Fosi Audio V3 Mono Amplifier Review

[NTK]

Unless I have misunderstood, this is the issue, the signal level voltage, required to obtain full output from an XLR balanced input is double that that is normally available from unbalanced RCA. Connecting an unbalanced RCA output signal to a balanced XLR input will work but may limit the power output of the connected power amplifier.

Yep. With 20 dB gain (= 10X voltage amplification), a 2 V max input can give a maximum 50 W into 8 ohm (= 20^2/8), or 100 W into 4 ohm, etc. The recent trend of imposing low gain by amplifier manufacturers limits the usefulness of the balanced inputs.

 

[antcollinet]

Yep. With 20 dB gain (= 10X voltage amplification), a 2 V max input can give a maximum 50 W into 8 ohm (= 20^2/8), or 100 W into 4 ohm, etc. The recent trend of imposing low gain by amplifier manufacturers limits the usefulness of the balanced inputs.

Which might be a problem when driving from RCA outputs. But most balanced outputs can do 4V output (or more) which with 20dB will allow 4x the power you mention above.

 

[roog]

Well the soldering of cables has been done and a V3 is sat behind each speaker and they seem happy enough. My ATC SCM40 loudspeaker specifications state that they do 85dB @ 1W @ 1metre and they perform well. My normal amp, a 90W per ch class A/B effort lies cold!

After a couple of hours at my normal listening levels, ‘comfortable’ think loud enough to annoy the ‘mother-in-law’ the V3s are warm to touch and the 48V 5A power bricks are cold.

This is probably no surprise to you lot. :0)

 

[GabrielPhoto]

This is not a huge surprise. They will only have a benefit if:

1 - you have audible ground loop noise
2 - the cable is specifically constructed as described above by @NTK with separate ground wire and 0V/negative reference wire running the length of the cable**, so three wires in total. In which case you should get in the region of 30dB reduction in the ground noise.

** many or most RCA to XLR just run two wires and connect negative terminal to ground inside the XLR cable.

View attachment 413569
Yes

Ok thats good BUT then you replied that the monoprice cable has 3 wires and it still didnt do anything positive when I tested it, in fact the opposite. Like I actually got more hiss and less spl when I tested it with the Monolith 7x.
I am going to try that BB22 and see what I get with that.

 

[antcollinet]

Like I actually got more hiss and less spl when I tested it with the Monolith 7x.

The SPL makes sense if your monolith (as is common) has less gain on the balanced input.

Hiss could make sense if the hiss is Monolith amp hiss - and nothing to do with the cable, except that you have to turn the amp volume up to compensate for the lower gain on the balanced input.

LIke I said above. Balanced cables are only a solution to noise picked up on the cable (or generated in the cable earth as a result of ground currents). They can do nothing for other sources of noise.

 

[GabrielPhoto]

The SPL makes sense if your monolith (as is common) has less gain on the balanced input.

Hiss could make sense if the hiss is Monolith amp hiss - and nothing to do with the cable, except that you have to turn the amp volume up to compensate for the lower gain on the balanced input.

LIke I said above. Balanced cables are only a solution to noise picked up on the cable (or generated in the cable earth as a result of ground currents). They can do nothing for other sources of noise.

Ok but my point is, why I got more hiss and one db less of output with that rca to xlr monolith vs my rca to rca Blue Jeans LC-1.
That was my point. So I literally gained nothing but more hiss and less output at least with the Monolith amp. So your thought is the XLR on the Monolith has an issue?

 

[antcollinet]

Ok but my point is, why I got more hiss and one db less of output with that rca to xlr monolith vs my rca to rca Blue Jeans LC-1.
That was my point. So I literally gained nothing but more hiss and less output at least with the Monolith amp. So your thought is the XLR on the Monolith has an issue?

Not possible to say categorically in your specific case without specifically examining your gear to work out where the noise in the system is, and what the gain structure is.

I've given a couple of reasons why it MIGHT be happening.

 

[SMen]

Yep. With 20 dB gain (= 10X voltage amplification), a 2 V max input can give a maximum 50 W into 8 ohm (= 20^2/8), or 100 W into 4 ohm, etc. The recent trend of imposing low gain by amplifier manufacturers limits the usefulness of the balanced inputs.

+1 - Topping I understand have been 'canny' about gain for best measurement results - lower gain for better measurements in the amps, and then (having just been reading about their Centaurus DAC) they have switchable balanced outputs to increase a typical 4v up to 5v (or 2v to 2.5v in the case of RCA). So this seems a bit 'canny' too. I am pretty sure it was a youtube video about measurements by 'Goldensound' that he pointed out that the gain in a Topping was also optimized for the measurement equipment most often used for measuring such devices.

But then the use case of RCA to balanced is maybe not what the manufacturers need to optimize for. I might get a set of those cables just to have though - interesting about the correct wiring for noise @antcollinet .

 

[ah-ra]

If there is, I haven’t seen it. My dad listens a few hours a day with the V3 Monos I gave him, driving Maggie LRS+ to levels a good bit higher than I listen to, and has had zero issues so far.

-Ed

Does the Fosi V3 match well with the LRS+? I have the original LRS and am looking for a good amp to combine it with. At least the original LRS habe somewhat exaggerated mids, which can be annoying if the amp sounds too harsh. Yes I know some people don't believe amps can sound different, but to some extent for me they seem to do...

I remember you also had the b100 from topping which has far less power, but did you try those with the LRS as well? If so, how do they compare.

 

[Deleted member 72219]

Does the Fosi V3 match well with the LRS+? I have the original LRS and am looking for a good amp to combine it with. At least the original LRS habe somewhat exaggerated mids, which can be annoying if the amp sounds too harsh. Yes I know some people don't believe amps can sound different, but to some extent for me they seem to do...

I remember you also had the b100 from topping which has far less power, but did you try those with the LRS as well? If so, how do they compare.

The V3 Mono pair wonderfully with the LRS+!

I would not attempt to drive LRS+ with B100. Nowhere near enough power. Maybe B200…maybe.

-Ed

 

[Bleib]

I’m currently soldering the shortest speaker cables that I have ever made :0)

The only thing I might be concerned about is the big magnets on the speaker drivers. It's the only thing I can think of which could alter normal operation

 

[roog]

The only thing I might be concerned about is the big magnets on the speaker drivers. It's the only thing I can think of which could alter normal operation

Hopefully with the drivers halfway up the height of the speaker enclosure and the V3s about an 1 1/2" off the ground I should be OK. Only thing I ever buggered up when working on speakers was my mechanical watch!

 

[C0mbat]

I have the Fosi Audio V3 Monos and was wondering if I will be able to perceive any increase in perceived sound quality by "upgrading" to one of the many Hypex based amps? I listen at levels around 65-70db and currently only use the amps above 85hz as I'm using a high pass filter on the WiiM Ultra with the Kef KC62 sub doing the grunt work below 85hz. I've been more than happy with the Fosi Audios so will spending £800+ doing anything for me?

 

[somebodyelse]

I have the Fosi Audio V3 Monos and was wondering if I will be able to perceive any increase in perceived sound quality by "upgrading" to one of the many Hypex based amps? I listen at levels around 65-70db and currently only use the amps above 85hz as I'm using a high pass filter on the WiiM Ultra with the Kef KC62 sub doing the grunt work below 85hz. I've been more than happy with the Fosi Audios so will spending £800+ doing anything for me?

I'd go with 'unlikely' - at those volumes you're unlikely to be pushing the power too hard, so I guess you've not hit clipping or overheating problems.

 

[gwing]

I have tried many rca to xlr cables and never found one that was actually any better than a high quality rca to rca in fact if anything it was worst like with the monolith 7x
If you got a recommendation I would give it a shot

I think you should be able to get improvement by using an RCA/XLR adapter provided it is one wired as described above but it is a compromise compared to using two true XLR devices. It depends how much you want this, but what I do and therefore I guess my recommendation is to use the optical output from the Wiim to an external XLR DAC, which likely also gives the opportunity to have a proper physical volume control.
Ah, just realized this is an old post I replied to. I'll leave it here anyway though.

 

[GabrielPhoto]

I think you should be able to get improvement by using an RCA/XLR adapter provided it is one wired as described above but it is a compromise compared to using two true XLR devices. It depends how much you want this, but what I do and therefore I guess my recommendation is to use the optical output from the Wiim to an external XLR DAC, which likely also gives the opportunity to have a proper physical volume control.
Ah, just realized this is an old post I replied to. I'll leave it here anyway though.

Just to confirm,I got that monoprice cable again and tested with my new amp and same thing. I have to adjust the level boosting 6db to match the SPL of the rca to rca which then makes noise louder than with the rca to begin with

 

[cfwotzka]

I have the Fosi Audio V3 Monos and was wondering if I will be able to perceive any increase in perceived sound quality by "upgrading" to one of the many Hypex based amps? I listen at levels around 65-70db and currently only use the amps above 85hz as I'm using a high pass filter on the WiiM Ultra with the Kef KC62 sub doing the grunt work below 85hz. I've been more than happy with the Fosi Audios so will spending £800+ doing anything for me?

I own different Hypex-Modules based amps including. Nilai500 and at least I think Fosi Mono's are even par

 

[Deleted member 72219]

I own different Hypex-Modules based amps including. Nilai500 and at least I think Fosi Mono's are even par

Have you compared the newer Nilai/nCoreX modules against the original core modules like NC252MP? Is the difference even audible or is it mostly just more power?

-Ed

 

[cfwotzka]

Have you compared the newer Nilai/nCoreX modules against the original core modules like NC252MP? Is the difference even audible or is it mostly just more power?

-Ed

Unfortunately not. I've have only NC400, NCx500 and UCD2K beside the Nilai500 here. In summary to my ears Nilai500 is most musical (but a bit to cold for my ears although driven by tube preamp). more fun is Fosi V3 Mono and even better 3E Audio modules that I built two mono amps on.
Looking forward these days to receive the new 3E Audio finished mono amps.

 

[antcollinet]

Just to confirm,I got that monoprice cable again and tested with my new amp and same thing. I have to adjust the level boosting 6db to match the SPL of the rca to rca which then makes noise louder than with the rca to begin with

That is an odd result. Because all you are doing is compensating the 6dB lower gain on the XLR input that the RCA already has. So the effective gain when you've turned up the XLR inputs is the same as on the RCA inputs.

At the very least it suggests the noise is not ground loop noise picked up along the cable, but must be picked up inside the amp AFTER the gain stage. I'd be looking at proximity of the amps to sources of interference.