Purchased from: Belfield Music
Ease of Use — 10
It's very simple: turn the knobs and stop when you like the sound. There are no patches or memory. It's plug and play. The manual is basic but that's all you need for a unit such as this. The unit has standard input and out jacks as well as a balanced out to go directly into a mixing console. The ground-lift switch is there but I've never needed it.
One minor issue though, and this will not effect my rating: when I had a high pitched buzzing/squealing on the Behringer GDI21, I contacted Behringer customer support. They were utterly hopeless and made the claim that they didn't think that the unit was faulty. But they couldn't provide an explanation for the squealing either. By coincidence, I found out that the power supply caused this squeal. I haven't tested it with the BDI21 yet (I have used batteries so far), but Behringer don't seem to have adequately trained technicians in-house. They appear to have outsourced customer service to someone in the US.
Sound — 10
The BDI21 is a real surprise. I bought it so that I could run a bass into my DAW with some prospect of a half decent sound. As far as the bass sound was concerned, I was taken by the BDI21. It did give the bass a round, tube-type sound. The sound was somewhere between an old Laney tube head that I used to own in the '80s and something like a Trace Elliot or a Gallien Kruger - depending on the settings. The treble, bass and presence knobs were no real surprise. However, the "drive" and "blend" knobs turned the bass from a nice, tubey-sounding bass to a growling '70s monster with overdrive. The more you turn the 'blend' know clockwise, the more "tube" and distortion it adds, For $55.00 it was worth the risk and I won.
But wait, there's more! I am actually a guitar player and only play bass on the odd recording. I was equally surprised that when I plugged my guitar into the BDI21, it made it sound like a real tube amp, straight into my DAW. When the "blend" knob was all the way to the left, it sounded like a Fender Twin. Turned to the right, it distorted nicely and gave a good crunch sound. The tone overall added "life" to the dull DAW recording, similar to an exciter, but better, more natural. Overall, the blended sound was more like an overdrive Fender Twin a la The Shadows or '60s rock bands.
I have now two uses for this: for bass and guitar - for DAW and live, should I ever play live again.
Reliability & Durability — 10
As with most Behringer gear, they usually have a nice design. Durability in this case is not an issue. The plastic top is quite thick, the base is metal with rubber feet and the knobs have rubber grips. As I haven't played live for a while, I couldn't tell whether or not the unit would break. But let's face it, I have seen idiots on stage literally jump on their pedals. Then they get angry because it broke. As far as I am concerned, the pedal will last for years if used with respect.
The other thing to mention is that the battery lasts for a long time as the unit consumes little power. Either the batteries have got better over the years or the unit uses less power. I used it for hours on an almost flat battery without starting to fart or buzz. This makes a 9 V adapter redundant for live gigs - meaning less can go wrong.
Overall Impression — 10
I've been playing since 1974. Yes, I'm old. I play a mix of rock-pop/fusion/acid jazz and have a custom made Richards guitar, a Strat and a modified Ibanez RG550 plus five other guitars. The bass is a custom Fender Jazz Bass. I also use a Korg Toneworks AX1500G, a Behringer wah, Behringer GDI21, a Zoom MS-50G into a Vox Valvetronix and Bugera 4x4 box. I record for most of the time. I looked at other bass pre-amps but wanted something cheap for a few recordings. Like I said before, the unit sounds very good. I'd definitely buy it again if it broke.