Other analogue equipment, like tube preamps, does make sense, but as the digital effects get better, there's not all that much to gain by spending tons of $ on analogue equipment.The long and the short of it is, that analogue equipment is cool, but often costs too much and is unreliable.I see no problem in that, even if you're trying to get a vintage'ish sound.Quite on the contrary actually: If it hadn't been for cheap hi-res sound cards, I could never have afforded to experiment and record as much as I have.There are many other suitable echo units/pedals out there and some of them are better than my DD-3.
I wrote two e Books about playing rockabilly guitar.
The sound was very Many Rockabilly guitarists play a '59 Fender Bassman (or similar) - vintage or reissue. I found a way to get around that and always have the same "Bassman-sound" no matter what volume I'm playing at...
I often get asked how I set the Sans Amp GT2 pedal to get a vintage sound.
Anyway, I AM in good company with the DD-3 as Scotty Moore (Elvis Presley) also is using one nowadays alongside with a chorus (to emulate the frequency impurity of a tape echo). I haven't tried this one myself, but the online sound samples on BOSS' website sound pretty convincing to me.
However, I'd like to mention some alternatives: Other effects : Distortion : The BOSS FBM-1. I still prefer the Sans Amp though, and I think it's more HI-FI than the BOSS (It SHOULD be actually, because it's a studio effect, which is a notch or two above a guitar pedal in sound quality).