I was a bit hesitant about buying this, Class D, very inexpensive :S But Im glad I did...

Where to start.. Class D amps.. So amp's come in basically 3 types, Tube, Solid State, and Class D. Tube amps have that nice warm tone and gorgeous sounding harmonic distortion, breakup and compression, plus there loud for the watts, but unfortunately cost a fortune. Solid State amps tend to just have raw power and balls once you get up there in the watts, but sound a bit sterile compared to tubes. Class D or digital amps always sound incredibly detailed but cold and sterile to my ears, they tend to put out what you put in without warming anything up or rounding off the bad edges. Also 200 Watts Class D is volume wise about the same as a 30-50 watt tube amp. But as this was for a second guitar rig using some preamps, a G Major FX and a Harley Benton 2x12 Vintage Cab I already owned I didn't want to be shelling out $600-$1000+ on a tube amp, well not at the moment.

Initially I had some problems dialing in a good tone, I think the amp probably needed some run in time to take out a little new amp harshness, and while it didnt sound like a cheap $200 combo when I had a solid state preamp hooked up it, it wasn't doing it for me it tone wise. Solid State preamp and Class D power amp, probably not a good way to go :(

Next up I hooked up a 20 year old Digitech tube preamp, with a bit of EQ tweaking and a OCD clone as a boost I was happily rocking out thinking this sounds pretty good.

Then 2 days ago the AMT SS-10 I ordered turned up. OMG, chimey cleans, gorgeous slight blues breakup, and the crunch / high gain have a great tube compression, and it sounds almost as if there's some power tube breakup and sag going on in the tone. I was in guitar nirvana gurning away like an idiot. After I finished playing Van Halen's "Panama" solo I thought "damn my playing doesn't usually sound that good".

So there you go.. Class D... **** in = **** out, great tone in will equal great tone out. Very transparent and it's not going to hide or warm anything up.

A couple of other things...

* I did A/B it against a blackstar HT5 power stage a few weeks back and the HT5 sounded flat and muddy in comparison.
* It's not hugely loud. I dont know if it would run stereo 4x12 cabs at gig volume, but in bridged mode it should be fine for a single 4x12.
* What's with the dodgy cheap knobs Thomann? It feels like they are glued on too :(
* The tone pot values are a bit too sensitive as well, 10 to 2 o'clock is about all that's usable.
* If you're thinking about getting one of these.. I did try running the 2x12 cab in stereo , but I was getting some weird phase cancellation, probably due to stereo FX.
* Very light.
* Runs cold.
* If you have a high end ( or new model ) modeler this would probably work very well to, unfortunately I don't have any good modeling gear anymore to test with.

I was planing on replacing this with a 20 Watt tube amp when I had the cash, but if my feelings about the ATM don't change, and I don't end up putting the AMT in my main rig, I don't think I'll bother... Great inexpensive power amp if you have a good front end \m/

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.

I got this amp based on a gut feeling I had, and also the postive reviews it has received here on this website. Also look at the sales of this amp, it is proving popular.

I have moved over to using rack equipment in the last year and I wanted to buy a new power amp. I was considering going for a plain old clean power amp used for general sound applications. I then stumbled upon a few power amps designed specifically for guitar. The Rocktron Velocity was one. That lead me to this site, which then introduced me to the Harley Benton GPA-400. Immediately what appealed to me was the 100watts more than the Rocktron and also the cheaper price!!! Before I bought the amp I had contacted Thomann pre release of the amp. One of their technicians told me the amp was designed to compete with the likes of the Velocity amp. This got me very curious indeed. Also very excited. It wasn't until a year later however that I actually got to buy the amp and try it for myself.

Before I got a chance to buy this amp I noticed it had been selling well. In fact it's currently 81% of peoples choice of guitar power amp from this website. So I guess you could say it's popular.

Ok so I got the amp, within a matter of minutes I had it set up to run 4 speakers cabs. Four 2x12" cabs easily connected to the GPA-400. It has 4 speaker outputs! This great. It makes it more flexible. Each channel (A and B on the amp or Left and Right to me and you) has 2 speaker outputs each. If you connect a speaker cab to each of the speaker outputs on one channel you get a parallel speaker load of the two cabs. In my case I had 2 cabs at 16ohms, this in parallel worked out as 8ohms. So this was the same for both channels meaning I had 8ohms load in channel A and 8 ohms load in channel B. This then means the GPA-400 is able to run at 200watts output. Ok so 200watts was my output and now I had to see if that was loud enough for my band. Yes it was!!! I found I had to set the knobs at 2or 3 o clock on each channels volume control in order to be loud enough. This meant that I still had more to travel with each volume control and that means if I needed even more volume, I had there on tap should it be required.

Well it was not required I am happy to say but is good to know you have head room. I have to also mention that had I been running the amp at 4ohms each side I would have had a total of 400watts output as opposed to the 200watts I was using, so this means the GPA-400 is capable of even more volume!!! Good to know these things.

As I was testing the amp I had the "Resonance" and "Presence" controls centred. They have an indent to find the centre so I am assuming that centre is 0 and left is - value and right is + value. I began with both controls centred as I say, and after a while I added in a little presence to give a tiny bit more Hi end to my sound. What is really good about these controls is that you can centre them before every gig and then say you need a bit more bass, you can adjust to taste depending on each venue you play. The same goes for the presence control. These controls are independent to each channel so you might want to run channel A a little brighter than channel B to help with stereo seperation or just to suit taste. It's really nice little features to have. These controls are controls that appear on the Roctron Velocity also and I'm assume they function similarly from what I have read. Both controls centred in my opinion sounded really good, not harsh, not brittle and dare I say warm sounding. I added a little presence each side purely to give a bit more cut through with my guitar sound.

I ran the GPA-400 using an ADA MP1 preamp placed in the FX loop of a Boss GT5. To me this combination sounded excellent. The GPA-400 really give my rig the power to get heard. It also complimented it somewhat. I made zero adjustments to my rig itself. I basically dialed in the little bit of presence on the amp and that was it! It could not have went any easier.

Looks of the GPA-400 are nice. It's simple and smart looking. It is also sturdy and pretty light! 2.5kg! It really is well made. The jacks all feel good quality and everything is nice and solid feeling to plug into. There are nice little led's at the front that can detect the signal coming into each channel. Nice little useful feature. There is also a peak light if say you were over loading. I couldn't test it to see if that worked because I guess I wasn't over loading and I didn't feel it was necessary to try to.

The only thing (and it's so minor I don't really need to mention it) is the control knobs feel cheap and are not to my taste. I rectified this by buying my own black and silver knobs to swap them out with. Just my own taste. One other minor issue I have just recalled is that I don't like that on the back of the amp Channel B is on the Right hand side and Channel A is on the left hand side. Why do I not like this? Because when you go back around to the front of the amp and you turn up the channel A volume or anything else on Channel A this is on the left hand side, but controls the speakers on the right hand side. In fairness I can see how this design flaw happened but it is a little bit annoying but seriously not important. My work around this was to swap the speakers on the right hand side into the left channel and left hand side speakers into the right channel, this means from the front of the amp the controls for each channel correspond with the speakers on the same side. Makes sense right?

Think I've covered everything. In short this amp is cheap, it's well made, it looks decent apart from the knobs, it's very powerful, it doesn't heat up much after several hours of use, it's light, it's cheap (of did I say that again?), it's very loud, has lots of head room and it also sounds great and feels great unlike some brittle sounding sterile PA amps. I would buy another if this one broke. In fact I may well do for a backup. I really do recommend this amp, I think it's a real gem and it's great Thomann are selling something of this quality for such a reasonable cost.

Bought this on a whim as other guitar specific power amps are very expensive and can take up lots of room in a rack system. I'm pairing this up with the highly underrated digitech gsp1101 and a stereo 2x12 with greenbacks. The results are jaw dropping, honestly! The GPA-400 provides lovely quiet, effortless clean power and the massive surprise is the built in eq... It's like buying a power amp and getting a free sonic maximiser! The downsides to the unit are the cheesy silver plastic knobs and nasty plastic jacks, otherwise I whole heartedly recommend this great value piece of equipment.

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 .