Harley Benton GPA-400

This guitar power amp deserves 5 stars if I were to evaluate the amp on its own. However, to my shock and awe, when I opened the box, there was a second hand, B-stock or reconditioned unit inside. How do I know? The unit was not wrapped in plastic, the on/off switch was still on and I could see fingerprints, dust and even a few scratched on the top of the unit.

I plugged it in never the less to see whether it was operational before contacting Thomann. I'm pragmatic when it comes to ordering goods from the other side of the planet. Thomann offered a discount which I accepted, including a 3-year-warranty. But it was disappointing that Thomann's warehouse didn't appropriately mark this amp for what it was: used.

Had the power amp sounded crap, I may have actually sent it back but this amp sounds amazing with my Hotone Ampero which I run through a Behringer Ultragain Pro, into this power amp and then into original 1970's greenbacks in stereo.

Before the GPA-400, I ran my Ampero through an LD Systems XS200. It sounded harsh, fizzy and sterile. When running through the power amp stage of my Laney IRT60-H, it sounded better but still fizzy. The GPA-400 hits the mark. It sounds great, whether because it's broken, bad quality or intended by design, it takes the fizzy and harsh trebles away. The presence controls are perfectly calibrated to take even more fizziness out of the signal and the resonance controls are also useful in dialing out flabby sub tones (or dialing them in if you're into djenting). A standard transistor power amp can't do that. This one can.

Overall, it makes my Ampero sound as if it's going through a $1,500 valve power amp. Gutsy, percussive yet soft. A bonus is that it's well built and light. Very light. Not sure whether that's because of a light weight transformer or not. The on/off switch is fine and I'm not fussed about the plastic knobs of the pots. The pots, by the way, are perfectly OK.

The GPA-400 has everything you need from a power amp, especially if you carry it around a lot. At only 3kg, it is so light that it makes travelling to gigs super easy.
There are two channels, each with two speaker connections (jack plugs), so simple and straight forward. The resonance and presence are effectively tone controls, similar to bass and upper mid - I know electronics experts will cringe about this description, but that's pretty much how they work. They can be quite handy for balancing up the tone of slightly different speaker boxes.
There is a push-button mute switch on the front, signal indicators and red clipping LEDs. I never got these to light up, because it is so devastatingly loud, I was frankly too scared.
The sound is clean, really really clean and the high frequencies can be a little bit shrill, but this can be mostly accommodated by EQ in the pre-amp.

So to summarise, a cheap, sturdily built, very light, tremendously loud power amp. It will not sound like an over-driven valve power stage (which will weigh ten times as much), but it will accurately reproduce anything your amp modelling effects unit delivers to it.
For the price, this is an excellent buy.

Check my quick review at : a bit more in depth though :
This is an epic amp and especially for the money , its built like a tank and has a reasonable tone although not as bright or punchy as its obvious competitors , as far as what this is up against the Rocktron Velocity series is obviously the number one and having owned both now I can see why , although this has plastic knobs and lacks the finesse construction wise of the rocktron it does a reasonable job trying to emulate the capabilities having almost identical specs .
the one place where this doesn't compare is in the actually tonality if the amp itself , it has the high and low shape controls but it lacks a certain brightness and full bottom end that the rocktron shines at , although the big problem here is that after years of use this has survived and after 6 replacements the Rocktron just broke down consistently.

In conclusion after road testing both units I have to say that this is more than worth the money and with some tweaking I got a crushing sound from it , so if your using in particular a preamp processor of the likes of the Kemper/AxeFx/Helix then this is a great value and easy to use unit that is small but does get hot so leave some breathing space lol , grab a bargain .

This is an update to the negative review that previously left. I'm leaving it below. The reason that the unit wasn't working was this it was not receiving the correct voltage. It is a European product and I live in the United States. After purchasing the correct transformer the unit worked great, I'm very happy with the unit. With that said, I do have some draw backs. I need the unit to fit in a rack. the unit itself does, but the transformer does not. So I have to keep the transformer outside of the rack. Eventually I will have to buy a deeper rack so the transformer will fit. It's an expense that I was not expecting, but considering the cost of the unit, it still makes sense. So just keep that in mind when buying this product.

(original review)
I received the GPA 100 yesterday. I hooked everything up and no sound is coming out of the unit. I've been writing customer service for 24 hours but I have not received a response. Very disappointing.