Amp makes whistle sound after turn off

Glen B · 04:16 PM

What would cause an otherwise normally functioning amp to make a whistle type sound a few seconds after power is turned off ?

moschfet · 10th April 2010, 04:13 PM

I would estimate, that are oscillations. Have you got an Oszilloscope?

PhaseLockLoopy · 10th April 2010, 04:17 PM

imbalance in power rail fall off causing instability - causing momentary oscillation in RC parts of the circuit -

Most good amplifiers return the Speaker solenoid first before powering down the rails

Glen B · 10th April 2010, 04:43 PM

The amp does not have output relays. Is there anything that can be done or does one have to live with the noise ?

mickeymoose · 10th April 2010, 07:42 PM

Is it an older Yamaha?
We installed 100+ in a stadium. On powering down they all did that. We nick-named it the Yamaha Fart

Glen B · 10th April 2010, 08:16 PM

Its a Rotel.

sumaudioguy · 11th April 2010, 03:46 AM

Yah like they say oscillation. Could be the rails but probably some section is loosing bias while another section is still functioning with the falling power supplies. With the no bias the compensation does not work and off it goes into oscillation. How to fix? How about a different amp?

Glen B · 11th April 2010, 05:30 AM

Thank you for the replies, and insight into the problem.

10th April 2010, 04:08 PM	#1
Glen B diyAudio Member Join Date: Feb 2005 Location: New York	Amp makes whistle sound after turn off What would cause an otherwise normally functioning amp to make a whistle type sound a few seconds after power is turned off ? Last edited by Glen B; 10th April 2010 at 04:16 PM.

10th April 2010, 04:17 PM	#3
PhaseLockLoopy diyAudio Member Join Date: May 2008 Location: On a mushroom	imbalance in power rail fall off causing instability - causing momentary oscillation in RC parts of the circuit - Most good amplifiers return the Speaker solenoid first before powering down the rails __________________ Hum likes to have a nice "Noise to Signal" ratio To "Hum" is to be noticed Quality hum is when it pours out of Electrostatic speakers

11th April 2010, 03:46 AM	#7
sumaudioguy diyAudio Member Join Date: Jan 2010 Location: Midwest U.S.A.	Yah like they say oscillation. Could be the rails but probably some section is loosing bias while another section is still functioning with the falling power supplies. With the no bias the compensation does not work and off it goes into oscillation. How to fix? How about a different amp? __________________ What the other guy said----Standing on the shoulders of giants. New avatar- no more little array

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
My alpine amp makes a high pitch squeaking sound	weesatron	Car Audio	67	29th October 2008 09:49 PM
Freaky Whistle in Guitar Amp	Trout	Tubes / Valves	47	9th January 2006 05:42 PM
With one makes more sound!	destroyer X	Solid State	43	8th June 2004 11:11 AM
What makes different speakers sound ... different?	cuallito	Multi-Way	16	14th April 2004 01:13 AM
What makes the most sound improvement?	BlackDog	Chip Amps	19	29th February 2004 07:56 PM


	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

10th April 2010, 04:13 PM	#2
moschfet diyAudio Member Join Date: Jul 2008 Location: Hannover	I would estimate, that are oscillations. Have you got an Oszilloscope?

10th April 2010, 04:43 PM	#4
Glen B diyAudio Member Join Date: Feb 2005 Location: New York	The amp does not have output relays. Is there anything that can be done or does one have to live with the noise ?

10th April 2010, 07:42 PM	#5
mickeymoose diyAudio Member Join Date: Nov 2008	Is it an older Yamaha? We installed 100+ in a stadium. On powering down they all did that. We nick-named it the Yamaha Fart

10th April 2010, 08:16 PM	#6
Glen B diyAudio Member Join Date: Feb 2005 Location: New York	Its a Rotel.

11th April 2010, 05:30 AM	#8
Glen B diyAudio Member Join Date: Feb 2005 Location: New York	Thank you for the replies, and insight into the problem.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read