tape compression and saturation can not be emulated
properly in the digital domain yet and bucket brigades
have their own thing going.
I think its not about warble and flutter, because a well
maintained tape echo, with fresh tape will not do that.
Also there is no signal degradation but, as mentioned
above, tape compression and saturation.
If one really wants to have tape echo than a real tape
delay unit is mandatory anything else can only be a
close approximation.
Its like the age old (it seems) question, what comes
close to a TS. The answer is: a TS!
Right now I am experimenting with two Revox B77 as
delay units. I have used these babies in the 80ies
two have my own Frippertronics.
You would never believe how much difference in sound
the brand of the tape will make ....
Maybe some people here remember the cassette tape recorders
and the different tapes one could buy: chrome coated tape for example.
Do you remember the difference in sound?
Now think about those tapes in the delay units ....
Has this ever been discussed?
Conclusion:
Tape delay units all sound a bit different (almost like fuzzes)
depending on maintenance status and usage of tape and so on ...
If you would try to emulate a tape in the digital domain,
there are far more parameters than the usual settings, delay units use.
With a 'simple' stomp box one can only emulate a specific tape delay unit.
I think the Skreddy does that. It emulates the specific delay the
builder used to sculpt the sound after.