This is a FET preamp fitted with 2 individual channels (Gain, Treble, Middle, Bass, Volume). It also offers a presence and a deep control, and a master volume, All 3 knobs are shared by the two channels.
The preamps comes with no manual and a somewhat cheapish power adapter. One may think that someone is trying to cut down costs and boost profit at Diezel... if we didn't know better!
The aluminium body is thick, sturdy and quite bulky, and yet the preamp is rather light (1.3kg). The Zerrer offers no less that 6 kinds of outputs so most situations should be covered! We have a "amp in", a "poweramp in" that can also be used as a "stereo FX loop" (send/return), a "compensated output" (w/ cab sim) for mixing desks, a headphones out (ofc w/ cab sim), an external footswitch control in case we want to trigger the Zerrer from a distance, and finally an "auxiliary in" with two independent volume knobs to plug in our MP3 player or other sources!
The Zerrer is a true bypass preamp, but when activated sound only goes through when connected to the "amp in" output...which is obviously when we need it! Otherwise the bypass footswitch is used to mute the preamp.
I'll be honest I think the preamp LOOKS pretty bland and common...knobs are not of the Diezel type and the overall design could easily be improved but, hey, aesthetic is only second to tone! And in that department the Zerrer delivers big time!
If you're already familiar with Diezel amps, clean/crunch channel is from D-Moll and lead channel is VH4 (channel 3)
If you're not, let's say that gain-wise channel 1 goes from a Fenderish or JC clean type tone to a big crunchy JTM or JCM800+. You can dirty the clean channel VERY progressively. Channel 2 more or less picks it up from there and brings us into high gain territories. Think VH4, Herbert or 3x Rectifier (the amount of gain, not the tone!).
Tone-wise, the Zerrer brings us Diezel signature sound. It's extremely sensitive to attack and picking styles (just like a real good quality TUBE amp, no less!), and of course the guitar you'll plug into it will greatly influence the tone. Honestly it's so impressive to hear how responsive it is that I need to mention it once more! I've had many preamps and amps over the course of the last decades, and this one ranks at the very top for sure!
Depending on how high you set the channel volume, EQs will be relatively or extremely sensitive. Basically if channel volume is full on, the tiniest turn of a knob has a huge impact on the tone. When channel volume is set at noon, it is more what you'd expect from a standard amp or preamp.
It is only my opinion but I believe the Zerrer needs to be plugged into a sort of poweramp. I use a torpedo and the combination of the two is terrific! I also tried to plug the Zerrer into Recabinet 4 and it sounded pretty good, though not quite as good as into the torpedo. The Headphones out in comparison sounds like plugged into an IR file. When I first used it I found the tone somehow lackluster. Mind you, it's quite decent and pretty usable and useful when on the road for sure, (and better than any mass-market modeler out there!) but still, we're a far cry from what a "fully fledged" (so to speak) Zerrer can deliver!
My previous preamp was a Mesa boogie V-Twin (good tone, but definitely not as versatile as the Zerrer) The Zerrer is definitely as responsive as the V-twin, even more actually IMHO. I have also owned a Herbert for several years (the first models) . To very briefly compare the two, the Herbert is way more versatile than the Zerrer, and is also voiced slightly differently, so the Zerrer can only mimic a fraction of what the Herbert can do, but it's not all that bad, as with a bit of extra EQing, I can get close enough anyway ...and it's way more convenient to carry around than a 30kg head and a 4x12!! But Peter, if you read me, we also need a Herbert preamp!
All in all, I'm very pleased and satisfied with the Zerrer. It is a frigging great piece of gear that delivers an awesome tone, plus, it's portable and very versatile. Once more Diezel puts out an excellent product on the market and above all one that should disappoint none! It's small in size but delivers big time! If you're looking for a high quality and portable preamp at an affordable price, just grab one, you just can't be disappointed!