. Adding the Aperion super tweeters helped open the top up a bit. Thomas from Thomas and Stereo likes his Gallion tube amp with his 707s and I'm positive a rouge audio chronus mag 3 would work as well. Thanks

@@ufarkingicehole Thomas and I chatted a couple weeks back, I shoul get the Gallion in at some point for review, might be a couple months though as all the review samples are currently out. Thanks for the pairing info.

Just ordered today. Hope to change my old nad 3020 from 79 with this in my kitchen and sell it. Hope to get more than the cost of Fosi. Takes less room on the board ?

That's a great idea! I have been looking at tube gear lately, hopefully have some items for the channel in the coming months.

Yeah no excuses on audio equipment taking up too much space with these! How do you like the xt20, I actually have a pair of those as well.

@@MattCoykendall1 I love the Polk's ! Plenty of bass and they eq'd up good too

I appreciate the watch, glad you enjoyed it!

Thanks for sharing Anthony!

This is not variable unfortunately.

@@MattCoykendall1 thanks for responding. I was planning to buy it to use it with bookshelf with subwoofer. But it not being variable output, will make using active subwoofer with it challenging.

Agreed, these are great for all the smaller "extra" spaces

It will do it easily and a good use case for this amp. I own one btw.

One thing to note...I have Volumio on a SBC with a $50 iFy power supply feeding a $1k DAC (S.M.S.L SU-10), a $1.2 k preamp (Schiit Freya+ with Russian tubes) and ~1K speakers (Elac UBR62 Unify Reference), so I've got pretty good gear. It no doubt takes good gear all throughout the chain to really notice how good how good Starkrimson Amps are.

I wish someone would take a look at the Mini GaN 5 from Premium-Audio.. It's small and weighs 5 lbs, but very powerful. It's driving my Maggie's

I will take a peek over at Premium-Audio site, see if I can find a contact.

@@MattCoykendall1 Tom is the contact… by email only

Thanks for the suggestion Neil, I am going to put in an order for the OPA627 modules, thats the perfect price range for something like this. The Sparkos is certainly interesting as well but your getting into a price nearly the same as the amp. Depending how the OPA627 goes I may pick up the Sparkos just for the sake of experimentation.

@@MattCoykendall1 Right - the OPA627 dual mono modules are quite excellent. I have tried them both in my AkitikA PR-102 preamp, and my Geshelli J2S. The PR-102 had OPA2134 chips, which are very good and are tonally similar, but the OPA627 are significantly better at soundstage and layering and textures. In the J2S, I have compared the OPA1612, the OPA2134, the OPA627 dual mono, and the Sparkos SS3602. That's the order of my increasing preference - the 1612 are fine as far as they go - they are shallower soundstage and less detailed and less layered. The 2134 are fuller sounding, and have more depth and layering, and a bit better dynamics. The 627 are a significant jump up in depth and width and layering. Their detail and textures are very very good. The SS3602 takes it up even more - they have more detail (while seemingly less bright) than the 627, and have an immensely deep and wide soundstage. Layering and textures are just phenomenal. Once you hear this DAC with the Sparkos - you will want nothing less. And I am now trying the Sparkos in the AkitikA PR-102 - and I will be trying a Muses02 op-amp (about $44 from Mouser) soon. After I break it in, I will be deciding whether to spring for the Sparkos SS2590 dual mono - which seems like it could be the last preamp I will ever need.

Opa627 is supposed to be very good BUT it hasnt been available for years, most sold today are fakes.

@Douglas Blake The 4558 is underrated. That and the 4556. You can parallel these, giving enough current to drive most headphones and it sounds pretty good for the simplicity.

@@peterlarkin762 That would explain the low price. They do sound good,, though. If they are clones, then they are at least available.

3.5 mm to RCA (female) adapter. Then run male RCA to your subs. Done. However, the pre-out is not variable. So, the volume knob on this amp will not raise or lower the volume of the subs, meaning you will have to adjust the sub volume from the sub's own volume control. This was a big mistake by Fosi on my part.

I am not well versed on op amp replacements but Neil Blanchard commented about the OPA627 as well as the much more expensive Sparkos SS3602. A little further research may be required here as some op amps like the sparkos may need an additional riser to fit properly.

@@rosswarren436 I will check that out, thanks!

The LME49720 is obsolete, and is not that easy to find, but the LM4562 is a proven and very good sounding op-amp for HiFi. It is highly recommended, if you don´t want to spend the money for Sparkos dual opamps.

What speaker did you end up getting ?

I was wondering about the power ratings because it's supposed to be 300w per channel @4Ohms, using the larger power supply, right? Because I have no speakers that need that kind of power and I was wondering what I'd even pair this amp with. You're saying with the 32v power supply you get around 25w per channel @ 8Ohms?

What chip would you recommend in place of the 3255? I'm putting together a portable worksite stereo system and I was just about ready to pull the trigger on a board with 3255s..

@@MarkLada I just explain potential weakness of 3255 chip. For alertness. Unfortunately I won't recommend any other chips. Sorry.

@iblesbosuok I understand, and appreciate you pointing out the weaknesses of the chip.. I've done a lot of research, and I had not come across the information in your comment anywhere else, thank you.. If my line of thinking is correct.. 8.87 amps at 48 volts is 425 watts.. I'm not going to be pushing the chips that hard, so they should work for my application.. I only need 150 watts out of the front channel and 200 out of the sub, for the speakers I want to run..

Could this be the reason the power supply of bigger voltage is recommended for more power? And could it be possible between TI and Fosi/Douk/Aiyima, the designer implemented current limiter in the design so as to protect the typical customer who don't much modify their gear. What are the odds? ?

@@hcho8164 Nowadays, many users get bored quickly. So, this weakness is not a big problem.

Great questions!

No sir. Big mistake on Fosi's part by not making the pre-out variable.

It is fun

Hey Pedro, its certainly more feature rich being that it is a complete integrated amplifier. The sound I would say is better yes, but its certainly not far behind it if I'm being honest, the Yamaha just offers alot more, as it should when comparing prices, the 501 is around 5x the cost.

@@MattCoykendall1 Thank you so much.

true its not better to be fair just different/rare

I do! As well as Amazon music

The sound itself is very similar (same amp chip) but the the Fosi model will open you up to easier pairings with the tone controls. I personally dont make too many adjustments with tone controls but every once in a while certain speakers need a bump here and there to fit my personal taste. The Fosi should also put out more power than the original A07, it comes stock with a larger power supply so that may influence some speaker pairings.

@@MattCoykendall1 Ok, thanks a lot for the info.

FYI, the Aiyima A07 and Fosi BT20aPRO both come with the same 32v 5A power supplies. I believe tone controls soak up some power, and that may explain why the Aiyima A07 has more power output. Williston Audio Lab measured the Aiyima A07 at 95wpc@4ohm, and the FosiBT20aPRO at 70wpc@4ohm. But tone controls are a nice option to have.

Stereo

This amp can serve as an all in one, if you are OK with streaming Bluetooth from your phone, tablet, PC, etc, straight to the amp, then you don't need anything else. If you are a critical listener, than that's where the rabbit hole begins. If you want higher resolution streaming, you will want to add a WIFI streamer and then an external DAC (to do a better job of decoding the signal and improve the sound even further....this unit does not have a built in DAC only 1 analog RCA input and it has BT built in.).

Looking to add volume control to some active speakers?

Hey MG, I would be happy to answer that, I am not sponsored by Fosi. There are channel's who are such as cheapaudioman as he mentions in his video, but in my case I was simply sent the product to review. The reason you are seeing all of these at once is because we were asked to release the videos on April 10th as that is when they released the product for sale. They didn't provide a script or talking points, at least in my case I was not influenced to say anything specific about the product. The interaction was simply "would you be interested in reviewing this?" and once I confirmed they sent the tracking information and a link to their product. I will say some companies will try to guide the conversation, this was not the case with Fosi, thanks for asking, its a fair question!

@@MattCoykendall1 Thanks for the feedback. I appreciate your reviews. 👍

@@Mikegritz Thanks MG!

I thought the same way too. Thanks for clarifying.

Stereo

Not sure what the deal is, they must have used an old Amazon page to build this listing. It is definitely new!

I think they used a different chip earlier.

Yep, previously they used the TPA3116 on the non pro.

I will be doing to follow up with the Sparkos op amps I know for certain.

Not often I hear that on these for the price we pay. Pairing issue with the speakers, actual amp had issues or just not your cup of tea?

Thanks for the suggestions Lemarr, I will take that into consideration on future videos.

I got one of these for my son with the 32V smps and a pair of mini monitors and a powered sub running off the speaker outputs. I was SHOCKED at the sound quality. I got a V3 for my workshop, where I also have some Dynaco tube gear. The ST35 is a bit warmer, but the V3 is perfect for its price as a backup and for when I need to save space on the bench.

no not really

Hi Paul. I think it's unfair to generalise. I run both high quality 300b and el34 tube amps and two good solid state amps outputting 215w and 150w in 8 Ohms, in different systems. I bought this Fosi amp out of curiosity as to what modern class d can do. You know, while it can be a little bright with certain tracks and tone controls at neutral, it sounds remarkably good to my ear and not harsh at all. It won't be replacing any of my ( much ) more expensive amps anytime soon, but it sounds incredibly good for the price, and I haven't changed the op amps yet. Class D has come a long way. I think you might be surprised if you try it.

Marantz had great gear no denying that but these days that Marantz tax is super high that many can't or won't pay.

Gotta love the ol LSIM series Polks!