Re: Maxon AD999 . . . what can you tell me about this delay ?
Yes, I own one.
It is mounted on my board and I leave it on all the time set for a very faint, slight slap-back delay. I run a Strymon El Capistan in front of it, and the Maxon makes the Strymon sound more analog. The two of them together sound substantially better together than either alone even though the Maxon is adjusted to only effect tone and not the delay effect.
As a stand alone delay I was immediately impressed with the precision of the Maxon and with the very uniform way that the delays trail off. The only downside, as is to be expected of any analog delay with extended delay time capability, is that it is rather dark sounding. It cannot compare with my old Deluxe Memory Man with the apparently no longer available Panasonic bucket brigade chips with respect to high fidelity repeats.
Another thing that surprised me is that it (the AD999) is capable multiple repeats, that is long feedback settings, without going into self oscillation (which I've never had any use for). I mean, it will self-oscillate, but not as early as many others.
It is a great delay for adding thickness that doesn't get in your way and , as I said, it is very predictable ... just too dark for me ... not muddy, but the repeats are noticeably lacking in highs and each successive repeat gets darker.