Hum Ho - Page 3 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

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 15th November 2010, 06:30 PM   #21
wicked1 is offline wicked1  United States
diyAudio Member
 
wicked1's Avatar
 
Join Date: Jan 2008
Location: Midwest
I just want to mention....... W/ my phono amp I had hum I could not resolve. Moving the amp out about 3 inches from the position it was in cleared the issue!!!!!
My phono amp is point to point (my first p2p), so I was SURE it was an issue I created. I re-wired that amp countless times trying to repair it. I gave up.
one day while moving things around in my living room the hum went silent! After investigation I figured out that literally, about 6 inches forward placement of the amp removed the hum!!!! I still have no idea why. There are no high voltage wires running past where it was sitting, or anything.

Last edited by wicked1; 15th November 2010 at 06:35 PM.
  Reply With Quote
Old 15th November 2010, 06:36 PM   #22
20to20 is offline 20to20  United States
diyAudio Member
 
20to20's Avatar
 
Join Date: Jun 2010
Location: W-S, NC
Quote:
Originally Posted by wicked1 View Post
I just want to mention....... W/ my phono amp I had hum I could not resolve. Moving the amp out about 3 inches from the position it was in cleared the issue!!!!!
My phono amp is point to point (my first p2p), so I was SURE it was an issue I created. I re-wired that amp countless times trying to repair it. I gave up.
one day while moving things around in my living room the hum went silent! After investigation I figured out that literally, about 3 inches forward placement of the amp removed the hum!!!! I still have no idea why. There are no high voltage wires running past where it was sitting, or anything.
I solved a problem like that in the same way once. You'd be suprised to learn how far a power transformer can throw an EMI field. I had a turntable about 18 inches away from my amp and had low hum on the phono input. I was shifting my stuff around and found the hum got louder and softer as I moved the amp around. The magnetic cartridge was getting hit by EMI. Had nothing to do with the phono ground line which was good. Unbelievable.
  Reply With Quote
Old 15th November 2010, 06:42 PM   #23
diyAudio Member
 
imfree707's Avatar
 
Join Date: Oct 2010
Location: Tenn Loop Ranch, Lebanon, Tn.
Send a message via Yahoo to imfree707
Default Illegal?

Quote:
Originally Posted by 20to20 View Post
Any outlet that has the safety ground tied to the neutral is creating a very short ground loop instead of a long one that would be formed at the breaker panel. Since the hum is variable with volume control it suggests the hum is coming from the outside and not getting shielded or isolated.
Hi Guys, neutral-grounding is almost certainly illegal and can be dangerous. Loss of neutral, upstream from the outlet, will put the outer surfaces of any equipment supplied by that outlet at AC Line potential. It can create severe hum because, under heavy circuit loading, the couple volts drop in the current-carrying neutral wire will be on the chassis of audio equipment supplied by the neutral-grounded outlet. A "don't try this at home" in my book!
__________________
A stiff power supply in a great-sounding amp is always better for you than a stiff drink.
  Reply With Quote
Old 15th November 2010, 06:42 PM   #24
wicked1 is offline wicked1  United States
diyAudio Member
 
wicked1's Avatar
 
Join Date: Jan 2008
Location: Midwest
My TT is a direct drive. Technics.. so, yeah, I can see some magnetic interference coming from the motor in that.
  Reply With Quote
Old 15th November 2010, 06:45 PM   #25
el156 is offline el156  Portugal
diyAudio Member
 
el156's Avatar
 
Join Date: Apr 2010
Location: ALBUFEIRA ;PORTUGAL
What i know for sure is that here in Portugal we can NEVER connect the neutral and ground together,the three poles are totaly different circuits!
We can create serious problems with the electricity Company doing that!
And maybe with everything you connect to the outlet!
EL156
  Reply With Quote
Old 15th November 2010, 06:55 PM   #26
M Gregg is offline M Gregg  United Kingdom
diyAudio Member
 
M Gregg's Avatar
 
Join Date: Jun 2010
Location: UK
Quote:
Originally Posted by el156 View Post
What i know for sure is that here in Portugal we can NEVER connect the neutral and ground together,the three poles are totaly different circuits!
We can create serious problems with the electricity Company doing that!
And maybe with everything you connect to the outlet!
EL156
Just for interest it causes havoc with Earth leakage circuit breakers

Regards
M. Gregg
__________________
What is the sound of one hand clapping?
  Reply With Quote
Old 15th November 2010, 06:56 PM   #27
20to20 is offline 20to20  United States
diyAudio Member
 
20to20's Avatar
 
Join Date: Jun 2010
Location: W-S, NC
Quote:
Originally Posted by wicked1 View Post
My TT is a direct drive. Technics.. so, yeah, I can see some magnetic interference coming from the motor in that.
Sorry to hear that. I have a few (too many) Technics DD's and haven't had motor noise. Sometimes the 4 contacts inside the arm at the headshell get a little corroded. Maybe not providing a good contact on th (-) of one of those. The cables take a lot of abuse where they pass through the base, too. An intermittent conductor there will pick up hum for sure.
  Reply With Quote
Old 15th November 2010, 07:05 PM   #28
wicked1 is offline wicked1  United States
diyAudio Member
 
wicked1's Avatar
 
Join Date: Jan 2008
Location: Midwest
Quote:
Originally Posted by 20to20 View Post
Sorry to hear that. I have a few (too many) Technics DD's
Heh, me too... 5 of them! (obviously was in to electronic music, dj'ing etc in my past) Wiring wasn't the issue.

Thinking about it again I'm guessing it's interference from my other amps. They're arranged vertically shelves. Phono on bottom, then pre, then main amp above that. I'd guess some interference was radiating down from the pre's PS, above the phono.

Last edited by wicked1; 15th November 2010 at 07:07 PM.
  Reply With Quote
Old 15th November 2010, 07:07 PM   #29
20to20 is offline 20to20  United States
diyAudio Member
 
20to20's Avatar
 
Join Date: Jun 2010
Location: W-S, NC
Quote:
Originally Posted by imfree707 View Post
Hi Guys, neutral-grounding is almost certainly illegal and can be dangerous.

A "don't try this at home" in my book!
I hesitated to suggest he call the local electrical inspector and ask about it. He'd probably want his address and the name of the electrician.
  Reply With Quote
Old 15th November 2010, 07:11 PM   #30
diyAudio Member
 
Join Date: Nov 2010
Quote:
Originally Posted by 20to20 View Post
Does that amp use a tube rectifier?
The amp has four KT-88 output tubes, four 6SN7 tubes and two 12AX7 tubes. Rectifier........does that have something to do with Preparation H?

Quote:
Originally Posted by 20to20 View Post
When you turned up the bias current, did the high pitched whine come from the amp itself or the speakers?
After turning up the bias, the amp would make a high-pitched whine during warmup only. Not through the speakers.....the amp was making the whine.

I am hearing, and partially understanding, the discussion about grounds and neutrals and input devices perhaps having floating ground values.......and what I'm hearing is basically that some of these devices, chassis' output/input circuits may be carrying voltage. The message to me is to be careful, and perhaps power everything down and unplug it before touching. Did I get that right?

Also, if I unplug everything when I get home, then power the amp up using a proper, 3-conductor outlet, and do the same to input devices, there is a chance the hum will not reappear? I'd be happy to do that.
  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
What ho, chaps! Doomlord_uk Introductions 15 7th December 2009 03:22 PM
What ho Audiopeeps from London markolexus Introductions 4 11th October 2008 07:07 PM
Dayton HF or HO? Ranthum Subwoofers 1 4th December 2006 02:21 PM
Ho HUMMM! Brownlow Solid State 8 1st June 2004 03:42 PM
Insulators for ho-3?? CryingDragon Solid State 10 24th November 2002 03:25 AM


New To Site? Need Help?

All times are GMT. The time now is 12:59 PM.


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