why there is a spike sound output from the speaker when turn off?

motbuddy · 09:51 AM

hi,
i'm using a DIY pre-amp kit with 3-way tone control and also a power amplifier. then i connect the final output to a speaker. Whenever i turn off the switch, i can hear a "spike" sound coming out from the speaker. How can i solve this problem?

thank you.

motbuddy · 4th March 2010, 01:39 AM

anyone can help?

thanks.

Andrew Eckhardt · 4th March 2010, 01:48 AM

When you open the power switch the field collapses in the power transformer core generating a large inductive voltage spike on the windings that often causes a bit of arcing and a nice jolt of noise through any amplifiers that are still active. If you get lucky enough to open the switch the moment the AC line crosses zero everything turns off in a much better behaved fashion than when the voltage is at peak.

john curl · 4th March 2010, 02:48 AM

Spark coil effect.

wwenze · 4th March 2010, 05:42 AM

O.o .........

Threadstarter do you mean pop? Or like "piak piak" kind of sound? Usually happens a few seconds after cutting the power?

indianajo · 5th March 2010, 09:48 PM

I got annoyed at the the click when I turn off my 1972 manufactured ST 120 amp. I salvaged out a dead PC power supply, in it were several MOS suppressors. They are not marked with a part number, but they are marked with the UL and CSA logos, and look like blue disks. They can be found near the power fuse. I put it across the primary of my power transformer, near the power switch. I installed a terminal strip so that I would not have to solder directly to the power strip nor have these short lead devices dangling in the air with exposed leads. The snap at turnoff has been much reduced. If you live in a 250 VAC mains area, make sure the logo of you local standards agency is on the part. For example, I think Europe uses VDO, all though I am not an expert on that. A .47 uf capacitor will also help reduce noise, if certified for installation across the power mains it will also have these rating agency logos on it.

motbuddy · 8th March 2010, 04:26 AM

Quote:

Originally Posted by wwenze

O.o .........

Threadstarter do you mean pop? Or like "piak piak" kind of sound? Usually happens a few seconds after cutting the power?

is a POP sound. happen once i turn off the main power.

ratza · 10th March 2010, 06:17 AM

2n2/1kV capacitor across power switch and RF filtering on inputs will do the job.

3rd March 2010, 09:49 AM	#1
motbuddy diyAudio Member Join Date: Jan 2010	why there is a spike sound output from the speaker when turn off? hi, i'm using a DIY pre-amp kit with 3-way tone control and also a power amplifier. then i connect the final output to a speaker. Whenever i turn off the switch, i can hear a "spike" sound coming out from the speaker. How can i solve this problem? thank you. Last edited by motbuddy; 3rd March 2010 at 09:51 AM.

5th March 2010, 09:48 PM	#6
indianajo diyAudio Member Join Date: Jan 2010 Location: Jeffersonville, Indiana USA	turnoff suppressor I got annoyed at the the click when I turn off my 1972 manufactured ST 120 amp. I salvaged out a dead PC power supply, in it were several MOS suppressors. They are not marked with a part number, but they are marked with the UL and CSA logos, and look like blue disks. They can be found near the power fuse. I put it across the primary of my power transformer, near the power switch. I installed a terminal strip so that I would not have to solder directly to the power strip nor have these short lead devices dangling in the air with exposed leads. The snap at turnoff has been much reduced. If you live in a 250 VAC mains area, make sure the logo of you local standards agency is on the part. For example, I think Europe uses VDO, all though I am not an expert on that. A .47 uf capacitor will also help reduce noise, if certified for installation across the power mains it will also have these rating agency logos on it. __________________ Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,SP2-XT's, T-300 HF Projs, Steinway console, Herald RA88a mixer, Wurlitzer 4500

10th March 2010, 06:17 AM	#8
ratza diyAudio Member Join Date: Dec 2007 Location: Sibiu, Romania	2n2/1kV capacitor across power switch and RF filtering on inputs will do the job. __________________ Any solution is a compromise.

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4th March 2010, 01:39 AM	#2
motbuddy diyAudio Member Join Date: Jan 2010	anyone can help? thanks.

4th March 2010, 01:48 AM	#3
Andrew Eckhardt diyAudio Member Join Date: Nov 2005 Location: PA	When you open the power switch the field collapses in the power transformer core generating a large inductive voltage spike on the windings that often causes a bit of arcing and a nice jolt of noise through any amplifiers that are still active. If you get lucky enough to open the switch the moment the AC line crosses zero everything turns off in a much better behaved fashion than when the voltage is at peak.

4th March 2010, 02:48 AM	#4
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	Spark coil effect.

4th March 2010, 05:42 AM	#5
wwenze diyAudio Member Join Date: Mar 2008	O.o ......... Threadstarter do you mean pop? Or like "piak piak" kind of sound? Usually happens a few seconds after cutting the power?

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