Go Back   Home > Forums > > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubelab Discussion and support of Tubelab products, prototypes and experiments

Thread Tools Search this Thread
Old 1st March 2011, 08:11 PM   #11
boywonder is offline boywonder  United States
diyAudio Member
boywonder's Avatar
Join Date: Jan 2008
Location: So.Cal.
I have a couple of 600V 10X probes.

With inputs shorted:

At C5 ripple is 250mv PP (around 88V RMS) @ 120Hz. C5 is a 180u Pana TS-UP bypassed with a 100u/370VAC motor run. Disconnecting the 100uf motor run yields 350mv PP at C5.

At C7 ripple is 60mv PP (around 21V RMS)....freq reading on my Dig scope was all over the place.

Last edited by boywonder; 1st March 2011 at 08:21 PM.
  Reply With Quote
Old 17th March 2011, 03:56 AM   #12
boywonder is offline boywonder  United States
diyAudio Member
boywonder's Avatar
Join Date: Jan 2008
Location: So.Cal.
Default It wasn't filament hum at all......

I finally figured out the problem and it's fixed. I'm running a 9 conductor umbilical between the power transformer chassis and the amp chassis. The safety ground from the power entry module in the power transformer chassis is tied to a ground stud in that chassis, then on to the amp chassis to another ground stud which serves as the star ground for pretty much everything in the amp chassis.

Initially, to save on umbilical conductors, the power transformer CT was tied to the ground stud in the transformer chassis, resulting in the safety ground and signal ground sharing the same conductor in the umbilical (apparently not a good idea).

I ended up with one extra umbilical conductor (not used) in the initial build, so I used this conductor as a dedicated line to bring the power transformer CT up to the amp chassis ground stud.

Now with the inputs shorted I'm measuring about 1.5mv rms at the speaker terminals and the hum is barely audible on my 95db sens speakers with my ear right next to them.

And finally..one correction to my prior post: The C5 and C7 ripple rms values should be 88mv and 21mv, not 88V and 21V.
  Reply With Quote
Old 17th March 2011, 08:08 AM   #13
Ian444 is offline Ian444  Australia
diyAudio Member
Join Date: Nov 2008
Location: Brisbane QLD
Ha! Well done! Good find!
  Reply With Quote
Old 17th March 2011, 06:43 PM   #14
rknize is offline rknize  United States
diyAudio Member
rknize's Avatar
Join Date: Feb 2009
Location: Chicagoland
Send a message via AIM to rknize Send a message via Yahoo to rknize
Glad you figured it out. Ground loops are a pain. Just to make life easier, I've been using Pete Millett's "ground loop breaker" trick in my new amps. Makes my setup much less finicky about what is plugged into what and which outlet that are plugged into, etc.
  Reply With Quote


Reducing filament hum in a Tubelab SEHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Tubelab SE with 2A3 Hum Doc Jr 8156 Tubelab 22 26th February 2011 08:34 PM
Filament switching off in Tubelab SE Nikon1975 Tubelab 1 23rd February 2010 04:01 PM
Hum Troubleshooting on My Tubelab SE with 2A3 Doc Jr 8156 Tubelab 2 13th August 2009 04:32 AM
Novel method to reduce filament hum in SE Amp? dshortt9 Tubes / Valves 9 26th April 2009 06:37 PM
Tubelab SE input tube filament Evenharmonics Tubelab 3 25th January 2009 12:10 AM

New To Site? Need Help?

All times are GMT. The time now is 06:44 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio