It's a class D poweramp that keeps things as simple as they can be.
The front hosts the input plug (1/4", 10kOhm) and the master pot.
The rear hosts the power plug, on/off switch and the speakon plug for the cab.
The powerswitch lights up when the unit is active. That's it.
The used materials, workmanship and finish are top notch, everything looks and feels very high quality.
The amp is shipped with a nice suitcase style case and a power chord.
It is a perfect tool for those who want to:
1) Use a pedal or other non-19" preamp
2) Run a mismatched combination of cabs (connect one cab to the head and one cab to the sumo which is fed from the line out, so you can regulate the power for each cab separately)
3) extend a system that runs at its limit (head with maximum number of cabs already connected or combo amp with no ext. speaker output)
4) in a pinch, convert a passive cab to an active one
5) experiment with bi-amping setups
6) want to run their pedalboard straight into the cab(s).
The use of a dedicated poweramp always brought the problem that all poweramps that allow connecting a bass setup usually come in 19" format.
A 19" unit outside a rack is big, difficult to transport and not very professional to look at.
Enter the Sumo. It's tiny. It's light. And it's quite easy to transport - and to top that off, it even comes in a tiny case.
It does 600W @4 Ohms and has a frequency response of +-1dB from 20Hz to 20kHz.
So whatever you put in comes out totally uncolored on the other end - only a lot louder.
GSS made a very simple yet very flexible tool for the working bassist that is not limited to bass at all. It's a poweramp that will amplify anything as long as it is in the frequency range suited for the human ear. So in a pinch, you can use it to power any cabinet you set it on, provided it has at least 4 Ohms and you have a line level signal to feed it.
I'm quite happy with my purchase and already tried a few applications listed above, with great success.
My version is made for European voltage, but they also come in a 110V version for the US.
I ordered it directly from the GSS website and payed through Paypal. The shipping was quite fast.
I feel that I need to add that all my contacts with GSS through their website and via email were handled extremely well. The person on the other end was very competent and knew all the products I inquired about inside and out and proved to be not only very helpful, but also friendly. Something that has become quite rare in recent times.