The Behringer DD400 is a cheap digital delay pedal aimed at guitarists on a very tight budget. It features Level, Feedback, and Time controls, as well as six delay modes to choose from.
Level controls the wet/dry mix of the signal - 'MIN' being 100% dry, and 'MAX' being 100% wet (repeats only). Feedback controls the amount of repeats, from one repeat to nearly infinite repeats (they start diminishing after a fair amount of time). Time controls the delay time, the range of which depends on the selected Mode. The shortest delay time is no delay at all, while the longest delay time lasts 1,3 seconds.
The DD400 can run in three different modes: mono delay, stereo delay, and 'hold'. The mono and stereo delays are split into three delay time ranges to make dialling in the right delay time a bit easier. The 'hold' mode makes it possible to sample and hold (loop) up to 1,3 seconds of the input sound. It's not nearly enough to use it as a proper looper, but it can create some cool glitchy sounds if used correctly.
A hidden feature of the DD400 is tap tempo. Pressing down on the switch and holding it until the LED blinks makes it enter 'tap tempo' mode. The pedal will then interpret the next few taps as repeat time. Unfortunately, this feature seems more like a side-effect of the pedal's design, which is probably why it wasn't marketed. The tap tempo tracks faster than it should, so what is tapped will end up being a noticeable amount faster. This makes the tap tempo unreliable, but not completely unusable.
Sound quality is good. There's no apparent 'tonal footprint'. The pedal uses buffered bypass.
The DD400 is made out of a thick plastic and uses plastic knobs for controls. Despite its build, the pedal is surprisingly very sturdy. It survived stomps and drops without a scratch, and outlived some of the pedals I thought were of a much better build quality.
Overall, it's a good pick considering the cheap price tag. It does exactly what a delay should do. The extra bells-and-whistles (tap tempo, 'hold' mode) may not be useful to everyone, but they're included as 'features' of the design and not as specifically developed selling points.
Personally, if I could change one thing about this pedal, it would be to add trailing delays after the pedal is turned off. The way it currently is, once you turn the pedal off the wet sound cuts out completely instead of letting the repeats fade out. An effects trail would be a welcome addition.
One final note: get the DD600 if you can find it for a similar price. It has more features and almost no drawbacks of the DD400.