Both my Fosi Audio Monoblock V3 stopped working (help!)

[Discharge]

I've been really enjoying my Fosi Audio Monoblocks as a stop gap for when my new amp arrives, I want to listen to some music last night after a horrible week and no sound...

I have plugged the same sources into my vintage NAD 3030 and they work fine, so it's either the monoblocks/power supplies or the cables.

I doubt very much whether both cables would fail at once, there was no puff of smoke or bad smell from the amps.

Both the red LED come on and the blue LED on the power supplies (I've tried both auto and on), I can hear the relays click and a little pop on the speakers and they start to get warm as though theyre doing "something" but alas no sound.

Ive unplugged the powersupplies and im going to leave them for an hour to see if somethings has tripped inside them but nothing else that's on the same plug board has any issues other than the Fosi chain.

Any ideas? could really do without this

The power supplies arent Fosi but they are 48v and 10A

 

[Raiju]

Are you using correct input setting on amps (rca/xlr)?

 

[Ruediger]

That and auto vs. on is about all that could be set wrong.

 

[Discharge]

It was faulty, Fosi have refunded me quickly as theyre out of stock at the moment.

Despite the problems I will probably get another and keep the pair as a backup for my E406 clone, since they do sound good through the KEF 105/3 but they dont drive my KEF 105 Series 1 very well.

 

[Joe Smith]

I am a supporter of Fosi in general but I think the V3 monos have ongoing design issues and/or QC issues. I imagine they will soon be discontinued and replaced by the new mono amps.

 

[Discharge]

I think you might be right, I had a look at the Aliexpress store and theyre out of stock atm.

Website doesnt say theyre discontinued but I did think it was strange that they refunded me before even recieveing the faulty one back...

 

[Redacted]

It's intriguing/annoying that both failed in the same way at the same time - as I understand it.

It does lead to speculation about a design fault, possibly being PSUs that are prone to mains-borne spikes. I've had a couple of unrelated items that stopped working, both of which were permanently 'on', if not 'active', and the replacements for which I now switch off at the mains sockets, just in case. In fact, during big storms, I now switch off many things with soft or remote power-on, like the TVs, stereo, etc., at the sockets - just 'cos I'm paranoid, doesn't mean they're not all out to get me....

 

[RandomEar]

@Discharge Just out of interest, could you tell us a little bit about how you were using them? Are they switched on/off daily? Are they on a power strip? Is the DAC or pre-amp feeding them grounded (three prong plug)?

 

[Discharge]

It's intriguing/annoying that both failed in the same way at the same time - as I understand it.

It does lead to speculation about a design fault, possibly being PSUs that are prone to mains-borne spikes. I've had a couple of unrelated items that stopped working, both of which were permanently 'on', if not 'active', and the replacements for which I now switch off at the mains sockets, just in case. In fact, during big storms, I now switch off many things with soft or remote power-on, like the TVs, stereo, etc., at the sockets - just 'cos I'm paranoid, doesn't mean they're not all out to get me....

It turned out it was just one of them which had blown, I think the first one breaking had caused the second power supply to trip as when I unplugged them for the best part of 2 weeks (I was quite fed up). When I came back to them one started working.

So I took all the same cables and put them into both amps and only the one was sending a signal to that speaker.

 

[Discharge]

@Discharge Just out of interest, could you tell us a little bit about how you were using them? Are they switched on/off daily? Are they on a power strip? Is the DAC or pre-amp feeding them grounded (three prong plug)?

The signal chain was Turntable/CD Player > Wiim Ultra > Fosi Mono V3's > KEF 105/3 or KEF 105 Series 1.

I left the amps on the auto setting which definately seemed to work as the orange LED would shut off shortly after I had finished listening.

Yes they were on a power strip.

No it was an RCA cable, not XLR.

 

[RandomEar]

Thanks. Definitely does not sound like a use case that should cause any issues at all

Just one more thing to clarify: Since you relied on the auto detection, I assume the PSUs were getting power continuously, right? So the system wasn't disconnected from mains daily using a switch on the power strip or something like that?

 

[Discharge]

I wasnt switching the strip off so the PSUs were constantly getting power

 

[JSG1469]

I ordered the v3 monoblocks to power a separate system and right out of the box was a no go. Nada, zilch. Checked all connections, cables, selector switches. Double checked my Schitt volume control. They power on and warm up but no sound. I reinstalled the old Kenwood back in the chain and music was present. I immediately boxed them up and sent them back for an exchange after reading other users having similar issues. I'm wondering if Amazon is repackaging defective units and sending back out. I have received products from them that did not seem to be factory packaged.

 

[Discharge]

I ordered the v3 monoblocks to power a separate system and right out of the box was a no go. Nada, zilch. Checked all connections, cables, selector switches. Double checked my Schitt volume control. They power on and warm up but no sound. I reinstalled the old Kenwood back in the chain and music was present. I immediately boxed them up and sent them back for an exchange after reading other users having similar issues. I'm wondering if Amazon is repackaging defective units and sending back out. I have received products from them that did not seem to be factory packaged.

I bought mine directly from the company on Aliexpress, mine both worked for about a month before the one broke. Like you it still got warm, it's as though the amp is generating the signal but for whatever reason its not getting to the speaker maybe the switches where faulty?

They were out of stock on the Fosi website for a while, so possibly there was a bad batch.

Did you use XLR or RCA?

 

[JSG1469]

I bought mine directly from the company on Aliexpress, mine both worked for about a month before the one broke. Like you it still got warm, it's as though the amp is generating the signal but for whatever reason its not getting to the speaker maybe the switches where faulty?

They were out of stock on the Fosi website for a while, so possibly there was a bad batch.

Did you use XLR or RCA?

I tried both, even though the xlr was an adapter to rca going in to schitt.