Sony vFET Illustrated build guide

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Hi Rich, Glad you are still enjoying your Vfet Amp.

I enjoy the Sony Vfet part 2 driver stage so much that I now have 4 different versions with different output sections. I have the original Sony dual vfet pp, a Tonkin MU follower SE, a ZM DEF R3 and a MOSFET Puck PP. They all sound great and they all sound different. It seams like the output impedance and the Harmonic structure seems to make the big difference. The puck amp has the lowest output impedance at .023, no surprise with global feedback. Then the DEF, original Sont Vfet part 2 and Tonkin MU follower. You end up with damping factors 350, 80,65, 20 respectively. They each reacted differently with the variations in speaker impedance. The lower the more control the higher the more bloom. This comes across as louder with speakers that are under damped and need the amp to keep thing in check. The new SE vfet amp has a output impedance of 1.36 ohms so about DF 6. This seems to be the biggest reason that it can play much louder.

I do like the new SE Vfet amp, it sounds very nice on the horns. That is why I made the Big Tonkin version. If you look at Ben’s thread there are some graphs there.

My two cents,
 

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Hi Chuck,

Happy July 4th! Thanks for explaining the relationship between output impedance, damping factor and underdamped speakers. I thought that this would explain why the Sony VFET complementary pair amp sounds like such a great match to the KEF LS50’s. I listened to Miles Davis’ “Kind of Blue”, Patricia Barber’s “Night Club”, Morton Gould and his orchestra performing Aaron Copland’s “Billy the Kidd” and “Rodeo”, and the complete “La La Land” soundtrack experience. With such a range of music and genres, the system played everything beautifully.

I have a matched pair of those Tokin THF-51S SITs, so I will weigh my options on what to do with those gems when new designs for these NOS devices emerge. For now, I am quite happy with the Sony VFET, which you helped me in setting the bias adjustments when I first built it. Thanks again!
 
I am making amp with K60 & J18.
If the DC offset and noise of the finished amp are small enough, I wanna use it as a headphone amp for my power hungry headphone(AKG K1000 120Ω/74dB).
Is this a bad idea?
I don't want to burn my headphone (and my brain).
 

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Joined 2004
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I'm routinely running the HD800 and K1000 off the diy Sony Vfet amp with K82&J28 parts. There is enough voltage gain to use unity gain preamp such as the DCB1 or B1. With attention to wiring and ground layout there is no audible hum. The sound is extremely good in my opinion.

With the K60&J18 you can use half the bias of the K82&J28. There has been some discussion on the K60&J18 version recently.

Edit: starts at #4114 https://www.diyaudio.com/forums/pass-labs/276711-sony-vfet-amplifier-2-a-83.html#post6192741
 
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Official Court Jester
Joined 2003
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put your DVM at output, and observe behavior during powering up and down cycles
MAX function is useful for that

measure with no load, then repeat measurements with 120R resistor as load

if you find any substantial peak (say that 1V is equal to 8mW - do your math here what SPL is that), then use cap in between

1000uf , proper bypass, and you're good
 
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I finally found the time to finish my Sony push-pull amp, completing the VFET 'triple crown' :D (CD single-ended, CS single-ended, CD push-pull). Certainly you could argue that I should add a CS complimentary amp to that list, maybe a circlotron too... but three seems like a good stopping point, and it works with my analogy :)

What a fantastic amp!! It went together without a hitch, thanks largely to this build guide and Nelson's documentation. I'm still waiting on some little PCBs I made for the hockey puck bridge rectifiers I'm using, but I'm calling this one 'done'.

A perfect summer-time amp, and it easily gives my other amps a run for their money. Probably the quietest amp I've built too.

A big thanks to:

Dennis Hui. Such an amazing guy, Dennis is the reason I was able to build this amp. He supplied me with the P-channel VFETs I was missing, the convenient t-brackets for transistor mounting, and plenty of encouragement. Thanks again, Dennis – your kindness and gratitude are so, so appreciated!

Nelson for this superb design, your continued support, and your endless generosity

Randy Thatcher for these great PSU boards. Work like glue :)

Jim and crew for the great build guide and documentation.

ZM for being ZM. I blame you! :D

DIYaudio is such an amazing place and full of so many amazing people. I'm continuously humbled and inspired by the people in this hobby. Thank you!

:worship:
 

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I finally found the time to finish my Sony push-pull amp, completing the VFET 'triple crown' :D (CD single-ended, CS single-ended, CD push-pull). Certainly you could argue that I should add a CS complimentary amp to that list, maybe a circlotron too... but three seems like a good stopping point, and it works with my analogy :)
:worship:
We want know the difference on triple crown !!
please talk about
tnx