Humming Zen V4 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Pass Labs This forum is dedicated to Pass Labs discussion.

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
Thread Tools Search this Thread
Old 21st April 2006, 04:05 PM   #1
diyAudio Member
Join Date: Nov 2004
Location: Halifax, N.S.
Default Humming Zen V4

Hi all,

I've had my Zen V4 running for a while now with only one remaining problem (thanks to those who helped me with the last ones! :-). The amp exhibits a fairly loud hum.

I've constructed it dual-mono in the same chassis (two IEC AC connectors and everything), so I didn't put two rectifier bridges on each channel as depicted in the schematic. My simple grounding scheme is depicted below (if I can figure out how to attach a picture). If you're familiar with the V4 board from Pass DIY, you'll know that the left-bottom bolt hole is connected to PCB ground, which is then supposed to be connected to chassis. But when I was tapping the holes in the heatsink, of course I broke a tap in that hole, so I re-routed the ground to another PCB bolt. Chassis ground is the heatsink, because the rest of my case is made of wood.

I've tried a couple of things so far - basically making sure that both channels were separate. This seems to be the case now.

When I was testing the amp on my test speaker, I didn't notice any hum, but I assumed this was just due to really poor frequency response on my test speaker ($20... new). But it turns out that I get the hum when the inputs for both channels are connected - I would only test one channel at a time.

I have a passive pre-amp and sure enough, when I crack open the case, all four ground lugs on the RCAs are connected by one big wire. Could this be the problem, or do I need to bust out the second rectifier bridges?

Attached Images
File Type: jpg groundscheme.jpg (18.6 KB, 303 views)
  Reply With Quote
Old 21st April 2006, 05:40 PM   #2
diyAudio Member
Join Date: Nov 2004
Location: Halifax, N.S.
Default Second Rectifier Bridge

Well, it would seem I didn't search hard enough:

In this thread (which I ran across looking for something else), Mr. Pass recommends using the second rectifier even in mono.

Just a couple of questions about this before I go ahead with it. Does the isolating bridge really need to be 35A? I've got some spare 25A bridges sitting around which I could use...

Also, do these need to be mounted on the sinks? This would be a real pain in the neck - removing the sinks at this point would require some major effort. :-)
  Reply With Quote
Old 21st April 2006, 05:49 PM   #3
Account Disabled
Join Date: Aug 2002
Location: Near to the Pacific Ocean
25A is acceptable, IMHO.
No current would flow through it in normal woring condition.
Only when there is a problem, the bridge will work as a current bride to the life protective earth, but in short time till the fuse blows off. I think that using the right size of fuse is essential for overall safety.

  Reply With Quote
Old 23rd April 2006, 04:21 AM   #4
diyAudio Member
Join Date: Nov 2004
Location: Halifax, N.S.
Default !

Thanks for the help again jh6you. :-)

Well it works! The hum is gone - after nearly two years of off-and-on work on this thing, my Zen V4 is finally working as well as I'd hoped. The next one will probably be an EL84 PP UL. :-)

I'll get to posting some pictures at some point. Maybe after this album. hehe

- Jeremy
  Reply With Quote
Old 26th April 2006, 08:30 AM   #5
diyAudio Member
Join Date: May 2004
Location: TONGEREN

I'm buisy with building an Aleph 3 now :-) small remark on you next project I've a home made EL84 but i've have changed it into triode setting it has more control over the bass driver but u reduce the outputpower but u have a better sound. So if you have some high rendement speakers you should go for the triode setting for the PP 84 :-) with no feedback

Greetz and good luck with your tube project
  Reply With Quote


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
Humming Jorgitox Solid State 19 29th November 2007 02:42 PM
Amp (A30) humming when XLR plugged in HeadSh0T Pass Labs 5 20th January 2005 04:27 PM
Why is my snake humming? Pbassred Everything Else 12 6th January 2005 10:05 AM
Humming GC fireman Chip Amps 9 8th August 2004 06:44 PM
humming amp Pumuckel Pass Labs 10 26th February 2004 12:40 AM

New To Site? Need Help?

All times are GMT. The time now is 04:35 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2