Jfet BOZ - Page 92 - 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 23rd July 2010, 05:57 PM   #911
Paper mache horn fabricator
diyAudio Member
 
carpenter's Avatar
 
Join Date: Mar 2002
Location: Oregon City, Oregon
What bridge is that?
__________________
I enjoy audio so much that I constructed a web site. I share my ideas at: www.inlowsound.com
  Reply With Quote
Old 23rd July 2010, 06:08 PM   #912
flg is offline flg  United States
diyAudio Member
 
flg's Avatar
 
Join Date: Jul 2005
Location: North East
I duno. It's an old part. Not exactly an LDO but, maybe your right?
__________________
"It was the perfect high end audio product: Exotic, inefficient, expensive, unavailable, and toxic." N.P.
  Reply With Quote
Old 23rd July 2010, 06:10 PM   #913
Paper mache horn fabricator
diyAudio Member
 
carpenter's Avatar
 
Join Date: Mar 2002
Location: Oregon City, Oregon
huh?
__________________
I enjoy audio so much that I constructed a web site. I share my ideas at: www.inlowsound.com
  Reply With Quote
Old 23rd July 2010, 06:22 PM   #914
diyAudio Member
 
vdi_nenna's Avatar
 
Join Date: Oct 2000
Location: PA, USA
Blog Entries: 1
Send a message via Yahoo to vdi_nenna
Carpenter,

It's a Vishay 3 amp 200v bridge, nothing fancy. Compared to others, it had a lower Forward Voltage drop @ lower currents. The spec sheet graph explained it.
Might not even be special in the above mentioned. Just what I found.

GBPC102-E4/51 Vishay Semiconductors Bridge Rectifiers
__________________
I build, therefore I am.
  Reply With Quote
Old 23rd July 2010, 06:44 PM   #915
Paper mache horn fabricator
diyAudio Member
 
carpenter's Avatar
 
Join Date: Mar 2002
Location: Oregon City, Oregon
Thanks. Always on the lookout for special parts for special needs.
__________________
I enjoy audio so much that I constructed a web site. I share my ideas at: www.inlowsound.com
  Reply With Quote
Old 9th August 2010, 02:59 PM   #916
Skorpio is offline Skorpio  Denmark
diyAudio Member
 
Join Date: Mar 2004
Location: Denmark
Quote:
Originally Posted by juma View Post
JFET BOZ idea in this thread is troubled with too much gain that 2SK170 gives. To make it acceptable we attenuated the input signal and overloaded the output, whic are not my favorite strategies, so I tried it a bit differently: small negative power supply to Source pin so we can have small gain (6-12 dB, 2 x - 4 x) and high bias (5.5 mA with 7.5 mA Idss JFET) at the same time.
Negative PS is made from 3 x 1.2V rechargeable battery cells or cell-phone battery (most of them are 3.6 V). With 5.5 mA draw either will last for a long time.
I used existing +24V PS but higher PS voltage (up to +35 V) won't change anything important.
Playing with R3, R4 and -PS voltage may give other interesting results. This version works nice for me.
This JFET BOZ can put out clean 5V RMS and it drives F5 very nicely. For some other uses as a preamp it will love B1 on its' output.
A simpler alternative to a negative supply is to lift the Source with a resistor between 270-470Ohm. This will lower gain, but then you need to use a cap on the input. Very nice sound...
  Reply With Quote
Old 9th August 2010, 04:26 PM   #917
juma is offline juma  Germany
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Berlin
Quote:
Originally Posted by Skorpio View Post
A simpler alternative to a negative supply is to lift the Source with a resistor between 270-470Ohm. This will lower gain, but then you need to use a cap on the input. Very nice sound...
Skorpio, with such a high value of Rs (and still keeping the single rail PS) you'll get the Id of 1mA or so and your Drain will be only 2-3 V far from the PS voltage, leaving you with a very small output voltage swing. So, you'll have to use higher value of Rd to compensate for a such a low Id and to get you further from the +rail. That will cause a higher gain again, but this time you set the JFET deep into non-linear region of transfer characteristic and your THD explodes.
Anyway, this might sound great if you use it as an electric guitar preamp (you'll have that trash-metal guitar sound), otherwise, about 200mV is the max input signal you can bring in without causing the clipping (max output swing would be about 1V rms).

Why do you tink that input cap is needed in this case? If your idea is more complex than just changing the Rs value, please attach the schematic.

Last edited by juma; 9th August 2010 at 04:35 PM.
  Reply With Quote
Old 9th August 2010, 06:10 PM   #918
Skorpio is offline Skorpio  Denmark
diyAudio Member
 
Join Date: Mar 2004
Location: Denmark
Hi,

It is not changing the 10ohm Rs, but connecting another Rs in series with the original. The 1M gate must still connect to the 10 Ohm, so gate is no longer reffered directly to 0V, therefore AC coupling the input.

It is like biasing a tube when you have a large kathode resistor. You split it in two and refer the gate to the junction.

My values are: Supply=18V, Rd=1K, Id=8mA and using 2sk147 jfets with IDSS=11mA
  Reply With Quote
Old 9th August 2010, 07:23 PM   #919
juma is offline juma  Germany
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Berlin
Now it's clear what you mean - here is the picture for those willing to try.

This way you can extend the input signal level up to 1Vpeak and output up to 3Vpeak. Compared to neg. rail version this is still an inferior solution - you still got higher THD and lower signal level headrom, but yes, it will perform better than simple single rail version
Input cap shouldn't be a problem, with Zin=1M this cap can be as small as 47-100nF, so a good one shouldn't be expensive.

Anyway, changing the JFET to J310 (Vishay) is better solution with simple signal rail version (no input cap, no level shifting, no neg. rail, 6-10dB gain, large signal headroom - 5-6Vpeak at output).
Attached Images
File Type: gif ab.gif (2.5 KB, 708 views)

Last edited by juma; 9th August 2010 at 07:27 PM.
  Reply With Quote
Old 10th August 2010, 08:22 AM   #920
Skorpio is offline Skorpio  Denmark
diyAudio Member
 
Join Date: Mar 2004
Location: Denmark
Yes, just like that....I use it until I get my modified BoZ finished
  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 04:18 PM
Can I replace BF245C JFET with J201 JFET? bigmike216 Parts 2 7th December 2005 07:50 AM
How to use Jfet? lumanauw Pass Labs 5 7th April 2005 04:12 AM


New To Site? Need Help?

All times are GMT. The time now is 02:15 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