Fosi Audio V3 Mono Amplifier Review

[roog]

Orient it with the holes top and bottom instead of on the sides and the dissipation will probably be improved. Keep some space on all sides for convective airflow.

Agreed, I was starting to think along these lines if only to maintain access to the switches on the front whilst the cabling can leave via the side, as you suggest with the enclosure in this orientation the ventilation holes on the sides would be top and bottom.

I am thinking metal plate bracket which will add a little more surface area to dissipate heat.

 

[roog]

I gave both V3's a light work out with a, 8ohm power resistor load and took some simple measurements not distortion or noise as those have been covered by my betters.

The resistor got 'toasty' the amp did not.

 

[antcollinet]

I plan to do the same. I ordered two properly shielded 3m RCA cables and two 36V/6A power supplies.
What makes me worry are the possible vibrations from the speakers.
But I think digitial devices with clocks are more sensitive than amps (see active speakers).

Solid state electronics of any type will not generate anything audible from vibration. You don't even have to think about it.

 

[GabrielPhoto]

For subwoofers and tactile devices I think the Behringer A800 would be better than the Fosi V3 mono even with the 48v 5A power, am I correct?

 

[roog]

For subwoofers and tactile devices I think the Behringer A800 would be better than the Fosi V3 mono even with the 48v 5A power, am I correct?

The behringer has quite the power for the money

 

[roog]

I’m currently soldering the shortest speaker cables that I have ever made :0)

 

[roog]

You may want to use XLR signal cables rather than RCA to minimise interference.

Sadly the Wiim Ultra doesn’t have XLR Outs so unbalanced RCA it is

 

[Danielck78]

Sadly the Wiim Ultra doesn’t have XLR Outs so unbalanced RCA it is

I might be asking a stupid question, will using RCA to XLR better than RCA to RCA? Sorry newbie here.

 

[NTK]

I might be asking a stupid question, will using RCA to XLR better than RCA to RCA? Sorry newbie here.

Your question is not stupid It is vastly better to use a RCA to XLR adapter cable, but the cable needs to be constructed to the highlighted configuration:

You can find the original full document in this link (only section 9 is applicable to this discussion, above is page 17):

https://www.hypex.nl/media/85/b5/1c/1646058855/NC400_04xx.pdf

[Edit] However, the balanced input to the Fosi V3 Mono has only 20 dB gain (whereas the unbalanced input can be as high as 31 dB). Depending on the output level of your source, you may not be able to drive the V3 Mono to full output power.

 

[Danielck78]

Your question is not stupid It is vastly better to use a RCA to XLR adapter cable, but the cable needs to be constructed to the highlighted configuration:
View attachment 413501
You can find the original full document in this link (only section 9 is applicable to this discussion, above is page 17):

https://www.hypex.nl/media/85/b5/1c/1646058855/NC400_04xx.pdf

[Edit] However, the balanced input to the Fosi V3 Mono has only 20 dB gain (whereas the unbalanced input can be as high as 31 dB). Depending on the output level of your source, you may not be able to drive the V3 Mono to full output power.

Do u have any brand recommendations?

 

[GabrielPhoto]

Your question is not stupid It is vastly better to use a RCA to XLR adapter cable, but the cable needs to be constructed to the highlighted configuration:
View attachment 413501
You can find the original full document in this link (only section 9 is applicable to this discussion, above is page 17):

https://www.hypex.nl/media/85/b5/1c/1646058855/NC400_04xx.pdf

[Edit] However, the balanced input to the Fosi V3 Mono has only 20 dB gain (whereas the unbalanced input can be as high as 31 dB). Depending on the output level of your source, you may not be able to drive the V3 Mono to full output power.

I have tried many rca to xlr cables and never found one that was actually any better than a high quality rca to rca in fact if anything it was worst like with the monolith 7x
If you got a recommendation I would give it a shot

 

[NTK]

Do u have any brand recommendations?

Monoprice makes one. I have no personal experience with it. Some people found it to be OK, some didn't like its build quality.

Amazon.com

 

[GabrielPhoto]

Monoprice makes one. I have no personal experience with it. Some people found it to be OK, some didn't like its build quality.

Amazon.com

That is one I actually tried with the Monolith 7x and Starke Fiera8 and it was not better than the RCA to RCA. In fact, I recall with the Monolith I had higher hiss with like a 1db less of output when measuring both setups which i found odd.
Since RCA to XLR does not make it balanced, and I have short runs, I dont see the value on going with such a cable but I am always interested in other opinions.

 

[NTK]

That is one I actually tried with the Monolith 7x and Starke Fiera8 and it was not better than the RCA to RCA. In fact, I recall with the Monolith I had higher hiss with like a 1db less of output when measuring both setups which i found odd.
Since RCA to XLR does not make it balanced, and I have short runs, I dont see the value on going with such a cable but I am always interested in other opinions.

View attachment 413510

The recommendation by Hypex (Bruno Putzeys) is based on sound engineering principles which are explained in the linked article.

The better but a lot more expensive way, per Rane Note 110, is to transformer isolate the unbalanced connections (see Rane Note figure 2 and below).

PI-2XX | Jensen Transformers

The design begins with a rugged flanged enclosure that comes standard with gold plated XLRs and a removable screw-down barrier strip for easy installation in NEMA enclosures. Plug and play easy to use, this passive interface does not require any power to work. Inside are two Jensen high...

www.jensen-transformers.com

or

RANE - BB22

The Rane BB22 Balance Buddy is a handy professional-grade tool used to provide isolation for and convert unbalanced -10 dBV consumer level RCA outputs up to balanced +4 dBu professional XLR inputs.

www.ranecommercial.com

 

[antcollinet]

I have tried many rca to xlr cables and never found one that was actually any better than a high quality rca to rca

This is not a huge surprise. They will only have a benefit if:

1 - you have audible ground loop noise
2 - the cable is specifically constructed as described above by @NTK with separate ground wire and 0V/negative reference wire running the length of the cable**, so three wires in total. In which case you should get in the region of 30dB reduction in the ground noise.

** many or most RCA to XLR just run two wires and connect negative terminal to ground inside the XLR cable.

 

[Owis]

** many or most RCA to XLR just run two wires and connect negative terminal to ground inside the XLR cable.

The monoprice one linked at the top of the page has three wires though yes?

 

[Down South]

I have the two monos on top of each other (the DAC on top). Yesterday, after the monos had to work for several hours while watching TV at normal room volume, both of them suddenly produced an unpleasant noise in parallel, in addition to the normal sound. First quietly and then gradually increasing to a certain level.
I touched the amplifiers and both were very warm, despite the low volume. Turning it off and on didn't help. The noise came back immediately, a little quieter than before but rose back to the previous level.
The noise is independent of the volume set on the DAC.

I use the RCA inputs at 25 dB gain and RCA outputs on the DAC.

Can someone help me with this problem. Has anyone else had this too?

not a good idea to stack the amps and then with the DAC on top. If you use all three vertically on two pieces of narrow stone or wood with the orange side pieces removed you will create a flow of air - conduction current. This will seriously lower the operating temperature and life of the components.

 

[antcollinet]

The monoprice one linked at the top of the page has three wires though yes?

Yes

 

[roog]

[Edit] However, the balanced input to the Fosi V3 Mono has only 20 dB gain (whereas the unbalanced input can be as high as 31 dB). Depending on the output level of your source, you may not be able to drive the V3 Mono to full output power.

Unless I have misunderstood, this is the issue, the signal level voltage, required to obtain full output from an XLR balanced input is double that that is normally available from unbalanced RCA. Connecting an unbalanced RCA output signal to a balanced XLR input will work but may limit the power output of the connected power amplifier.

 

[jyrg]

I just bought a set of Elac Vela 407.2 at a great price and need an amp. I have a xduoo TA-66 headphone amp which can also be used as a pre-amp. Should I just hook the speakers directly to a Fosi V3 mini or is there any advantage in getting the Monos and using them with my pre-amp?
The TA-66 does have a very nice volume control knob....

TLDR:

JDS Atom DAC --> Fosi V3 Mini (32V 5A) --> Elac Vela 407.2

OR

JDS Atom DAC --> xDuoo TA-66 --> Fosi V3 Mono (48v 5A) --> Elac Vela 407.2


Speaker specs:

Type	2 ½-Way, Bass Reflex
Woofer	2 × 150 mm Ø, AS-XR Cone
Tweeter	JET 6
Magnetic Shielding	No
Crossover Frequency	450 | 2400 Hz
Frequency Range (IEC 268-5)	30 - 50000 Hz
Sensitivity	88 dB at 2.83 V/m
Suitable for amplifiers from	4Ω - 8Ω
Recommended Amplifier Power	40 - 300 W/channel
Nominal | Peak Power Handling	130 W | 170 W
Nominal | Minimum Impedance	4Ω | 3.2Ω at 200 Hz
Finishes	Black High Gloss, White High Gloss, Walnut High Gloss
Accessories Included	Plate with Spikes and Washer
Optional Accessory	Speaker Grilles
Height x Width x Depth	1000 x 229 x 266 mm
Weight	19.1 kg

Or should I buy something totally different? I think there is no point in spending more money than what the Fosis cost?