DIY Sony VFET pt 2 (N-Channel Build)

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Bones13

Bones13

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Joined 2006
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It lives! I scored a pair of original N-Channel boards from Papa a good while back. After several fits and starts I have it running. (one side would never run - loose output wire to speaker terminal, and then a non-functional RCA cable) - sheesh.

I want thank Nelson Pass (and his crew) for a fine contribution to the community with these circuits, in their many forms. (and ALL the other things he does for DIYAudio)

I also want to thank Mark Johnson for the TUBA board, and Bon Homme Richard input cards. I fell in love with the AD797 in my M2x amps. I have a set of Pequod boards if I want to try others. And if I get itchy enough to fool around some more, I will try to adjust the Dreadnought cards.

The amp sounds great. It needs a good bit more volume than my 100 watt amps, but it is a clear amp, with some delicacy.

Last bit before close up is installing the LED.

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Bones13

Bones13

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Joined 2006
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They are quite good.

Easy to lift and carry, don’t get hot, true balanced input. Linear PSU monoblocks.

And voiced by a veteran tube amp designer/builder. Precise, yet not edgy like some class D amps. Just warm enough to work just right with my tube pre-amp (ModWright LS 300) and Daedalus Muse Studio speakers. At least to my preferences at 64 years old.

You can read flame wars about the Atma-Sphere Class D amps on other forums. I’m keeping mine.
 
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Bones13

Bones13

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Joined 2006
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Mark Johnson said:
Whoa!! Tuba and N-channel VFET were made for each other; I'd bet your unit has less hum than just about every other N-VFET out there. It's probably the undefeated champion of lowest-crosstalk too. Good on ya!
Click to expand...
No hum, and there is neither start, nor stop, thump.

I am getting 33.7v out of each side (under load), with the 2v drop setting. expected? I could set the OS voltage at 14, and input the 7v drop on the BHR (based on the 33.7v)
 
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Mark Johnson

Mark Johnson

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Joined 2011
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The output boards wouldn't be too useful unless you also had a pair of Nelson's custom milled, drilled, and tapped aluminum T-bar heatsink adapters, which mate with both the PCB and with the diyAudio Universal Mounting Specification ("UMS") drilling template. (Link 1) . . . . (Link 2)

Remember, VFET pt 2 (N-Channel Build) uses VFETs and MOSFETs in the TO-3 steel butterfly package.
 
E

Enochrome

Member
Joined 2011
Hi all,

Built a sony vfet n-channel couple of years ago with everyone’s kind help. Life got crazy and I moved putting the vfet in a box. Just took it out to power my NS-1000. Letting it warm up, I then played some music, which sounded ok but got some static in one channel. Went to power it down and noticed one side was warm and the right side cold. Opened it up and measured the voltage as explained in the build guide and I got 24v on the cold side and 20v on the left channel. I re-biased the right channel to 20v but still the temperature discrepancy? The vfet and heatsink are cold; did I blow the vfet?

Any help much appreciated.
 
Zen Mod

Zen Mod

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Joined 2003
zenmod.in.rs/
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Enochrome said:
I re-biased both channels to 14v. I measured Vdc on the problematic right channel for both R1 and R2 and I got no Vdc reading. I also checked R1 and R2 on the left channel and got 1.3v. The power supply is the stores Meanwell 36v.
Click to expand...

post pics, we need to see your wiring but also soldering job

confirm that you have both GND and +V properly connected to pcb in question - put black probe on GND point on PSU, then check with red probe what reading you have at GND point on channel pcb, same as +V on pcb
 
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