Fosi Audio V3 Amplifier Review

[Jimbob54]

my Denon is a PMA 700AE stereo integrated with pre-out. It has a direct source button and a button to exclude the power circuit to the speakers
connections:
Denon pre-out --- miniDSP input ------- miniDSP out ------- Fosi v3 input -----speakers

And for the benefit of new readers, just remind us why you can't go :

Source(s) - minidsp- denon - speaker and just use that as the sole amp?

Or even sources-minidsp-fosi-speakers?

 

[antcollinet]

I see. Since you never actually know if you are clipping some dynamic peaks, I guess you could use a bigger power supply for peace of mind though

You could. Or you could just ask "can I hear any distortion at my highest listening volume" and if the answer is no, get your much lower cost peace of mind that way.

 

[musica]

And for the benefit of new readers, just remind us why you can't go :

Source(s) - minidsp- denon - speaker and just use that as the sole amp?

Or even sources-minidsp-fosi-speakers?

no, I want to use the Denon as a preamp and the Fosi as a power amp. Is that really not possible?

 

[Jimbob54]

no, I want to use the Denon as a preamp and the Fosi as a power amp. Is that really not possible?

Yes, but you are having difficulty with gain staging. Life is a lot easier with only one amp.

 

[early rejecter]

And for the benefit of new readers, just remind us why you can't go :

Source(s) - minidsp- denon - speaker and just use that as the sole amp?

Or even sources-minidsp-fosi-speakers?

There’s an extensive thread here — IIRC he wants a physical volume control (i.e. not the MiniDSP remote) for several sources, and it needs to be upstream of the MiniDSP which is being used as a high/low pass filter for the power amp and a powered subwoofer.

 

[musica]

excuse my ignorance, but what does the lower or higher earnings entail?

 

[Jimbob54]

There’s an extensive thread here — IIRC he wants a physical volume control (i.e. not the MiniDSP remote) for several sources, and it needs to be upstream of the MiniDSP which is being used as a high/low pass filter for the power amp and a powered subwoofer.

Yes, I know that. But sadly we now have all this info in multiple different threads which means covering a lot of ground everytime. One question seems to lead to another etc etc. And then we end up way off topic on a review thread.

 

[Jimbob54]

excuse my ignorance, but what does the lower or higher earnings entail?

Not sure that translated properly. Earnings?

 

[ninetylol]

From the two spreadsheets from Fosi for V3 and V3 mono it seems a normal V3 with 48v10a supply gives the same power as 2x V3 monos with 48V5A supply. So i guess you dont really pay for more power but for prestige, better sinad and post feedback.

 

[musica]

Not sure that translated properly. Earnings?

what is the profit for an amplifier and how many db would be right?

 

[ninetylol]

what is the profit for an amplifier and how many db would be right?

Maybe use deepl.com or something, noone understands you.

 

[Jimbob54]

what is the profit for an amplifier and how many db would be right?

I get the sense you mean "gain" as thats the term I used earlier. Not the technical answer here but you seem to be struggling to get the input/ output levels right between Denon/ Mini DSP/ Fosi as others have said, you are clipping outputs/ inputs trying to find the right balance. In my opinion you are mixing too many variables.

 

[somebodyelse]

This is the 'gain' we're talking about: https://en.wikipedia.org/wiki/Gain_(electronics)
For amplifiers we're talking about voltage gain.

 

[Sokel]

I get the sense you mean "gain" as thats the term I used earlier. Not the technical answer here but you seem to be struggling to get the input/ output levels right between Denon/ Mini DSP/ Fosi as others have said, you are clipping outputs/ inputs trying to find the right balance. In my opinion you are mixing too many variables.

And we don't even know if miniDSP's is set right,cause if it's set at the 0.9V input voltage setting,no scheme will be right.

Edit:if it's the HD is 2/4V so ok,but this has to be defined.

 

[musica]

The miniDSP 2x4 HD can be set for an analog input sensitivity of 2 Vrms or 4 Vrms. The defaultas shipped is 2 Vrms.The 4 Vrms setting is useful if a source device produces more than 2 Vrms.

 

[antcollinet]

Not sure that translated properly. Earnings?

Gain?

I think he is not understanding the issue of gain staging.

EDIT : ninjad - multiple times. Shutting up.

 

[musica]

Gain?

I think he is not understanding the issue of gain staging.

EDIT : ninjad - multiple times. Shutting up.

yes

 

[antcollinet]

yes

It is simply the issue of undestanding input and output voltages of devices.

As you've described, the 2x4HD is set for 2V max input. So you need to make sure the source to that (Denon in this case) is not outputting more than 2V - or use the 4V setting.

Then you need to understand if a device has internal gain (if it amplifies or reduces the voltage from input to output). The 2x4 HD can do both depending on the settings. Worse - if you input the full 2V to the 2x4 HD, and then the filters inside actually increase that further in the digital domain, you can get digital clipping (when the result of the DSP is greater than 0dB FS).

And then what output voltage the 2x4 will output from the input voltage, any gain and filtering - and what the next device in the chain (Fosi) can accept (or needs).

Gain staging is about understanding the gain of each stage in the system (each device), and ensuring that it is all set up to work correctly.

 

[musica]

It is simply the issue of undestanding input and output voltages of devices.

As you've described, the 2x4HD is set for 2V max input. So you need to make sure the source to that (Denon in this case) is not outputting more than 2V - or use the 4V setting.

Then you need to understand if a device has internal gain (if it amplifies or reduces the voltage from input to output). The 2x4 HD can do both depending on the settings. Worse - if you input the full 2V to the 2x4 HD, and then the filters inside actually increase that further in the digital domain, you can get digital clipping (when the result of the DSP is greater than 0dB FS).

And then what output voltage the 2x4 will output from the input voltage, any gain and filtering - and what the next device in the chain (Fosi) can accept (or needs).

Gain staging is about understanding the gain of each stage in the system (each device), and ensuring that it is all set up to work correctly.

Can these too many variables also affect the spatiality of music?

 

[antcollinet]

Can these too many variables also affect the spatiality of music?

No - as long as you are not getting it wrong, and causing clipping somewhere. The best place to check is in the MiniDSP user interface which will tell you what levels it is working with.