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#421 |
diyAudio Member
Join Date: May 2012
Location: Vancouver
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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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#422 |
diyAudio Member
Join Date: Feb 2004
Location: Davis,CA
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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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#423 |
diyAudio Moderator
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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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Illustrated Build Guides - Pass F4 - Pass B1 - Pass F5 - Pearl 2 - O2 HPA - Hagerman Bugle 2 - Pass Aleph J - Me at BA '13 -Pass F5Turbo - BA-3 Amp - BA-3 Preamp - F6 AmpCampAmp |
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#424 |
diyAudio Member
Join Date: Feb 2004
Location: Davis,CA
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Thanks Jim
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#425 |
diyAudio Member
Join Date: Jul 2015
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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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#426 |
diyAudio Member
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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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#427 |
diyAudio Member
Join Date: Jun 2003
Location: Mitzpeh Aviv
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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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#428 |
diyAudio Member
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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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#429 |
diyAudio Member
Join Date: Dec 2004
Location: Pa, USA
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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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#430 |
diyAudio Member
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Mmmmmhmmmmm. That it does.
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