What are the trim knobs on a DJ mixer? What is the purpose of trim knobs? How to use the trim knobs on a DJ controller? The proper use of gain/trim knobs on a DJ mixer is a pretty important matter. Did you know that you can use your trim knobs for more than just simple gain control? In this article I’ll go over the most common uses of gain/trim knobs on a DJ controller and how to set them properly.
Gain / trim knobs vs. volume faders on a DJ mixer
Gain/trim knobs and channel volume faders might seem like they do the same thing, but they work at different points in the signal chain. The gain/trim knob sets the input level of the channel before the channel fader, while the volume fader controls how much of that already adjusted channel is sent into the mix.
In general mixer volume faders (the volume control faders in the middle section of your mixer) are used only when you’re actively performing a transition between two or more tracks. In most styles of DJing, you don’t normally use your volume faders for general gain control or trim corrections when one track is louder than the other (as you do with gain/trim knobs).
If you’re still getting familiar with the rest of the controls on your mixer, I’ve explained the main parts of a DJ controller here.
In a typical mix, you’ll usually have the channel fader fully up once a track is playing at its normal level, and use it mainly for transitions or other deliberate volume changes. If one track is simply louder or quieter than another, the gain/trim knob is generally the better place to correct that difference.
When one of your tracks is much quieter than the others, or you find that one of your songs is significantly louder than the others you want to use the gain/trim knobs on your mixer. These knobs are meant to be used for track volume level corrections when there is a noticeable difference in loudness between two or more tracks.
You can use them both to correct the track levels and to make sure that your tracks won’t clip. The gain/trim knobs are one of the most important elements of a DJ mixer – you should simply think of them as separate volume control knobs for each mixer audio channel, enabling you to correct volume differences between tracks without the need to touch the master volume knobs or channel volume faders.
So the quick summary is:
- Gain/trim knobs – set and correct the pre-fader level of each mixer channel.
- Channel volume faders – control how much of each channel is sent into the mix and are commonly used during transitions.
Of course there are always some exceptions when it comes to using volume faders only for transitions and for specific mixing techniques, as many DJs can have different preferences. On some older DJ equipment (especially older simplified entry level DJ mixers) there might not be any gain control knobs at all (although that’s pretty rare). Then you would be forced to use the mixer faders for direct channel gain control.
Anti-clipping measure for DJs
First of all, the gain/trim knobs on an audio mixer are there to help you ensure that your tracks don’t clip. Clipping happens when an audio signal is pushed beyond the maximum level a particular stage of your audio chain can handle. The peaks of the waveform get cut off, which results in audible distortion and loss of dynamics. When audio starts clipping, you will experience crackling, distorted audio, greatly reduced audio dynamic range and on some sound systems. A heavily clipped signal played loudly through a sound system can also put unnecessary stress on the speakers.
How to prevent audio clipping during your DJ set? There are two elements of a DJ mixer that will help you deal with clipping – level meters and gain/trim knobs. The level meters – sometimes casually called VU meters – are the LED indicators that let you monitor the signal level of each channel. The gain/trim knobs you already know.
As a rule of thumb, avoid keeping your channel levels in the red. A brief peak isn’t automatically a disaster on every mixer, but constantly redlining gives you less headroom and increases the chance of clipping that you often won’t be able to hear straight away especially when you’re facing the back of a very large, high-powered sound system.
The exact meter scale differs between mixers and controllers, so there isn’t one universal dB number that applies to every device. In general, set your trim so the loudest parts of the track sit comfortably below the clipping/red area while still giving you a healthy signal level.
Use the level meters as your main reference and your ears as a second check. Don’t wait until you can clearly hear distortion before backing the gain down.
Trim knobs level balancing (gain staging)
As mentioned above, one of the primary uses of the gain/trim knobs is gain staging – setting the audio levels on your mixer channels in a way that they are all balanced and don’t exceed the desired audio volume output levels.
Different tracks can have noticeably different perceived loudness because of the way they were recorded and mastered. This is especially noticeable when mixing music from different eras, genres or releases.
Using gain / trim knobs on your DJ mixer or a DJ controller, you are able to manually balance the maximum volume of your tracks, so that when you play them one after the other, there won’t be any drastic changes in volume between them.
Autogain and auto trim features
Auto Gain is a software feature that automatically applies a gain correction when you load a track, based on the loudness information calculated during track analysis.
Serato, Rekordbox, Traktor and VirtualDJ all have their own versions of this feature. It can do a good job of getting differently mastered tracks into roughly the same ballpark before you start mixing.
I still wouldn’t completely forget about the gain knobs, though. Auto Gain isn’t perfect, and using multiple decks, EQ boosts, effects or unusually dynamic tracks can still change your levels quite a bit. Keep an eye on the meters and correct the gain manually when needed.
How loud should you really go when mixing live?
A general rule during any kind of gig or performance, is that it’s almost always better to start out with a little bit less volume and then gradually build up to your desired sound output level over time. It is always better to hear “hey, turn it up!” than “could you please take it down a notch”. Setting your master or channel levels too high can introduce clipping and distortion long before the sound system actually needs more volume.
An exception would be any kind of music festival or DJ competition during which the main sound output and PA systems are managed by audio engineers live. In that situation, your job is mainly to send the sound engineer a clean, unclipped and reasonably consistent signal and follow their instructions regarding your output level.
The conclusion – trim knobs / gain knobs on a mixer
Trim knobs or gain control knobs are present on most audio mixers and DJ controllers. They are used mainly for:
- Level balancing / gain staging.
- Preventing mixer audio channel output from clipping.
Most major DJ software also offers some form of Auto Gain that can, to a certain degree, automatically compensate for loudness differences between analyzed tracks. It’s useful, but you should still keep an eye on your channel and master level meters and make manual corrections when needed.
Remember to watch your levels, don’t redline and stay cool! Rock on!