August 18, 2010

Review: Behringer A500 power amp

Update (March 2013): I posted previously that this amp had failed. However, it turns out that it was in fact the IEC power cord that failed, a rare problem and fortunately one that is easily solved. However, I do still hesitate to recommend this amp due to problems with one of the inputs. Since this is a popular page, I'm leaving it here but I'd suggest people consider Emotiva power amps.

Behringer A500 is one of the best value power amps on the market. I have used this amp in my active system for a number of years and find it's performance to be quite respectable.

Aesthetics and build quality

For many the looks will be a stumbling block to uncovering a bargain. The attenuators and face plate are plastic and do appear a little cheap. The lights on the front show the output level are a little more bright than many would like. With the lights down low for a movie they are over-bright and can't be dimmed.

The case seems sturdy enough and for the price there is nothing to complain about regarding it's quality.

Looking inside the box, you can see the power supply certainly does appear decent.


Both balanced and unbalanced inputs are provided, along with a choice between two different speaker cable outputs. Bridging is included for 8 ohm loads, but conventionally it is stable into 4 ohm loads and provides 230w into 4 ohms or 160w into 8 ohm loads, or 500w when bridged into 8. Clip indicators warn of over driving.

No muting relays

Unfortunately this amp does not provide muting relays. A conventional hifi amp provides relays which prevent thumps when the system is powered up or down. After switching on such an amp, there is a delay of about 5 seconds followed by a click. In those 5 seconds, the amp remains switched off. Other components up the chain might have thumps that could get through at this point and they can be irritating or even destructive. When powering down, muting relays disconnect the outputs before any thumps get through.

This is one corner I wish Behringer did not cut. Suitable relays cost about $10 each and while this might sound trivial, electronics at this price point eliminate everything they can.

Sound quality

In my blind test results post, I mentioned one test in which this amp was found comparable with much a more pricey amp. In keeping with that result, I have found it to be quite decent. Others have reported less than flattering results, but I always take these kinds of reviews with a pinch of salt. I use this amp in an active system driving only the midrange, so I can't comment too much on the top end or bass performance.

You won't find a long subjective description here with words like liquid midrange, shimmering highs and you definitely won't hear words like rhythm, pace and timing! But I will simply comment that the sound quality differences between this amp and one many times the price are far smaller than many audiophiles would have you believe.

Woofers gone mad

In 2010 I witnessed a system that used this amp to power some dipole sub drivers. I was watching the lights get very close to clipping as I was concerned the amp was running hard. Then something strange and disturbing happened that sent onlookers into a mad rush to shut down the system, including myself. The drivers were moving wildly at very high excursion, yet the music did not seem to demand this. They were moving as if playing sine waves or test tones. We shut the system down to avoid failure, then started scratching our heads about the cause. After some digging around and discussing the issues with two suitably qualified experts, I came across an answer that makes sense.

It was clear that the driver and amp got caught in a feedback loop, very similar to what occurs in PA setups. We all know the scenario - if the mic is in the direct line with the speakers, the mic picks up the sound from the speakers and tries to amplify it further, resulting in a loud high pitched noise. In this case, the drivers were acting as the microphone. Why doesn't that happen all the time? Normally the amplifier has a damping factor, which prevents this from happening. The situation is made worse by the use of high levels of global negative feedback, which is used to give a lower distortion figure.

Now there is one missing piece in the puzzle - why didn't the damping factor prevent the feedback loop, as would normally be the case? Some amps have their damping factor drop to zero when clipping occurs. It would appear that this is such an amp. Once a certain clipping threshold is passed, the damping factor protection is removed leaving the drivers vulnerable. Had the system been left on, say to break in the woofers, it's possible they could be fried.

Where not to use this amp

This amp should not be used for dipole woofers as it has been found to be unreliable as described above. It should also not be used with drivers that may be sensitive to damage resulting from power on/off transients. In particular it should not be used in an active system for the tweeters. I also don't recommend it for demanding high power applications or subwoofers. I would hesitate to use this amp for demanding speakers such as electrostatic speakers.

Suitable uses 

This amp would make an idea upgrade to the main channels of a home theatre system. Where you have pre outs on your AV receiver, you could use this for the mains. It's an ideal amp for most conventional stand mount or floorstanders. It's a good amp for a studio system, and for domestic 2 channel and multi channel systems.

Others have had apparently good results in using this amp to drive subs, so your experience may vary. I would not use this amp in that way - the Europower amps are in my view a much better choice.


Is it a giant killer? I can't say that it is comparable in all respects to many of the amps it will be compared to. No doubt many will consider it alongside more expensive options like Emotiva, NAD and Rotel. All of these products have advantages beyond the sound that make them still worth considering. However, at the price there are few other options and overall I'd call this amp a very attractive option for those who appreciate bang for buck.

Futher reading

The Audio Critic have a very good review of this amp which includes measurements.

Audio Critic Review 


  1. Hi Paul,

    I have a question regarding the feedback loop you talked about. I have a Behringer EP4000, and this is driving a Tempest X2. It is running at 4 ohms bridged.

    I have been told that when the amp is bridged that you should leave the channel 2 gain untouched (i.e. at minus infinity according to the labelling), and use the channel 1 gain to adjust the output of the sub.

    I had used it like this for months and was really disappointed with the result, as I thought a tempest with an ep4000 would be good. So I used the sub minimally and had the gain turned right down so it was barely providing any bass reinforcement.

    Anyway, one day I was just fiddling with the channel 2 gain and put it in the middle, and then it sounded really good. So I tested it further and noticed the impulse response and the accuracy of the bass was much better. I tried turning the Channel 2 gain to +32 and the result was something similar to how it was at minus infinity. Through trial and error and by ear (yes I know that's now very accurate haha) I have found +22 on Channel 2, and then whatever gain necessary for Channel 1 is the best sounding, most accurate and by far the most enjoyable to listen to.

    I also noticed that when the Channel 2 gain was set to +32 or minus infinity and it was played at moderate volumes, the sub would start playing a bass note and then continue playing almost like a sine wave but with increasing amplitude until I turned the Channel 1 gains down physically.

    This basically sounds like what you were talking about with the A500, and it seems as if the amplifier was caught in a feedback loop. But you said this usually occurs due to minimal damping when clipping, but the EP4000 was playing no where near the maximum power let alone clipping, so I would have assumed that this was not the case? So yeah I just thought I would see what you thought of this, and thought you might be interested in hearing about what I have experienced with my amp.

    1. I hooked up an A500 to a pair of paradigms just for a livingroom listening test of my system.

      I did not check the mono switch on the back of amp because I had no manual and didn't even think it was in bridged mode(s).

      Naturally I turned up both volume knobs, assuming it was in stereo, but found one channel seemed inappropriately matched in volume.

      Fiddling with the volume knobs I was instantly aware (sitting between the speakers) that the phase of the music was being swung in and out as the right channel (2) was turned up.

      I thought to myself some jackass has mis-wired the phase, and dismantled the unit. At first I didn't even notice the mono-switch near the outputs bottom (its all coloured black).

      I discovered that someone had indeed subbed the right (2) volume pot, with a (non-clicking) one, and removed the mini-circuit board as found on the original (left, ch 1) pot.
      I immediately assumed they wired it backwards, but this didn't make sense, and I then assumed there was some trick or hidden switch to get inputs and outputs both in mono or stereo, and something was out of sync.

      I went on the net and discovered the location of the 'mono' switch from the manual (I am cheesed I didn't see it before), and discovered it was indeed in mono. So I switched it to stereo.

      I noticed in horsing around that my left paradigm was popping and sounding crunchy, but it was intermittent and assumed it was just distortion or a bad connection in my mixing console (Soundcraft!) or the music source (a cheap keyboard with a demo switch playing a hokey 80s tune).

      I never thought to check if my speakers were pumping in and out inaudibly at some subwoofer frequency, and now I wonder if I damaged them by allowing the voicecoils to cook!

      Because of this, and your posts here, I have come to the conclusion that Behringer warns not to turn up the right channel volume in mono mode for a really good reason. i.e., as you have noted, a some low subwoofer frequency, the feedback systems move out of phase, and you can get a feedback loop between channels or between speaker and amp (?!?)

      Because of this I see no good reason to use the unit in mono-mode, which seems like an ill-thought out kludge that should be avoided.

      On the other hand, I do suspect that if you use the mono mode, you should not only leave the right volume off, but also REMOVE the INPUT to channel 2! This seems to be a source in the phase/feedback problem.

      The amp probably works fine with only one music signal in channel 1, and with channel 2 turned completely off.

      I don't think driving 1 or 2 cabinets on one side or both will make any difference, but I wouldn't recommend you only hook drivers up to one side in mono mode. Something about output transistors with no load doesn't sound wise. There is a middle phone jack marked for mono use, and I think that if you want to use the amp in mono mode, you had better use this jack, and not the normal outputs, either the posts or the separate outputs.

      I suggest you use the mono output jack to ensure that both sides see a proper load, and if you want to hook up more than one speaker cabinet then use a y-chord or hardwire two speaker lines in parallel to a single phone jack.

      I hope this helps. No warrantees.
      My amp is now functioning fine in stereo mode, so I have no complaints about the price. I can pan inputs to both sides, and have effectively mono without any worries caused by risky hookups.

      In the past, I seem to recall that amps wired mono generally fail catastrophically more often than running channels separately, but that may not apply to the most recent designs.

  2. I have not run the Europower for any amount of time in bridged mode, but you should check the manual for how to do it correctly. It's been so long I don't remember. You should also get the same power with each channel driving individual VCs.

    I've never seen the Europower unstable, but it doesn't sound like you are talking about the same thing. It appears that you may not have set it up correct. Check the manual!

  3. Hi Paul,

    The thing is I had it set up exactly as Behringer recommends for bridged operation in the supplied manual, and I have checked to make sure I had it set up properly multiple times to see why it sounded so poor.

    Then I checked on some forums (not sure which one exactly) and that confirmed that I had it setup correctly. The thing is no matter where I looked (apart from the Behringer manual) there was almost no mention of Channel 2 gain, and I was surprised how much of an audible difference (in terms of response, not output) changing that made.

    Yeah I thought I would bridge the amp so I could control the sub output through the one gain control, but it is probably a good idea to try powering through 2 channels to see if there is much difference.

    The behringer manual says turn the channel 2 gain as far to the left as possible.

  4. Paul,

    Adding relays for the outputs isn't difficult or expensive. Apart from $10 for a pair of relays, there are only a few passives, couple of $ at most.

    The output oscillations you mention with the OB's make me think that the amp is faulty as it's design is very conventional

  5. Hi Paul

    Thanks for all the information on your website.

    I know you don't recommend using the A500 to drive subs. However, I fear that the EP2500 (and the EP4000 successor) might have too much power that will kill my sub.

    The sub is rated at RMS 180W - can the A500 handle it easily? Or can I get the EPs to match in output to the sub?


  6. For a single sub it's much easier to get a plate amp. You might consider an O Audio 300w or 500w - well designed and good value. The reason for using pro power amps is to get a lot of power for two subs cheaply but you need to add a crossover with some gain in it - a plate amp provides that. For one sub with moderate power demands you can't beat a plate amp.

    Also keep in mind that more amp power means headroom which is a good thing. For home theatre, excursion is the limiting factor. For music, that is where you can cook a driver with too much continuous power that eventually causes the coil to overheat. You avoid that by simply not running it for a long time at a high level. Having a lot more amp power than the driver thermal power rating means you can cook it, but sensible use will prevent that happening.

    It's like having a high powered car. A powerful engine doesn't make you drive at 250 kph!


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