Читаю Gearslutz по теме, вот один чел что написал (четко и взвешенно):
I haven't found the ideal DI yet. It amazes me that it doesn't seem to exist.
Passive Electric guitars and Basses are very sensitive to the input impedance which they feed into. A Piezo pickup is even more sensitive.
When they are presented with a medium to low impedance they see it as a partial short circuit. The tone is literally sucked out of them. The audible result is less volume, less bass, and less treble. Miserable.
Passive DI boxes are basically transformers. Because of this they cannot achieve very high input impedance. They would be typically around 50K Ohms.
Contrast this with a DI specifically optimised for Piezo's and such, e.g. the Countryman FET85. It's input impedance is 11M Ohms. Yes eleven million.
Valve amps have typical input Z of at least 500K.
The kicker in all of this is that most DI's have input and output jacks for linking on to the tuner, the amp etc. These Jack sockets are wired in parallel. This means the whatever item in the chain has the lowest input impedance will dominate. e.g. a tuner with 50K input impedance will ruin all the benefit of a Hi Z DI.
Even worse, some active DI's have decently high input Z, but this disappears when the -20dB pad is engaged. The otherwise excellent BSS does this as far as I can remember. The also excellent if somewhat elderly Boss DB1 has a good input Z. It uniquely has a buffered output and a parallel. The buffered can be used to drive your tuner, effects, long lines to an amp in another room etc. etc. Brilliant device. BUT, the pad drops the impedance, dramatically.
So if any finds a transparent active DI with over 1Meg input Z and a buffered output, needs to be capable of battery operation, please let the world know.
The Baggs instrument Pre, DI, is very close to this ideal.
Could do with less controls, no eq and such, plus a bit of ruggedising.
The IBP products get good press, but again a lot of stuff not necessary in a DI, and some of the necessary missing.
As I said at the start, quite amazing that no-one has done this right.