Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Pass Labs This forum is dedicated to Pass Labs discussion.

F3 Builders Thread
F3 Builders Thread
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 14th August 2017, 05:11 PM   #581
JeffYoung is offline JeffYoung  Ireland
diyAudio Member
 
JeffYoung's Avatar
 
Join Date: Jul 2017
Location: Ireland
F3 Builders Thread
I think (hope?) I'm getting near my final board layout.

I've changed the output caps since the big Panasonics are NLA: I'm using a pair of Wurth 8200uF electrolytics and a Mundorf 8.2uF polypropylene jelly roll.

I've also added a film cap (6.8uF polyester) to the Cmultiplier output.

F3 Builders Thread-f3-legend-jpg

F3 Builders Thread-f3-layout-jpg
Attached Images
File Type: jpg F3-layout-small.jpg (91.8 KB, 665 views)
File Type: jpg F3-legend-small.jpg (101.6 KB, 660 views)
  Reply With Quote
Old 20th August 2017, 08:33 PM   #582
JeffYoung is offline JeffYoung  Ireland
diyAudio Member
 
JeffYoung's Avatar
 
Join Date: Jul 2017
Location: Ireland
F3 Builders Thread
Discussion over on the DEF amp thread regarding protecting JFETs with zeners has led me to try and understand the F3 a bit better.

As I understand it, an N-channel JFET is a normally-on device which can be turned off by applying a negative voltage potential between its G and S. In the case of the LU1014, -1V should give a fully-off state.

The LU1014 spec also says "Device fully ON with Vgs = 0.7V", suggesting that a bit of positive bias is OK. So I guess fully open to fully closed is a Vgs of +0.7 to -1V. (Unless that positive bias part isn't linear, in which case we'd still want +0 to -1V.)

The F3 holds the LU1014's S at +1.1V. Its G is fed over a 9.1K/47.5K voltage divider, which should give 0.84Vin, or +1.2 to -1.2V for a consumer-level +1.4 to -1.4V signal.

That gives us a Vgs of +0.1 to -2.3V, which doesn't seem to fit with my calculated on/off range. What am I missing?
  Reply With Quote
Old 20th August 2017, 09:22 PM   #583
Zen Mod is offline Zen Mod  Serbia
Official Court Jester
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
F3 Builders Thread
feedback?
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
  Reply With Quote
Old 20th August 2017, 11:11 PM   #584
JeffYoung is offline JeffYoung  Ireland
diyAudio Member
 
JeffYoung's Avatar
 
Join Date: Jul 2017
Location: Ireland
F3 Builders Thread
Yikes. I haven't a clue what to do with that.

Let me try and make a stab at it. The feedback is out of phase, right? Which means it will compress the input waveform? So with, for instance, 50% feedback we might expect a +/-1.2V signal to go to +/-0.6V?

(Feedback is usually measured in dB. How does that correlate to my 50% figure?)

I've either got the wrong end of the stick, or I'm missing something else. Even with 50% feedback (which I doubt), that +/-0.6V signal will give us a Vgs from -0.5 to -1.7V, which still descends well below the pinch-off Vgs.

My head hurts....
  Reply With Quote
Old 22nd August 2017, 01:30 PM   #585
JeffYoung is offline JeffYoung  Ireland
diyAudio Member
 
JeffYoung's Avatar
 
Join Date: Jul 2017
Location: Ireland
F3 Builders Thread
Any thoughts on my above conundrum? My curiosity has gotten the better of me....
  Reply With Quote
Old 22nd August 2017, 02:03 PM   #586
Zen Mod is offline Zen Mod  Serbia
Official Court Jester
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
F3 Builders Thread
for proper analysis "all" you need is calculus of OLG (open loop gain) then it's easy going backwards , to determine either feedback (amount ) or CLG (closed loop gain)

moi being lazy to calc now ...... or even fire up LTSpice and search for all necessary thingies
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
  Reply With Quote
Old 22nd August 2017, 05:35 PM   #587
JeffYoung is offline JeffYoung  Ireland
diyAudio Member
 
JeffYoung's Avatar
 
Join Date: Jul 2017
Location: Ireland
F3 Builders Thread
Thanks, Zen Mod. Sounds like I need to learn LTSpice....
  Reply With Quote
Old 22nd August 2017, 07:07 PM   #588
Zen Mod is offline Zen Mod  Serbia
Official Court Jester
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
F3 Builders Thread
roughly ....... for 1W/8R at output , you need 2V6pp at input

LU sees 210mVpp between gate and source

that , by mu crude LTSpice sim
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
  Reply With Quote
Old 18th November 2017, 11:02 AM   #589
JeffYoung is offline JeffYoung  Ireland
diyAudio Member
 
JeffYoung's Avatar
 
Join Date: Jul 2017
Location: Ireland
F3 Builders Thread
I've been practicing my toner transfer and etching skills. While I've learned a lot, one of the things I've learned is that I don't enjoy toner transfer or etching.

So it's back to the drawing board to produce Gerbers for a fab house. I did up a board for a pair of bridge rectifiers (with snubbers) that is currently with EuroCircuits, and I have a first draft for a dual mono PSU.

I did both those sans schematic, but KiCAD appears to work more efficiently from a schematic, so I've also done a first-draft schematic for the left channel.

Comments welcome.
Attached Images
File Type: jpeg double bridge kicad.jpeg (70.6 KB, 146 views)
File Type: jpeg F3tribute PSU pcb.jpeg (439.6 KB, 58 views)
Attached Files
File Type: pdf schematic.pdf (80.7 KB, 15 views)
  Reply With Quote
Old 7th December 2017, 01:06 AM   #590
JeffYoung is offline JeffYoung  Ireland
diyAudio Member
 
JeffYoung's Avatar
 
Join Date: Jul 2017
Location: Ireland
F3 Builders Thread
Left channel:
Attached Images
File Type: jpg F3-left-top.jpg (463.7 KB, 58 views)
File Type: jpg F3-left-bottom.jpg (325.0 KB, 52 views)
  Reply With Quote

Reply


F3 Builders ThreadHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
ezDAC v.1.5 Builders Thread ezkcdude Digital Line Level 366 14th March 2013 04:31 PM
A-X IP Issues (split from Builders thread) tomchaoda Pass Labs 107 16th October 2011 03:05 AM
one for the box builders offroadbum Car Audio 2 11th October 2004 10:19 PM


New To Site? Need Help?

All times are GMT. The time now is 09:50 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki