<<When I entered 0491 (aud) nothing happened>>
Then the code is not in your remote, if it was the LED would have flashed twice indicating that the code was accepted.
<<the remote seems to accept it but the power-off does not power off the AMP.>>
If the code really was accepted, was the power button the only button you tried?
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what are they.>>
Check my site.
Rob.
http://www.hifi-remote.com