Arcam Delta 290 - which ones are "the drivers" ?

Finally, what goes on in the speaker outputs - before relay (source master switch is set to normal, tuner input sockets are grounded, volume pot is at minimum position)?
DSC_3969.JPG


Powering up - some expected mild disturbance settling in some seconds. Speaker relay activation delay is ca 6...7 seconds so there is time enough for the output lines to settle:
Delta 290 03 Q1-Q101 source (SPK out) powerup.jpg


Powering off - some disturbance is invoked some seconds after switching off the power.
Delta 290 06 Q1-Q101 source (SPK out) poweroff.jpg


Activating speaker output relays does not cause any substantial impulse:
Delta 290 04 Q1-Q101 source (SPK out) speakers 1 and 2 connect on.jpg


But deactivating them does - yet, this is measured without output load connected so with connected speakers it is probably dumped by them:
Delta 290 05 Q1-Q101 source (SPK out) speakers 1 and 2 connect OFF.jpg


There was some strange disturbance earlier when activating the speaker connection relays when using "External input" i.e. the PWR AMP IN (grounded) sockets.
DSC_3970.JPG


Now when repeating the situation everything is back to normal again - perhaps the Normal/External input switch made better contact this time, do not know.
Delta 290 07 Q1-Q101 source (SPK out) PWR AMP IN grounded powerup.jpg
 
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Thanks a bunch, Madis, great work!
Yeah, well, I just restored the flow of electrons 🙂
Nevertheless this amplifier has lots of hidden potential (as described in previous posts) but that is up to you how to tackle them.
Personally I would start sorting things out from the "end of the process" - it is no use to fix the phono stage if the preamp and final stage will dump all improvements...