JackandCoke

I got this error when I tried registering my HD500 a few days ago, it turned out I was trying to use a O instead of a 0 for one of the numbers in the serial number. You've probably already gone through all that, but just in case... I hope it helps.

The 'looper' is a simple recording/playback device. You can't change the tone of the looper. That said, in POST mode (where the looper is recording after effects have been added to your signal) you can change the patch you use for each layer of the loop you're recording. Record your first loop, hit Play/Stop to continue the playback... disengage the looper by hitting the Looper button. Change the patch you're using (select A-D for the patch of your choice). Re-engage the looper by hitting the Looper switch again then hit Rec/Overdub to record your next track. It's a little bit of dancing, but it's logically thought out.

The closest HD equivalents might be the Tweed B-Man (model of a '58 Bassman), or even the Divide 9/15. You'll likely just have to try substituting a few amps to see what's close.