If you’re an audio engineer, you’ve probably noticed the 500 series versions of your favorite gear.

But what exactly does this mean? Given the choice, why do some people select the 500 series, and some purchase the standard rack mount versions? There is so much debate on this topic. So today, I’ll go into what I’ve learned so far about the pros and cons of 500 series versus rack mount gear.

What is the 500 Series?

So, we all know what our standard rack mount gear looks like, but what makes something a 500 series device? 500 series gear was originally created by API, and can be things like compressors, EQs, and preamps. They created small versions of gear like this:

And built them so that you can mount multiple pieces of this type of gear (generally 2-10 pieces) onto one rack mountable or freestanding chassis, like this:

You might have heard this chassis being called a “Lunchbox”, which is the term that API assigned to it. On the most basic level, the chassis holds the units, supplies power to the units, and supplies input and output routing to each unit that you snap into it. A fancier chassis might have additional options such as stereo linking, and extra routing choices or summing capabilities for the multiple units hooked into it.

As 500 series gear became more popular, other companies jumped into the 500 series game. To get into that sector of the market, they often just adapted full size versions of their gear into smaller versions that are compatible with API’s 500 series format. Nowadays, with the commercial success of 500 series gear, you can find a wide array of gear options in the 500 series format.

So what’s the Difference?

500 series units have a lot of advantages, mostly having to do with convenience and flexibility. First of all, the compact nature of these 500 series modules makes them easier transport. This has made them easy and convenient to bring to something like a mobile recording session. You can also mix and match a variety of gear into a smaller and more convenient space. With more gear easily within reach, this can be good for both ease of use, ergonomics, and for space saving purposes. The individual 500 series units will also easily pop into and out of the chassis, without any cables or patching. So they’re conveniently swapped out to fit your whim.

They’re also cheaper. I mean, sure, you have to purchase the chassis. But once you’ve purchased that, the individual units are much cheaper than their full sized counterparts. Overall, a chassis containing multiple 500 series units will be cheaper than the standard versions of those same units.

Great! So why would anyone pick the full sized gear?

Well, here’s where this becomes more of a debate. Many engineers argue that comparable 500 series gear will sound just as good as the full size gear. Other engineers argue that there are subtle differences, and will often purchase the full size gear because of these perceived differences. I mean, just take a look at a Gearslutz thread on the subject, and you’ll see how heated the debate can get. Unfortunately, there aren’t very many readily available A/B tests on this subject, but if you find one, I’d love to see it! I personally haven’t done an A/B test, so I’m not going to pretend to make a sound quality argument one way or another.

However, I do think we can use logic to approach the argument. There are inherent differences, and people wonder what is sacrificed with 500 series gear to hit the lower price point. There is one big difference that some engineers argue affects the quality; with 500 series units, you have multiple units sharing the same power supply. This means that the power supply is sometimes different than the full sized gear version. People in favor of full sized gear argue that the 500 series gear tends to have lower voltage than the full sized gear, and this can lower the quality of your audio output. Of course, drawing the conclusion that the 500 series has lower voltage depends heavily on the specific 500 series unit in question, and varies based on manufacturer. Taking it a step further and arguing that the lower voltage affects audio quality is another step entirely.

Some people argue that the components in 500 series gear might be “cheaper”, which can affect quality. That makes sense logically, the 500 series is built for a lower price point. But again, those components will vary based on manufacturer, so you can’t really make a blanket statement about it. Some engineers say that some of their 500 series version of their gear works just fine, but might distort a little more easily, or behave slightly differently, while other 500 series versions of their gear work just as well as the original. Again, that makes sense. The 500 series gear had to be redesigned to fit the chassis standard, so of course they might behave slightly differently!


My conclusion is that with everything varying on manufacturer, there is no concrete conclusion on sound quality. With that said, I think it’s fine to use 500 series gear professionally. Many of the top studios that I’ve been in use both standard and 500 series gear, and no one seems to complain. Plus, the 500 series versions work fine from my experience. If you’re trying to make a really thorough purchasing decision, you could call the manufacturer and ask them about the differences between the standard and the 500 series versions of the gear in question, and make the decision from there.

But you know, it’s such a hotly debated topic, and we know the variables that affect sound quality are dependent on the manufacturer and specific gear. Plus, no one seems to concretely agree on whether sound quality is sacrificed with 500 series gear. This leads me to believe that, logically, the answer is that in at least some cases, it’s not. After all, even some engineers that argue that there is a difference will tell you it’s not significant enough to avoid purchasing the 500 series. Maybe the argument is more of a principles argument, and isn’t as practically relevant as some might lead you to believe? So I’d say go for it, and get some 500 series gear. Just make sure you do your proper research before purchasing. But you already know that you should research all your gear purchases, right?

Questions? Comments? As always, please share in the comments below!