Fosi BT20a Max

[Joe Smith]

I read one early review that noted the volume control at low level is not great - which is one of the few nitpicks I had with their P4 preamp. Maybe the same motorized pot is used. I found that the best thing to do was to set a mid level with the P4 and then dial in the lower level I needed with the pot on the amp (V3, Aiyima A07MAX, etc.). But using the new BT20, I won't have a preamp in the chain. So I will see how that volume control does. Low level listening in nearfield is a lot of what I do (50 - 60 db) so that is a critical thing for me.

 

[Bleib]

Curious how it measures and if the PFFB implementation is done well, but with the multiple inputs and tone control it's a very interesting device for my household, with our different needs and tastes. Hopefully there will be an option without power supply, I have enough of those laying around.

Write them an email, perhaps they can offer without the supply. I also have a 48v 6A laying about ...

 

[MarekRMac]

I read one early review that noted the volume control at low level is not great - which is one of the few nitpicks I had with their P4 preamp. Maybe the same motorized pot is used. I found that the best thing to do was to set a mid level with the P4 and then dial in the lower level I needed with the pot on the amp (V3, Aiyima A07MAX, etc.). But using the new BT20, I won't have a preamp in the chain. So I will see how that volume control does. Low level listening in nearfield is a lot of what I do (50 - 60 db) so that is a critical thing for me.

Hi, I’ve got the same issue with my Fosi V3. It has a kind of “dead zone” on the volume knob. When I want to listen at a low volume, it’s sometimes not possible — it’s off, then silent, and then suddenly a bit too loud. I’m also missing tone controls, so I thought the BT20 MAX would be a great option, but if it has volume control issues as well, unfortunately it’s not suitable for me either.

 

[Joe Smith]

Hi, I’ve got the same issue with my Fosi V3. It has a kind of “dead zone” on the volume knob. When I want to listen at a low volume, it’s sometimes not possible — it’s off, then silent, and then suddenly a bit too loud. I’m also missing tone controls, so I thought the BT20 MAX would be a great option, but if it has volume control issues as well, unfortunately it’s not suitable for me either.

I'll report back after I get my test unit. See how it does with the different power brick, too.

I can recommend the Schiit Saga 2 as a preamp with great low level volume control - the special 64-step resistor attenuator they used in it is wonderful. Perfect channel matching and great level control. Plus a remote etc. While the P4 offers great value, and the motorized pot is nice, it did lack the ability to dial in well for quiet listening. IMO the pot in the V3 is a little better than the P4, but still not ideal, yeah.

Thought: Have you tried working that V3 pot a bit with power off, back and forth several times from lowest to highest position? Sometimes that can open up a pot a bit and help reduce or eliminate that dead spot.

 

[obsessive9119]

The opportunity to redesign the FOSI V3 with PFFB has been missed

Hopefully we’ll see a new V3 Stereo and/or an updated ZA3 without the tone controls and BT. Personally I could live without the HPF too, but I’d like to keep the trigger input.

 

[putridspecies]

Ordered one of these as I was looking for something with at least 2 rca inputs, no DAC/ADC, remote control and some sort of sub/pre out. I already have a streamer with a decent DAC and a turntable that I want to connect without any analog to digital conversion, and this fits the bill perfectly. A bit pricier than the normal fosi offerings, but I already had a 48v power supply and after the 20% off discount comes out to under $200 ($184 to be exact - US based) I thought it was worth the shot. We’ll see how well it performs in comparison to my daily driver , the topping pa5 II plus

 

[Bleib]

Wrote them an email. The amp won't be sold without a PSU

 

[kishanpatel995]

I wouldn’t be surprised at all if the Douk Audio A5 equipped with opa828 would blow it out of the water for clarity and tonal value especially in the low frequencies….if you know the opa828 you will know exactly what I am talking about. Feed that A5 with a Muses 02 based dac and done…just my penny as they say….and nice that they have included this on the same remote as the P4 and ZP3 which are all different looking machines…bit of square there and curve here dear….forward thinking in design would be an attractive quality to grasp and I think HR dept should have their eyes open a little wider….leaving very little breathing space in these designs is adding to the general patina of a ‘throwaway product’ which eventually most seriously people will grow tired of quickly and look elsewhere especially if certain parts can only be replaced with an larger equivalent, it’s an issue I am currently having with an capacitor that arrived with dents. For the sake of 2mm the whole design of the amp is out of sync because the casing is packed so close to the internal caps and board.

Currently some parts that most of these brands maybe NOS which is ok but if that is the case then it would make sense to compensate for replacement parts that are current or at least complimentary in regard to brand quality if jumping from Rubycon to Nichicon for example which in regard to an 63v 3300uf cap there is a 2mm difference in diameter with the closest match. It would not harm the unit using if 5mm clearance was implemented on the edges and top of the unit, just saying….

still learning all this so apologies if this is a silly question, what makes the douk a5 better with the opa828?

 

[Joe Smith]

Wrote them an email. The amp won't be sold without a PSU

That's a shame, as yeah, I imagine many of us have a lot of power bricks now accumulated with the various mini-amps. I never bought a 48v one, so if Fosi sends that with my unit, no objection... I imagine Fosi makes a fair bit of profit on selling the power bricks. Compared to some other Fosi offerings, the price for this is a bit high, so interested to see how she plays...

 

[Joe Smith]

still learning all this so apologies if this is a silly question, what makes the douk a5 better with the opa828?

You've got people here who swear by one particular internal op-amp or another...and a lot of people who feel that op-amp swapping is generally pointless (and occasionally, damaging to the amp, as a mis-match can cause oscillation). As for me, I did a few swaps with free samples from one discrete type manufacturer, and with inexpensive IC ones, and could hear no discernible difference. It's a rabbit hole I think many of us would advise you not to go down. Changes in speakers or rooms are far more important to improving one's sound.

 

[Bleib]

That's a shame, as yeah, I imagine many of us have a lot of power bricks now accumulated with the various mini-amps. I never bought a 48v one, so if Fosi sends that with my unit, no objection... I imagine Fosi makes a fair bit of profit on selling the power bricks. Compared to some other Fosi offerings, the price for this is a bit high, so interested to see how she plays...

I think it might also have a thing to with warranties. People might not have the right kind of PSUs so Fosi's own might be a safer option

 

[kishanpatel995]

You've got people here who swear by one particular internal op-amp or another...and a lot of people who feel that op-amp swapping is generally pointless (and occasionally, damaging to the amp, as a mis-match can cause oscillation). As for me, I did a few swaps with free samples from one discrete type manufacturer, and with inexpensive IC ones, and could hear no discernible difference. It's a rabbit hole I think many of us would advise you not to go down. Changes in speakers or rooms are far more important to improving one's sound.

thats fair, i was looking at the douk a5 and topping mini 300 as options so that kinda clears it up for me. will likely go with the topping. was also considering the fosi bt20a max that just launched but idk about that one yet.

 

[motleypixel]

Here's my review. I've had it since Dec. 22, 2025. I'm anxiously awaiting @amrim's review. That being said, it honestly sounds fine, not any different than my BT30D Pro. Unfortunantly I don't have a BT20A Pro to compare. What I like most is tone control defeat and the 80Hz high pass filter option. You can hear that damn fan though so if you are listening near field that could be a problem. Finally, I concur with others on the volume and lack of fine-tuning, the dead-band is just too big.

 

[Jeromeof]

hear that damn fan though so if you are listening near field that could be a problem

Yes, I have one and in general it has great features and sounds exactly as it should. But there should be a way to turn off the fan or at least have it dynamically turn off if the unit tests hot as I can hear it from 5-6 feet away ( when no music is playing ).

 

[motleypixel]

Yes, I have one and in general it has great features and sounds exactly as it should. But there should be a way to turn off the fan or at least have it dynamically turn off if the unit tests hot as I can hear it from 5-6 feet away ( when no music is playing ).

I plan to modify mine with a small SPDT push-button to close/open one of the DC legs to the fan

 

[Bleib]

Hmm, a fan. Sounds like they used a too small one, that's why it's audible

 

[Joe Smith]

Someone in another thread said it could be disconnected inside the case?

 

[motleypixel]

Someone in another thread said it could be disconnected inside the case?

Yes it can, but I want to emphasis that it's true you can hear it when there's no music playing and you are sitting close. I would say if you are in an average home listening room (office/den) and sitting in "the spot" you would likely be at least 8ft away and would not be able to hear it. If you use it on a desk where you work and your head is w/in say 3-4ft of it then sure you may want to open up the case and unplug it. Just realize this will "VOID" warranty

 

[Joe Smith]

My head will be about 3 -4' away from it in my nearfield setup, so we shall see. I don't mind a bit of a wooosh as long as it's inaudible when music is playing.

 

[Ropeburn]

Why is it so hard for people to accept that some people can hear the difference,

Because this

envy, jealousy, ignorance, inexperience, physical deficiencies…

isn't it, but indeed this:

the mind is quizzically engaged to say the least

...on the part of the listener who knows nothing about audiopsychology but is convinced his crude fleshy sensors called ears, delivering a signal processed by the highly capable reality simulator and illusion generator called brain is somehow superior to technical equipment specifically designed (and managing) to beat human hearing by half a dozen orders of magnitude.