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

Voltage regulator bypass questions
Voltage regulator bypass 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 1st December 2019, 04:36 PM   #31
Abtr is offline Abtr  Netherlands
diyAudio Member
 
Join Date: Apr 2015
Quote:
Originally Posted by jan.didden View Post
Someone *probably* thought that he/she could lower the noise after the regulator further. But trying that it would completely swamp the low output impedance of the regulator. Like, you have a reg with less than 1 ohm Zout, which means the output voltage it is rock-steady with all the variations in load current that happen while amplifying a signal.

Now you place a Very Large resistor in series, wasn't it 4.7 ohms? So if the load current varies, so does the supply voltage, undoing what the regulator was for in the first place.

Then you place some capacitance after that 4.7 ohms. Tat helps for low output impedance but such a cap has easily a larger ESR than the regulator Zout, and especially at higher frequencies ruins it because of parasitic inductance.

Such a capacitor after a regulator (without the R) is not there to lower the regulator Zout but only for stability; the regulator is 'better' than that cap anyway.

So such things as R65 + cap are done by people with enough knowledge to be dangerous ;-)

Jan
Thank you! One more question. In addition to bypassing R65 I'm thinking about removing the caps after R65 and replace them with a single Kemet A750 cap (aluminum propylen) of several hundred uF to improve transient response. Would that be a good idea? Note that the LT3045 regulator board is connected through 10cm long wires to the crossover board's VIN connectors.
  Reply With Quote
Old 2nd December 2019, 08:43 PM   #32
Abtr is offline Abtr  Netherlands
diyAudio Member
 
Join Date: Apr 2015
So I bypassed R65 on both crossover boards and it's a major upgrade. Thanks again! It's now easy to 'listen into the music'. Different instruments/tracks can be easily distinguished and overall sound is more alive and involving.

I think I'll leave the output caps (C16 and parallel capacitors) in place for now. I suppose they can't do much (if any) harm in a strictly analogue audio application.

Any thoughts will as always be much appreciated!
  Reply With Quote
Old 3rd December 2019, 08:33 PM   #33
Abtr is offline Abtr  Netherlands
diyAudio Member
 
Join Date: Apr 2015
Ow, and bypassing R65 got rid of a slight hum which was audible at max volume without signal.

All in all it really surprises me how much difference a power supply or voltage regulating circuit can make in terms of sound quality!

Thanks for the help!
  Reply With Quote
Old 5th December 2019, 11:39 AM   #34
carlmart is offline carlmart  Brazil
diyAudio Member
 
Join Date: Mar 2001
Location: Brazil
Quote:
Originally Posted by jackinnj View Post
I thought it might be instructive to put into a picture what PRR and others have related. C3 is "parameter selected" for 1pF or 100nF. All the other values are per the datasheet. (with a little parasitic inductance thrown in for good measure). The dark blue line shows the effect of the additional capacitor -- an additional impedance peak with Q~=2.9, so phase margin is only 18 degrees.
Can you upload the asc file for this simulation?

Thanks!
  Reply With Quote
Old 5th December 2019, 09:13 PM   #35
jackinnj is offline jackinnj  United States
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Voltage regulator bypass questions
Quote:
Originally Posted by carlmart View Post
Can you upload the asc file for this simulation?

Thanks!
I think this is the one.
Attached Files
File Type: asc LT3045.asc (2.1 KB, 3 views)
  Reply With Quote

Reply


Voltage regulator bypass 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
Voltage regulator prefixes and capacitor source questions bblument Parts 20 29th March 2016 12:35 PM
Maida regulator ADJ bypass kacernator Power Supplies 3 19th January 2014 10:26 AM
on chip negative voltage regulator with positive supply voltage gvsrkprasad Power Supplies 3 20th February 2013 03:19 PM
Please help me understand the voltage regulator with external bypass BJT? Fusion916 Solid State 11 15th November 2012 07:59 PM
LR8N3 Regulator -- Bypass the ADJ pin jackinnj Power Supplies 1 10th December 2007 06:26 PM


New To Site? Need Help?

All times are GMT. The time now is 12:23 PM.


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