hiraga class a 20w. hum - 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 4th January 2012, 10:43 AM   #1
diyAudio Member
 
Join Date: Apr 2011
Default hiraga class a 20w. hum

hey. finally got to work my hiraga class a amp. www.tcaas.btinternet.co.uk/hiraga3fig1.gif. its powered by rod elliots power supply +-24v. sound.westhost.com/p89-f1.gif. the problem is that the amp hum, the hum changes depending on engine revs, electric windows etc. where should i look for a solutution to my problem. thanks
  Reply With Quote
Old 4th January 2012, 11:28 AM   #2
diyAudio Member
 
KatieandDad's Avatar
 
Join Date: Nov 2011
Location: UK
If you are using the SMPS Rod Elliot Car PSU the "Hum" is almost certainly not supply related.

Try rerouting your cables, I would suggest that you are picking up hum on the cabling.
  Reply With Quote
Old 4th January 2012, 11:33 AM   #3
diyAudio Member
 
Join Date: Apr 2011
maybe you have some guidelines to rerouting cables? here is the photo to make things more clear ImageShack® - Online Photo and Video Hosting
  Reply With Quote
Old 4th January 2012, 11:40 AM   #4
diyAudio Member
 
KatieandDad's Avatar
 
Join Date: Nov 2011
Location: UK
Try disconnecting the INPUT phono leads and shorting the INPUTs.

This will tell you wether the problem is coming from outside of the box.

I also note that the amp is not yet in a vehicle.

If you are powering it with a 115-24V adaptor, that could be the source of your hum. Try just using a car battery.
  Reply With Quote
Old 4th January 2012, 11:48 AM   #5
diyAudio Member
 
Join Date: Apr 2011
the problem is that the hum is actuallly beginning when the amplifier itself is in the car and when the headunit is connected. there is no hum when the haedunit is off. but the problem is not in the headunit. because the car amps that i have installed at the moment do not hum.
  Reply With Quote
Old 4th January 2012, 11:53 AM   #6
diyAudio Member
 
KatieandDad's Avatar
 
Join Date: Nov 2011
Location: UK
Sounds like you have a cabling problem as I originally intimated.

Check the cables carefully and make sure that the audio cables are run down the opposite side of the vehicle to the power cables.

You might also like to think about interconnects that don't use the shield for signal.

ie. Use a twin core screened cable, using the two cores for signal and signal return, connect the shield ONLY at one end to signal return.
  Reply With Quote
Old 4th January 2012, 12:03 PM   #7
diyAudio Member
 
Join Date: Apr 2011
the audio cables are separated from power cables. seems that the problem is in the amp. more thoughts would be great.
  Reply With Quote
Old 4th January 2012, 12:04 PM   #8
pergo is offline pergo  Italy
diyAudio Member
 
pergo's Avatar
 
Join Date: Dec 2008
ground loops


Do you have power supply input ground and signal ground (secondary ground) decoupled?!
  Reply With Quote
Old 4th January 2012, 12:09 PM   #9
diyAudio Member
 
Join Date: Apr 2011
Quote:
Originally Posted by pergo View Post
ground loops


Do you have power supply input ground and signal ground (secondary ground) decoupled?!
i'ts my first project, could you provide more info on ground decoupling?
  Reply With Quote
Old 4th January 2012, 12:19 PM   #10
pergo is offline pergo  Italy
diyAudio Member
 
pergo's Avatar
 
Join Date: Dec 2008
12V input is referred to power ground (- pole of the battery) but the signal ground cannot be referred to that.

You have a center tapped transformer, do you?

Your signal ground is the center tap, so the Higara's GND is the center tap of the secondary.

So you've a secondary floating ground. Good. Now you've to connect the signal ground (center tap) and the power ground (12V side) with 1k resistor // 100nF capacitor (in parallel).

With this solution, grounds are decoupled by 1k//100nF and you won't have any ground loop.


This method is use in every modern car amplifier.

See this:

Click the image to open in full size.

Last edited by pergo; 4th January 2012 at 12:21 PM.
  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
Hiraga 20W class A grataku Solid State 663 26th November 2014 03:34 PM
Hiraga 20w AB class search? tadiam Solid State 0 18th April 2008 07:47 PM
PCB hiraga 20w ninoslav Solid State 0 22nd March 2007 10:58 AM
Hiraga 20W - thermal issues Mikie Solid State 9 16th November 2004 09:07 PM
Hiraga 20W Class-A Geoff Solid State 8 5th November 2003 06:55 PM


New To Site? Need Help?

All times are GMT. The time now is 01:57 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