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.

RO85 Zen
RO85 Zen
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 27th August 2011, 12:13 PM   #1
buzzforb is offline buzzforb  United States
diyAudio Member
 
buzzforb's Avatar
 
Join Date: Oct 2010
Location: Burlington, NC
Default RO85 Zen

I was wanting to try and build a R085 version of Zen. I have a pretty decent grasp of what is happening with the standard version, but have a question about using the depletion mode device. I want to use a standard ccs(non aleph) in place of bulbs or resistors because i can only get a 50V rail out of my current trafo selection and need the extra efficiency. I am having trouble figuring out what determines the drain potential of the the signal fet when using both a ccs and a self biased Jfet. Does the ccs look like an infinite impedance and is therefore ignored, with the speaker taking the place of the Rl.
  Reply With Quote
Old 27th August 2011, 05:03 PM   #2
Nelson Pass is offline Nelson Pass  United States
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
RO85 Zen
That's a good question. The Zen amp does have feedback, and you can use
that to determine Drain voltage, but it gets a little complicated when you have
a depletion mode device, as the Gate voltage has to be negative with respect
to Source. You could use lots and lots of degeneration (large Source resistor
to ground), but that cuts into your open loop gain.

If you have a small low current negative bias voltage available, you can use
it to bias the Fet through the feedback loop and this way you can run the
Fet without degeneration.

  Reply With Quote
Old 27th August 2011, 05:16 PM   #3
buzzforb is offline buzzforb  United States
diyAudio Member
 
buzzforb's Avatar
 
Join Date: Oct 2010
Location: Burlington, NC
Without dual rails, that is going to require a second trafo and PSU, correct. How much is enough and how do i come to that figure? Would a bootstrap cs perform better than DeLite setup? How would it compare to version in previous question, which i believe would be the illegitimate cousin of the F2. Sorry about all the questions

Last edited by buzzforb; 27th August 2011 at 05:26 PM.
  Reply With Quote
Old 27th August 2011, 05:55 PM   #4
Nelson Pass is offline Nelson Pass  United States
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
RO85 Zen
You can rig a "negative supply generator" off of your existing transformer.

Here's one.

Attached Images
File Type: jpg neg-bias.jpg (52.6 KB, 830 views)
  Reply With Quote
Old 27th August 2011, 06:21 PM   #5
buzzforb is offline buzzforb  United States
diyAudio Member
 
buzzforb's Avatar
 
Join Date: Oct 2010
Location: Burlington, NC
Thanks. I don't have all the parts, so i will build the DeLite today and do this one next. Do C2 and R1 pull the signal down to lower diodes?
  Reply With Quote

Reply


RO85 ZenHide 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
FREE: Pass Zen & Bride of Zen Kits. axissilverhand Swap Meet 10 2nd December 2010 06:01 PM
FS: Big Zen Amp, Zen 4 stuff, misc. picker Swap Meet 7 11th November 2007 12:06 AM
Zen & Zen Variations-Part.2 billy Pass Labs 1 7th August 2002 06:24 PM
Bride of Zen or Balanced Zen Line Stage? Mach_Y Pass Labs 9 28th November 2001 11:07 PM
Zen or Bride of Zen as Headphone AMP? Hauke Headphone Systems 5 2nd October 2001 06:33 PM


New To Site? Need Help?

All times are GMT. The time now is 03:06 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki