Driver flexing when amp switches on

[luckiestmanalive]

I leave my Plinius 2100i on but obviously I have to turn it off occassionally. When I turn it on there is a few seconds pause before the amp switches out of mute and when it does so the mid-drivers of my speakers flex in and out a few times before settling down. This has always been the case but I am curious about why it occurs and if it is normal for Plinius amps or for other amps?

I've also noticed that the flexing is extremely obvious on only one speaker - the other only moves fractionally. Can anyone tell me why that would be the case? Could it be a difference between the loudspeakers (I replaced the wiring and crossover in one speaker) or in the amp (I think the previous owner had a single cap replaced)?

[ajst2duk]

Suggests DC on the output? try it with source unplugged to see if it still happens? Actually this happened to me with a plinius amp, but the culprit was the DAC (tube output stage) it had me stumped as both ouotpiut caps on the dac and input caps on the amp should have blockled any DC ?? I dunno that doesn't really help ?

[Owen Young]

Try swapping spkr cables, one end only. This should tell you whether it is spkr or further up the chain.

I wouldn't be concerned unless the movement is large cone excursions, ie. more than when the spkr is playing music.

DC signal would move the cone one direction only.

[too_tall]

DC signal is also going to move the cone in the specific direction, and then hold it there. A DC offset is nasty, and melts voice coils. What your describing is a very low frequency "wobble" which may just be the power supply stabilizing. Still surprises me if its still stabilizing after the relay has closed though.

[Michael Wong]

My old Plinius 8200P did this too, another reason to never turn it off.

[ajst2duk]

My old Plinius 8200P did this too, another reason to never turn it off.

Yeah well thats what I had - but the mute came on on powerup so I never blamed it on the amp?

[luckiestmanalive]

Thanks, for the advice guys. I changed the speaker cables around and tried turning the amp on and off a few times on CD (connected) or tape 2 (not connected). I am now no longer sure there is any difference between the speakers and there doesn't seem to be any difference whether or not a source is connected.

As the flexing is not violent and it appears to be normal, I will just continue to leave the amp on from now on.