Zen I/V Converter - Page 3 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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 10th September 2010, 12:03 PM   #21
regal is offline regal  United States
diyAudio Member
 
Join Date: Jan 2004
Location: MD
Quote:
Originally Posted by EUVL View Post
This is a quick & dirty schematics just to show the idea of a cascoded complementary JFET IV.
I hesistated to call it cascoded Zen IV, as it is more of a "Blowtorch IV".

Balanced DAC current is fed to the sources of the input jfets, whose gates are tied to ground.
R2,3,19,21 are bias resistors for the folded cascode MOSFETs (say 200R).
Conversion gain (I to V) is set by R22,24.
One may add additional electrolytic caps to parallel R5,6,16,17.
And R1/18, R4/20 can be replaced by constant current diodes for further improved PSRR.
The rails can now be quick a bit lower than +/-30V.
And the choice is not affected by changes in IV conversion gain and first stage bias.
So one can increase R22,24 (say to 2.4k) and use multiple JFETs in parallel without changing Vsupply.
When using JFETs in parallel, R2,3,19,21 wants to be reduced by N (no.of JFETs in parallel).

No coupling output caps, but consumes quick a bit more current.


Patrick


Problem with this is you would be stuck with balanced ouput and the input would require 2 extra DACs. R2R DAC chips aren't chip or easy to find these days.

If you forgo the coupling caps, the output would be around 0V, I would think that a simple servo filtered below 1 hz or less could null the DC offset and be cheaper than buying a quad blackgates. The lower cost would keep it Zen-like IMO
  Reply With Quote
Old 10th September 2010, 12:06 PM   #22
regal is offline regal  United States
diyAudio Member
 
Join Date: Jan 2004
Location: MD
If you forgo the coupling caps, the output would be around 0 V DC since this is split supplied. Can't see a reason not to DC servo unless you just happen to have 4 expensive blackgates in your pocket
  Reply With Quote
Old 10th September 2010, 12:18 PM   #23
nar is offline nar
diyAudio Member
 
nar's Avatar
 
Join Date: Apr 2002
Location: near the sea
Just came across this new I/V stage which looks damn good
I made a .pdf file of the article which I found a little hard to find inside DiyAudio, that could probably be attached on the first post too

Best regards,

nAr
Attached Files
File Type: zip Zen_I-V.zip (451.1 KB, 1130 views)
__________________
"... Audio needs the thinnest wire ..." Rowan McCombe ... I hear it !!!
"Just 'cause they can't hear or sense it themselves doesn't mean you can't !" Allen Wright Allen was right ...

Last edited by nar; 10th September 2010 at 12:27 PM.
  Reply With Quote
Old 10th September 2010, 12:23 PM   #24
diyAudio Member
 
Join Date: Sep 2001
Location: Düsseldorf Germany
Quote:
Originally Posted by Zen Mod View Post
there are some funny parts , placed in drains of each jfet ;

they're called resistors , and they're handy for decreasing voltage in appropriate nodes


Hihihi

I could have used my brain...
  Reply With Quote
Old 10th September 2010, 01:31 PM   #25
regal is offline regal  United States
diyAudio Member
 
Join Date: Jan 2004
Location: MD
Quote:
Originally Posted by oliverniekamp View Post
Hihihi

I could have used my brain...
Its fine, I'm using mine trying to figure out a DC servo scheme to eliminate the expensive sound degrading coupling caps. Wish I knew SPICE.


Anyone have a Spice model for this up and running yet ?
  Reply With Quote
Old 10th September 2010, 01:53 PM   #26
CeeVee is offline CeeVee  Portugal
diyAudio Member
 
CeeVee's Avatar
 
Join Date: Dec 2006
Hi guys,

Two of my favorite topics: UGS and IV converters.....in no particular order!

Philippe: since you use the ad1865 current mode is it safe to assume that this chip expects 0V at that pin ?

I'm thinking of trying this with a 1738 ( in a Shanling CD Player ) which expects 2.5V at the current output pin.

Just to compare with a Drek conversion i did with Zen-Mod's precious help

I made a mother board for IVs and PSU just so i could test different solutions....here is the chance.

Not that i'm unhappy with what i got but DIY is an itch that doesn't go away.........

Late edit: I'm curious about the UGS solution by will invest my effort on the present ZEN IV.

Last edited by CeeVee; 10th September 2010 at 02:01 PM.
  Reply With Quote
Old 10th September 2010, 01:58 PM   #27
regal is offline regal  United States
diyAudio Member
 
Join Date: Jan 2004
Location: MD
Maybe some of us, actually a lot of us don't like the sound of heavy NFB. I would say Mr PA0SU that this isn't the place to Pimp your website. You are kind of insulting a highly regarded designer and many of us take offense.

And Thankyou Mr Pass for sharing this new design with us, we do appreciate it.
  Reply With Quote
Old 10th September 2010, 02:06 PM   #28
CeeVee is offline CeeVee  Portugal
diyAudio Member
 
CeeVee's Avatar
 
Join Date: Dec 2006
Hi guys,

Two of my favorite topics: UGS and IV converters.....in no particular order!

Philippe has posted a UGS based IV in the article coments,since one has to use use the ad1865 ( in his particular case ) current mode is it safe to assume that this chip expects 0V at that pin ?

I'm thinking of trying this ( ZEVN IV ) with a 1738 ( in a Shanling CD Player ) which expects 2.5V at the current output pin.

Just to compare with a Drek conversion i did with Zen-Mod's precious help

I made a mother board for IVs and PSU just so i could test different solutions....here is the chance.
  Reply With Quote
Old 10th September 2010, 02:07 PM   #29
juma is offline juma  Germany
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Berlin
Quote:
Originally Posted by regal View Post
.. to eliminate the expensive sound degrading coupling caps....
How about using 0.1uF instead of bulky 10uF? It's possible if the ZEN I/V is loaded by B1 running at approx. +/-10V (it's easy to scale down from +/-30V). Additional benefit is higher drive capability.
  Reply With Quote
Old 10th September 2010, 02:17 PM   #30
diyAudio Member
 
Join Date: Jun 2002
Location: Italy
Very nice, loved the D1 for long time . Will try this as soon I will find a nice usb or spdif dac with current output .

Any suggestions ??
  Reply With Quote

Reply


Hide 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Zen I/V Converter Nelson Pass diyAudio.com Articles 13 19th June 2011 11:04 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 09:16 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2