Preamp Power Supply Suggestions - Page 2 - diyAudio
Go Back   Home > Forums > General Interest > Car Audio

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 22nd August 2006, 01:47 AM   #11
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi Tom,
If you generate +- 12 ~ 15 VDC, you can run your circuit off higher rails.

I didn't see your actual preamp circuit.

-Chris
  Reply With Quote
Old 22nd August 2006, 02:32 AM   #12
TomSSS is offline TomSSS  United States
diyAudio Member
 
Join Date: Aug 2006
The preamp circuit is actually an attenuation circuit. I just called it a preamp to simplify things. The input signal is AC coupled and and then biased to Vcc/2 using an artificial ground circuit. I've attached a drawing showing the Linear Regulator and the Artificial ground. At the time of the design I was hoping that separating the chassis ground and circuit ground with a 100 ohm resistor would be enough to bring the signal above the noise level.

I've decided to change to the switching power supply. If I do that I can eliminate the Linear Regulator and the artificial earth. I'm hoping in the end the cost to build the switcher will be about the same as the linear IC and artificial ground, and I'll get better results.

Regards,
Tom
Attached Images
File Type: jpg circuit.jpg (20.4 KB, 145 views)
  Reply With Quote
Old 22nd August 2006, 02:37 AM   #13
TomSSS is offline TomSSS  United States
diyAudio Member
 
Join Date: Aug 2006
And the linear power supply with artificial earth
Attached Images
File Type: jpg ps.jpg (39.0 KB, 146 views)
  Reply With Quote
Old 22nd August 2006, 02:43 AM   #14
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
That's a lot of work for an attenuator. Why not try a simple potentiometer in the RCA line?
  Reply With Quote
Old 22nd August 2006, 02:52 AM   #15
TomSSS is offline TomSSS  United States
diyAudio Member
 
Join Date: Aug 2006
I agree, it is a lot of work for a simple attenuator. And for most cases a simple mechanical log pot would work great. But, a digital attenuator is being used, so it gets a little bit more complicated.
  Reply With Quote
Old 22nd August 2006, 12:53 PM   #16
diyAudio Member
 
N-Channel's Avatar
 
Join Date: Mar 2003
Location: Sol System
Send a message via AIM to N-Channel
Tom,

That's about it. I agree with Perry that you MUST use a transformer for true ground isolation to get the desired noise reduction.

Try this link at National on Isolated SimpleSwitcher PSUs:

http://www.national.com/an/AN/AN-1095.pdf

and this one on a three-output LM2577-based isolated DC-DC converter.

http://www.national.com/an/AN/AN-777.pdf

In it, the two bipolar voltages are (+/-7.5V). For greater headroom, increase the turns using the calculations there to get (+/-12 to 15V).

Good info there, and I have to imagine theae were done specifically with audio applications in mind.
  Reply With Quote
Old 24th September 2006, 08:57 PM   #17
TomSSS is offline TomSSS  United States
diyAudio Member
 
Join Date: Aug 2006
Thanks for all help. I built a couple of different switchers to test out. The audible noise problem I was having is gone. However, I am seeing 100kHz noise on the primary and secondary side. I will most likely build an LC filter to get rid of this.

Tom
  Reply With Quote
Old 25th September 2006, 03:48 AM   #18
diyAudio Member
 
N-Channel's Avatar
 
Join Date: Mar 2003
Location: Sol System
Send a message via AIM to N-Channel
Tom,

An L-C filter is a good idea. I would cross-couple the windings of both the (+) and (-) outouts together (opposite phase, of course) to provide for better cross-regulation in the event of sudden input voltage changes or output current demands. This should attenuate the 100kHz switcher noise present to almost undetectable levels. Also, if you pop open your typical AT or ATX PSU, you will fing that the BIG yellow/white multi-winding toroid in the output section does this.

Even better, do this: L-C-L-C for both (+) and (-) buses, where the first Ls are the cross-coupled inductors, and the second Ls are individually wound.
  Reply With Quote
Old 26th September 2006, 04:30 AM   #19
TomSSS is offline TomSSS  United States
diyAudio Member
 
Join Date: Aug 2006
Any recommendations on filter topologies. I only have experience with the cookbook filters (Butter, Cheby, Bessel) and digital filters.
  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
LP12 Motor and Power Supply suggestions dsavitsk Analogue Source 7 30th September 2011 01:10 AM
suggestions for new power supply transformer eduard Power Supplies 0 15th June 2008 11:58 AM
Power supply suggestions needed Budric Parts 6 17th February 2008 05:49 AM
LM3886 power supply suggestions? DrFrankenstein Chip Amps 7 7th February 2007 09:16 PM


New To Site? Need Help?

All times are GMT. The time now is 01:48 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