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If you're using typical L/R speakers you won't notice this low frequency thumping on the CP80-1 voice.
If you hook up a sub then it will drive you mad. The thumping occurs with each key press on the front end and stays the same pitch no matter what note you play.
It sounds like a kick drum strike with each press. Maybe you can hear it best in headphones but on my 12" JBL sub it's very loud.
A CP80’s sound was created using 88 small microphonic pickups mounted in a baby grand shaped enclosure - one per note. (The ‘thump’ is too remind you why there are such things as Equalizers)... an open microphone will pickup all sounds within the CP80.
The thumping can be heard when playing an actual CP80 with the power turned off... it is a mechanical device. The mechanical noise is apart of the sound. The Key mechanism’s noise includes the fixed pitch thump of the action. Subs tend to emphasize the low end. If you don’t like it in your sub, de-emphasize it. Quickest way is to EQ
It is not that prominent under normal circumstances... (certainly not more than playing an actual CP80). I do not doubt that a sub-woofer might just bring that thump a bit too far out front...
Thanks BM. In comparison, the CP80 2 on the YC doesn't do this at all. True that most players will not notice it if they aren't using a sub.