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

Instruments and Amps Everything that makes music, Especially including instrument amps.

Amplifier HISSIN Noise ? What Causes this ??
Amplifier HISSIN Noise ? What Causes this ??
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 10th October 2019, 02:36 PM   #1
John Spofford is offline John Spofford
diyAudio Member
 
Join Date: Oct 2019
Location: Boston Mass
Default Amplifier HISSIN Noise ? What Causes this ??

Im New Here, Im a Novice DIY Electronic hobbyist ...I have a small shop with Meters, Scopes, Tools ......etc

I Have a Behringer Loudspeaker, a B615D 1500 Watt PA Speaker with Amp Built in. When you power up the Speaker ( with no input ) the Louder the Volume Knob goes, The Louder "white noise hissing " it does. The customer says never did this before.

I Checked for the Caps being buldged, or any cold solder joints. What Causes or most likely creates this Noise ?? is there testing I Can do ??
  Reply With Quote
Old 10th October 2019, 03:42 PM   #2
Osvaldo de Banfield is online now Osvaldo de Banfield  Argentina
diyAudio Member
 
Osvaldo de Banfield's Avatar
 
Join Date: Dec 2011
Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
Hiss is noise, and can have more than one source. I can say, a high frequency oscillation, or a leak in a capacitor or a semiconductor, between others. You will need to measure some point with an oscillo for more confiable response.
__________________
Osvaldo F. Zappacosta. Electronic Engineer UTN FRA from 2001.
Argentine Ham Radio LW1DSE since 1987.
  Reply With Quote
Old 10th October 2019, 05:48 PM   #3
Enzo is offline Enzo  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Lansing, Michigan
Hiss is usually caused in a gain element, like a transistor or op amp.
  Reply With Quote
Old 10th October 2019, 05:57 PM   #4
nigelwright7557 is offline nigelwright7557  United Kingdom
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
Resistors etc can cause noise.


Johnson–Nyquist noise (thermal noise, Johnson noise, or Nyquist noise) is the electronic noise generated by the thermal agitation of the charge carriers (usually the electrons) inside an electrical conductor at equilibrium, which happens regardless of any applied voltage. Thermal noise is present in all electrical circuits, and in sensitive electronic equipment such as radio receivers can drown out weak signals, and can be the limiting factor on sensitivity of an electrical measuring instrument. Thermal noise increases with temperature. Some sensitive electronic equipment such as radio telescope receivers are cooled to cryogenic temperatures to reduce thermal noise in their circuits. The generic, statistical physical derivation of this noise is called the fluctuation-dissipation theorem, where generalized impedance or generalized susceptibility is used to characterize the medium.

Thermal noise in an ideal resistor is approximately white, meaning that the power spectral density is nearly constant throughout the frequency spectrum (however see the section below on extremely high frequencies). When limited to a finite bandwidth, thermal noise has a nearly Gaussian amplitude distribution.[1]
__________________
PCBCAD51 download or CDROM October 2019 version out now ..https://www.murtonpikesystems.co.uk
  Reply With Quote
Old 10th October 2019, 06:04 PM   #5
rayma is offline rayma  United States
diyAudio Member
 
Join Date: Apr 2011
Quote:
Originally Posted by John Spofford View Post
When you power up the Speaker ( with no input ) the Louder the Volume Knob goes,
The Louder "white noise hissing " it does. The customer says never did this before.
Does it hiss with a shorting plug in the input socket?
  Reply With Quote
Old 10th October 2019, 06:30 PM   #6
Mark Tillotson is offline Mark Tillotson
diyAudio Member
 
Join Date: May 2018
Location: Cambridge UK
Without any input plugged in the the amplifier sees all the noise from its input load resistance which is usually 100k or so - this will normally be quite audible.


With a signal source plugged in and powered up (but not playing anything) the hiss should be much lesss.


Note that some modern mp3 players and phones etc power down their audio output stages when not in use, leading to very obvious hiss. No pro audio device should display this woeful behaviour though.


A work-around is a low impedance load resistor on the input (say 1k or so) to limit the effect.
  Reply With Quote
Old 10th October 2019, 09:52 PM   #7
John Spofford is offline John Spofford
diyAudio Member
 
Join Date: Oct 2019
Location: Boston Mass
Thanks for all the replies, Im Learning here, I have a Scope and I can read Schematics OK..( at times ) I DO
  Reply With Quote
Old 10th October 2019, 10:08 PM   #8
John Spofford is offline John Spofford
diyAudio Member
 
Join Date: Oct 2019
Location: Boston Mass
Default Take a Listen

YouTube

I have Schematics , Can anyone walk me through where to make testing Points ?
Attached Files
File Type: mp4 1500 Watt Noise.mp4 (2.91 MB, 12 views)

Last edited by John Spofford; 10th October 2019 at 10:15 PM. Reason: Forgot PDF
  Reply With Quote
Old 10th October 2019, 10:20 PM   #9
MAAC0 is offline MAAC0  Portugal
diyAudio Member
 
Join Date: May 2010
Bear in mind, on the Behringers when the knob is above middle position You are at mic level amplification. It's perfectly normal. Behringer stuff is well known for hissing, but that isn't hiss. It's noise. It shouldn't make noise under middle position.

Last edited by MAAC0; 10th October 2019 at 10:22 PM.
  Reply With Quote

Reply


Amplifier HISSIN Noise ? What Causes this ??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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
ultra low noise power supply and low noise amplifier ambrosia168 Power Supplies 8 13th October 2017 02:43 PM
Amplifier noise - please help! tibrocks Chip Amps 8 11th February 2017 05:29 PM
RF noise from PC through amplifier Less Opinion PC Based 11 23rd December 2016 02:03 AM
Amplifier Noise Jesús Puerto Solid State 1 11th April 2004 01:07 PM
Amplifier Noise, who wants to help :) Tensop Solid State 11 8th October 2003 01:08 AM


New To Site? Need Help?

All times are GMT. The time now is 06:49 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki