Fosi v3 Mono - User Impressions | Owner's Thread

[MCH]

This would combine the mono L/R signals into a single stereo plug, but the amp has only mono inputs.

The idea is to use only one of the RCA and leave the second not connected. The objective is not to short the second signal to ground as @Sokel pointed out in post #51. TRS to single rca cables with the ring floating are rare.

 

[antcollinet]

If only I didn’t need to make TWO stereo unbalanced connections. Starting to feel like I’m talking to a bunch of bots.

Each RCA is only ONE unbalanced connection. You need two (one on each amp) for stereo.

This is no difference from using the balanced connection. Each balanced connection is just one of the stereo channels. No matter whether you used the balanced or unbalanced connections, you need two cables from your source. One to each amp. I'm not getting your problem with the RCA.

If your source is a 3.5mm TRS jack, then you need 3.5mm trs to 2xRCA cable. For your turntable, just 2xRCA to 2xRCA. Or you use one of the TRS to RCA splitter connectors linked above, together with one 2xRCA to 2xRCA, and swap the cable between sources.

 

[CheesyTacos]

The idea is to use only one of the RCA and leave the second not connected. The objective is not to short the second signal to ground as @Sokel pointed out in post #51. TRS to single rca cables with the ring floating are rare.

The balanced circuit will take the intersection of the signals on each wire, so any information carried on only on left or right channel would be eliminated as noise, right? Also, how would any output make it to the other stereo channel?

I don’t see any explanation of why shorting the 2nd signal and ground together is a problem. Since the audio output sounds ok and there is no volume loss, it makes me think that the circuit is intended to detect this scenario and drop back to an unbalanced connection. And the fact that the jack size is the same makes me think ts and trs were intended to have some level of interoperability to begin with (the way a 3.5mm plug can have a 4th ring for mic but still backwards compatibility for use as stereo signal only).

Each RCA is only ONE unbalanced connection. You need two (one on each amp) for stereo.

This is no difference from using the balanced connection. Each balanced connection is just one of the stereo channels. No matter whether you used the balanced or unbalanced connections, you need two cables from your source. One to each amp. I'm not getting your problem with the RCA.

If your source is a 3.5mm TRS jack, then you need 3.5mm trs to 2xRCA cable.

Because I have two devices that I am trying to connect to the amp. They both output unbalanced signals, and there is only one set of RCA (aka pair aka one Left and one Right) jacks intended for connecting one device. So when I go to plug device 2 in I would put it in the RCA jacks if the plugs from device 1 weren’t already there. The problem with them is that they are already in use.

 

[drmevo]

Because I have two devices that I am trying to connect to the amp. They both output unbalanced signals, and there is only one set of RCA (aka pair aka one Left and one Right) jacks intended for connecting one device. So when I go to plug device 2 in I would put it in the RCA jacks if the plugs from device 1 weren’t already there. The problem with them is that they are already in use.

Does the turntable have volume control (pretty uncommon on decent units)? If not, how are you planning to manage that?

I think what a couple of folks are getting at is that you’d ideally have some type of preamp between the two sources and these power amps.

 

[Deleted member 72219]

If only I didn’t need to make TWO stereo unbalanced connections. Starting to feel like I’m talking to a bunch of bots.

My guy, my original suggestion still stands: a preamp with multiple single-ended inputs will solve your problem. It doesn’t even matter if the output is balanced or single-ended if you plan to just use it with V3 Mono monoblocs. A preamp with balanced output will cost more and may not be worth the difference in cost.

Calling us bots won’t endear us to help you in the future.

-Ed

 

[Guddu]

My guy, my original suggestion still stands: a preamp with multiple single-ended inputs will solve your problem. It doesn’t even matter if the output is balanced or single-ended if you plan to just use it with V3 Mono monoblocs. A preamp with balanced output will cost more and may not be worth the difference in cost.

Calling us bots won’t endear us to help you in the future.

-Ed

+1

Why don’t you keep it simple with a rca switch or multi-input pre-amp, you have many options under 50$.
It will also save you balanced input for another proper balanced output gear, and everything would work as it is supposed to be.

 

[CheesyTacos]

Does the turntable have volume control (pretty uncommon on decent units)? If not, how are you planning to manage that?

I think what a couple of folks are getting at is that you’d ideally have some type of preamp between the two sources and these power amps.

I see the confusion regarding the number of inputs. I intended to post this in the ZA3 user impression thread. That device is similar but has stereo inputs and volume control. This was my fault, sorry!!

 

[CheesyTacos]

My guy, my original suggestion still stands: a preamp with multiple single-ended inputs will solve your problem. It doesn’t even matter if the output is balanced or single-ended if you plan to just use it with V3 Mono monoblocs. A preamp with balanced output will cost more and may not be worth the difference in cost.

I'm not completely opposed, but I'd rather not spend extra money, add another piece of equipment to the signal chain, and have another piece of equipment that needs somewhere to live, if I get the same behavior from the existing circuit in the fosi amp... which is why I was trying to understand what is the downside of using the balanced jack for an unbalanced plug? It seems entirely plausible that this is a supported usage scenario by the device.

 

[Deleted member 72219]

I'm not completely opposed, but I'd rather not spend extra money, add another piece of equipment to the signal chain, and have another piece of equipment that needs somewhere to live, if I get the same behavior from the existing circuit in the fosi amp... which is why I was trying to understand what is the downside of using the balanced jack for an unbalanced plug? It seems entirely plausible that this is a supported usage scenario by the device.

Here you go, sir—much more affordable:

Amazon.com

If I’m not mistaken, given this is a dummy box, ASR types will advise that this should not affect sound quality.

-Ed

 

[Guddu]

‘Omitting to targeted queries’

I was trying to understand what is the downside of using the balanced jack for an unbalanced plug? It seems entirely plausible that this is a supported usage scenario by the device.

It will work, as long as signal and ground are present. Loads of plugs available (for about 10$ for a pair) with proper RCA to XLR where pin 1 & 3 are jumpered for ground and 2 for signal.
Downside - nothing except you consumed balanced input for unbalanced but thats your intended use here.
However, I totally doubt that a vendor would suggest customers to do that.

 

[YesChickenNuggets]

Thinking about ordering a pair. Can you guys tell me how the Ssssssssssss performance is? Is it louder or softer than say a V3 vanilla or A07 with the dial turned to the top middle?

 

[antcollinet]

The balanced circuit will take the intersection of the signals on each wire, so any information carried on only on left or right channel would be eliminated as noise, right?

That is mot making any sense to me. It might help if you draw a wiring diagram.

I don’t see any explanation of why shorting the 2nd signal and ground together is a problem.

Technically this will work and give you an output. However the way these amps work (I believe) with a balanced signal each of the balanced signals goes to one half of the btl amp. If you connect one side to ground the one half of the amp does nothing and the amp can only output 1/2 of the maximum voltage, limiting power by a factor of 4. The amp can only output 1/4 of rated power. .

 

[Guddu]

After running for about 2 Week
——————————————-
- working strong
- no issues observed other than pop sound
- runs a little warmer in general, however gets hot if drove hard which should not be a surprise
- 48v 10a with splitter cable works fine
- auto sense feature works just fine
- I ran these in a smaller room about 12 x 12‘ and these were good enough with more than required loudness, however, I ran these in living room over the weekend and I had to run it to their fullest to get required loudness making me realize they might suffer if you have large area to cover

Overall, probably the best available cheaper monoblock with very respectable performance.

 

[Sgt. Pepper]

I have KEF LS50 Metas. They require a fair amount of power to drive. They're in a 20x15 room. From all the glowing reviews, I thought these might be the way to have true monoblocs. Anyone with a large room using them with demanding speakers? If so, what's your opinion on music filling the room?

 

[drmevo]

I have KEF LS50 Metas. They require a fair amount of power to drive. They're in a 20x15 room. From all the glowing reviews, I thought these might be the way to have true monoblocs. Anyone with a large room using them with demanding speakers? If so, what's your opinion on music filling the room?

I don’t have the V3M’s yet, but I do have an Aiyima A07 Max (36v/6A PSU) which is the same chip, driving LS50 Metas in a somewhat similar room. I have plenty of power to spare with the Aiyima, and that’s just one amp in stereo mode.

Just a side note, music for sure “fills the room” when used with my sub, but no matter how much power you throw at the LS50s, I don’t think they’ll ever be as enveloping as larger speakers in decent-sized rooms. I might bump up to R3s myself someday for that reason, but I do love the imaging and detail with the LS50s.

 

[Guddu]

I have KEF LS50 Metas. They require a fair amount of power to drive. They're in a 20x15 room. From all the glowing reviews, I thought these might be the way to have true monoblocs. Anyone with a large room using them with demanding speakers? If so, what's your opinion on music filling the room?

Don’t know how loud you might go to realize room filling to your likings but v3 pair should be okay providing 70+ watts each channel, as long as your dac/pre-amp is decent.
You can use google to find calculator to find the power you might need for your desired spl, give it a try.

 

[Sgt. Pepper]

Thank you. I run a sub with the Metas. That makes all the difference.

 

[Deleted member 72219]

I have KEF LS50 Metas. They require a fair amount of power to drive. They're in a 20x15 room. From all the glowing reviews, I thought these might be the way to have true monoblocs. Anyone with a large room using them with demanding speakers? If so, what's your opinion on music filling the room?

I’m running a pair of LS50 Metas with an SVS SB-3000 sub in a room bigger than that, with a pair of ZA3s driving the KEFs and it gets plenty loud. This setup can easily overpower the room if I really crank it. You should be more than okay with a pair of the V3 Monos in your room driving LS50 Metas.

-Ed

 

[Sgt. Pepper]

I’m running a pair of LS50 Metas with an SVS SB-3000 sub in a room bigger than that, with a pair of ZA3s driving the KEFs and it gets plenty loud. This setup can easily overpower the room if I really crank it. You should be more than okay with a pair of the V3 Monos in your room driving LS50 Metas.

-Ed

Thanks!

 

[Electric_Haggis]

Hi all. I have 2 x PSB Imagine Surround S bipoles for side surrounds, yet to be installed.
(Presonus actives for all other channels).
These side surrounds will be 1.8m on either side of the MLP in a 3.5m wide x 5.5m deep room.
Pre-pro will be an Anthem AVM70, balanced cables to the amp.

How would these compare to the Topping PA5 II or SMSL AO200 Mk2 ?

Thanks in advance!