Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Pass Labs This forum is dedicated to Pass Labs discussion.

B1 Buffer Preamp
B1 Buffer Preamp
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 5th October 2018, 07:07 AM   #4491
mjf is offline mjf  Austria
diyAudio Member
 
Join Date: Jan 2009
Location: Austria
using a res as a ccs is the simple solution ("poor man's ccs" ).
imho a fet ccs has an "output res" in the 100k region............if you want to substitute the fet ccs with a res you should use 100k or better - but this does not fit into most schematics (exept some tube amps or sowhat).
have a look into the textbooks.........
  Reply With Quote
Old 6th October 2018, 01:39 AM   #4492
helitim is offline helitim  Canada
diyAudio Member
 
Join Date: Dec 2015
Location: Newfoundland
mjf,

Thank you for your response. Currently I am using the ARRL handbook as a reference. I also have a couple of Douglas Self's books, and Bob Cordell's book. Approx 14 years ago I was taught some of this stuff in school, but haven't used it in years, and didn't get very deep into it at that time.

Now I am trying to recover the knowledge I had, and add to it . I like to understand how all the components interact and create the finished product.

- Tim
  Reply With Quote
Old 7th October 2018, 05:20 AM   #4493
helitim is offline helitim  Canada
diyAudio Member
 
Join Date: Dec 2015
Location: Newfoundland
I was using bad models in spice. I found better ones, and now I can simulate the same output for I-R1 or I-R3 using an 833.33 ohm resistor.
Attached Images
File Type: png SimJFET.png (30.5 KB, 411 views)
File Type: png SimR.png (30.4 KB, 415 views)
  Reply With Quote
Old 10th October 2018, 09:29 PM   #4494
helitim is offline helitim  Canada
diyAudio Member
 
Join Date: Dec 2015
Location: Newfoundland
mjf,

When you say "output res", are you referring to the resistance of the preamp, as seen by(from the perspective of) the next stage "looking back"?
  Reply With Quote
Old 11th October 2018, 09:32 AM   #4495
mjf is offline mjf  Austria
diyAudio Member
 
Join Date: Jan 2009
Location: Austria
........."output res" correctly: output impedance of the drain lead J2....
(output res is a simplifikation).
  Reply With Quote
Old 16th October 2018, 04:40 PM   #4496
helitim is offline helitim  Canada
diyAudio Member
 
Join Date: Dec 2015
Location: Newfoundland
So assuming that the output signal of the above two circuits(post 4493) behaves the same with JFET 2, or R9(~830k) installed; would it be correct to say that the both have different output impedances? Do you think it would be safe(won't damage anything) to build both and compare? This is completely a thought experiment for me at this point, so that I can better understand Nelson's choices in this design. Thanks.
  Reply With Quote
Old 16th October 2018, 08:50 PM   #4497
mjf is offline mjf  Austria
diyAudio Member
 
Join Date: Jan 2009
Location: Austria
imho output impedance is dominated by J1...........

R9 is 833ohms - not 833kohms. you can try out 910 or 820ohms.

the ccs should give better linearity, that means lower distortion.
a distortion sim (fourier analysis) could show this.........
  Reply With Quote
Old 16th October 2018, 09:12 PM   #4498
helitim is offline helitim  Canada
diyAudio Member
 
Join Date: Dec 2015
Location: Newfoundland
Quote:
Originally Posted by mjf View Post
imho output impedance is dominated by J1...........
Perfect, that's what I thought. Now I understand what you meant.

I used 833 in the sim, I don't know why I wrote 833k. Just got ahead of myself I guess!

Thanks for all the help!
  Reply With Quote
Old 17th October 2018, 09:08 PM   #4499
nilsW is offline nilsW  Sweden
diyAudio Member
 
Join Date: Jan 2006
Location: Stockholm
Default I managed to put my B1 together!

I am now a proud owner of a working B1!
No critical listening just two hours testing that it works hooked up to an old amp and it does!

This is my first build ever, and this thread has been a great help. Thanks to everyone!

It is the kit from Jim`s audio.

For C100/C200 1,5 uF caps were supplied. Normally these are 1uF. Should I change those to 1 uF?
Attached Images
File Type: jpg 2BFBED1F-77E1-4CB4-9619-CCAEA7200F85.jpg (692.6 KB, 175 views)
File Type: jpg 14030FFA-BB79-4435-8118-F120B62C5623.jpg (520.8 KB, 174 views)
  Reply With Quote
Old 18th October 2018, 02:52 PM   #4500
WBS is offline WBS  United States
diyAudio Member
 
Join Date: Jan 2007
Location: Napa Valley
B1 Buffer Preamp
I'm curious why you would buy a B1 kit from someone in China (did he steal the design?) instead of buying a pcb and matched jfets from PassDiy. Even more curious is why you would then post on the Pass thread asking for advice. Why don't you ask Jim about the values for C100/C200?
__________________
"Why do we try to fool the ear? Because it makes people happy and it makes it easier to listen to stuff."
Nelson Pass, BAF 2012
  Reply With Quote

Reply


B1 Buffer PreampHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
buffer/preamp? TheDriver41 Chip Amps 2 3rd October 2004 08:40 AM


New To Site? Need Help?

All times are GMT. The time now is 07:05 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki