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 30th March 2008, 02:24 PM   #41
housing is offline housing  Hong Kong
diyAudio Member
 
Join Date: Nov 2006
Hello spzzzzkt,

Are the LT1117's 3-LEAD PLASTIC SOT-223? They have different leg configuration with the LM340MPX-5.0.

Can zener diodes really be paralleled? Never heard of it! Only know CRD can be paralleled and zener can be put in series.


  Reply With Quote
Old 30th March 2008, 09:01 PM   #42
diyAudio Member
 
spzzzzkt's Avatar
 
Join Date: May 2005
Location: Melbourne
Hi Housing,

Thanks for pointing out to the LM340 pinout. Checked the data sheets, and you are correct, the pinouts are different. My bad. The LM317 pinout is the same but output noise is the same and ripple rejection only slightly better. Probably not worth changing, unless someone has a suggestion for a better part. Pity that Spencer threw the 7805's overboard in this case as they are a better part than the LT replacement. I suspect Mr. Colburn had a clue or two about parts selection.

In regards to parallel zeners, you read should the link on 3pin regs above for reasoning on use of parallel zeners. The argument is that paralleling halves the impedance of the zener. It certainly seems to work ok, and has been widely used in the "raygulator" discussed in the "Marantz CD63 & CD67 mods list" thread.

As a side note, the output impedance of the LM3x7's of the could be further improved by separating the adjust pin gnd and load gnd as described by Werner Ogiers. I can't see how this can be done easily with the current board.
http://www.tnt-audio.com/clinica/reg...edance1_e.html

cheers
Paul
  Reply With Quote
Old 30th March 2008, 09:05 PM   #43
diyAudio Member
 
spzzzzkt's Avatar
 
Join Date: May 2005
Location: Melbourne
Quote:
Originally posted by Dave
Spencer,

I think the 47uH inductors you have inline with the PCM63 supply rails might be a concern. These will form a resonant circuit with the 47uF capacitors, resonant frequency will be 3.386kHz right in the audio band.
The characteristic impedance is 1 ohm so the DC resistance of the inductor and/or ESR of the cap might be enough to damp it properly but could be worth double checking.

Dave
Hi Dave

So this resonance would show up as an oscillation on the V+/V- lines? How would we test for this phenomena?

cheers
Paul
  Reply With Quote
Old 31st March 2008, 04:00 AM   #44
housing is offline housing  Hong Kong
diyAudio Member
 
Join Date: Nov 2006
Hello Paul,

This device REG104GA-5 or REG104FA-5 looks very good. But again different pinout, and worst still a 5-pin device.
  Reply With Quote
Old 31st March 2008, 04:07 AM   #45
diyAudio Member
 
spzzzzkt's Avatar
 
Join Date: May 2005
Location: Melbourne
Looks like the LT1117's stay for the moment then
  Reply With Quote
Old 31st March 2008, 08:59 AM   #46
Dave is offline Dave  New Zealand
diyAudio Member
 
Join Date: Oct 2001
Location: New Zealand
spzzzzkt,

The resonance could lead to very poor transient response on the output of the filter. When the load current steps up the output voltage will drop and ring if the damping is not enough. Perhaps more of a concern is if the load current steps down, in this case the output of the filter will overshoot as energy that was in the inductor is transfered to the capacitor, if the overshoot voltage is enough it could destroy the load. Again there is the potential for ringing. Best bet is to ensure that the filter is properly damped. Play with it in a spice simulator.

Dave
  Reply With Quote
Old 31st March 2008, 03:52 PM   #47
housing is offline housing  Hong Kong
diyAudio Member
 
Join Date: Nov 2006
Quote:
Originally posted by spzzzzkt
Looks like the LT1117's stay for the moment then
Will Burr Brown's Reg1117A-5 be better sounded although their specifications are almost the same except that the Reg has a current output of 1A?

  Reply With Quote
Old 31st March 2008, 09:04 PM   #48
ctong is offline ctong  United States
diyAudio Member
 
Join Date: Jun 2005
Location: Clemson, South Carolina
Can the IV and output stages be used with DACs accepting DSD signals such as PCM1738 and PCM1792? These DACs are Sigma-Delta type for PCM signals.
__________________
CT
  Reply With Quote
Old 31st March 2008, 10:04 PM   #49
diyAudio Member
 
spzzzzkt's Avatar
 
Join Date: May 2005
Location: Melbourne
Quote:
Originally posted by ctong
Can the IV and output stages be used with DACs accepting DSD signals such as PCM1738 and PCM1792? These DACs are Sigma-Delta type for PCM signals.
There is a thread dealing with D1 I/V and the PCM1738:
D1 output stage and PCM1738
  Reply With Quote
Old 31st March 2008, 10:09 PM   #50
diyAudio Member
 
spzzzzkt's Avatar
 
Join Date: May 2005
Location: Melbourne
Quote:
Originally posted by housing

Will Burr Brown's Reg1117A-5 be better sounded although their specifications are almost the same except that the Reg has a current output of 1A?
I think that question can only be answered by listening tests not spec racing. Maybe Spencer had some specific reason for choosing the LT part?
  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
The Pass Pub: The High-End Off Topic Thread Zen Mod Pass Labs 16004 Today 08:24 AM


New To Site? Need Help?

All times are GMT. The time now is 09:05 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