Jfet BOZ - Page 97 - 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 3rd November 2010, 09:18 PM   #961
diyAudio Member
 
mhouston's Avatar
 
Join Date: Feb 2006
Location: Victoria, Australia
Quote:
Originally Posted by Electrolastic View Post
If you've read all the posts in this thread, you might have seen some posters here raised the source resistor from 10 ohm to 22 ohm and used 16V instead of 35V for power supply. You may want to try that.
You're right I have not read all the posts. I always felt that the higher the operating voltage the better. I can see that raising the very low 10 ohms would bias the FET differently and provide a little more local negative feed back.

The top end appears a slightly shrill where the B1 seems a lot smoother in the upper-mid to treble region. BoZ has more bass though.
  Reply With Quote
Old 27th November 2010, 05:35 AM   #962
diyAudio Member
 
mhouston's Avatar
 
Join Date: Feb 2006
Location: Victoria, Australia
I have just finished a capless SE BoZ. Listening to it now.

My new Oppo BDP=83SE has input caps but my 6AS7 SET has no input caps. So make a preamp with no input caps but good output caps. In this capless SE version of BoZ I have no input caps but retained the 10uf polypropelene caps for the output. Also the output caps have been snubbed by 0.1uf polies.

Nelson suggests a total of 30,000uf for his B1 whose PS I stole a few ideas from. But only having 10,000uf caps I used three to get the filtering/storage up. Also I used a simple RCRCRC filter network. 1ohm/10,000uf/10ohm/10,000uf/1ohm/10,000uf. Each 10,000uf cap is snubbed. Silver plated wire wrap wire is used throughout. Input hookup wires and power wires were threaded through tiny bead chokes. Multiple earths (negative voltage) connections were made. Bitumanised Al foil laid in the top and bottom of the Hammond anodised Al case. Silver solder, Alps pot and 4oz brass added once more to a quality build.

Hard to judge sound quality at this point with only a brief listen. I will follow up. Not sure it can out "B1" the B1 but it does have stacks of gain. Huge sound stage - massive.
Attached Images
File Type: jpg BoZSEss.jpg (125.3 KB, 885 views)
File Type: jpg BoZSEFinishedss.jpg (112.0 KB, 853 views)

Last edited by mhouston; 27th November 2010 at 06:04 AM. Reason: Typo
  Reply With Quote
Old 25th December 2010, 10:30 PM   #963
diyAudio Member
 
mhouston's Avatar
 
Join Date: Feb 2006
Location: Victoria, Australia
I thought you may be interested in this. Because BoZ has such a low parts count I figured it could build it on itself. I don't need input caps or attenuator in my system so these have not been added here. I do need output caps. Big brown polys (10uf) are perfect for constructing the whole preamp on.

No 20,000uf of storage in this build but still some low ESR storage caps to help with smoothing and the bottom end. With no interconnecting wire and true component-2-component construction signal path is as long as the components and solder joints (silver solder) are all halved.

I should have this cased and playing in the next few days.

BoZ on a Cap (minimalist BoZ) • DIY Audio Projects Forum
Attached Images
File Type: jpg BoZoaC8.jpg (81.7 KB, 731 views)
File Type: jpg BoZoaC9.jpg (73.4 KB, 707 views)
  Reply With Quote
Old 25th December 2010, 11:14 PM   #964
juma is offline juma  Germany
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Berlin
Nice build !
  Reply With Quote
Old 25th December 2010, 11:39 PM   #965
kp93300 is offline kp93300  Malaysia
diyAudio Member
 
Join Date: Mar 2007
Default J310

Hi JUMA,
I have your version of the pre and sounds excellent with the power supply borrowed from the half completed Bf862 .
I would like to know whether with the input of 21V dc, do I need to change any values ? I refer to the voltage at R3 after the BC548.

thanks

regards
kp93300
Attached Images
File Type: png jboz j310 + cap_mult-sch-1.png (1.9 KB, 740 views)
  Reply With Quote
Old 25th December 2010, 11:56 PM   #966
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
hi,
you may need to trim R3 & R5 down slightly to bring up the operating current at the new lower voltage. But try it as is.
__________________
regards Andrew T.
  Reply With Quote
Old 26th December 2010, 12:32 AM   #967
diyAudio Member
 
mhouston's Avatar
 
Join Date: Feb 2006
Location: Victoria, Australia
Quote:
Originally Posted by juma View Post
Nice build !
Thanks. I called it BoZoaC (BoZ on a Cap).
  Reply With Quote
Old 26th December 2010, 09:06 AM   #968
juma is offline juma  Germany
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Berlin
Quote:
Originally Posted by kp93300 View Post
Hi JUMA,
I have your version of the pre and sounds excellent with the power supply borrowed from the half completed Bf862 .
I would like to know whether with the input of 21V dc, do I need to change any values ? I refer to the voltage at R3 after the BC548.

thanks

regards
kp93300
If you use shunt reg from BF862 preamp you don't need cap multiplier.
With 21V PS voltage you can expect a bit less swing at the output (about -15%).
The drain of the JFET should sit at voltage of +V/2 + 1V and the ratio of Rs and Rd should be 1:3.
Rs defines Id and Rd defines voltage at drain.
  Reply With Quote
Old 27th December 2010, 08:00 AM   #969
diyAudio Member
 
mhouston's Avatar
 
Join Date: Feb 2006
Location: Victoria, Australia
Finis: Yes it is complete and in it's hand made plastic case (lel). All wiring is wirewarp wire. Here three lithiums power the preamp. Of course any high performance 9V battery, even rechargables could be used. I like lithiums.

At the last minute I added a 0.01uf poly to the power section right at the input to the BoZoaC engine (I could hear Gio whispering "de-couple"). Just one 0.01uf poly to ensure no HF gets into the PS. I'm pleased with the build and assembly.

I am listening to it now from my new Oppo BDP-83SE. It sounds better than my BoZSE capless-or is it. Though this preamp requires 10 or so hours of use to relax the big 10uf 100V ploypropelene output caps and settle the 2 X 1000uf 35V low ESR electros the sound is very immediate, bass seems to be at full weight (I don't believe it) and in all a very natural balance with, comparitively, mids slightly forward.

I thought BoZSE had added additional bass weight due to its 30,000uf of storage caps. But I am sensing this minimalist BoZ has the same bass performance with a fraction of the storage caps? Is it the 27V battery PS?? And I may have better mids??!!??

I cannot play LPs due to the fact I cannot attenuate my phono preamp enough. I may add a pot or an attenuator switch to this BoZ build. So far I'm very pleased. Very impressed. It sounds very quick!
Attached Images
File Type: jpg BoZoaC11.jpg (86.6 KB, 417 views)
File Type: jpg BoZoaC12.jpg (100.0 KB, 240 views)
File Type: jpg BoZoaC13.jpg (91.8 KB, 298 views)
  Reply With Quote
Old 27th December 2010, 10:16 AM   #970
kp93300 is offline kp93300  Malaysia
diyAudio Member
 
Join Date: Mar 2007
Quote:
Originally Posted by AndrewT View Post
hi,
you may need to trim R3 & R5 down slightly to bring up the operating current at the new lower voltage. But try it as is.
HI andrew,
I tried it without any change in the values and it sound fine.
thanks

kp93300
  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 12:00 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