Grounding for an external power supply - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 April 2012, 02:42 AM   #1
JVDM is offline JVDM  Australia
diyAudio Member
 
Join Date: Nov 2008
Default Grounding for an external power supply

Hi all,

I'm embarking on my first gainclone attempt, using the chipamp.com kits. I have assembled the two LM3886 amp modules, and the power supply PCB.. The plan is for an external power supply unit, using a 300VA toroidal with dual 25V secondaries.

My current concern is with the grounding of the unit, given I'll be using an external PS.

At the moment, I'm thinking of using a 5 conductor umbilical, carrying P+ve, PG+ P-, PG-, and a ground connection between the amp chassis and the power supply chassis and the amp boards grounded in the amp chassis.

An alternative would be a 6 core umbilical, allowing the P+, PG+, P-, PG-, CHG and the amp chassis ground point. With this method, I could star-ground everything back in the power supply chassis, without having to ground the CHG in the amp unit.

Does this make sense? Which would be the best strategy?

Cheers,
JD
  Reply With Quote
Old 14th April 2012, 09:17 AM   #2
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
That investment and the wiring makes more sense as a dual-mono or monoblocs.
  Reply With Quote
Old 14th April 2012, 10:07 AM   #3
JVDM is offline JVDM  Australia
diyAudio Member
 
Join Date: Nov 2008
I had originally intended to build a pair of monoblocks, each with external PS's, and bought 2 amp modules and 2 PS modules. However, I switched to a stereo with a shared external power supply to simplify things. I could quite easily run a separate power supply for each channel, but that would mean running 2 umbilicals, or one with more conductors. I could probably manage dual monoblocks with external power supplies (like the original gain card) if I spring for another enclosure. Would the improvements be noticeable?

All of these options would still leave me with the grounding issue though. Do I ground the amp pcb in the amp chassis, or run a ground for both the chassis and the pcb separately back to the safety ground in the PSU via the umbilical?
  Reply With Quote
Old 14th April 2012, 12:08 PM   #4
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Do not put the Main Audio Ground in the PSU or that vicinity.

Bring the PSU Zero Volts to the amplifier's Main Audio Ground.
__________________
regards Andrew T.
  Reply With Quote
Old 14th April 2012, 02:37 PM   #5
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
It is a good time to review Star Grounding and power supplies at Decibel Dungeon:
Building a Gainclone chip amp power supply.
If the server is not responding well enough to display photos, you can use the PDF backup file.
  Reply With Quote
Old 14th April 2012, 04:31 PM   #6
AlexQS is offline AlexQS  United States
diyAudio Member
 
Join Date: Jan 2012
Location: Pacific Northwest
Quote:
Originally Posted by JVDM View Post


At the moment, I'm thinking of using a 5 conductor umbilical, carrying P+ve, PG+ P-, PG-, and a ground connection between the amp chassis and the power supply chassis and the amp boards grounded in the amp chassis.

An alternative would be a 6 core umbilical, allowing the P+, PG+, P-, PG-, CHG and the amp chassis ground point. With this method, I could star-ground everything back in the power supply chassis, without having to ground the CHG in the amp unit.
I am trying something simular with an Audio Sector kit.

What AndrewT says makes the most sense to me, and I have also come accross agreement to this in other reading.

I made an umbellical, but haven't had a chance to try it yet. I have been focused on other areas recently, volume-pots and whatnot.

I am new to chip-amps, but the theorie lines up with other things I have learned in my years. When I was a kid, my friends and I became pretty darn good at installing car-audio stuff. If you put an audio amplifier in the trunk of a car, you must make sure that the ground wire from the amp is of at least equal guage wire (or larger) than the voltage power input wire, and also that the ground wire is as short as possible between the ground of the amp, and the chassis of the vehicle. Make it too long (like running a line all the way back to the ground of your fuse block under the bonnet) and you'll hear the cars engine in your speakers. Ideal way is to screw the ground line to the metal of the car as close to the amp as possible.

I realize I'm comparing apples and oranges here, but I think the theorie is the same in both places, "keep the line between the amplifier and chassis ground as short as possible".

So, use 5 conductors, not 6. Using 6, and running earth to your amp chassis, and then running CHG from the star of the board all the way back to the PSU, seems to me that this would create a big loop inside your umbelical.

Do a google search for something like, "Patek Grounding Audio Sector Peter Daniels" Keep in mind that the amp boards are different. The star point of the audio sector board is OG, where as I believe it may be CHG on the chipamp board. I think the photo might be helpful to you, even though they are different kits.


p.s. Remember to twist the pairs.
  Reply With Quote
Old 14th April 2012, 04:56 PM   #7
AlexQS is offline AlexQS  United States
diyAudio Member
 
Join Date: Jan 2012
Location: Pacific Northwest
Quote:
Originally Posted by AlexQS View Post
So, use 5 conductors, not 6. Using 6, and running earth to your amp chassis, and then running CHG from the star of the board all the way back to the PSU, seems to me that this would create a big loop inside your umbelical.

Do a google search for something like, "Patek Grounding Audio Sector Peter Daniels" Keep in mind that the amp boards are different. The star point of the audio sector board is OG, where as I believe it may be CHG on the chipamp board. I think the photo might be helpful to you, even though they are different kits.
On seccond thought, don't pay too much attention to me.... I just confused myself.

Here's photo I meant to point you to: AudioSector-chip amp kits, dacs, chassis

I can't see where the "5th" conductor is to connect amp-chassis back to earth in the mains plug. Maybe it's another line outside the umbelical???
  Reply With Quote
Old 15th April 2012, 02:41 AM   #8
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
The confusion is because those kits are specifically designed to make compact monobloc amplifiers. I will try adapt them for you. Please check other references for comparison and safety.

You can make a first start by equipping both chassis with earth ground cable. It may be good to complete most testing prior to installing the kits into the chassis.

To simplify your wiring and avoid loops with stereo builds, solder a jumper from PG+ to PG- at your power boards. This will reduce the confusion. You now have a Zero Volt ("CG") cable and therefore wiring standards for stereo amplifiers can work as expected.

And, see CarlosFM attachment for umbilical cable wiring.
The audiosector power board needs 3300uF caps added. The chipamp.com power board needs the 10,000uF changed for 3300uF. The chipamp.com amplifier boards need 470uF to 1500uF (same as the audiosector amp board) caps on the power rails of the amplifier boards instead of that 100uF mistake.
BOTH amplifiers need a pair of 10,000uF caps inside the amplifier enclosure (equally VERY close to the amplifier boards) and it is this (zero volt, "CG") Star Ground point where speaker negative (speaker return) and earth ground meet up with the zero volt cable. See attachment. See National Semiconductor datasheets for your chips. See also star grounding.
Note that the 100nF caps below are lossy polyster dip caps (internally a snubber), and do buy an extra pair of this type 100nF to use for your output zobel caps.
Attached Images
File Type: gif Carlosfm c 2004_umbilical.gif (10.3 KB, 161 views)
  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
external power supply, rectifier in or out? poolorpond Power Supplies 26 28th November 2011 05:13 PM
1820m with external power supply? jbop PC Based 0 5th May 2010 11:53 AM
Grounding for monoblocks using single external supply GregH2 Construction Tips 0 29th November 2009 08:03 AM
External power supply audiolace Parts 5 18th January 2007 02:13 PM


New To Site? Need Help?

All times are GMT. The time now is 11:09 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