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FLUX Volot - teardown, inside picture

trl

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This is a teardown of a FLUX Volot headphones amplifier manufactured by Flux Lab Acoustics, a company from Ukraine. The headamp was provided to me by a friend, asking me nicely to make it run again, after he already swapped a defective toroid transformer inside (provided by manufacturer free of charge). Seems that when the transformer got broken the main fuse got broken too, sit was an easy task for me to replace it, although I now need to readjust the BIAS voltage for both channels as well.

As per manufacturer specs, the output power would be:
  • @600Ohm: 1W RMS per channel
  • @300Ohm: 1.7W RMS per channel
  • @32Ohm: 16W RMS per channel
with a THD of 0.002%, so quite a beefy headphones amplifier, one of the most powerful from the world. Let's see some guts below.


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On the left we have the small SMPS (for Eco reasons and for power On/Off) and the toroid transformers for the bug power supply

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I think I've seen heatsinks smaller than these in speakers amplifiers and AV Receivers too

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Two toroid transformers for the amplifier and a smaller one for the digital board

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Side image with the volume control relays and the big blue smoothing capacitors

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TORENERGO (another UA company) custom made toroid transformers (2 x 31V/1.2A for the amplifier)

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The four 22.000uF/63V caps look like we're talking about a 2 x 500W speakers amplifier, not about a headamp. BTW, I love the transparent protection sheet on top.

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No no-name caps? Hmmm...

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Several U820 diodes (8A nominal / 16A peak) summing rectifier bridges for the power stages.

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22,000uF, P/N: E36D630HPN223MC67M, Diam. x Length: 2.000" x 2.625" (50.8 x 66.68 mm)
Maximum ESR (mΩ) at 25C @120Hz: 13.8mΩ, Rated Ripple Current (A rms) at 85C @120Hz: 7.91A.


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Volume control with arrays of resistors and relays (rather noisy).

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Fujitsu/Takamasawa 12V relays taking care of the input XLR plugs

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OMRON G2R-1-E 16A/30VDC high capacity SPDT relays

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KSE340 500mA/20W NPN transistor

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KSE350 -500mA/20W PNP transistor

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TOSHIBA 2SC5200 15A/150W NPN transistor + TOSHIBA 2SC4793 driver transistor

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TOSHIBA 2SCA1943 -15A/150W PNP transistor + TOSHIBA 2SA1873 driver transistor (not 100% sure this was the driver)
Usually these powerful transistors are used in up to 100 W/ch. speakers amplifier, like the one designed by Rod Elliot and named P3A or Project 3A:

p3a-f1.gif
The best output transistors for P3A would probably be the 2SA1943/2SC5200 pair; there are quite a few threads on diyaudio about this schematic, but there are several builds on AliExpress that can be ordered for DIY or fully built and tested. Such an amplifier can push up to 100W per speaker with proper heatsink installed, so finding such powerful transistor pairs in a headphones amplifier might seem a bit overkill, although Volot was designed to drive power hungry headphones.


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Rusted screw heads were found, not sure what happened and what humidity and salty air was in the home of the owner.
However, I measured about 0 Ohms from the screws to the amplifier case, so grounding is not affected.



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Flux Lab Acoustics recommendations for setting the BIAS voltage in Volot headamp


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Me setting up the BIAS voltage, as per Flux's recommendations
 

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ObjectiveSubjectivist

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That's some serious amplifier.
Some time ago I was considering buying one.
Who knows maybe in the future...
 
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trl

trl

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Manufacturer states that VOLOT is still their best headamp, although their dual mono Mentor bridged would be a better choice for those looking to drive very low sensitivity cans.

On a side note, here's how relays sound while changing the volume (with case closed and 1m away the sound is much lower):

 
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