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Sony Vfet Illustrated build guide
Sony Vfet Illustrated build guide
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Old 9th January 2018, 01:47 AM   #421
Ben Mah is offline Ben Mah  Canada
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Another beneficial addition are transformer snubbers between transformer secondaries and diode bridges. See "simple no-math transformer snubber using Quasimodo test jig" in the Power Supply forum for information.
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Old 9th January 2018, 03:46 PM   #422
flocchini is offline flocchini  United States
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Default FE as linestage

Can the Sony VFet front end be used as a linestage/preamp as has been done with the BA3?

Thanks

Bob
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Old 9th January 2018, 03:59 PM   #423
6L6 is offline 6L6  United States
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Sony Vfet Illustrated build guide
Sure! The Vfet front end is basically the same front end as the BA-3 with a cascode to protect the Jfet from the higher voltage rails.

I’d just use a BA-3 FE, as it skips the cascade and has placement for the output cap on the PCB, and you get the addition of the P3 potentiometer.
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Old 9th January 2018, 04:49 PM   #424
flocchini is offline flocchini  United States
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Thanks Jim
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Old 10th January 2018, 06:21 PM   #425
Msr Mojo is offline Msr Mojo
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Default P1 and P2 pot values

Did I miss something?
Were the VFET part 2 P1 and P2 pots changed from 5Kohm to 500 ohm for the supplemental kits?
I got (4) 500 ohm pots, (no 5Kohm units) in each supplemental kit.
Is there a post I can refer to?
Thanks.
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Old 10th January 2018, 07:33 PM   #426
wdecho is offline wdecho  United States
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Sony Vfet Illustrated build guide
The build requires (4) 500 ohm and (4) 5K ohms pots. If you use Fairchild mosfets you need to change the 500 ohm pots for 1K pots to be able to bias properly.
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Old 12th January 2018, 08:15 AM   #427
Arye is offline Arye  Israel
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Default PSU caps

Hi to all
There's a good bargain for screw terminal caps on Ebay (18000uf 80v 85c).
Will you recommend it for the PSU?
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Old 17th January 2018, 01:37 AM   #428
delecoy is offline delecoy  United States
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FINALLY found time to finish my vfet amp. After installing the vfets and reading through the article on the firstwatt website one last time I fired it up.....and had less than 50mv across R32 on both sides, as well as less than 50mv offset at the output. It was almost too easy. I only had to slightly tweak P1 on both sides to get offset close to 0. The pots are MUCH more stable with the vfets in. In all seriousness, I'm concerned I'm somehow missing something, because it was so stable on first power on. R32 is 18mv...ish on both sides ( ready to be brought up to 100mv ), offset at the outputs +- 10mv - never more. Going to check the front end values one last time then hook it up to some cheap speakers for a test run.

Any reason not to proceed?

Last edited by delecoy; 17th January 2018 at 01:50 AM. Reason: Clarity
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Old 17th January 2018, 01:51 AM   #429
PJN is offline PJN  United States
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Not only will it make your cheap speakers sound good, it will make your fancy ones sound great.
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Old 17th January 2018, 03:28 AM   #430
delecoy is offline delecoy  United States
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Mmmmmhmmmmm. That it does.

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