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Amp turn off THUMP!!!

75.137.4.230
Posted on December 1, 2016 at 08:22:35
mgbpuff
Audiophile

Posts: 307
Location: Georgia
Joined: June 13, 2009
Contributor
  Since: October 4, 2009
 I have a 7 channel Sherbourn PT7-350 in my HT system (it's a monster at 125 lbs). On turning it off, either via trigger or directly at the amp via the on/off pushbutton, the amp sends a surge through the left front speaker only. I'm thinking that there must be a defect in the power supply discharge circuit (either a failed resistor or perhaps a relay). What do you think?

 

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RE: Amp turn off THUMP!!!, posted on December 1, 2016 at 10:41:14
E-Stat
Audiophile

Posts: 37589
Joined: May 12, 2000
Contributor
  Since: April 5, 2002
 My XPA-5 cousin doesn't do that. I would contact Emotiva.

 

RE: Amp turn off THUMP!!!, posted on December 1, 2016 at 10:58:05
mgbpuff
Audiophile

Posts: 307
Location: Georgia
Joined: June 13, 2009
Contributor
  Since: October 4, 2009
 Sent them an E-mail and posted question on their site. No one will respond.

 

RE: Amp turn off THUMP!!!, posted on December 1, 2016 at 11:24:14
SpotcheckBilly12345
 First thing that I'd try would be to switch LF & RF speaker wires at the back of your amp to see if the thump follows the wires, IOW will the thump now move to the right speaker? This is just a diagnostic step but it will help a technician in his diagnosis.

If you cannot get any help from Emotiva on their website (nothing new) you might try phoning them direct and speaking to "Big Dan". If he won't help all I can suggest is to find a local tech.

Cheers,
SB

 

RE: Amp turn off THUMP!!!, posted on December 1, 2016 at 11:38:06
The Dill
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Posts: 2197
Location: Portland, Oregon
Joined: July 1, 2004
Contributor
  Since: February 3, 2016
 Does it happen when the volume control is all the way turned down?

 

RE: Amp turn off THUMP!!!, posted on December 1, 2016 at 11:57:31
E-Stat
Audiophile

Posts: 37589
Joined: May 12, 2000
Contributor
  Since: April 5, 2002
 Phone: 615.790.6754 or 1.877.EMO.TECH (1.877.366.8324)

I recently had difficulty updating BIOS and gave them a call.

 

RE: Amp turn off THUMP!!!, posted on December 1, 2016 at 12:30:15
mgbpuff
Audiophile

Posts: 307
Location: Georgia
Joined: June 13, 2009
Contributor
  Since: October 4, 2009
 Yes. It's independent of volume and even happens if the preamp is off and the amp is turned on and off at the amps pushbutton.

 

I would, posted on December 1, 2016 at 12:59:00
Awe-d-o-file
Dealer

Posts: 21037
Location: 50 miles west of DC
Joined: January 10, 2004
 Closely inspect the LF speaker wire and it's connections at each end and I assume you are following the power amp rule: last on, first off.


ET

"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

 

RE: I would, posted on December 2, 2016 at 07:15:29
mgbpuff
Audiophile

Posts: 307
Location: Georgia
Joined: June 13, 2009
Contributor
  Since: October 4, 2009
 The wire is good. A Marantz AV7702 controls on/off. The 'on' of the amp is definitely after the pre-pro on, but the off appears to be almost simultaneous. However, leaving the pre-pro energized and turning the amp off manually causes the same thump.

 

RE: I would, posted on December 2, 2016 at 10:36:17
Awe-d-o-file
Dealer

Posts: 21037
Location: 50 miles west of DC
Joined: January 10, 2004
 I guess I'm going to agree with your original diagnosis then. Remember it only takes one thin strand....


ET

"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

 

RE: Amp turn off THUMP!!!, posted on December 2, 2016 at 17:53:10
FenderLover
 I remember a friend had a big amp a billion years ago & it would do this all the time, from brand new. Both turning on and off. I think it was a Marantz. We ended up wiring wire-wound 50-watt, 10-ohm resistors across the B-channel speaker terminals.

He'd flip the front switch from A to B, before turning the amp on or off.

 

RE: Amp turn off THUMP!!!, posted on December 3, 2016 at 05:28:01
mgbpuff
Audiophile

Posts: 307
Location: Georgia
Joined: June 13, 2009
Contributor
  Since: October 4, 2009
 Ha! Thanks for that! My amp doesn't have A/B outputs. It is so damn heavy and on a recessed shelf, that I groan when I even think about wrestling with it. I'm 75 and not as strong as I used to be. Otherwise I would at least take it out, open it up and take a look to see if there is anything obvious.

 

RE: Amp turn off THUMP!!!, posted on December 3, 2016 at 06:45:49
fredtr
Audiophile

Posts: 1987
Location: Phoenix
Joined: January 4, 2005
 I tried to find a schematic, didn't have any luck. If the cause is a power supply problem, like a double ended supply and the capacitors on one supply side discharges faster than the other, you would probably hear the thump out of more than one channel, so i'm guessing the problem is in that one channel. As a practical solution, due to weight and inconvenience, leave it powered on.

Depending on the circuit, there are a lot of pieces of equipment where turning it off and on is much harder on the equipment than leaving it on. I have a Sony surround sound receiver that has, other than during power outages, been left on for about 18 years now.

 

RE: Amp turn off THUMP!!!, posted on December 3, 2016 at 08:53:48
mgbpuff
Audiophile

Posts: 307
Location: Georgia
Joined: June 13, 2009
Contributor
  Since: October 4, 2009
 Thanks! I may just do that (leave it on). I'll disconnect the trigger. The amp works fine on all channels including the thumping left channel. If I continue allowing the thump/surge, I may eventually damage that speaker (it is a Sonus Faber Grand Piano Home tower).

 

RE: Amp turn off THUMP!!!, posted on December 3, 2016 at 10:48:02
bare
Audiophile

Posts: 1879
Joined: April 14, 2009
 IMO it's Broken somewhere! Get it Fixed.. is the simple answer.
No worth owning setup should do that. All Brochure babbles aside.
Either that or wait 'till it messes your speakers.
Then you get to fix Both.

 

Exactly, posted on December 3, 2016 at 11:28:47
E-Stat
Audiophile

Posts: 37589
Joined: May 12, 2000
Contributor
  Since: April 5, 2002
 When all else fails, call the manufacturer. :)

 

RE: Exactly, posted on December 4, 2016 at 21:51:23
A.Wayne
Audiophile

Posts: 2527
Location: Front row center
Joined: November 30, 2011
 LOL :)

 

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