Anti Thump Circuit

DXRulz · 10-08-2009, 21:04

Just wondering what this is and what it does!

chrisjr · 10-08-2009, 21:57

If it is on a HiFi power amp it is probably a circuit to protect the speakers from switch-on thumps.

On my Denon amp the speakers are disconnected by a relay for about 5 seconds after switching on. This allows the power supply to settle down and stabilise. Otherwise as the power supply sorts itself out it can produce some quite violent voltage swings on the output of the amp.

This produces a loud thump noise in the speakers, hence the name. In extreme cases it can actually damage the speakers.

DXRulz · 10-08-2009, 22:15

When i turn my Sherwood RX-2030R integrated tuner/amp on, no sound can be heard until a click is heard 5 seconds later, then it is ready to use. I'm assuming that is to do with this anti thump circuit?

mikeydb · 11-08-2009, 08:17

I have an NAD C320BEE and this does the same as others have mentioned, power on, and then wait a few seconds, a click is heard, and then it's ready to use.

chrisjr · 11-08-2009, 08:57

The clicks will almost certainly be the relays in the speaker feeds switching over.

You can also get similar thumps generated by the other devices in your system, eg a CD player. That is why it is often recommended that the amp be the last thing switched on and the first switched off. If you have the volume cranked up to 11 then it is possible the switch on thump from the CD player could give you a nasty surprise

fdp · 11-08-2009, 11:42

An example of a pro power sequencer from Sudiospares.

10-08-2009, 21:04	#1
DXRulz Forum Member Join Date: Dec 2006 Location: Oswestry, Shropshire Posts: 4,196	Anti Thump Circuit Just wondering what this is and what it does!

10-08-2009, 21:57	#2
chrisjr Forum Member Join Date: May 2004 Location: Reading Posts: 27,916	If it is on a HiFi power amp it is probably a circuit to protect the speakers from switch-on thumps. On my Denon amp the speakers are disconnected by a relay for about 5 seconds after switching on. This allows the power supply to settle down and stabilise. Otherwise as the power supply sorts itself out it can produce some quite violent voltage swings on the output of the amp. This produces a loud thump noise in the speakers, hence the name. In extreme cases it can actually damage the speakers.

10-08-2009, 22:15	#3
DXRulz Forum Member Join Date: Dec 2006 Location: Oswestry, Shropshire Posts: 4,196	When i turn my Sherwood RX-2030R integrated tuner/amp on, no sound can be heard until a click is heard 5 seconds later, then it is ready to use. I'm assuming that is to do with this anti thump circuit?

11-08-2009, 08:17	#4
mikeydb Forum Member Join Date: Feb 2004 Location: Bristol. Posts: 1,783	I have an NAD C320BEE and this does the same as others have mentioned, power on, and then wait a few seconds, a click is heard, and then it's ready to use.

11-08-2009, 08:57	#5
chrisjr Forum Member Join Date: May 2004 Location: Reading Posts: 27,916	The clicks will almost certainly be the relays in the speaker feeds switching over. You can also get similar thumps generated by the other devices in your system, eg a CD player. That is why it is often recommended that the amp be the last thing switched on and the first switched off. If you have the volume cranked up to 11 then it is possible the switch on thump from the CD player could give you a nasty surprise

11-08-2009, 11:42	#6
fdp Guest Join Date: Sep 2005 Posts: 623	An example of a pro power sequencer from Sudiospares.

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Anti Thump Circuit