B1 Buffer Preamp - Page 10 - 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 1st July 2008, 04:35 AM   #91
diyAudio Member
 
mpmarino's Avatar
 
Join Date: Jun 2004
Location: Crunchville, where I don't fit in.
Congrats Nelson

You are on a roll - a looong roll. Thanks for taking us along for the ride.
__________________
Crazy Yankee.
  Reply With Quote
Old 1st July 2008, 07:22 AM   #92
Vix is offline Vix  Yugoslavia
diyAudio Member
 
Vix's Avatar
 
Join Date: Nov 2003
Location: Somewhere on Planet Earth
Hi,

I was wondering if it would be more convenient to use a dual power supply, +-9 v . This is because it seems easier to 'transform " this buffer into a first or a second order active crossover if it uses a dual PSU.

If so, R2, R3, R103, R203, D1, C2 and C3 would be removed. A resistor would be attached from the gate of Q100 (Q200) to ground, and, if you want to make a 1st order high pass filter, C100 (C200) could be scaled down for a specific frequency. For a second order high pass filter, I would add another resistor going from the source of Q100 (Q200), then to the front of C100 (C200), plus one more cap...(you know the topology of the second order high pass filter).
Please let me know if this idea doesn't work...

Regards,

Vix
  Reply With Quote
Old 1st July 2008, 07:40 AM   #93
MRupp is offline MRupp  Germany
diyAudio Member
 
MRupp's Avatar
 
Join Date: Dec 2003
Location: Frankfurt area
Quote:
I would chose a Idss for the current sink that is a few mAmps lower so that the upper one is running a bit under its Idss, this to avoid gate current.
Following previous discussions on diyaudio I think this is not strictly true. You can forward bias this particular JFET to between +0.2 and +0.3. Volts, depending on chip temperature, before you see any significant gate currents, and running the JFET at full IDSS appears to be about optimal.
__________________
Martin Rupp
  Reply With Quote
Old 1st July 2008, 12:40 PM   #94
diyAudio Member
 
Join Date: Jun 2002
Location: Italy
Today I builded the Circuit . Values are ok , it works . But the LSK389 are pretty hot . Is that normal?

Also ... may I go for R105 and R205 to 100Kohm ?


  Reply With Quote
Old 1st July 2008, 01:02 PM   #95
udailey is offline udailey  United States
diyAudio Member
 
Join Date: Mar 2008
Stefano,
How does it sound!?
Uriah
  Reply With Quote
Old 1st July 2008, 01:13 PM   #96
diyAudio Member
 
Join Date: Jun 2002
Location: Italy
I am listening to the F5 and going to test with the F3 too .

Very good for now .

  Reply With Quote
Old 1st July 2008, 01:22 PM   #97
diyAudio Member
 
Join Date: Jun 2006
Question third small blue colour capacitor

Hi friends,
I just look into internal photos of B1 ( attached on enjoythemusic web site - review ) and I see third small ( blue colour ) capacitor laying between both channels in the middle of the PCB. His two traces coming directly into direction of both 2SK170 transistors on right channel. One leg of this small one connect probably GATE in first transistor and SOURCE in other one. I don`t see such small capacitor on attached circuit diagram !
  Reply With Quote
Old 1st July 2008, 01:51 PM   #98
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
Do not judge a book by it's cover.

The B1 schematic does contain 3 of the Beyschlag MKP416 caps.
Although the 1uF value only comes in 15mm lead spacing, it's safe to assume it has it's leads soldered to pads at the bottom and not at the top.
The one you see is a ground trace, the gate of the bottom JFET connects to it, as does bypass cap C3 of the voltage divider.
Which makes the second trace the one that supplies the 9Vdc to the gates of both input JFETs through the 1M resistors, and why the 2 traces run between both channels.
  Reply With Quote
Old 1st July 2008, 03:11 PM   #99
massimo is offline massimo  Italy
diyAudio Member
 
Join Date: Dec 2002
Location: Milan, Italy
Jacco is right: most probably the loonely blue cap in the middle of the borad is C3. Good idea to place it closer to the Jfet: it lowers the impedance of the tracks.
It looks like Nelson uses (at least in pictured unit) some BC polyester (mylar) caps for C3, C100 and C200 even if in the article he suggested some BC polypropylene ones for C100 and C200 (according to the Digikey part number).
The latter are grey instead of blue and much bigger (15 mm leads spacing instead of 5 mm).
I don't think the polypro caps are soldered underneath.
  Reply With Quote
Old 1st July 2008, 03:31 PM   #100
diyAudio Member
 
despotic931's Avatar
 
Join Date: Jan 2008
Send a message via AIM to despotic931
Quote:
Originally posted by fredlock
Mr. Pass, would this passive preamp be compatible to F5 amp? What I meant is, it might not drive the F5 to full swing or performance. Your thoughts?

I am also interested in the B1 with the F5, well actually I'm really interested in the B2 driving two F5s... Will i need a preamp with more gain to really drive the F5s, or will the B1/2 handle it?
  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
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 01:15 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