Some help with output transformers induced hum - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves
Home Forums Rules Articles diyAudio Store Gallery Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 6th September 2015, 09:30 PM   #1
00940 is offline 00940  Belgium
diyAudio Member
 
Join Date: Sep 2003
Location: Liège
Default Some help with output transformers induced hum

I've just finished wiring a small heapdhones amp. It's nothing fancy, basically a derivative of the bottlehead crack: ecc82 gain stage +6080 in cathode follower + parafeed output transformers.

But I'm getting some low hum. Not crazy loud but noticeable. If I remove the 6080, the hum is still there. If I move the output transformers as much as the leads allow (still with the ecc82 in circuit to load the power transformer), no hum audible. So I'm affraid they're too close to the toroidal power transformer...

Changing the layout or the case is a bit difficult... should I just move those transformers to an external box or does someone have another suggestion ?
Attached Images
File Type: jpg WP_20150906_22_16_30_Pro.jpg (146.2 KB, 73 views)
File Type: png Capture.PNG (12.7 KB, 73 views)
__________________
Ben.
  Reply With Quote
Old 6th September 2015, 09:53 PM   #2
diyAudio Member
 
knockbill's Avatar
 
Join Date: Feb 2013
Location: SE PA
Can you put a metal shield around the OPTs... to isolate them from the rest of the amp?
__________________
Regards,
John
  Reply With Quote
Old 6th September 2015, 10:40 PM   #3
diyAudio Member
 
Alastair E's Avatar
 
Join Date: Feb 2004
Location: South Wales
Try changing the transformer's orientation....

Turn 'em sideways or upside down--or both...

try same with toroid too.
__________________
Das Beste Oder Nichts
  Reply With Quote
Old 6th September 2015, 10:53 PM   #4
00940 is offline 00940  Belgium
diyAudio Member
 
Join Date: Sep 2003
Location: Liège
Quote:
Originally Posted by knockbill View Post
Can you put a metal shield around the OPTs... to isolate them from the rest of the amp?
I can search for something suitable. It's not going to be easy...

Quote:
Originally Posted by Alastair E View Post
Try changing the transformer's orientation....

Turn 'em sideways or upside down--or both...

try same with toroid too.
Changing the output transformers's orientation doesn't seem to change the hum much. Only distance does the trick. I'll try tomorrow with the toroid.
__________________
Ben.
  Reply With Quote
Old 6th September 2015, 10:55 PM   #5
diyAudio Member
 
Rundmaus's Avatar
 
Join Date: Aug 2005
I once solved a hum problem by twisting not only heater wiring, but also HV and signal wiring with its corresponding return/ground wire. Hum gone!

Regards,
Andreas
  Reply With Quote
Old 6th September 2015, 10:57 PM   #6
diyAudio Member
 
knockbill's Avatar
 
Join Date: Feb 2013
Location: SE PA
With the mostly wood base theres' not much shielding, and its a small box,,, I've taken a piece of metal and moved it between txs or tubes etc, to find teh cause of hum,,, If it stops teh noise, you can probably figure a way to install it permanently...
Good luck...
__________________
Regards,
John
  Reply With Quote
Old 7th September 2015, 01:58 PM   #7
00940 is offline 00940  Belgium
diyAudio Member
 
Join Date: Sep 2003
Location: Liège
Well, I decided to remove the output transformers and give them their own external box. It's going to be less work than trying to work within the box.

With only caps from the cathode followers to the output, the amp is dead silent into senn hd650 and hd25.
__________________
Ben.
  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
Hum pickup from line output transformers Deco-Doctor Tubes / Valves 15 15th June 2014 11:33 AM
Can AC wires induce hum in output transformers? Rob11966 Tubes / Valves 6 27th March 2009 12:18 AM
Choke induced Hum Sheldon Tubes / Valves 47 4th November 2005 10:55 PM
Hand induced hum on JLTi copy, any ideas?? jsaults Chip Amps 8 27th April 2005 11:19 PM
transformer magnetic induced audio hum Wardsweb Chip Amps 1 6th May 2004 09:54 PM


New To Site? Need Help?

All times are GMT. The time now is 07:19 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright ©1999-2016 diyAudio

Content Relevant URLs by vBSEO 3.3.2