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Fosi Audio V3 Mono Amplifier Review

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 16 1.9%
  • 2. Not terrible (postman panther)

    Votes: 27 3.3%
  • 3. Fine (happy panther)

    Votes: 158 19.1%
  • 4. Great (golfing panther)

    Votes: 625 75.7%

  • Total voters
    826
To be honest the picture becomes not clearer. On what MV we have 1.1-1.4 Volt on the preouts, when speaker level trim is 0 and audio source signal is 0DB?
Roughly about as shown in the table you got from Gemini. As I posted before, the only thing I said was wrong was about the 1.2 V at volume 82.5, it should be 2 V as per Amir’s measurements. Gemini’s calculations is correct.

If you have more questions I will respond in a few hours when I get home. I hate typing on the phone.
 
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Another issue is the volume setting. My denon shows db from 0 (reference) down to about -80. Depending on internal settings it might also go as high as +12.

Your volume control is showing 79 as the highest down to 40. So this is not a DB dispaly- though the calculation behaves as though it is in db steps. (Each 3dB being 1/root 2 of the higher value.)

So 40 low to 79 high makes no sense (unless the Denon can be set to show a percentage - I'm not sure about that. But then why only go up to 79?
 
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denon can be set to dB or a Volumen scale 0-98; 80 = ref 0dB, so 40 = -40 db (used nightly when wifey and kids sleep); wanted to know how much the output voltage is to get a intention for my gain chain Denon pre out to ADC -10dBV to DAC +4dbu to Fosi V3 mono XLR in.
 
Thanks, you said 1.2 V and that made me wonder. If ASR is the reference, it should be about 2 V, input being 0dBFS.
ASR uses 2V as a nominal 0dBFS as that's more or less the de facto reference level for HiFi - because HiFi doesn't have a standardised reference level. More often than not they end up pretty close to that level, though we find a few capable of a bit more or less. AV kit is different - they have defined standard levels (although there are some minor differences between the standards they generally follow). There are also cases where manufacturers decide it's worth exceeding the relevant standards - like accepting HiFi DACs might produce higher output levels, so making sure your analog inputs can handle that level as well as the lower AV standard levels.
 
To be honest the picture becomes not clearer. On what MV we have 1.1-1.4 Volt on the preouts, when speaker level trim is 0 and audio source signal is 0DB?

Okay, got home, done my calculations and here's the table (I did do a quick check and the numbers look right, but if anyone find something wrong, please let me know so I can fix/edit it.

Note: Your AI (Gemini) table is correct in terms of the calculations as @antcollinet said before, but the numbers are not quite right because their assumptions appear to be based on 1.4 V at MV=80, I don't know why they assume that. Amir did the measurements and he typically set volume to 82.5 as he would get roughly 2 Vrms, and that's his standard for measuring pre out unbalanced/RCA output.

1783113441800.png


Reference graph based on Amir's review/measurements on the AVR-X4700H:

1783113736250.png
 
ASR uses 2V as a nominal 0dBFS as that's more or less the de facto reference level for HiFi - because HiFi doesn't have a standardised reference level. More often than not they end up pretty close to that level, though we find a few capable of a bit more or less. AV kit is different - they have defined standard levels (although there are some minor differences between the standards they generally follow). There are also cases where manufacturers decide it's worth exceeding the relevant standards - like accepting HiFi DACs might produce higher output levels, so making sure your analog inputs can handle that level as well as the lower AV standard levels.
Of course, also, the 2 V at volume 82.5, 0dBFS input is what Amir found for the D+M AVP/AVRs, other brands could well be different.
 
Thanks for the interesting answers. But then why, if I use the pre-outs of the Cinema 70s and connect them to a 3e Audio A5, I hear about 8 dB less than if the speakers were connected directly to the Marantz? To level the volumes, I have to go into the Marantz settings and increase the volume of the speakers connected to the 3e Audio A5.
 
But then why, if I use the pre-outs of the Cinema 70s and connect them to a 3e Audio A5, I hear about 8 dB less than if the speakers were connected directly to the Marantz?
Because in your current configuration, the 'Cinema 70s -> Speakers' chain has 8dB more gain than the 'Cinema 70s Pre out -> 3e Audio A5 -> Speakers' chain.

You can change gain via the Marantz volume control, the A5 RCA gain toggle, and the A5 volume knob.
 
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and does this depend on the fact that the pre-out of the 70s cinema outputs at a low voltage? The A5 already has the gain set to high and the volume bypassed.
 
and does this depend on the fact that the pre-out of the 70s cinema outputs at a low voltage? The A5 already has the gain set to high and the volume bypassed.
The signal gain of your chain is made up of DAC gain (how much Line voltage your DAC puts out for a given input signal) and Amp gain (how much your Amp amplifies the Line signal).
 
and does this depend on the fact that the pre-out of the 70s cinema outputs at a low voltage? The A5 already has the gain set to high and the volume bypassed.
If you go with rca into the A5 and set it to high gain (26dB) the input sensitivity of the A5 is 1.75V. That’s pretty high. Even if you set the MV at 80/80 (and get blown out of your room), it’s not enough; look at pengs helpful table. My hearing level is max. 65 MV = only 0.267V. That’s why I have a little ADC/DAC between my Denon and my Fosi/3eaudio amps, for a hotter signal.
 
If you go with rca into the A5 and set it to high gain (26dB) the input sensitivity of the A5 is 1.75V. That’s pretty high. Even if you set the MV at 80/80 (and get blown out of your room), it’s not enough; look at pengs helpful table. My hearing level is max. 65 MV = only 0.267V. That’s why I have a little ADC/DAC between my Denon and my Fosi/3eaudio amps, for a hotter signal.
Yes, in fact, I also have Klipsch speakers that are efficient and the volume can even be at 50 at times... can you link me to these objects that you use to increase the voltage? (if I understood their purpose correctly)
 
Thanks for the interesting answers. But then why, if I use the pre-outs of the Cinema 70s and connect them to a 3e Audio A5, I hear about 8 dB less than if the speakers were connected directly to the Marantz?

The A5 has a gain setting of low (23 dB) and high (29 edit: typo, it should be 26dB), versus the Marantz power amp gain of about 28.5 to 29 dB so there is a difference of as much as 6 dB if you have your A5 set to 23 dB gain. If you are getting 8 dB difference, when it should only be 3 dB difference (you said you set it to high already and bypass volume) something is wrong and you should investigate and hopefully identify the reason. May be somehow you are not really on volume bypass? Just to be double sure/safe, turn the volume knob to maximum anyway.

To level the volumes, I have to go into the Marantz settings and increase the volume of the speakers connected to the 3e Audio A5.

That's the way to do it, nothing wrong with that.
 
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The A5 has a gain setting of low (23 dB) and high (29 dB), versus the Marantz power amp gain of about 28.5 to 29 dB so there is a difference of as much as 6 dB if you have your A5 set to 23 dB gain. If you are getting 8 dB difference, when it should only be 3 dB difference (you said you set it to high already and bypass volume) something is wrong and you should investigate and hopefully identify the reason. May be somehow you are not really on volume bypass? Just to be double sure/safe, turn the volume knob to maximum anyway.



That's the way to do it, nothing wrong with that.
Yes, with the gain set to high, I get a significantly lower volume with the 3e audio A5, while it should be more or less the same. In my ignorance, I thought this difference was due to the low voltage supplied by the Marantz pre-out (1.2V) compared to the sensitivity of the 3e audio A5 of 1.75V.
 
and does this depend on the fact that the pre-out of the 70s cinema outputs at a low voltage? The A5 already has the gain set to high and the volume bypassed.
No, if it is then you will have the same issue with the speakers connected directly to the Marantz. Again, you should not be getting 8 dB difference, should only be 3 dB, may be +/- 0.5 dB. Double check everything, and you will find the culprit.
 
The A5 has a gain setting of low (23 dB) and high (29 dB), versus the Marantz power amp gain of about 28.5 to 29 dB so there is a difference of as much as 6 dB if you have your A5 set to 23 dB gain. If you are getting 8 dB difference, when it should only be 3 dB difference (you said you set it to high already and bypass volume) something is wrong and you should investigate and hopefully identify the reason. May be somehow you are not really on volume bypass? Just to be double sure/safe, turn the volume knob to maximum anyway.



That's the way to do it, nothing wrong with that.
the a5 is 23/26; the a7 is 26/29 in both cases single-end. with xlr it’s 17dB (a5) and 20dB (a7)
 

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the a5 is 23/26; the a7 is 26/29 in both cases single-end. with xlr it’s 17dB (a5) and 20dB (a7)
Thanks, that was just a typo, I know it is 26, that's why I told him the difference should only be 3 dB vs the Marantz build in power amps, edited now.
 
Yes, with the gain set to high, I get a significantly lower volume with the 3e audio A5, while it should be more or less the same. In my ignorance, I thought this difference was due to the low voltage supplied by the Marantz pre-out (1.2V) compared to the sensitivity of the 3e audio A5 of 1.75V.
You are not the only one, lots of people would take the 1.2 V as the maximum and worry about nothing. Reality is, the maximum is much higher, at least that is the case for D+M AVRs/AVPs, and also the fact is, in many cases even 1.0 V could be high enough. Not everyone has low gain power amps, and/or low sensitivity speakers, long seating distance, listen to close to reference level. Obviously higher voltage capability is typically preferred, wouldn't hurt anyway, even if one does not need more than 1 V.
 
I measured five minutes ago with the sound level meter, 8dB difference with gain on high...same speakers and same distance
 
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