Go Back   Home > Forums > >

Pass Labs This forum is dedicated to Pass Labs discussion.

Buffer with Dual N-Ch Jfets and Dual Power Supply
Buffer with Dual N-Ch Jfets and Dual Power Supply
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
Old 31st March 2019, 04:56 AM   #31
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
Yes, but it will increase your ourput impedance.


Patrick
__________________
xen-audio.com
  Reply With Quote
Old 31st March 2019, 02:29 PM   #32
vdi_nenna is offline vdi_nenna  United States
diyAudio Member
 
vdi_nenna's Avatar
 
Join Date: Oct 2000
Location: PA, USA
Buffer with Dual N-Ch Jfets and Dual Power Supply
Getting better results with BF861b jfets.
By that I mean I have 2sk170 b grade jfets that potentially match up with bf861b.
Attached Images
File Type: jpg bf861B_idss_01.jpg (392.7 KB, 313 views)
__________________
I build, therefore I am.
Do not create problems where there are none.
  Reply With Quote
Old 6th April 2019, 06:04 PM   #33
vdi_nenna is offline vdi_nenna  United States
diyAudio Member
 
vdi_nenna's Avatar
 
Join Date: Oct 2000
Location: PA, USA
Buffer with Dual N-Ch Jfets and Dual Power Supply
Built the buffer from figure C. Used 2sk170 with 9.76 idss on top and a BF861 with 9.64 idss on the bottom. Offset is 63mV.
Ran audio through the buffer to an amp and speakers, and then shut off the buffer and audio stopped. It works! Had this thought that the signal might somehow bleed thru to the amp, but it didn't.
Attached Images
File Type: jpg Buffer_sk170_bf861.jpg (482.3 KB, 256 views)
__________________
I build, therefore I am.
Do not create problems where there are none.
  Reply With Quote
Old 6th April 2019, 06:08 PM   #34
Zen Mod is online now Zen Mod  Serbia
Official Court Jester
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Buffer with Dual N-Ch Jfets and Dual Power Supply
cap on output ?

tested difference between cold/hot offset?
__________________
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 6th April 2019, 06:30 PM   #35
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
You can use a higher Idss BF861 for the current source and trim its current with a source resistor.
Then you have a better chance to come below 63mV opffset, which is a lot for a JFET follower.

For other hints, refer to these :
B1-Turbo on a Chip
(post #136)
NJFETs for Source Follower Applications


Patrick
__________________
xen-audio.com
  Reply With Quote
Old 6th April 2019, 07:05 PM   #36
vdi_nenna is offline vdi_nenna  United States
diyAudio Member
 
vdi_nenna's Avatar
 
Join Date: Oct 2000
Location: PA, USA
Buffer with Dual N-Ch Jfets and Dual Power Supply
No cap. I let the circuit run for 1 hour.
Thought someone said a cap on the output would degrade a simple circuit like this?

I have the higher idss j113, but they are in the 20mA range. The bf861-b are pretty much 6mA to 10mA range, for the 15 pieces I tested. I might have 2sk170s that are 15mA or more. Part of the fun is using jfets that are available for not a lot of money.

For the dropping resistor, are there any other considerations besides simple ohms law?

I'll check out the links. Thx.
__________________
I build, therefore I am.
Do not create problems where there are none.
  Reply With Quote
Old 6th April 2019, 07:16 PM   #37
vdi_nenna is offline vdi_nenna  United States
diyAudio Member
 
vdi_nenna's Avatar
 
Join Date: Oct 2000
Location: PA, USA
Buffer with Dual N-Ch Jfets and Dual Power Supply
I see the tips on the first page. Thx!
__________________
I build, therefore I am.
Do not create problems where there are none.
  Reply With Quote
Old 6th April 2019, 07:24 PM   #38
Zen Mod is online now Zen Mod  Serbia
Official Court Jester
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Buffer with Dual N-Ch Jfets and Dual Power Supply
will cap degrade or not is one issue , while completely other issue is output DC offset, of much greater importance to solve , even with cap if there is no other way

do what Patrick wrote - choose adquate specimens for CCS , then introduce source pot to set Iq , thus output offset

it must be close to 0 , except when you deliberately are choosing different voltage level , but even then you must make it in a way that it's settable
__________________
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 6th April 2019, 07:44 PM   #39
vdi_nenna is offline vdi_nenna  United States
diyAudio Member
 
vdi_nenna's Avatar
 
Join Date: Oct 2000
Location: PA, USA
Buffer with Dual N-Ch Jfets and Dual Power Supply
Ok, I understand. How do I find yfs?
Datasheet gives a range or typical.
__________________
I build, therefore I am.
Do not create problems where there are none.
  Reply With Quote
Old 6th April 2019, 08:03 PM   #40
Mark Johnson is online now Mark Johnson  United States
diyAudio Donor
diyAudio Member
 
Mark Johnson's Avatar
 
Join Date: May 2011
Location: Silicon Valley
Buffer with Dual N-Ch Jfets and Dual Power Supply
I've been pleased with the CCS loaded buffer circuit shown below. Output is AC coupled so its offset is always zero. Always. Notice that the CCS control voltage is regulated twice, for extra EXTRA amounts of PSRR.

_
Attached Images
File Type: png sch.png (32.4 KB, 252 views)
  Reply With Quote

Reply


Buffer with Dual N-Ch Jfets and Dual Power SupplyHide this!Advertise here!
Thread Tools

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
Dual jfets kinku Parts 5 20th April 2017 04:21 PM
Who wants 2SK194 Dual Jfets, C3381/A1349 Gr dual pair BJT? Junm Swap Meet 0 28th October 2015 03:17 PM
FS: Dual Jfets in metal can. Tarasque Swap Meet 2 26th July 2015 10:26 PM
Dual supply B1 Buffer andreaemme Pass Labs 0 5th January 2014 09:58 AM
Dual JFETS on EBAY Andypairo Swap Meet 7 11th December 2003 11:04 AM


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 © 2021 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright ©1999-2021 diyAudio
Wiki