The Phonoclone and VSPS PCB Help Desk - Page 225 - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

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 14th March 2013, 12:30 AM   #2241
Bibio is offline Bibio  Scotland
diyAudio Member
 
Bibio's Avatar
 
Join Date: Mar 2009
is the LED indicator for the power supply a 12v or just your regular 2.5v?
  Reply With Quote
Old 14th March 2013, 12:37 AM   #2242
rjm is offline rjm  Japan
Richard Murdey
diyAudio Member
 
rjm's Avatar
 
Join Date: May 2004
Location: Kyoto
Blog Entries: 103
About the resistor values, it's part of a CRC filter designed to attenuate the high frequency noise generated by the LM7x12 voltage regulators. The larger it is the better it works as a filter, but the impedance of the power supply at low frequencies increases proportionally.

I think 10 ohms is a maximum value for the amount of resistance you want to put there, you might want to try less or none at all (jumper).
__________________
RJM Audio (phonoclone.com / G+)
  Reply With Quote
Old 14th March 2013, 12:38 AM   #2243
rjm is offline rjm  Japan
Richard Murdey
diyAudio Member
 
rjm's Avatar
 
Join Date: May 2004
Location: Kyoto
Blog Entries: 103
Quote:
Originally Posted by Bibio View Post
is the LED indicator for the power supply a 12v or just your regular 2.5v?
Just a regular led, that's why the series resistor is there.
__________________
RJM Audio (phonoclone.com / G+)
  Reply With Quote
Old 14th March 2013, 12:43 AM   #2244
Bibio is offline Bibio  Scotland
diyAudio Member
 
Bibio's Avatar
 
Join Date: Mar 2009
thought so.. cheers Richard
  Reply With Quote
Old 14th March 2013, 09:09 AM   #2245
rjm is offline rjm  Japan
Richard Murdey
diyAudio Member
 
rjm's Avatar
 
Join Date: May 2004
Location: Kyoto
Blog Entries: 103
Default X-reg

Did up a quick-and-dirty sim of the X-reg voltage stabilizer in LTSpice.

I works! (duh...)

Kinda fun to play with. The spice file is attached.
Attached Images
File Type: png xreg00.png (95.9 KB, 136 views)
Attached Files
File Type: zip xreg 00.zip (1.5 KB, 9 views)
__________________
RJM Audio (phonoclone.com / G+)
  Reply With Quote
Old 14th March 2013, 09:27 AM   #2246
vulejov is offline vulejov  Serbia
diyAudio Member
 
vulejov's Avatar
 
Join Date: Aug 2010
Looks like there is no need for X-reg.. works just like LM78/79.
  Reply With Quote
Old 14th March 2013, 09:45 AM   #2247
vulejov is offline vulejov  Serbia
diyAudio Member
 
vulejov's Avatar
 
Join Date: Aug 2010
Quote:
Originally Posted by rjm View Post
About the resistor values, it's part of a CRC filter designed to attenuate the high frequency noise generated by the LM7x12 voltage regulators. The larger it is the better it works as a filter, but the impedance of the power supply at low frequencies increases proportionally.

I think 10 ohms is a maximum value for the amount of resistance you want to put there, you might want to try less or none at all (jumper).




I can not hear any difference between resistor and jumper..
Does it make sense to put a small inductivity instead of resistor?
  Reply With Quote
Old 14th March 2013, 02:32 PM   #2248
rjm is offline rjm  Japan
Richard Murdey
diyAudio Member
 
rjm's Avatar
 
Join Date: May 2004
Location: Kyoto
Blog Entries: 103
Quote:
Originally Posted by vulejov View Post
Does it make sense to put a small inductivity instead of resistor?
I thought about that, but I tried that idea long ago on a different RIAA preamp, and the result was quite awful. Perhaps the inductance (high Q tank circuit) interacts with the high feedback op amp IC adversely?

You are welcome to argue that LM7812 is sufficient, given surface noise of the record, parasitic noise coupling, op amp PSRR etc. etc. Indeed from a databook perspective the 3 terminal regulators don't seem bad at all**. I prefer the X-reg though, in direct listening comparison I found it far superior to LM7812 or LM317.

**The LM78xx series is quoted for 72 dB ripple rejection at 120 Hz and 50 microV noise for 10-100k bandwidth. I've just shown that the X-reg has a ripple rejection of 120 dB at 100 Hz. The noise floor is about the same, 50 microV (calculated), but the difference is that above 2 kHz the LM7812 drops below 60 dB ripple rejection. The X-reg (LTSpice simulation) still gives 120 dB ripple rejection at 10 kHz, and 107 dB at 100 kHz, where the LM7812 is down to 40 dB. Without compromising output impedance like a CRC filter would. So the difference here is easily demonstrated at least.
__________________
RJM Audio (phonoclone.com / G+)

Last edited by rjm; 14th March 2013 at 02:38 PM.
  Reply With Quote
Old 14th March 2013, 04:44 PM   #2249
diyAudio Member
 
dimkasta's Avatar
 
Join Date: May 2010
Location: Athens
About the LM7812, I remember reading somewhere (I think Salas threads) that its sweet spot for noise rejection is when Vin is more than 8V over Vout. Which makes sense when thinking the Power Humpty output which is around 23V
  Reply With Quote
Old 15th March 2013, 01:20 AM   #2250
rjm is offline rjm  Japan
Richard Murdey
diyAudio Member
 
rjm's Avatar
 
Join Date: May 2004
Location: Kyoto
Blog Entries: 103
(Vin-Vout) = 7-8 V seems about right, yes. That's what most people will end up with naturally anyway.
__________________
RJM Audio (phonoclone.com / G+)
  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



New To Site? Need Help?

All times are GMT. The time now is 12:26 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