Rod Elliot P3A amp noises - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 18th March 2003, 05:30 PM   #1
tktran is offline tktran  Australia
Account Disabled
 
Join Date: Mar 2003
Location: Perth
Default Rod Elliot P3A amp noises

Hello all,

I have built my first amp- the Rod Elliot P3A.

However there exists a small amount of hum. I
have yet to build a preamp so at the moment I have a
pot to control volume, and whilst the hum is soft it
seems to be loudest at min volume and softest at ~ 1/3
max volume. Culd it be the pot that's causing the 50Hz hum?

Is there a way to test the source of the hum? I have
access to multimeters and a CRO.

In other designs eg. commercial, the transformer is
usually situated at the far left/right of the case,
the PCB on the other side and an internal heatsink in
the middle, which also acts to shield the PCB/input
from the supply.

I made the mistake of putting the transformer at the
front centre of the case, and PCB at centre rear,
connected to an external heatsink. I did this because
I wanted the amplifier weight to be evenly distributed
(for carrying safety) however now there is nothing
shielding the transformer from the pcb.

Is it worth shielding the transformer? If so, how?
Or should I relocate the transformer?

Thanks.
  Reply With Quote
Old 18th March 2003, 07:47 PM   #2
paulb is offline paulb  Canada
diyAudio Member
 
Join Date: Jun 2001
Location: Calgary
Hum can be induced into your input wires. Try shorting the input right at the PCB to see if that helps. Although if it's loudest at minimum volume, it's doubtful this would help.
I used an external power supply for my P3A for exactly this reason; I had problems with a previous amp. With the previoius amp, I was able to move the input wires around to minimize the hum. Maybe you can do some wiring (input, power, or output) rearrangement to reduce your hum.
  Reply With Quote
Old 18th March 2003, 08:04 PM   #3
diyAudio Member
 
Cradle22's Avatar
 
Join Date: Jan 2003
Location: Dortmund, Germany
Hi!

But most of the time you got hum in an amp like P3A because of improper grounding.

Use a real star ground, with no connection to chassis (all connections to ground go to that star ground)

Earth the chassis via the earth of the mains cable, and then make a connection from star ground to chassis via a resistor (about 100 Ohms), bypassed by a capacitor (with mains voltage rating, better more), for example Wima MKP10 0.47 uF 400V AC.

Today I fired up the testing version of my P3A (both channels), in somewhat the same layout you used (but not in metal chassis, have yet to gather enough money for chassis... ), and no hum was audible!

Actually the first amp I build that worked from the start on (and seems to be real nice...)

You can also try using shielded cables from input connectors to amp.

Bye,

Arndt
__________________
************************
A Sacrifice For Freedom
  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
Clicking noises... audio-kraut Digital Source 2 23rd December 2006 04:06 PM
HK 730 making noises... RockysDad Solid State 2 24th December 2005 01:45 AM
QUAD ESL 63 noises tabaregg Planars & Exotics 2 15th December 2004 11:28 PM
Capacitors and noises? eeka chu Parts 0 7th February 2004 10:25 PM
Powered Mixer Noises guitargully Solid State 0 9th January 2004 10:52 PM


New To Site? Need Help?

All times are GMT. The time now is 09:00 AM.


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