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Fosi Audio V3 Mono Amplifier Review
- Thread starter amirm
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If it is, it has nothing to do with the power supply I would think. More likely device to device tolerances.
Unless one of the supplies has a significantly higher voltage than the other. Seems unlikely.
It actually won't matter much unless he drives power close to the current limit of the smaller supply.
First of all, I totally love my V3 Monos. I run them for about a year now and only have one "problem":
They are set to "Auto Power" and lower gain, get their signal from a Marantz receivers (NR1510) pre-outs.
From time to time they react to "sparks" in the powergrid and turn on, while the receiver is off. Typically when someone slowly engages a lightswitch or a mobile (fast-)charger stops charging the phone. I don't hear that crack when they are on, I can only hear it upstairs in my main listening room, when listening to my lowest output MC cartrigdes (+68dB Gain)
Is there anything I can do, that isn't voodoo? I already use double-shielded RCA cables and firrite chokes to the power cables. As the Marantz doesn't offer symmetrical XLR Outputs I don't think a cinch>XLR cable would be any better.
They are set to "Auto Power" and lower gain, get their signal from a Marantz receivers (NR1510) pre-outs.
From time to time they react to "sparks" in the powergrid and turn on, while the receiver is off. Typically when someone slowly engages a lightswitch or a mobile (fast-)charger stops charging the phone. I don't hear that crack when they are on, I can only hear it upstairs in my main listening room, when listening to my lowest output MC cartrigdes (+68dB Gain)
Is there anything I can do, that isn't voodoo? I already use double-shielded RCA cables and firrite chokes to the power cables. As the Marantz doesn't offer symmetrical XLR Outputs I don't think a cinch>XLR cable would be any better.
RandomEar
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Seeing that they turn on based on the RCA inputs in your case, chokes on power cables won't change a thing. There seems to be a tiny voltage spike induced on your RCA lines coming from the Marantz. However, that unit seems to be a class II device (no safety ground), so the case and RCA ground should be floating, just like on the V3 Monos. What else is connected to the Marantz? A PC or streaming device?
Since my first guess would be a grounding issue, it might be enough to connect the case of the Marantz to a safety ground. But errors like this are tricky to nail down. You should also check all your outlets in the house and make sure that they are wired correctly - especially the safety ground (there are cheap plug-in testers for this).
MajorTom
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Hi guys,
Happy with my v3 mono (one psu 48v 10A for both). I'm using Aiyima t8 as preamp dac. It works great except when I want to push up the volume (and damage my ears but it is so good to disturb my neighbors )
So, the T8 output voltage is 1.9v. Would it make a difference if i change the dac, for instance with a fosi zd3, or topping dx3pro ? These dacs show output of 2.1 or 2.4v.
Same if I connect with xlr instead of rca?
As a noob, I will listen to your advices
Happy with my v3 mono (one psu 48v 10A for both). I'm using Aiyima t8 as preamp dac. It works great except when I want to push up the volume (and damage my ears but it is so good to disturb my neighbors )
So, the T8 output voltage is 1.9v. Would it make a difference if i change the dac, for instance with a fosi zd3, or topping dx3pro ? These dacs show output of 2.1 or 2.4v.
Same if I connect with xlr instead of rca?
As a noob, I will listen to your advices
Pulkass
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The mini monos v3 are powering my 3 way - mid section- 5 amps in total. I can t still give a sonic valutation, it was very good few days ago when the mids were driven by a fosi stereo amp. It stunned me listening to things l had never perceived on very familiar recordings. My dac is a smsl do200 pro.
The input sensitivity of the Fosi V3 Mono is 2 VRMS (SE) or 4 VRMS (XLR). An input of that amplitude will drive the amp to its maximum output at a specified level of distortion. A signal of higher amplitude may produce higher volume, but at higher distortion.
I haven’t measured the Fosi amp, but measurements I’ve made of the Aiyima A7 and the 3e Audio A7 using different input signal amplitudes both showed the amps clipping well before the specified input sensitivity.
Doing what you propose may generate more volume (how much is TBD) but it will certainly result in higher levels of noise. You would also run the risk of damaging your drivers (particularly the HF) by sending clipped signals.
Thank you for your reply!
The Marantz is connected to an LG TV (HDMI eARC), a Sony BD/CD Player (HDMI), A Fosi X5+ancient Sony Turntable(RCA), a Network-Switch (grounded) (Cat 6E) and FM/DAB Antenna (F-Type - not other devices connected to the antenna-array).
Probably the Switch is source of my trouble, it has a separate Ground Cable connected to its racks ground as it links up to another switch on a different powercircuit, but it would be most typical. I had to adopt the house as far as possible, as wireless LAN doesn't really work well. So the network structure relys on only 3 main cables that connect the 10G switches in each part to the router and the desktop switches or devices, where needed. The one to the living room is the only non optical cable (Office and Upsairs switch are connected via fibre)...
Yesterday I tried an OEHLBACH "Audio Linear 8" Filter (1:1 transformers) between the Marantz and the V3s, that seems to help!
If you are using CAT6E from network switches (or anything else) to your sound system then make sure to instead use non grounded i.e. UTP cables, even CAT5 will do nicely.
Did you notice any difference in performance?
I have a pair of v3's powering some kef q concerto meta's and I'm not sure if I am imagining it, but the bass feels a little thin compared to when I demoed them at the store, and the bass driver has almost no excursion compared to the store demo, at similar volumes (not matched exactly, because I forgot to take a measurement).
Is it possible the v3 is struggling to drive the speakers around 80-100hz range? And would swapping the power bricks to 2* 48v10a offer any kind of improvement?
Impedance graph from Erin's audio corner attached.
Attachments
Seems unlikely given their capability to near double power between 4 and 2 ohms.
Most likely the difference in bass between store demo and home is going to be speaker/room interaction, room treatment and or room correction/EQ. Excursion at similar volume will depend massively on room size and listening distance - even discounting your inability to match levels.
Are you able to determine input voltage from source into the amp? Will give an idea of how much power you are actually asking them to deliver.
What is your source? How are you controlling volume.
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Groovy
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The gray curve shows the impedance response with impedance correction. Without impedance correction circuit, the red curve (higher resistance) applies.
Do you use a correction device? Was a correction device used during the demonstration at the store?
Do you use a correction device? Was a correction device used during the demonstration at the store?
staticV3
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The gray curve show's the speaker's equivalent peak dissipation resistance.
It's the resistance that would result in the same power output from a Class A/B or Class B Amplifier.
OTOH, EPDR does not apply to Class D Amps, so there only the normal impedance response matters.
Thanks for the clarification.
I just bought the speakers a few days ago so maybe the woofer surrounds need to break in a bit longer.
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To be frank my room is terrible, a fairly cluttered living space in an open-plan house with a sliding door/glass on one side and open space on the other
Using a Marantz nr1710 avr which I think delivers 1v through the preouts @ vol 82.5 which I would never get to, I would listen at 70 at the absolute max, but mostly 60.
V3 set to low gain, volume controlled via the avr, streaming FLAC files from local devices around the house via heos..
Edit: have been trying out using pure-direct mode. I need to try re-running audyssey because I haven't done that since buying some new speakers.
Edit2: after some of these replies, I realised I should probably have the v3's set to high gain given the quite weak pre-out voltage, also if the nr1710 behaves similarly to the 1510 then best performance is at only 1v. Will have another proper listen tomorrow once I don't risk waking up the family
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Should have high gain ??? If you don't have low impedance speakers and want to maximise the signal sent to them from a 1v source then sure, set the gain high.
but
If it is loud enough for you already then don't change the setup for something that will have no value to you and instead keep the gain at the lower setting and your input signal high so you can enjoy lower noise levels for the same listening volume.
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