Jfet BOZ - Page 104 - 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 16th May 2011, 05:26 PM   #1031
ramallo is offline ramallo  Europe
diyAudio Member
 
ramallo's Avatar
 
Join Date: Nov 2004
Location: Madrid
Send a message via Skype™ to ramallo
After several turns around the boz (Raising the voltage, feedback loop, more value to the source resistor, less value the supply resistor .....), I left the boz like is. I found that is very critic to the supply alimentation, for my 8mA IDSS 2SK170BL the best value for the lowest distortion is 15,55V, I changed the zener to a TL431 with pot (For a fine tuning).

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
The schematic
Click the image to open in full size.
__________________
Happiness is a warm soldering iron
  Reply With Quote
Old 16th May 2011, 09:57 PM   #1032
diyAudio Member
 
mhouston's Avatar
 
Join Date: Jan 2006
Location: Victoria, Australia
Nice build.
  Reply With Quote
Old 16th May 2011, 11:08 PM   #1033
ramallo is offline ramallo  Europe
diyAudio Member
 
ramallo's Avatar
 
Join Date: Nov 2004
Location: Madrid
Send a message via Skype™ to ramallo
Quote:
Originally Posted by mhouston View Post
Nice build.
Thanks!
__________________
Happiness is a warm soldering iron
  Reply With Quote
Old 17th May 2011, 02:13 AM   #1034
anilva is offline anilva  India
diyAudio Member
 
Join Date: Mar 2004
Location: Bangalore
Quote:
Originally Posted by ramallo View Post
After several turns around the boz (Raising the voltage, feedback loop, more value to the source resistor, less value the supply resistor .....), I left the boz like is. I found that is very critic to the supply alimentation, for my 8mA IDSS 2SK170BL the best value for the lowest distortion is 15,55V, I changed the zener to a TL431 with pot (For a fine tuning).

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
The schematic
Click the image to open in full size.
I am using a similar board. If I understood your post, you removed the 25k trimmer pot at the input and replaced with a step attentuator of similar value as volume control isn't it? You also seem to have 3 input with selector switch. Any passive network used there?

Thanks.
__________________
DIY F5, F5T, F6, Aleph J, Fostex 206 based BLH, Altec Onken with 515B LF & 288H HF, Technics SP10 MKII & EMT938 turntables
  Reply With Quote
Old 17th May 2011, 08:49 AM   #1035
Manu is offline Manu  Europe
diyAudio Member
 
Manu's Avatar
 
Join Date: Nov 2002
Location: Vienna, Ostrich
Very nice

Manu

Quote:
Originally Posted by ramallo View Post
.. I left the boz like is ...

Click the image to open in full size.
__________________
Manu, masked agent of entropy & ZMs Čiko
  Reply With Quote
Old 17th May 2011, 09:57 AM   #1036
ramallo is offline ramallo  Europe
diyAudio Member
 
ramallo's Avatar
 
Join Date: Nov 2004
Location: Madrid
Send a message via Skype™ to ramallo
Quote:
Originally Posted by anilva View Post
I am using a similar board. If I understood your post, you removed the 25k trimmer pot at the input and replaced with a step attentuator of similar value as volume control isn't it? You also seem to have 3 input with selector switch. Any passive network used there?

Thanks.

Yes, I didn't used the board potentiometers and I added a 20K step attenuator. The selector are a 2 Way 6 positions, but I use just two. Also I changed the zener by a TL431 on a small board.

I use all wires with screen for get the best crosstalk, but the earth of the inputs is conected to the output conector and these to the board.

This is the input:
Click the image to open in full size.is

And this is the 431 board:
Click the image to open in full size.

431 layout
431
__________________
Happiness is a warm soldering iron
  Reply With Quote
Old 17th May 2011, 11:13 AM   #1037
anilva is offline anilva  India
diyAudio Member
 
Join Date: Mar 2004
Location: Bangalore
Thanks. I am in the process of putting this into a box.
__________________
DIY F5, F5T, F6, Aleph J, Fostex 206 based BLH, Altec Onken with 515B LF & 288H HF, Technics SP10 MKII & EMT938 turntables
  Reply With Quote
Old 17th May 2011, 12:07 PM   #1038
ramallo is offline ramallo  Europe
diyAudio Member
 
ramallo's Avatar
 
Join Date: Nov 2004
Location: Madrid
Send a message via Skype™ to ramallo
Quote:
Originally Posted by Manu View Post
Very nice

Manu
Thanks Manu,

I had a big surprise when I started to read this thread and I saw that this chinese pcb is a copy of your pcb.

Thanks for your pcb design!
__________________
Happiness is a warm soldering iron
  Reply With Quote
Old 1st July 2011, 07:41 PM   #1039
cjkpkg is online now cjkpkg  United States
diyAudio Member
 
Join Date: Aug 2008
Location: Roswell GA
OK...I built mine apparently with 2sk370's originally must be thats what I had laying around....

So one channel had been going wonky and I ruled out the coupling caps and everything else but the JFETS...It has a lot of hours on it so I figured lets change out the JFETS and see if that helps...

All I have left now are a handful of 2sk170s so I plopped a pair in. Distortion city!!! These are the BL type but with the source and drain resistors I had in place all I could eek out of them was 6ma.

I dropped the drain resistor to 1K from 2.2K and dropped the source resistor down to 5 ohms(all I had was another pair of 10ohm resistors).

This cranked the 2sk170s up to about 8.5mA and boy is the sound sweet again!!!

I took the old JFETBOZ out and just plugged the ipod into the F4(with integrated BA2 front end) and while it sounded great the gain was just quite not enough....

Now with the JFETBOZ back in action all is right with the world again!

If it weren't for Diyaudio I would never know where to immediately hone in to troubleshoot this awesome little preamp. THANK YOU!
  Reply With Quote
Old 24th August 2011, 03:43 PM   #1040
diyAudio Member
 
binhaudio's Avatar
 
Join Date: Aug 2009
Location: HCM-NT-PY
Hello everyone! after the reference and read all 104 pages of the pre JFET Boz, I decided to install this pre discount.
Map that I choose to do is follow the plan of ramallo because my transformers and capacitors suitable voltage. when done, I tried the pre transplant with my computer speakers.
Unexpectedly! JFET with two children but that the sound quality of this pre show or out of my imagination. Bass is deep and warm voice is smooth and rustic MID, also known TRELLE the towering and clear to the exotic.
Before I installed the pre this was my computer speakers are performing normally and faint. but when the pre transplant into the speakers of my computer completely makeover scholarship and I am extremely interested in the pre this.
Please thank Nelson PASS and everyone on the forum was to share knowledge and experience for me.
because my English ability is very bad so I used google translate to translate it a bit confusing. expect people to sympathize.
And here's a picture of my pre Boz JFET
Attached Images
File Type: jpg IN SIDE.jpg (121.1 KB, 258 views)
File Type: jpg PRE JFET BOZ.jpg (124.1 KB, 246 views)
File Type: jpg TONG QUAN.jpg (82.0 KB, 221 views)
  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
JFet BOZ Tyimo Pass Labs 14 30th April 2006 03:18 PM
Can I replace BF245C JFET with J201 JFET? bigmike216 Parts 2 7th December 2005 06:50 AM
How to use Jfet? lumanauw Pass Labs 5 7th April 2005 03:12 AM


New To Site? Need Help?

All times are GMT. The time now is 07:36 PM.


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