Transformer hum on leach amp, turn on / off thump - 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 17th August 2008, 06:46 PM   #1
diyAudio Member
 
wigginjs's Avatar
 
Join Date: Dec 2003
Location: Columbia, SC
Default Transformer hum on leach amp, turn on / off thump

What causes transformer hum when I turn on an amp? Also turn on / off thump? This amp hasn't always done this, but it's been sitting for a while. Any ideas?
__________________
The Four Chairs
DIY Home Theater
  Reply With Quote
Old 17th August 2008, 07:17 PM   #2
diyAudio Member
 
Join Date: Apr 2003
Location: Portland,Oregon
Blog Entries: 4
Send a message via AIM to DigitalJunkie
Could be leaky filter caps.
  Reply With Quote
Old 17th August 2008, 08:26 PM   #3
Account disabled at member's request
 
Join Date: Aug 2008
Could be a grounding issue, try cleaning up the chassis earth connection or re'seat it, maybe turn the transformer a few degrees can help>>>> if its Toroidal!
  Reply With Quote
Old 17th August 2008, 08:55 PM   #4
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
do we want this moved to the permanent "Leach amp problem" thread?
__________________
regards Andrew T.
  Reply With Quote
Old 17th August 2008, 11:14 PM   #5
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
Doesn't seem like a design specific complaint to me, it seems rather generic in nature.
__________________
Candidates for the Darwin Award should not read this author.
  Reply With Quote
Old 18th August 2008, 02:40 AM   #6
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
Is it a self build, or a Leach that was pre-built and sold?
If it's a pre-built chances are the smoothing caps have had it, and could be going short hence causing the toroid hum.

It could also be DC on your mains but i'd guess youd notice other devices buzzing too.
  Reply With Quote
Old 18th August 2008, 01:37 PM   #7
h_a is offline h_a  Europe
diyAudio Member
 
h_a's Avatar
 
Join Date: Sep 2006
Location: Graz, Austria
Quote:
What causes transformer hum
DC - either on primary or secondary side. On secondary easily avoided by using 2 bridges (if symmetrical rails are used), on primary there exist DC-filters.

The probably annoying noise aside it shouldn't do any harm.

Have fun, Hannes

PS: the mechanism behind turn on/off thumbs is also still unclear to me; I sometimes hear that different impedances on the balanced inputs can cause this (blame your preamp) or that the caps for both rails need different times to charge up. Maybe someday I have a satisfying reply to this
  Reply With Quote
Old 18th August 2008, 05:48 PM   #8
diyAudio Member
 
wigginjs's Avatar
 
Join Date: Dec 2003
Location: Columbia, SC
Actually, the transformer doesn't continue to hum. There is a hum when I initially turn it on that fades out within 3 or 4 seconds. Then it is quiet. At the same time there is an initial "thump" that forces my woofer and mid-range drivers to peak excursion in my passively crossed speakers.

rocco:

Could you please elaborate on "grounding issue"? What should I look for?
__________________
The Four Chairs
DIY Home Theater
  Reply With Quote
Old 19th August 2008, 03:03 AM   #9
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
Ah, this sort of turn on thump is often normal. The buzzing is simply the transformer under stress as it tries to charge empty capacitors.

It's possible your amp had some kind of power-on delay circuit which has stopped working, and this is why you get the thump.
  Reply With Quote
Old 19th August 2008, 12:06 PM   #10
diyAudio Member
 
wigginjs's Avatar
 
Join Date: Dec 2003
Location: Columbia, SC
jaycee:

I didn't add any additional circuitry to the amp and the leach amp doesn't have any sort of integrated "soft start" circuit. I did, however, add some additional line-level active filters at one point (a linkwitz transform and additional EQ), but I have since removed them. As I recall, the thump and buzzing started to occur when I removed those circuits, but all they were really attached to is the RCA inputs and I've restored the original connections just as they were.
__________________
The Four Chairs
DIY Home Theater
  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
class d turn on thump jol50 Car Audio 15 9th July 2009 08:31 AM
turn off thump jayme Tubes / Valves 6 23rd September 2007 07:40 PM
Leach Amp turn on thump? wigginjs Solid State 5 1st March 2006 01:32 AM
Zen amp turn-on thump robertpear Pass Labs 5 5th January 2001 12:23 AM
Zen amp turn-on thump. vdi_nenna Pass Labs 2 22nd October 2000 07:27 PM


New To Site? Need Help?

All times are GMT. The time now is 03:24 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