Cmoy Pre-Amp ground hum - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 31st May 2008, 01:53 PM   #1
sled108 is offline sled108  United States
diyAudio Member
 
sled108's Avatar
 
Join Date: May 2008
Location: Deep in the Heart of North Jersey
Default Cmoy Pre-Amp ground hum

This might be a real simple problem, but the threads about ground hums are many, and I've not found a simple answer so far.

What I have here is a Cmoy Pre-Amp powering a TA2024 Amp.

The problem is a ground hum increasing with volume, with no inputs connected and even on the 9V.

This I can easily remove by touching the front face plate.

Am I overlooking a basic grounding rule?
If so, can someone please tell me how to ground this properly?

Thanx...
Attached Images
File Type: jpg cmoy pa inside.jpg (48.4 KB, 299 views)
  Reply With Quote
Old 31st May 2008, 02:51 PM   #2
Minion is offline Minion  Canada
diyAudio Member
 
Join Date: May 2006
Location: Cowican Bay , vancouver island
Do you have your face plate grounded?? if you don"t then that just might fix it , if you Do then I suggest maybe try removeing the ground from the face plate....

Cheers
  Reply With Quote
Old 31st May 2008, 03:26 PM   #3
diyAudio Member
 
theAnonymous1's Avatar
 
Join Date: Feb 2004
Location: Anonymityville
Quote:
Originally posted by Minion
Do you have your face plate grounded?? if you don"t then that just might fix it , if you Do then I suggest maybe try removeing the ground from the face plate....

Cheers
I agree, but to be more specific I would connect the ground from the face plate to the ground directly at the potentiometer.

It's interesting your using what looks like one of the small green ALPS RK097 series pots. I used one of these as a passive pre in a TA2022 amp and also had hum. The hum would disappear if I removed the pot from the front of the chassis or if I grounded the signal at the pot to the chassis. There was no hum at all before I installed the pot and the signal ground was never connected to the chassis.
  Reply With Quote
Old 1st June 2008, 12:24 AM   #4
Zigis is offline Zigis  Latvia
diyAudio Member
 
Join Date: May 2005
Location: Riga, Latvia
I use ALPS RK097 in CMoy amps, wen I touch pot's shaft there is hum. I ground shaft and hum gone.
Solder resistor legs cutoff to pots ground and bend it to front to touch metal part of pot .
  Reply With Quote
Old 2nd June 2008, 03:40 PM   #5
sled108 is offline sled108  United States
diyAudio Member
 
sled108's Avatar
 
Join Date: May 2008
Location: Deep in the Heart of North Jersey
I have both removed the Alps from the face plate, and grounded it and the plate to the board's ground and there was no change. The hum is still there... Maybe it's the Amp's PS....From a Canon Printer...
Next, I'll have to work up a 12v battery pack and see how that does.
  Reply With Quote
Old 2nd June 2008, 04:09 PM   #6
diyAudio Member
 
theAnonymous1's Avatar
 
Join Date: Feb 2004
Location: Anonymityville
If it goes away when you touch the front I doubt it's caused by the amps PS. There has to be some grounding problem inside the pre. Maybe a ground loop between the front and back plate?
  Reply With Quote
Old 3rd June 2008, 11:57 AM   #7
sled108 is offline sled108  United States
diyAudio Member
 
sled108's Avatar
 
Join Date: May 2008
Location: Deep in the Heart of North Jersey
Well it seems I've found the answer to my ground hum, and it is kind of stupidly simple...

When I designed this setup, I used (2) 3-Pole 3PDT switches for the input selectors to isolate the grounds. This causes an open ground hum when the switches are both off. Switching one on to an input solves that problem.

The ground hum never exists as long as you're listening to a source.
  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
Should I directly connect my signal ground to chassis ground? Bricolo Solid State 4 18th March 2014 09:42 PM
Active ground cmoy: Help me learn PCB design TheSeekerr Chip Amps 2 23rd July 2008 09:20 PM
Parallel LM3886, input ground, power ground, safety resistor and oscillations. markiemrboo Chip Amps 5 9th August 2007 03:50 PM
DC filament ground and high voltage ground mikeyho Tubes / Valves 0 15th September 2005 05:52 PM
does connecting mains ground with circuit ground create a ground loop? jarthel Everything Else 0 25th June 2003 12:55 PM


New To Site? Need Help?

All times are GMT. The time now is 04:42 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