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Fosi v3 Mono - User Impressions | Owner's Thread

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Guddu

Guddu

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Great review! What I am very interested in - given the 5W standby use - is the following: after the amp goes into auto off (so after 10 minutes), you disconnect the power plug (e.g. via the smart plug you use), and later turn in back on with the plug: does the amp turn on in standby mode (so without any 'plop'), or does it turn back on in 'on' mode?

Hopefully you can do this little test, as this might provide a smart home ready solution to the high standby power usage.

Just tested as you wanted, here it goes:

> When amplifier is in standby i.e., mode = Auto, power on/off operation on wall plug or smart plug does not move it to ON.
> On power ON by smart plug or cable in/out, amplifier stays in Auto (not turned ON) and pop sound is there and it's a bit louder than I would like it to be for protection of my speakers and peace of mind.
 

jvdburgt

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Just tested as you wanted, here it goes:

> When amplifier is in standby i.e., mode = Auto, power on/off operation on wall plug or smart plug does not move it to ON.
> On power ON by smart plug or cable in/out, amplifier stays in Auto (not turned ON) and pop sound is there and it's a bit louder than I would like it to be for protection of my speakers and peace of mind.
Thank you so much for trying! Good to know that a (well-designed) smart home solution is a viable option!

Basically, I could make an automation in home assistant to kill the power eg. 12 minutes after receiver is turned off, and to restore power when receiver is turned on :)
 

Rob_in

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Thanks for the info... may I ask what volume levels/attenuation (on the Topping E50) you generally run and absolutely max out at? Did you notice having to use more or less attenuation between Topping PA7 and Fosi V3 pair?

I ask because if I read correctly, your ELAC DBR62 speakers are rated at 120W/6 Ohm/86dB so in theory both the Topping PA7 and Fosi V3 pair can output a load more than the speakers can handle and imagine your E50 won't even get close to 0db?
 
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Guddu

Guddu

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Thanks for the info... may I ask what volume levels/attenuation (on the Topping E50) you generally run and absolutely max out at? Did you notice having to use more or less attenuation between Topping PA7 and Fosi V3 pair?

I ask because if I read correctly, your ELAC DBR62 speakers are rated at 120W/6 Ohm/86dB so in theory both the Topping PA7 and Fosi V3 pair can output a load more than the speakers can handle and imagine your E50 won't even get close to 0db?

I have this setup in a small room (11x10.5) and normally keep E50 around -25db for both PA7 (volume bypassed) and Fosi v3 mono both, I think their overall gain/output is very similar.
Around -15db it get's too loud for me.
 

EddNog

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A week and a day to go and then, first slowly, this thread will fill up with more impressions. Can't wait! :D
I’m SO ready!!!

-Ed
 

DannyBoyNYC

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Kudos to the first person to report measurements after an opamp switch (never gonna happen)!
 

G|force

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Thanks for sharing your thoughts and experiences with these @Guddu
If I was looking to drive some passive speakers, I would definitely try these. What I like most about them without trying them is that they could be powered directly from a PV 48V server rack battery.
 

Marss72

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Well guys, i have just pledged to 2x Fosi Audio V3 Mono ampflifiers. Don't know how it goes from here but i hope all goes well and i'll receive them soon
 

tranceFusion

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Can anyone tell me if I can use two unbalanced inputs into this amp by connecting the 2nd device using TS 1/4" cables into the XLR/Neutrik connector? Any issues or downsides with that?
 

Sokel

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Can anyone tell me if I can use two unbalanced inputs into this amp by connecting the 2nd device using TS 1/4" cables into the XLR/Neutrik connector? Any issues or downsides with that?
Mono jacks?
That will short cold and ground on amps side.

Just use an mono jack to RCA and connect it to the RCA input.
 

tranceFusion

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Mono jacks?
That will short cold and ground on amps side.

Just use an mono jack to RCA and connect it to the RCA input.

Sorry, I wasn't clear enough. I have two devices:

1) Turntable with RCA out
2) Apple Airport Express with 3.5mm out

I want to connect both of them to the amp and switch between them with the XLR/RCA switch.

I used a 3.5mm to double 1/4" TS cable to plug in the airport express and it "works", as in.. it sounds fine and the volume is reasonable.

What is the result of shorting cold and ground together? Is it possible the amp supports this scenario?

Is there a better way to connect one of the devices with unbalanced output to the XLR ports?
 

antcollinet

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Is there a better way to connect one of the devices with unbalanced output to the XLR ports?

Well if you are not prepared to make the special cable that'll adapt your unbalanced source to a balanced input, then the best way is to use the RCA input. That is what they are for.
 

EddNog

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Sorry, I wasn't clear enough. I have two devices:

1) Turntable with RCA out
2) Apple Airport Express with 3.5mm out

I want to connect both of them to the amp and switch between them with the XLR/RCA switch.

I used a 3.5mm to double 1/4" TS cable to plug in the airport express and it "works", as in.. it sounds fine and the volume is reasonable.

What is the result of shorting cold and ground together? Is it possible the amp supports this scenario?

Is there a better way to connect one of the devices with unbalanced output to the XLR ports?
A preamp with multiple single-ended inputs and a balanced output.

-Ed
 

tranceFusion

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Well if you are not prepared to make the special cable that'll adapt your unbalanced source to a balanced input, then the best way is to use the RCA input. That is what they are for.
I'm not really understanding the issue.. It seems like most sources online say that the result of the plugging the unbalanced output into the balanced input will just be an unbalanced signal.

"plugging unbalanced sources into balanced inputs causes no problems other than a 3dB level drop in some cases, depending on how the input stage is designed."

Aren't most solutions like a DI box just trying to maintain a balanced connection along as much of the cable run as possible? And with a preamp I still have to run the speakers to the preamp unbalanced.

If the amp had two sets of RCA inputs I would certainly use them.
 

MCH

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If the amp had two sets of RCA inputs I would certainly use them.
This might be a viable option if you don't want to DIY a cable. Please wait for others to confirm
Screenshot_20240609-085235.png
 

Sokel

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I'm not really understanding the issue.. It seems like most sources online say that the result of the plugging the unbalanced output into the balanced input will just be an unbalanced signal.

"plugging unbalanced sources into balanced inputs causes no problems other than a 3dB level drop in some cases, depending on how the input stage is designed."

Aren't most solutions like a DI box just trying to maintain a balanced connection along as much of the cable run as possible? And with a preamp I still have to run the speakers to the preamp unbalanced.

If the amp had two sets of RCA inputs I would certainly use them.
In that case this is the way to do it properly:

 
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