2 settings every preamp owner should know and use

David Mellor

David Mellor is CEO and Course Director of Audio Masterclass. David has designed courses in audio education and training since 1986 and is the publisher and principal writer of Record-Producer.com.

Thursday April 5, 2018
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If your preamp has both gain and level controls, you have a way of getting just the right amount of warmth as you record.

Universal Audio Solo/610

Take a look at the photo above. It doesn't matter what make the preamp is, nor whether it has tubes or transistors inside (although tubes will work better for this tutorial).

What I am interested in here is that this preamp has both a gain and a level control. But surely that is duplication. Aren't gain and level just two words for the same thing?

Well no. Level is how much a signal measures in volts, or how it compares to full-scale 0 dBFS once it is inside your DAW. Gain is a change in level. Gain can be positive or negative, and if it is negative it can be referred to as attenuation.

In this preamp, the gain control is labelled correctly. But the level control should really be called attenuation. But we won't worry about this further and just accept the labels as they are.

Here is the block diagram of this preamp, the Universal Audio Solo/610

Universal Audio Solo/610 block diagram

What we can see here is that the gain control determines the gain provided by the first tube, which is a 12AX7 type. The level control however merely reduces the signal level before the final output tube.

So suppose you have a singer in front of your favourite microphone. You can control the signal level going into your DAW with either the gain control, or the level control, or both. So how should you set these controls?

Going back to the title of this article, I said there are two settings that you should know. And these are...

I can't give you precise values because it will depend on how loud your singer sings and the sensitivity of your microphone. But all you need to make sure either way is that you have a good strong signal level going into your DAW and that you never see a red light in the channel while you are recording.

Since this is a tube preamp, you will expect it to provide lots of lovely warmth, which of course is a nice word we use to mean mild distortion. The higher the gain setting, the more the 12AX7 is pushed and the more it will distort.

With the gain control you can find a setting that gives you just the right amount of warmth you need. But suppose that you start seeing the red overload light in the channel of your DAW. That would mean clipping and horrible distortion.

But the solution is simple - turn down the level. So the gain-high/level-low combination will give you the warm sound you want.

But suppose you want a cleaner sound - as clean as this preamp can possibly provide. Easy too - turn down the gain and compensate for the lower output with the level control. This is the gain-low/level-high setting that gives maximum transparency.

Of course, there is an infinity of in-between settings you can use, but these two extreme settings of this preamp's controls should be something you fully understand and know what to expect in terms of sound texture and warmth.

What if your preamp uses transistors rather than tubes?

In general, if you want warmth from your preamp then you should choose a tube model. Transistor preamps are normally designed for accuracy rather than warmth, and when a transistor preamp is driven into distortion it can sound quite harsh, or very harsh when pushed to extremes. However if the sound of transistor distortion is what you want, and your preamp has both a gain and level control, then exactly the same will apply as for the tube preamp described above.

What if your preamp doesn't have these controls?

You're going to have to find a way of lowering the signal level after the output of your preamp. Since the output of your preamp is connected to a line input of your audio interface, you might be able to turn down the gain here. Or any other equipment that has a line input with a gain or level control might work, with all of its other controls set to a neutral position. You will have to listen carefully however to make sure that the warmth is what you want and you haven't strayed into harsh distortion or clipping.

An important point to consider

If you add any warmth or distortion to your signal at a point in the signal chain before you record it, you can never go back to the clean signal. Adding warmth in this way is an artistic decision that will stay with you all the way through to your mix your Grammy award.

Summary

Where a preamp has both gain and level controls, you have a way of adding just as much warmth as you like to the signal as you record it.

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