Fosi Audio V3 Mono Amplifier Review

[antcollinet]

Here's an idea to try: Take ONE of the outputs of your BTL output amplifier and put it through a 1000 uf 35 volt capacitor (With the + pointed towards the amplifier). Connect the + of your speaker to the - on the capacitor and the - of your speaker to ground (the - on your power supply input will do). By doing this you have done two things:

1. Lowered the amp's output voltage by 50% (and the power by 75%) and
2. Eliminated one output filter.

I'm curious as to how this improves the amp's high frequency response with only one output filter being used. I know this works successfully in the Loxjie A40 (It has a bipolar (+/-) power supply and it's - speaker terminals go to ground with only one filter in the + line).

I can only assume this is going to screw things up royally. The amp has been deisigned with the filtering in place for a good reason - and demonstrates already very good frequency response.

Why would you think this sort of hack would improve anything.

Not to mention you've put a large polarised cap into an AC signal path.

 

[Adrian Parker]

Hello, I too am excited to test these mini amps - to run cool in my shed in summer, is the plan.
I too got an email (spam folder - like most peeps) today with two vouchers, very confusing - as neither work (yet).

I did notice that PSU on the vouchers, one is 5A the other for a 10A unit, so maybe there will be even more headroom? Or are the PSU regional?

 

[Adrian Parker]

I got the same email this morning. Someone who's been down this path before will surely chime in, but my assumption is that the coupon link will work when the Kickstarter release goes live on 4/20. Followers went from ~250 to over 500 675 in about 3 days. Hopefully I don't miss the boat on the first run. Still waiting on a ZA3.

https://www.kickstarter.com/projects/fosiaudio/fosi-audio-v3-mono-power-amplifier - Now at 727

 

[Hunter Mike]

1- Thank you for info about input sensitivity. My few good dacs and pre amplifiers have high output impedance (from 600 ohm to 2,5 kOhm), for good match they need amplifiers only with high input impedance ( like 50-100 kOhm). Anyone know how high input impedance have Fosi V3 mono RCA inputs?

47kOhm for the RCA input.

 

[Hunter Mike]

I am curious about the standby power consumption. Has It been measured jet bij @amirm?

Standby, networked standby and Off mode

Off mode, standby and networked standby mode. Energy efficiency of products.

energy-efficient-products.ec.europa.eu

Does Fosi meet these requirements?

I just made some quick measurements. 48V5A supply. I have the ZA-3 but am assuming the PSU is the same for the V3.

PSU on, amp off 0.8W
PSU on, amp on 7.1W with no input signal.

I assume Fosi supplies the same PSU for everyone, with just a different AC connection based on region.

I have four plugged into one smart outlet so I can reduce power down to 0.5W, which is what the smart plug uses. I ask Alexa to turn on the amplifier and all four turn on. Then my processor triggers them on when it’s on.

 

[Billy Budapest]

I got the same email this morning. Someone who's been down this path before will surely chime in, but my assumption is that the coupon link will work when the Kickstarter release goes live on 4/20. Followers went from ~250 to over 500 675 in about 3 days. Hopefully I don't miss the boat on the first run. Still waiting on a ZA3.

I didn’t get any emails which is strange because I had registered.

 

[Bleib]

I didn’t get any emails which is strange because I had registered.

I had an email in the junk mail folder

 

[spandy]

I didn’t get any emails which is strange because I had registered.

It showed up in the Spam folder for me as well.

 

[audioje]

How does one use the early bird discount? I got an email but the coupons don't lead to a page where I can place an order.

Same here. And not sure why they included t-shirts haha.

 

[Billy Budapest]

It showed up in the Spam folder for me as well.

OK, I checked too and there it is!

 

[dpuopolo]

I can only assume this is going to screw things up royally. The amp has been deisigned with the filtering in place for a good reason - and demonstrates already very good frequency response.

Why would you think this sort of hack would improve anything.

Not to mention you've put a large polarised cap into an AC signal path.

Actually it should work just fine. Try it.

 

[Otovo]

I got the same email this morning. Someone who's been down this path before will surely chime in, but my assumption is that the coupon link will work when the Kickstarter release goes live on 4/20. Followers went from ~250 to over 500 675 in about 3 days. Hopefully I don't miss the boat on the first run. Still waiting on a ZA3.

Reply from Fosi.

"Hi,

Thanks for your attention on our V3 Mono Project.

Receiving this email means you're already part of our Early Bird event notification.
Our biggest discount is limited to the first 200 participants, on a first-come, first-served basis.
We recommend you also follow our project on Kickstarter, where you'll be alerted before the project kicks off.
Stay tuned for more updates from us!

Have a nice day!

Best Regards,"

 

[antcollinet]

I didn’t get any emails which is strange because I had registered.

I thought the same - then I found them in one of Gmails automatically sorted folders (promotions I think)

I actually don't think the vouchers do anything - there is no code on them or anything like that.

I suspect the 30% will just be the standard kickstarter early bird discount that anyone can get if they are quick enough.

 

[amix]

This spreadsheet may be useful to you:
[...]

To use it, login with your Google account and go to File->Make a Copy.

I added a column for 6Ω. Any idea how I could copy the formula into all rows at once? Thanks.

 

[amix]

Big brand companies must be in sheer panic

Not unless the rest of the package changes. Meaning integrated PSU and replacing those cheap stick-switches on the front with some nicely machined buttons.

I had a report from a manufacturer of High-End speakers, who uses the Fosi amps to install the speakers at customers. And true, people are amazed once they hear it! But he had to demo the amp to make them believe it. Before they just said: "Bah, Chinese crap!"

Also, for many guys, their amps are like cars: status symbols. Fosi can't win a prize here.

 

[staticV3]

I added a column for 6Ω. Any idea how I could copy the formula into all rows at once? Thanks.

6Ω added to the spreadsheet. Refresh the page to see it.

 

[amix]

6Ω added

Thanks a lot!
P.S. For consistency you may want to align the rounding.

 

[Ze Frog]

Not unless the rest of the package changes. Meaning integrated PSU and replacing those cheap stick-switches on the front with some nicely machined buttons.

Yeah, but to be fair Fosi aren't exactly too far off. Some nicer cases and inbuilt power supply as you say and they are pretty much there.

As for the toggle switches, kind of like them myself, like a switch to have an old school kind of quality. Best switchgear ever that I have experienced is the Denon PMA 110. That thing is so mechanically satisfying. I'll probably purchase one at some point on that fact alone.

 

[Bleib]

cheap stick-switches

I prefer these, easier to see their position

 

[amix]

I hope they also offer the 10A PSU in a double set. Especially since my PreAmp only has 1.5V on output.

Nah, I will need to find a new Pre, that helps to drive my Dynaudio Contour 1.3SE accordingly. Which brings me to another question: I assume more current in equals more current out, roughly? How could I determine, what current my speakers will see at the end? Dynaudio recommends high current amps for their speakers.