Thumps from Yamaha amp.

_oldtarf

Hello Everyone,

I hope this hasn't been answered allready but i need help with my new RM6000 speakers, specifically the sub.

When connected via the line in terminals from my Yamaha RXV440 it thumps on each change in the amps mode. I don't think this is related to the sub as my friends sub does it as well.

I have tried it connected the way Polk have recomended (speaker level not line level)and it dosn't do it but i don't want to run speaker cable all over the room if i can help it or loose the ability to change the sub volume remotely plus the amp outputs the full frequency range to all 3 front speakers and i'm worried about the power handling of the centre speaker.

McLoki

I assume you hear the thumps when your amp goes on or comes off of standby correct? If this is the case just turn your amp on (rather than signal detect) and plug your subwoofer into the power socket on the back of your amp. If this is not a valid solution for you - just turn your sub on and leave it on (you can plug it into a power strip and turn it off and on with that. - or just leave it on all the time)

Michael

[Deleted User]

Hello,
It is possible one of the components that is connected to your receiver has DC present at it's output. In other words, one of the devices that is connected to your receiver's inputs is placing a small DC voltage on the selector circuitry of your receiver. When you change an input selection this DC charge is dissipated and you hear a transient thump from your speakers. T check this theory, remove all of the connecting devices you have plugged into the receiver, except the sub-woofer and the speakers and the FM/AM antennas. Then go through a few input selector changes to discharge and residual DC that might be lingering on the selector. Hopefully, no more thumps. Then, one-at-a-time, re-connect the other components, checking for the thumping sounds after each re-connection. There will probably be one of your components that once re-connected will cause the thumping. This would be the component that needs exchange/service.
Ken

_oldtarf

Thank you both for your quick replies.

Michael the amp thumps both when switching on and off and when changing modes eg: cinema dsp to Dolby Digital as in the start of a movie and also when selecting different souces. Your question also got me thinking and it also does it when you disconnect the sub if it's still powering down.

Ken, that is certainly something i have never considered as we only changed the sub when testing, everthing else was still connected. As i didn't expect a reply so quickly i wired the whole thing up using the speaker connections and put it back inside the cabinet, so over the weekend i'll take it out and try your test, will try and get back to you in a few days.

dgs

I used to have an old Arcam stereo amp that would thump when I turned it on or off. In that case it was because there was no switching on the output stage (cleaner signal route). As a result when the amp powered up or down the big capacitors on the output stage would charge up or down - because no two capacitors are perfectly alike there would be a tiny difference between the current on the two channels which would result in a DC voltage difference between them - which would output as a low thump - often sounding like it travelled across the sound stage.

Most modern receivers have switching on the output stage that prevents this DC offset hitting the speakers - if you are hearing a thump on just one speaker this could be your problem however and may be just a "feature" of the amp.

_oldtarf

dgs - Thanks for your thoughts, in my instance the thump comes from the sub only.

Ken - I tested your idea and it still thumps with nothing connected after several switch changes.

McLoki - As the amp thumps when switched off only and also when changing surround modes i don't think independently switching it on and off would help.

Thanks for all your thoughts but as I have connected it up as per the instructions (speaker out) and it's working very well, and as the problem is in the amp i can't afford to have it looked at at this time so im going to leave it.