Fosi Audio V3 Mono Amplifier Review

[JimFarrell29]

Indeed.
I bought the Fosi because I wanted a flavour of Class D without the big price tag. If I could justify it I would get a Purifi Eigentakt based amp from someone like Boxem.
Unfortunately (or fortunately) I have a wide selection of Class A and AB amps I am very attached to.

Of course not - it is not intended to be.

The person I was replying to already has the Boxem. He was asking if he should "upgrade" to the Monos.

So in this case, the "upgrade" for lower objective performance, plus all the other differences discussed would cost additional money. It would clearly make no sense.

He has the better amp already.

D

 

[Doodski]

Indeed.
I bought the Fosi because I wanted a flavour of Class D without the big price tag. If I could justify it I would get a Purifi Eigentakt based amp from someone like Boxem.
Unfortunately (or fortunately) I have a wide selection of Class A and AB amps I am very attached to.

D

Hey Jim @JimFarrell29 are you from British Columbia south area? I grew up with a Jim Farrell.

 

[MichaelJ]

I just received two V3 Monos. They're replacing two ZA3s that were running in "mono" so that I can repurpose the ZA3s to other smaller systems in the house (and because I couldn't help seeing how the new V3 Monos compare...)

The system is digital and uses XLR connectors: MiniDSP SHD > (2x) Topping D30PRO > (2x) V3 Monos > passive bookshelves (I handle bass management in the SHD and cross over to (2x) powered subs)

First thing I noticed was that the gain on the V3 monos was much less that the ZA3s, which I had previously set to maximum on the volume knob. I ran in-room measurements at my listening position, and the difference is about 10db. I had to dial down the gain on my powered subs to match.

Is this what we'd expect? My assumption was that the ZA3 at full volume would be the same as the set gain on the V3 Mono.

 

[EddNog]

I just received two V3 Monos. They're replacing two ZA3s that were running in "mono" so that I can repurpose the ZA3s to other smaller systems in the house (and because I couldn't help seeing how the new V3 Monos compare...)

The system is digital and uses XLR connectors: MiniDSP SHD > (2x) Topping D30PRO > (2x) V3 Monos > passive bookshelves (I handle bass management in the SHD and cross over to (2x) powered subs)

First thing I noticed was that the gain on the V3 monos was much less that the ZA3s, which I had previously set to maximum on the volume knob. I ran in-room measurements at my listening position, and the difference is about 10db. I had to dial down the gain on my powered subs to match.

Is this what we'd expect? My assumption was that the ZA3 at full volume would be the same as the set gain on the V3 Mono.

No, I found the same. Comparing XLR to XLR, ZA3 at full volume is much louder than V3 Mono.

-Ed

 

[gwing]

I just received two V3 Monos. They're replacing two ZA3s that were running in "mono" so that I can repurpose the ZA3s to other smaller systems in the house (and because I couldn't help seeing how the new V3 Monos compare...)

The system is digital and uses XLR connectors: MiniDSP SHD > (2x) Topping D30PRO > (2x) V3 Monos > passive bookshelves (I handle bass management in the SHD and cross over to (2x) powered subs)

First thing I noticed was that the gain on the V3 monos was much less that the ZA3s, which I had previously set to maximum on the volume knob. I ran in-room measurements at my listening position, and the difference is about 10db. I had to dial down the gain on my powered subs to match.

Is this what we'd expect? My assumption was that the ZA3 at full volume would be the same as the set gain on the V3 Mono.

It will depend on the gain of your components but I'm a bit surprised. I run Wiim-> Aurora DAC/Pre -> XLR Monos ->89db speakers and there is many times the gain I need available - I run the pre at just a quarter turn on the volume knob to protect against full signal output.

 

[rwnano]

Harman Kardon AVR 3550 (2002) vs. [Harman Kardon AVR 240 with pre-outs + Fosi V3 next gen twin monoblocks] - projected difference in sound quality?​

Which system would sound better -

1. The Harman Kardon AVR 3550

https://www.fein-hifi.de/Surround-R...on-AVR3550-Digital-5-1-AV-Receiver::3557.html

vs.

2. HK AVR 240 with Fosi V3 next gen twin monoblocks on the Pre-Outs

https://www.newegg.com/harman-kardo...gKcp24j9IBeuyULqbh2xwZi3nEkhiI5XUUOFaiVa5VKeK

with SPEAKERS:

1. 89 dB inefficient Transmission Line speakers - Irving M Fried Signature A 6 &
2. Focal 706 V2

Rest of the chain:

Ubuntu Linux Laptop Spotify - Topping D10s DAC --> Amplifier --> speakers

* I use a cheap home theatre subwoofer thus its a 2.1 configuration

 

[NTK]

I just received two V3 Monos. They're replacing two ZA3s that were running in "mono" so that I can repurpose the ZA3s to other smaller systems in the house (and because I couldn't help seeing how the new V3 Monos compare...)

The system is digital and uses XLR connectors: MiniDSP SHD > (2x) Topping D30PRO > (2x) V3 Monos > passive bookshelves (I handle bass management in the SHD and cross over to (2x) powered subs)

First thing I noticed was that the gain on the V3 monos was much less that the ZA3s, which I had previously set to maximum on the volume knob. I ran in-room measurements at my listening position, and the difference is about 10db. I had to dial down the gain on my powered subs to match.

Is this what we'd expect? My assumption was that the ZA3 at full volume would be the same as the set gain on the V3 Mono.

If PFFB is implemented per the TI application note, part of the gain of the TPA chip is consumed by the feedback. See below for the example in the app note using TPA3251. The normal gain of the chip is 20 dB. 7.2 dB is used up by the PFFB in the example, leaving the gain of the final PFFB amplifier to be 12.8 dB.

 

[drmevo]

No, I found the same. Comparing XLR to XLR, ZA3 at full volume is much louder than V3 Mono.

-Ed

I found the same comparing to my Aiyima A07 Max, albeit using RCA for both.

However, the the V3Ms are roughly equivalent volume-wise to the Pascal amp in my integrated amp, which is now being used as a preamp. I find myself settling on the same volume levels for different inputs that I used previously. When I used the Aiyima for a short stint, I left its volume knob a few notches away from full to achieve the same. So, the V3Ms certainly don't seem underpowered or anything.

 

[EddNog]

I found the same comparing to my Aiyima A07 Max, albeit using RCA for both.

However, the the V3Ms are roughly equivalent volume-wise to the Pascal amp in my integrated amp, which is now being used as a preamp. I find myself settling on the same volume levels for different inputs that I used previously. When I used the Aiyima for a short stint, I left its volume knob a few notches away from full to achieve the same. So, the V3Ms certainly don't seem underpowered or anything.

No, definitely not underpowered. Just lower gain than ZA3 by a large amount. Not the same.

-Ed

 

[MichaelJ]

This is more of a general gain-stage question: But, assuming the DSP in the SHD has sufficient digital headroom built-in, am I correct that I’m better off, from a performance standpoint, using the lower gain V3 mono’s and listening closer to 0.0db on the MiniDSP SHD?

 

[jvdburgt]

Reading all the posts, just a general wondering, but I’m wondering how you all rate the coolness factor.

I come from a decent 5.2 setup with a Marantz SR6010 receiver, a Yamaha AX-892 to power the fronts (Monitor Audio GS10) and the center (Monitor Audio GSLCR) & surrounds (Minitor Audio RX1) via the Marantz, and 2x Monitor Audio RXW12 with their own internal 500W amp. I did away with the Yamaha, and now each speaker has its own V3M to drive it.

Now, to be fair, I haven’t driven the V3Ms to the max (yet) but they sound at least as good as the previous setup. Three things that make me happy at the moment:
1. Each speaker now has its own dedicated amp (and they are thus driven the exact same way)
2. Each speaker now has its own dedicated amp (which just looks fucking cool)
3. The whole “running hot” situation gave me a nice excuse to actively cool my media cabinet and with smart plugs on both ventilators (USB) and amps and automate the whole thing with Home Assistant

Now, with what I’ll get back for the Yamaha on eBay, the V3Ms hardly put a dent in my budget.

No measurements, nothing objective, just a little bit of geek happiness for a few extra bucks.

Just curious about your more subjective experiences with the new setup.

 

[antcollinet]

I just received two V3 Monos. They're replacing two ZA3s that were running in "mono" so that I can repurpose the ZA3s to other smaller systems in the house (and because I couldn't help seeing how the new V3 Monos compare...)

The system is digital and uses XLR connectors: MiniDSP SHD > (2x) Topping D30PRO > (2x) V3 Monos > passive bookshelves (I handle bass management in the SHD and cross over to (2x) powered subs)

First thing I noticed was that the gain on the V3 monos was much less that the ZA3s, which I had previously set to maximum on the volume knob. I ran in-room measurements at my listening position, and the difference is about 10db. I had to dial down the gain on my powered subs to match.

Is this what we'd expect? My assumption was that the ZA3 at full volume would be the same as the set gain on the V3 Mono.

ZA3 gain on XLR is 26dB. On the V3 mono, it is 20dB. You need double the voltage into the Mono to get the same output.

 

[Bleib]

ZA3 gain on XLR is 26dB. On the V3 mono, it is 20dB. You need double the voltage into the Mono to get the same output.

Isn't it ideal for a 4v pre-amp function from a DAC? I seem to recall reading it in this topic

 

[antcollinet]

Isn't it ideal for a 4v pre-amp function from a DAC? I seem to recall reading it in this topic

20dB is x10, so 40V out. This would be enough for 200W at 8 ohm, or 400W at 4 ohm. Both exceed the power rating of this amp - so yes it is more than enough for a 4V output source.

 

[MCH]

This is more of a general gain-stage question: But, assuming the DSP in the SHD has sufficient digital headroom built-in, am I correct that I’m better off, from a performance standpoint, using the lower gain V3 mono’s and listening closer to 0.0db on the MiniDSP SHD?

iI don't remember well but you might want to read minidsp instructions or their forum. iirc, if you use Dirac live, they recommend max of -10dB.

 

[Kimbrough Xu]

It occurs to me that the people here who want to try op amp changes could usefully A/B a mono track, and switch between one mono unit with one set of opamps, and the other with stock NE5532's. Put the speakers next to each other. Get a mate (or suitable relation) to switch so the listener is blind. This ought to settle things for the experimenters (themselves) - could they identify which was which?

A whole new purpose for mono power amps . Think I might give this a go for the hell of it. Rope in my kids.

Dont need to be that complicated, Fosi Audio LC30 is used for comparison.

 

[Kimbrough Xu]

Good to know. FYI I make my case on the basis that my power amps all have line out - suitable for daisy chaining (bi amping), or subs.

How do you set the crossover when bi amping?

 

[seaninbrisbane]

I'm just about to set up LCR speakers for the first time with three Fosi Monos plus a home theatre AVR (+ active sub). Am I correct in thinking that I should invert the red and black connections at the rear of the three mono amps?

 

[JeremyFife]

I'm just about to set up LCR speakers for the first time with three Fosi Monos plus a home theatre AVR (+ active sub). Am I correct in thinking that I should invert the red and black connections at the rear of the three mono amps?

Not necessarily.

#1 are you using balanced or single-ended connections?
#2 do you know what your AVR and sub do to the signal polarity

It seems to depend

My understanding is that the Fosi's maintain signal polarity when you use balanced connections (there is a little debate about that actually, hopefully someone can clarify) whereas the signal polarity is reversed when using single-ended connections.

So: IF you are using balanced connections AND your AVR/Sub also maintain signal polarity THEN connect everything up as normal.
Otherwise you need to work out what's going on and connect accordingly.

You can just wire it all up and listen to it too

 

[Bleib]

I'm just about to set up LCR speakers for the first time with three Fosi Monos plus a home theatre AVR (+ active sub). Am I correct in thinking that I should invert the red and black connections at the rear of the three mono amps?

Well, you have to measure things with the mic anyway right, and if it's a Denon it should check the phase anyway..