anti-thump circuit

bonsai171 · 1st March 2004, 02:23 AM

Hello, would it be possible to add an anti-thump circuit to my integrated amplifier? It is from the early 70's- a Sony Ta-1055, which is 35W X 2. Unfortunately, it creates a thump every time it is shut down, which rocks the 8" advent woofers in my speakers. The surrounds on these were recently replaced (maybe 2 or 3 months ago), and one of them is starting to tear- there is a small hole in it. So far the only way i have found to stop the thump when it is shut down it to turn off the main speaker switch, but it seems like if the switch is constantly pushed on and off, it might break. Would it be simple to add in an anti-thump circuit to save the surrounds on these speakers?? I don't have any experience working on stereo equipment, just basic soldering skills (from working on speakers). Is this doable? tia

Dave

Bill Fitzpatrick · 1st March 2004, 02:31 AM

It's hard to believe that a thump at turn off is going to put a hole in the woofer surround. Perhaps the new surround was damaged before or after installation.

Turn off thump is normal for some equipment and normally won't damage the speakers. Is it the same on both channels? Look at the woofers and see how far they move.

You could always leave it on all the time or maybe install an outboard toggle switch for the speakers if you don't think the built in switch can handle it.

paulb · 1st March 2004, 02:38 AM

http://sound.westhost.com/project33.htm

B.VDBOS · 1st March 2004, 03:00 AM

If your only problem is turnoff thump, a simple normaly open relay that powered by your on/off switch and conected your speaker outputs could be a easy solution, That way when you switch off the power the speakers will disconect from the amp

sobazz · 1st March 2004, 08:18 AM

How do you eliminate turn-on/off transients in a bi- or triamped speaker system where this could kill the tweeter?

tiagor · 1st March 2004, 10:16 AM

Quote:

How do you eliminate turn-on/off transients in a bi- or triamped speaker system where this could kill the tweeter?

Hi sobazz

The amp itself should provide a way for the tweeter from seeing any DC, but if in doubt, protect the tweeter with a capacitor(better yet, fix the amp or the equipment that is leaking the standing DC voltage).

You might also want to take a look at: http://www.mitedu.freeserve.co.uk/Design/dcthump.htm

Regards,

Tiago

5th element · 1st March 2004, 02:05 PM

DC on the output was not the issue sobazz was talking about. He was meaning on the initial powerup of the amplifier when you get a powerup thump put thru the speakers, how do you eliminate this.

The answer is the same and the circuit posted by paulb, this accomplish that.

The relays are off when the amp is off and are off when DC is detected at the output. When the amp turns on this is DC at the output, so the circuit will keep the relays open. After the amp has been on a few seconds and the output has steadied DC will drop to the standard few millivolts and then the relays will close connecting speaker to amp, therefore eliminating the thump at turn on. Woofers and mid/woofers wills survive this anyway tweeters are less likely to, I just put a cap in the way.

Im kinda paranoid about destroying expensive tweeters, so even if I had the DC protection thingy I would probably still use a cap. Even though the chance of the DC circuit failing is quite slim, id rather not take the chance in frying my tweets.

sobazz · 1st March 2004, 02:25 PM

Thanks. You're right, 5th Element, I didn't mean DC as such.

tiagor · 1st March 2004, 02:27 PM

Quote:

DC on the output was not the issue sobazz was talking about. He was meaning on the initial powerup of the amplifier when you get a powerup thump put thru the speakers, how do you eliminate this.

When you get the "thump" at the powerup, it is still DC coming to the speakers. Probably due to any standing DC voltage in the equipment passing through while a DC blocking cap is charging.

Quote:

Im kinda paranoid about destroying expensive tweeters, so even if I had the DC protection thingy I would probably still use a cap. Even though the chance of the DC circuit failing is quite slim, id rather not take the chance in frying my tweets.

Sure.. I couldn't agree more. But anyone who goes throught the trouble of bi/tri-amping a speaker is probably trying to avoid any passive component which may cause other kind of side effects anyway(as phase deviations caused by caps).

5th element · 1st March 2004, 02:50 PM

Quote:

[i]
Sure.. I couldn't agree more. But anyone who goes throught the trouble of bi/tri-amping a speaker is probably trying to avoid any passive component which may cause other kind of side effects anyway(as phase deviations caused by caps). [/B]

I agree too on this front, one of the reasons is to remove all passive components. This is one reason why I have a triamped system

, but id rather not take the chance in frying my ss97's

1st March 2004, 02:23 AM	#1
bonsai171 diyAudio Member Join Date: Dec 2002 Location: PA	anti-thump circuit Hello, would it be possible to add an anti-thump circuit to my integrated amplifier? It is from the early 70's- a Sony Ta-1055, which is 35W X 2. Unfortunately, it creates a thump every time it is shut down, which rocks the 8" advent woofers in my speakers. The surrounds on these were recently replaced (maybe 2 or 3 months ago), and one of them is starting to tear- there is a small hole in it. So far the only way i have found to stop the thump when it is shut down it to turn off the main speaker switch, but it seems like if the switch is constantly pushed on and off, it might break. Would it be simple to add in an anti-thump circuit to save the surrounds on these speakers?? I don't have any experience working on stereo equipment, just basic soldering skills (from working on speakers). Is this doable? tia Dave

1st March 2004, 02:05 PM	#7
5th element diyAudio Member Join Date: Oct 2002 Location: England	DC on the output was not the issue sobazz was talking about. He was meaning on the initial powerup of the amplifier when you get a powerup thump put thru the speakers, how do you eliminate this. The answer is the same and the circuit posted by paulb, this accomplish that. The relays are off when the amp is off and are off when DC is detected at the output. When the amp turns on this is DC at the output, so the circuit will keep the relays open. After the amp has been on a few seconds and the output has steadied DC will drop to the standard few millivolts and then the relays will close connecting speaker to amp, therefore eliminating the thump at turn on. Woofers and mid/woofers wills survive this anyway tweeters are less likely to, I just put a cap in the way. Im kinda paranoid about destroying expensive tweeters, so even if I had the DC protection thingy I would probably still use a cap. Even though the chance of the DC circuit failing is quite slim, id rather not take the chance in frying my tweets. __________________ What the hell are you screamin' for? Every five minutes there's a bomb or somethin'! I'm leavin! bzzzz! Droggon Attack!

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1st March 2004, 02:31 AM	#2
Bill Fitzpatrick diyAudio Member Join Date: Jun 2001 Location: Eugene, OR	It's hard to believe that a thump at turn off is going to put a hole in the woofer surround. Perhaps the new surround was damaged before or after installation. Turn off thump is normal for some equipment and normally won't damage the speakers. Is it the same on both channels? Look at the woofers and see how far they move. You could always leave it on all the time or maybe install an outboard toggle switch for the speakers if you don't think the built in switch can handle it.

1st March 2004, 02:38 AM	#3
paulb diyAudio Member Join Date: Jun 2001 Location: Calgary	http://sound.westhost.com/project33.htm

1st March 2004, 03:00 AM	#4
B.VDBOS diyAudio Member Join Date: Aug 2003 Location: Auckland, New Zealand	If your only problem is turnoff thump, a simple normaly open relay that powered by your on/off switch and conected your speaker outputs could be a easy solution, That way when you switch off the power the speakers will disconect from the amp

1st March 2004, 08:18 AM	#5
sobazz diyAudio Member Join Date: Apr 2003 Location: Jutland	How do you eliminate turn-on/off transients in a bi- or triamped speaker system where this could kill the tweeter?

1st March 2004, 02:25 PM	#8
sobazz diyAudio Member Join Date: Apr 2003 Location: Jutland	Thanks. You're right, 5th Element, I didn't mean DC as such.

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