Question on output hum on tube amp? - 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 2nd November 2006, 06:04 PM   #1
andy2 is offline andy2  United States
diyAudio Member
 
Join Date: Nov 2004
Location: Los Angeles
Default Question on output hum on tube amp?

I wonder how high output amplitude would cause a noticable hum?

At 60hz, what would the voltage amplitude do you think would begin to give an audible hum?

Above 10mv?
  Reply With Quote
Old 2nd November 2006, 06:12 PM   #2
bembel is offline bembel  Europe
diyAudio Member
 
bembel's Avatar
 
Join Date: Aug 2006
Send a message via Yahoo to bembel
P=U˛/R ! , just figure out how much dB vs signal

hope this helps !

PS: In silence, as a rough guess I wouls say near audible with my ears (as 10mV@8ohm= 10µW). though I didn't measured
__________________
Plus je pédale moins vite, moins j'avance plus vite !
  Reply With Quote
Old 2nd November 2006, 06:41 PM   #3
andy2 is offline andy2  United States
diyAudio Member
 
Join Date: Nov 2004
Location: Los Angeles
Quote:
Originally posted by bembel
P=U˛/R ! , just figure out how much dB vs signal

hope this helps !

PS: In silence, as a rough guess I wouls say near audible with my ears (as 10mV@8ohm= 10µW). though I didn't measured
So I guess your guess would be if you place your ear close enough, you will probably here it.
  Reply With Quote
Old 2nd November 2006, 06:54 PM   #4
bembel is offline bembel  Europe
diyAudio Member
 
bembel's Avatar
 
Join Date: Aug 2006
Send a message via Yahoo to bembel
yes, indeed

PS: just try to send an AF generator to a speaker to estimate (@60Hz or 120Hz for you) and just see ... (haven't time to do it now, but if you don't have a generator I can do it for you somewhere during the week).
__________________
Plus je pédale moins vite, moins j'avance plus vite !
  Reply With Quote
Old 2nd November 2006, 07:56 PM   #5
andy2 is offline andy2  United States
diyAudio Member
 
Join Date: Nov 2004
Location: Los Angeles
Quote:
Originally posted by bembel
yes, indeed

PS: just try to send an AF generator to a speaker to estimate (@60Hz or 120Hz for you) and just see ... (haven't time to do it now, but if you don't have a generator I can do it for you somewhere during the week).
I would appreciate it very much since I don't quite have the equipement.
Thanks.
  Reply With Quote
Old 2nd November 2006, 07:59 PM   #6
andy2 is offline andy2  United States
diyAudio Member
 
Join Date: Nov 2004
Location: Los Angeles
By the way, one more quick question, would 10 - 13mv of output noise be acceptable in a tube amp?
  Reply With Quote
Old 2nd November 2006, 08:24 PM   #7
bembel is offline bembel  Europe
diyAudio Member
 
bembel's Avatar
 
Join Date: Aug 2006
Send a message via Yahoo to bembel
have to measure, it depends, do you mean output on 8 ohm load, if not, then witch kind, RMS @ 60Hz ? How measured ?
__________________
Plus je pédale moins vite, moins j'avance plus vite !
  Reply With Quote
Old 2nd November 2006, 08:57 PM   #8
andy2 is offline andy2  United States
diyAudio Member
 
Join Date: Nov 2004
Location: Los Angeles
Quote:
Originally posted by bembel
have to measure, it depends, do you mean output on 8 ohm load, if not, then witch kind, RMS @ 60Hz ? How measured ?
Measured @ 8ohm peak to peak @ assuming 120Hz.

Thanks.
  Reply With Quote
Old 2nd November 2006, 09:09 PM   #9
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
OK, so that's about 3mVRMS, about -60dB below 1W. That's probably OK for speakers of normal efficiency, but I'd want to do better, especially if horns or high eff single drivers were being used.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 2nd November 2006, 09:34 PM   #10
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
I traditionally design my personal amplifiers (where cost is not a consideration) for 1mVrms or less of residual noise including hum/ripple and hiss. This is acceptable in my experience with speaker systems to 103dBspl or so.

My current diy Onken speaker system is >96dB efficient and 300B based SE amplifier output noise is <0.5mVrms, obviously the noise is just about inaudible.

My noisiest design is around 3mVrms and with over 20Wrms per channel was designed for speakers in the low 90dB range. Hum was not obtrusive with a pair of high efficiency speakers (100dB+) but was audible during silent passages from a meter away.

I don't use global negative feedback in any of my designs so this has to be achieved by careful layout and good power supply design.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  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
tube output chidpon Digital Source 1 12th October 2008 01:22 PM
SS or tube voltage amplifying stages in an amp with tube output? ray_moth Tubes / Valves 14 4th July 2007 03:09 AM
Octal tube as headphone amp output tube yagoolar Headphone Systems 6 25th November 2006 09:11 PM
Is it possible to get "tube sound" with just a tube preamp and chipamp output? Spasticteapot Instruments and Amps 43 15th May 2006 05:28 PM
Output Tube biasing for Toroidal Output Transformer gingertube Tubes / Valves 7 17th April 2005 04:40 PM


New To Site? Need Help?

All times are GMT. The time now is 06:14 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