Lm317/337 tracking preregs - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 12th August 2003, 01:58 PM   #1
diyAudio Member
 
5th element's Avatar
 
Join Date: Oct 2002
Location: England
Default Lm317/337 tracking preregs

Regulators.

Im in the process of adding regulators to my preamp and have built the tracking prereg circuit as illustrated in the LM317 data sheet http://www.national.com/ds/LM/LM117.pdf.

Now Im using apprx 18v input lines and the max voltage I can get on the output is only 8.54 volts. I was hoping to get about 15v, and im assuming that its impossible to get the full input on the output. Is the circuit running right?? and if so what can I change to increase the max output, if thats possible. Im all new to regulators so dont know much about them yet.

Cheers Matt
  Reply With Quote
Old 12th August 2003, 03:16 PM   #2
sam9 is offline sam9  United States
diyAudio Member
 
sam9's Avatar
 
Join Date: Jun 2002
Location: Left Coast
If you had said you were getting only 14V, but wanted 15V, I would have suggested the only route to be a bigger transformer But since what you are getting is only `8-1/2V, I suspect you have miswired the circuit. I can only suggest you re-check

8-1/2V just happens to be 1/2 of 17V which is a plausible voltage to achieve so keep an eye out for the possibility that you have inadvertently built in a 2:1 voltage divider somewhere. Most of my mistakes seem really simple and dumb - once resolved.
  Reply With Quote
Old 12th August 2003, 04:10 PM   #3
Bricolo is offline Bricolo  France
diyAudio Member
 
Bricolo's Avatar
 
Join Date: Nov 2002
Location: Grenoble, FR
please tell us if this circuit works good, when it will work correctly.

I never built it, but it looks interesting
  Reply With Quote
Old 12th August 2003, 04:59 PM   #4
JeLL-O is offline JeLL-O  Thailand
diyAudio Member
 
Join Date: Aug 2003
Location: Bangkok
THe circuit for the tracking pre-reg shown in the LM317 datasheet maintains a difference of 5 volts between the output of the first reg and the second reg. (720/240 +1 )*1.25=5 volts (ignoring Iadj)

Each LM317 needs a Voltage Out-In differential of at least 3 volts. This means that with an 18v input, the max you can hope for is 12v.

To get 15v, you need to start with approximately 25v, drop 5 volts in each reg, to end up with 15.
  Reply With Quote
Old 12th August 2003, 05:18 PM   #5
diyAudio Member
 
Join Date: Nov 2002
Location: Germany
Default Output Voltage

Minimum Input to Output Voltage is 3V for LM317, LM337. If you want you may use potentiometers in Adj paths, the you could regulate an output voltage.
LM317 and 337 have a cuurent limit. When current is too high then output voltage going low. Check output without preamp circuit. Those regulators have a thermal limit, so remember to use a heat sinks.
  Reply With Quote
Old 12th August 2003, 06:12 PM   #6
diyAudio Member
 
5th element's Avatar
 
Join Date: Oct 2002
Location: England
OK well I have it sorted, nothing really special needed. Loading the supply brought the supply rails up a few volts to 11.2. Then the variable resistor that adjusts the voltage when at max res1k gives the aforementioned 11.2volts. I added an extra 1k to this making min res 1k max 2k. Now I get 14.6 out of this which I assume is max for the loss of the regs.

I cant comment on the sound as of yet as im changing the case of my amp too which should be completed today or early tomorrow.
Pics to follow aswell. Ill keep you informed on the sound when I can

Matt
  Reply With Quote
Old 12th August 2003, 06:13 PM   #7
diyAudio Member
 
5th element's Avatar
 
Join Date: Oct 2002
Location: England
Thought I might add this quickly, I had previously listened to the pre at 17.5 rails unregulated, so it will be interesting to see how it sounds at 3v less but regulated.
  Reply With Quote
Old 12th August 2003, 07:44 PM   #8
ALW is offline ALW  United Kingdom
diyAudio Member
 
Join Date: Jun 2001
Location: UK
You should be able to run the tracking pre-reg at 2.5V (i.e. both resistors of equal value) - the dropout of most 317's is nowhere near 3V at low currents, and certainly 5V is overkill.

Decouple BOTH adj pins too, for best performance / sound.

Andy.
  Reply With Quote
Old 14th August 2003, 12:41 PM   #9
diyAudio Member
 
5th element's Avatar
 
Join Date: Oct 2002
Location: England
Ok well all is up and running. I had it going a few days ago but wanted to listen to evaluate the sound before posting.

The amp section I'd listened too before anyway and I knew it sounded good but not the preamp when regulated. The regs are all sorted and everything works fine.

All I can say is that it sounds better with new case and regs. I cant say if the amp sounds better with new case or the preamp sounds better with regs cause I changed both at the same time. But everything sounds more clearer, not clarity directly as clarity was never and issue before but more textured like everything is layered more clearly. Highs are more smooth, again wasnt an issue before really but they are, and stage depth (i find this really hard to actually perceive regardless of system) seems to be more realistic.

I will post pics when I get the digital cam upa nd running
  Reply With Quote
Old 14th August 2003, 02:50 PM   #10
diyAudio Member
 
Join Date: Dec 2002
Location: Houston
Default LM337 Tracking Reg

Matt,
It looks interesting. How did you impliment the LM337 tracking reg? The positive isa shown in the LM317 datasheet. How exactly did you build its compliment?

George
  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
Tracking problem, need help Assyst1606 Digital Source 21 19th October 2006 11:13 AM
Why not/yes, Dual tracking psu... gmphadte Solid State 2 14th February 2006 04:13 AM
Tracking down the CD-Pro2 Strohmie Digital Source 10 7th May 2004 05:47 PM
does linear POT have better tracking that a log one? jarthel Parts 2 28th June 2003 11:51 PM


New To Site? Need Help?

All times are GMT. The time now is 08:05 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