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Fosi Audio V3 Mono Amplifier Review
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Miser_Audioman
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Both mine are reversed
johnmartmill
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Wow, this is crazy. I mean I don't care how things are wired, but it gives me serious reservations about the quality of the product. How many people are going to run their speakers out of phase because they don't have a room correction software to check? This is bad, Fosi. This is really bad.
When a subwoofer needs to be integrated, you’d have to run the opposite phase to blend it in if you’re swapping from a different amp to these.
-Ed
I think I am now confusing myself. I posted over on the owner's thread about this.
Presumably if we test our v3 monos and find them out of phase we can just put the black into the red socket and vice versa - and then run the subwoofer as normal from pre-amp line outs. High level sums to mono anyway (with mine, if using one sub)
Presumably if we test our v3 monos and find them out of phase we can just put the black into the red socket and vice versa - and then run the subwoofer as normal from pre-amp line outs. High level sums to mono anyway (with mine, if using one sub)
Yes you can.
But I don't think there is a need to test - it looks like the Mono is inverting phase by design.
There seems to be some confusion though - why would Fosi invert phase by design?
I can see no problem if I connect my subwoofers through the high level.
But If I was to connect to the RCA out on my pre-amp ... then that's where it is all getting puzzling!
Post edit: I'm a couple of months away from my subwoofers to verify - Hopefully consensus will be reached here regarding this problem or not problem.
Conceivably something to do with PFFB architecture, or how they implemented that feature.
-Ed
Above my pay grade ... but I'll look forward to understanding if I should be reversing connections if I want to run a subwoofer! Or how I verify.
I used to put speakers facing each other to test phase (sound waves cancel each other out so sounds quiet).
If your subwoofer has phase controls, you may not need to flip speaker connections when blending it in anyway. My subwoofer has separate degree-by-degree phase adjustment from 0°-180° and then a separate phase flip option.
-Ed
Good point, they do indeed! I was not expecting my previous 3255 chip amp to be my verification tool for balanced, RCA inputs and speaker outputs mind you.
Sokel
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You better all check if this happens with both XLR and RCA.
They could differ and it's (sad to say) a newbie mistake that DIYers often do at the start of the hobby.
(then we learn
)
Major fail for a commercial product thought.
I wonder if the usual "reviewers" threw it in their systems with integrated subs as-is and then raved about "open" sound
They could differ and it's (sad to say) a newbie mistake that DIYers often do at the start of the hobby.
(then we learn
)Major fail for a commercial product thought.
I wonder if the usual "reviewers" threw it in their systems with integrated subs as-is and then raved about "open" sound
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Bleib
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"If it's a stereo preamp, you could play monophonic music through both channels and notice the bass level with just one channel playing and then both channels playing. If the bass increases when the 2nd channel is added, then the channels are in phase. If the bass disappears, then an out of phase condition exists."
So this is one way to check if the phase is OK
So this is one way to check if the phase is OK
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The best people to explain the circuit are @Fosi Audio
Could we please have clarification here? Reversal of phase from standard.
Or this will, I suspect, fester.
When I say "by design" I don't necessarily mean they intended to invert phase. I mean the devices are "as specified" or "as drawn". The design - if I am correct - is faulty.
IE it is not (IMO) a manufacturing fault in that the people building them are making mistakes. So I suspect that all devices will be inverted.
Apparently Fosi isn't the only company with opposite polarities for single-ended and differential inputs. For example:
www.stereophile.com
Audio Research Reference 160S power amplifier Measurements
Sidebar 3: Measurements
www.stereophile.com
I don't think we know if FOSI is different between balnaced/unbalanced yetApparently Fosi isn't the only company with opposite polarities for single-ended and differential inputs. For example:
View attachment 382117Audio Research Reference 160S power amplifier Measurements
Sidebar 3: Measurements
Do you people want me to do a test to see if running one V3 Mono balanced and the other channel single-ended and then level matched actually shows a phase mismatch? The level matching will be done with pink noise, a free app and *gasp* an iPhone mic, and the phase match/mismatch will be done *TRIGGER WARNING* by ear. However, I can do it very easily (since my preamp can output balanced and single-ended simultaneously, even in passive mode). And then report back?
Or you can just tell me that’s worthless to you and I’ll save my results for myself.
-Ed
Or you can just tell me that’s worthless to you and I’ll save my results for myself.
-Ed
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