_mr
24
I have the A4, OT and RYTM.
I agree with you, the RYTM is noisier than the A4 or OT.
And yes, I would expect the RYTM to be quiet like the A4, I don’t understand it either.[/quote]
But they are quite different.
The OT is a digital machine using only hi-fi D/A converters directly through its analog output amps.
The AF has 4 analog voices going through
[ul]
[li]an analog mixer stage, [/li]
[li]an analog volume pot, [/li]
[li]an analog output amplifier.[/li]
[/ul]
The AR has 8 analog voices going through
[ul]
[li]an analog mixing stage,[/li]
[li]an analog distortion,[/li]
[li]an analog compressor, [/li]
[li]an analog volume pot,[/li]
[li]an analog output amplifier.[/li]
[/ul]
The more, the merrier/noisier. 
Also: in the AF, the voices tend to be quite silent when not playing, thanks to their VCAs that end the sounds.
In the AR, the voices are noisier if the VCAs are left open. It can be wise to make sure the VCAs close when not playing, since there is no guarantee that they do just because the drum sounds have ended.