Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

First Linear Power Supply Build Questions
First Linear Power Supply Build Questions
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 21st August 2019, 03:24 AM   #1
LateraLiz is offline LateraLiz  United States
diyAudio Member
 
Join Date: Aug 2019
Default First Linear Power Supply Build Questions

Hi All!

I'm sort of new to the DIY audio and electronics scene, and this site has been providing me with a wealth of useful information for my journey thus far.

I have decided to build my own linear regulated power supply to provide the power I will need for an upcoming headphone amp I will be building. Since I'm no pro, I was hoping I could get some feedback on my design before building it, just in case I made some catastrophic mistakes in my design or anything like that. Its pretty simple and based off the LM317 adjustable voltage regulator. Most of the schematic is based on the information found in the LM317 datasheet. The requirements I have for this build is a clean source of about 30VDC at the output. I did the calculations and came up with the details and design listed on the attached photo of the schematic.

If anyone has a moment to look the schematic over for any mistakes or to give any feedback or criticisms of the design, I would be immensely grateful. Thanks!
Attached Images
File Type: jpeg ps-schematic.jpeg (751.2 KB, 403 views)
  Reply With Quote
Old 21st August 2019, 04:20 AM   #2
rayma is offline rayma  United States
diyAudio Member
 
Join Date: Apr 2011
The DC voltage on C1 should be around 32.5VDC at nominal AC line.
This means there should be more drop across the LM317 for good regulation,
mfr says 3V minimum under worst case, with low line. As is, I would only
expect 27VDC out with low line.

Last edited by rayma; 21st August 2019 at 04:31 AM.
  Reply With Quote
Old 21st August 2019, 04:37 AM   #3
LateraLiz is offline LateraLiz  United States
diyAudio Member
 
Join Date: Aug 2019
Thanks for the feedback, rayma.

Factoring in a 3V regulator dropout for the LM317 under worst case scenario, I would need a transformer rated for more than the current 24VAC in order to then achieve the desired 30VDC then right?
  Reply With Quote
Old 21st August 2019, 05:24 AM   #4
LateraLiz is offline LateraLiz  United States
diyAudio Member
 
Join Date: Aug 2019
So modifications on original design are changing the transformer, to a 115VAC primary, with 28VAC secondary @ 3.6A. With the rest of the schematic unchanged, it is my understanding that this design would then be able to produce the desired output of 30VDC?
  Reply With Quote
Old 21st August 2019, 06:02 AM   #5
abraxalito is offline abraxalito  United Kingdom
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
There's something to watch out for with LM317 and that's not exceeding the maximum in-out voltage (40V) under short-circuit conditions. In this case you might, under worst case input voltage and an output short, destroy the LM. What's the regulation on your transformer?

Also - do you know what maximum output current you'll be needing?
__________________
I know you think you understand what you thought I said but I'm not sure you realize that what you heard is not what I meant - Alan Greenspan
  Reply With Quote
Old 21st August 2019, 06:38 AM   #6
LateraLiz is offline LateraLiz  United States
diyAudio Member
 
Join Date: Aug 2019
Hi abraxalito,

Regarding your note on short circuit conditions, diodes D2 and D3 in the schematic are included based on the suggestion to include them on the LM317 datasheet. Specifically, in the event "the input is shorted to ground during a fault condition, protection diodes provide measures to prevent the possibility of external capacitors discharging through low-impedance paths in the IC" and D2 and D3 prevent capacitors discharging into the output of the regulator. Does this satisfy the concerns you mention?

Regarding the regulation of my transformer, I do not know if it does or doesn't have regulation. I intend to purchase either one of these to use for this project:

187F28 Hammond Manufacturing | Mouser
or
F8-28 Triad Magnetics | Mouser

As for maximum current output, I must admit I did not go through the calculations for current, and simply assumed between 1.5A or 3A would suffice for my purposes, at least for now. Still learning so this is one area I'm short on knowledge in.

Thank you for your comments!
  Reply With Quote
Old 21st August 2019, 09:28 AM   #7
sgrossklass is offline sgrossklass  Germany
diyAudio Member
 
Join Date: Nov 2004
Location: Germany
This may be a stupid question, but what kind of headphone amp needs a 30 V single supply these days? That would have to be a seriously oldschool concept, AC-coupled output and all. Even the JLH uses a split supply. Good luck with turn-on thump then.

A 100 VA xfmr seems a bit excessive, even Class A concepts tend not to run more than about 150 mA per channel. 1 A output probably is on the generous side already. Honestly I would consider it a bit worrying if you have no idea what your circuit is actually drawing.
  Reply With Quote
Old 21st August 2019, 10:07 AM   #8
jean-paul is offline jean-paul  Netherlands
diyAudio Moderator Emeritus
 
jean-paul's Avatar
 
Join Date: Sep 2002
Location: Germany
Why LM317? There are better ultra low drop regulator ICs availabe. I would use CLC filtering before the reg as well. With a modern IC you can probably use a 24V transformer and have less energy wasted in heat. Maybe not a design goal but cooler electronics also live longer. A key parameter is the desired output current.
__________________
It's only audio. Member of the non modular PCB design committee

Last edited by jean-paul; 21st August 2019 at 10:13 AM.
  Reply With Quote
Old 21st August 2019, 06:46 PM   #9
LateraLiz is offline LateraLiz  United States
diyAudio Member
 
Join Date: Aug 2019
Quote:
Originally Posted by sgrossklass View Post
This may be a stupid question, but what kind of headphone amp needs a 30 V single supply these days? That would have to be a seriously oldschool concept, AC-coupled output and all. Even the JLH uses a split supply. Good luck with turn-on thump then.

A 100 VA xfmr seems a bit excessive, even Class A concepts tend not to run more than about 150 mA per channel. 1 A output probably is on the generous side already. Honestly I would consider it a bit worrying if you have no idea what your circuit is actually drawing.
Fair question! So while the primary motivation for this supply is having enough juice for a beefy headphone amp, it will also sort of serve as a bench supply for other, non-audio projects.

When used for the headphone amp, I am using the Goldpoint VG2 circuit to split the supply up to +/- 15 VDC to power various versions of a cmoy, which I've found to serve me well as a learning model thus far.

With regards to my failure to follow the current, if I set my limit to having 1.5a of currents, that would be playing it safe as I know that doesn't exceed the limitations of any of the downstream parts or ICs i'm using. Upwards of that would be nice to have for other projects, but perhaps I'm trying to accomplish too much with one thing. Otherwise, I would appreciate any pointers on helping me achieve the maths needed to calculate my specific current needs. Thanks
  Reply With Quote
Old 21st August 2019, 06:49 PM   #10
LateraLiz is offline LateraLiz  United States
diyAudio Member
 
Join Date: Aug 2019
Quote:
Originally Posted by jean-paul View Post
Why LM317? There are better ultra low drop regulator ICs availabe. I would use CLC filtering before the reg as well. With a modern IC you can probably use a 24V transformer and have less energy wasted in heat. Maybe not a design goal but cooler electronics also live longer. A key parameter is the desired output current.
The short answer? LM317 makes for simple circuitry and its cheap. The long answer - I have oodles of heatsinks which I'll dive into to find an appropriate fit for this one for which would alleviate some thermal issues although still not efficient.

That said, what ICs do you have in mind as better alternatives?
  Reply With Quote

Reply


First Linear Power Supply Build QuestionsHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Questions about amp camp amp and linear power supply Jonse Pass Labs 22 17th February 2018 08:37 PM
Op amp Linear power supply Marksd Power Supplies 158 27th January 2018 09:44 AM
Linear DAC power supply jean-paul Analog Line Level 0 30th April 2015 11:53 AM
Help a novice steadily build a linear 12V power supply? SGK Power Supplies 117 27th May 2014 08:38 AM
Tubelab SE build and power supply questions. Binaural Tubelab 54 3rd March 2010 04:20 AM


New To Site? Need Help?

All times are GMT. The time now is 04:27 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki