Building a symmetrical psu B1 buffer - Page 152 - 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 June 2010, 07:57 PM   #1511
Blues is offline Blues  United States
Lightning In A Bottle
diyAudio Member
 
Blues's Avatar
 
Join Date: Sep 2003
Location: The Milky Way
Alon, I'd like to know your opinion with the LDR volume control when you get around to it. Thanks!
__________________
Life simplified! Leap into the Warpspeed wormhole... http://www.6moons.com/audioreviews/warpspeed/1.html
  Reply With Quote
Old 16th June 2010, 08:28 PM   #1512
Malka07 is offline Malka07  England
diyAudio Member
 
Join Date: Mar 2009
Quote:
Originally Posted by Blues View Post
Alon, I'd like to know your opinion with the LDR volume control when you get around to it. Thanks!
No problem Allan

At the moment i've been using a p2p b1 buffer with Alps blue in shunt mod with tx2575 nude resistors in series(Shunt Pot Volume Control - World-Designs-Forum). Sounds very transparent to me, so this is what i will be comparing the Ldr volume control with dcb1 to. Cant Wait.
  Reply With Quote
Old 17th June 2010, 01:36 AM   #1513
mr.duck is offline mr.duck  United Kingdom
diyAudio Member
 
Join Date: Jun 2006
What other JFETs could be used in place of 2SK170? Some not as good alternatives... What specs to look for?
  Reply With Quote
Old 17th June 2010, 01:38 AM   #1514
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Toshiba 2SK117. Sanyo 2SK222 (reverse pin order). Look for -0.5V pinch off @ 6-8mA IDSS. For the audio part lower gm than 170's will up the distortion. If you can solder SMT, use Philips BF862.
  Reply With Quote
Old 17th June 2010, 08:18 AM   #1515
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Power (P) = Voltage (V) squared, divided by Resistance (R).

You have 1.73V and 2.04V available to drive the CCS resistors.

The existing 68r dissipate ~ 2.04^2/68 = 61mW. ~10% of maximum power rating of a 600mW resistor.

Add an extra 200r (on the 1.73V side), it will dissipate 15mW, ~3% of maximum rating.

Replace all the 68r and the 200r with a single 20r resistor. Dissipation is now 208mW ~35% of maximum rating. It's going to be warm but reliable.
Try 10r, 416mW ~70% of maximum rating. It's going to run hot, it's value at elevated temperature will be significantly different from it's cold temperature and it may become unreliable.

I prefer to never run any resistor at >50% of maximum rating and in some parts of the circuit <<10% of maximum rating.
__________________
regards Andrew T.
  Reply With Quote
Old 17th June 2010, 12:17 PM   #1516
diyAudio Member
 
regiregi22's Avatar
 
Join Date: May 2009
Location: Madrid (Spain)
Quote:
Originally Posted by Malka07 View Post
Thank Andrew and regiregi22,

When my Ldr's arrive, i will finish up, and then listen to it as is. Let it burn in, and then i will add a 200ohm resistor that i have in my spares to balance the currents and listen for a change...i will then hotrod it and listen again for a change in sound.

When i hotrod, which resistor wattage will i need to use? i currently have 2, 1 watt 68r resistors, would it be ok for example to use???

68r(1 watt)//68r(1 watt)//15r(5 watt) = 10.408
on the 2.04v side...2.04/10.408 = 0.196ma

68r(1 watt)//68r(1 watt)//12r(5 watt) = 8.8696
on the 1.73v side...1.73/8.8696 = 0.195ma

Thanks for your help.

Alon
As a general thumb rule for this project, I recommend a 10ohm resistor per side and 5W rated. That is what I have. They get barely warm, just a bit hot. You could do with 4W resistors, but I wouldn't go lower.
__________________
diyAudio, doing it as big as you can, JUST BECAUSE WE CAN!
  Reply With Quote
Old 17th June 2010, 02:41 PM   #1517
mr.duck is offline mr.duck  United Kingdom
diyAudio Member
 
Join Date: Jun 2006
Quote:
Originally Posted by Salas View Post
Toshiba 2SK117. Sanyo 2SK222 (reverse pin order). Look for -0.5V pinch off @ 6-8mA IDSS. For the audio part lower gm than 170's will up the distortion. If you can solder SMT, use Philips BF862.
To my inexperienced eye, that BF862 looks like an absolute gem!

SMT on that scale should be no problem. Are there any other drawbacks or sonic inferiority compared to 2SK170?
  Reply With Quote
Old 17th June 2010, 03:02 PM   #1518
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
No. Can be better not worse.
  Reply With Quote
Old 17th June 2010, 05:23 PM   #1519
Malka07 is offline Malka07  England
diyAudio Member
 
Join Date: Mar 2009
Thanks Again Andrew and Regiregi22,

Correct me if im wrong, but my understanding is that when resistors are used in parralel, there wattage is added on, so for example a 68r(1 watt)//68r(1 watt)//15r(5 watt) would be equivalent to a 10r(7 watt) resistor???

However im not sure if i correct in this understanding

Alon
  Reply With Quote
Old 17th June 2010, 05:41 PM   #1520
Blues is offline Blues  United States
Lightning In A Bottle
diyAudio Member
 
Blues's Avatar
 
Join Date: Sep 2003
Location: The Milky Way
Alon,

The power will still be distributed accordingly with the most on the lower resistance as more current is passed.
__________________
Life simplified! Leap into the Warpspeed wormhole... http://www.6moons.com/audioreviews/warpspeed/1.html
  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
New-building of my B1 buffer Babowana Pass Labs 328 20th February 2010 01:14 AM


New To Site? Need Help?

All times are GMT. The time now is 03:10 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