tk49 Posted April 23, 2007 Share Posted April 23, 2007 I have a Harman Kardon Citation 12 power amp that I'm using with a Merlin pre (I love it) and Forte II's. I know there was a thread a couple weeks ago about the shut down sequence (follow the source). I have tried several ways and nothing will eleminate that thump. Right now I'm just leaving the amp on all the time. Any suggestions, do I need too have the amp looked at. t Quote Link to comment Share on other sites More sharing options...
RFP Posted April 23, 2007 Share Posted April 23, 2007 So the sucker still 'thumps' if you turn the amplifier off first? Dang! How about if you turn the volume down on the preamp first and then turn the amp off (OK... I'm really reaching here). Cheerz, Rob Quote Link to comment Share on other sites More sharing options...
mas Posted April 23, 2007 Share Posted April 23, 2007 You might consider a circuit such as: http://www.epanorama.net/circuits/ampdelay.html Quote Link to comment Share on other sites More sharing options...
wuzzzer Posted April 23, 2007 Share Posted April 23, 2007 Is there a switch or knob that will turn off output to the main speakers? If you turn that to off does it still thump? Quote Link to comment Share on other sites More sharing options...
Speedball Posted April 23, 2007 Share Posted April 23, 2007 When I switched from an old Conrad Johnson SS amp to a QSC SS amp, the thumping stopped. Quote Link to comment Share on other sites More sharing options...
tk49 Posted April 23, 2007 Author Share Posted April 23, 2007 The thump occurs no mater what I turn off first or last, there are only fuses no switches. I'm certain it has nothing to do with the Merlin, other than they make beautiful music together. I think it's like Mark says, that's the way those old amps run. My concern is damage to the speakers. I first ran the HK through a pair of NHT Three's and had a similar problem, but not to the extreme as the Forte's. Mark, is there any recourse? Is there anything wrong with letting it sit there and idle? Shorten it's life? t Quote Link to comment Share on other sites More sharing options...
jheis Posted April 24, 2007 Share Posted April 24, 2007 Had a Carver TFM-45 that did the same thing. I resorted to using a Niles speaker selector box that allowed me to turn off the speakers (disconnect them from the amp) before turning off the amp. James Quote Link to comment Share on other sites More sharing options...
pauln Posted April 24, 2007 Share Posted April 24, 2007 Thump is sometimes caused by DC offset out of spec.. With no signal there should be minimal juice going to the speakers. Most amps have an adjustment for each channel to get this down to a minimum value. Do you have a service manual for your amp? It should have the procedure for setting the DC offset. You will need to have a VOM and some alligator clips... might be worth checking. Quote Link to comment Share on other sites More sharing options...
tk49 Posted April 24, 2007 Author Share Posted April 24, 2007 Thanks for the recommendations, I will look into the speaker selector. Do you have a good source the Niles and the service manual? t Quote Link to comment Share on other sites More sharing options...
cyclonecj Posted April 24, 2007 Share Posted April 24, 2007 I have an older amp that farts out of one channel about 15 seconds after shutdown.... Quote Link to comment Share on other sites More sharing options...
jheis Posted April 24, 2007 Share Posted April 24, 2007 The Niles I used was a SPS-1. Cost about $60 ~15 years ago. Niles stuff is kind of pricey retail (big mark-up) but if you do a Google search you can find it much cheaper online. James Quote Link to comment Share on other sites More sharing options...
tk49 Posted April 24, 2007 Author Share Posted April 24, 2007 James, did you ever do an A/B comparison with and without the switch system, how did it effect your sound quality? t Quote Link to comment Share on other sites More sharing options...
Groomlakearea51 Posted April 24, 2007 Share Posted April 24, 2007 I have an older amp that farts out of one channel about 15 seconds after shutdown.... Now.... That's interesting!!!! Does it smell like garlic?[] Quote Link to comment Share on other sites More sharing options...
cyclonecj Posted April 25, 2007 Share Posted April 25, 2007 Now.... That's interesting!!!! Does it smell like garlic?[] Actually, it's more like buttered popcorn. Go figure.... Quote Link to comment Share on other sites More sharing options...
jheis Posted April 25, 2007 Share Posted April 25, 2007 t: I don't think there was any discernible difference in sound - if you're running one pair of speakers, it's just an in or out switch. James Quote Link to comment Share on other sites More sharing options...
tk49 Posted April 25, 2007 Author Share Posted April 25, 2007 James you have PM. t Quote Link to comment Share on other sites More sharing options...
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