Gain staging with SSL SiX and 2+

[Pat Waara]

I've been having some weird level problems with my recording setup (input levels seem inconsistent between sessions), which make me start thinking about my gain staging, particularly, between my SSL SiX mixer and my SSL 2+ audio interface. I have the mute/bus B sends going from my SiX to the inputs of my 2+, and the inputs of the 2+ have the line button depressed (on). My original thinking was I wanted to minimize the effect of the mic preamp in the SSL 2+. so I set the gain levels of the interface to 0 (completely counter-clockwise.) I have plenty of headroom in the SiX gain knob and channel faders to feed a strong signal to the 2+. Now I'm wondering if this is the best setup. First, does anyone know for sure if turning line level on the 2+ bypasses the mic preamp? I don't think it does. Second, should I have some gain level on the 2+? When you have multiple gain stages in your signal (e.g., instrument input, mixer gain and fader, audio interface gain, DAW gain), what is the best balance between each of them? My thinking was keep each stage as close to unity you can and get a strong signal, but what is unity on the audio interface, for example. Is it 0 (completely counter-clockwise) or at the mid-point (12 o'clock)? Any advice and guidance is greatly appreciated.

[KuruPrionz]

First, judge the actual gain of your audio chain by the meters on your DAW. Ignore the meters on your gear, too many variables and in the end what matters is the recording stage.

 

Next, do some homework. Since you have a question - does line level on the the 2+ bypass the preamp? - test it and see. If it does bypass the preamp, your gain controls for the preamp should not affect anything.

Leave the settings on the SIX the same, watch the meters on your DAW and attempt to adjust the gain levels on the 2+ while it is set for Line In. If the meter settings on the DAW do not change when you attempt to change the gain levels on the 2+, you have your answer - the preamps are bypassed and you are operating at Line Level which is usually set on an interface and cannot be a variation in gain staging.

 

That simplfies things. You can experiment with low gain levels at the inputs of the SIX and higher output levels and compare that sound to having higher input levels and lower output levels. Use a consistent sound source for the experiments, maybe run the Demo on a keyboard or drum machine through an amp and mic that. Or you could record a track, burn a CD and then mic the playback on your stereo. In both cases, leave the volume of the amp or stereo in the same place and do not move the microphone. That way you'll have something consistent to use for judging results.

 

Last but not least, try that same experiment using just the 2+ with the same mic in the same place and the same volume on the source. Turn up the gain on the mic pre until the meter on the DAW matches what you had when you were using the SIX.

 

You may find that you have 3 different but useful sounds there. That can be useful when you want to add backup vocals, a second guitar, etc.

[Mike Rivers]

I have the mute/bus B sends going from my SiX to the inputs of my 2+, and the inputs of the 2+ have the line button depressed (on). My original thinking was I wanted to minimize the effect of the mic preamp in the SSL 2+. so I set the gain levels of the interface to 0 (completely counter-clockwise.)

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The cardinal rule of gain staging is to get the input signal up to the system's internal operating level (generally close to "line level") as soon as possible and keep it in that ballpark. I see that this is your thinking, and that's good. You will have enough gain range to make small changes in level (6 dB or so) for balance when you're mixing several sources to one output, and to accommodate for more or less gain through a signal processor like EQ or a compressor. Use the channel input gain on the SIX to set this level. Press the PFL button and watch the channel meter. Set the gain for an eyeball average a bit above 0 on the channel meter. Make sure it doesn't go much above +10 when you think you've found a peak (there may be a higher one) or spend too much time below -10.

 

Now, set the channel fader to it's 0 position. This gets the signal out of the SIX's mic preamp up to the proper internal level.

 

I get why you want to use Bus B to feed the 2+. It has an independent output level, and by use of the Mute buttons, if you have several things plugged into the SIX's inputs, you can select the one or ones you want to send to the 2+ for recording. This is a good idea. For starters, set the BUS B output level knob to it's 0 position.

 

The 2+ doesn't have a mark on its input gain control to indicate "unity gain" so you'll need to rely on its meter. With a normal signal coming through, adjust the 2+'s input gain so that you don't go above -10 very often. Be aware that when the 2+ meter hits 0, you've reached clipping and you want to avoid that. This should give you the best signal-to-noise level through the system, and keep you in a safe headroom region.

 

First, does anyone know for sure if turning line level on the 2+ bypasses the mic preamp? I don't think it does. Second, should I have some gain level on the 2+?

 

Turning down the level definitely doesn't bypass the preamp, it just just sets it for minimum gain, and you rarely want that. Use the gain control for what it's for. I think that the Instrument input does bypass the preamp, but it's unbalanced and it's designed to operate at a lower level than the nominal output of the SIX. Use the line input and adjust the gain accordingly.

 

My thinking was keep each stage as close to unity you can and get a strong signal, but what is unity on the audio interface

 

You could test it, or ask SSL, but as long as the DAW input gain is at its nominal 0 level, the DAW level meter should correspond to the channel meter but give you more resolution in the critical -10 to 0 dBFS range. So keep an eye on the DAW meter when setting the channel gain on the 2+.

 

This should fix you up.

[Pat Waara]

Thanks for the feedback, Kuru and Mike. Sometimes you just have to stop a second, take a step back, and think about what you're doing for things to clear up. Mike, your advice is spot-on about not setting the 2+ input to 0. I'm not sure what I was thinking there. (Again, pause, step back, think.) It now seems obvious to me that I need to set the input gain on my SiX such that, with the faders at 0, that my meters are reading about 0 dB for the given recording source. I can then set the gain on the 2+ such that they also read about 0 dB. At that point, I should have a nice clean signal going into my DAW. I had confused myself by reasoning I did not want the effect of two mic preamps in my signal chain, thus keeping the gain low on my 2+ would minimize its impact, which is not true. However, I went to the source and asked SSL about the mic preamp when using the line in. This is what they said,

 

Thanks so much for reaching out. When you go in via the 1/4 input on the 2+ and hit the line button - you are bypassing the preamp. The 4K button however works for both inputs since it is after the preamplifier.

 

That makes me feel better about the signal chain.

 

The gain staging question came up because I recently purchased a Townsend Sphere L22. It works by recording a stereo signal from a front and back mic. There's a calibration step where you need to have the front and back mic at the same level, so that means I need to set six levels (three on channel one and three on channel two) to match the levels. I was getting some weird behavior trying to match the levels which made me trace my signal path and gain staging. I think I've got it all straightened out now. Thanks for the help and feedback.

 

Once I get some more experience with the Sphere L22, I will likely make a post about it. It's been reviewed to death, so I will probably focus on how it has helped me personally with my recording. (Spoiler alert: so far, so good.)

[Dr Mike Metlay]

I would love to hear your thoughts, Pat! I write online articles for Townsend Labs now and again; they're truly fine folks.

[Pat Waara]

I would love to hear your thoughts, Pat! I write online articles for Townsend Labs now and again; they're truly fine folks.

 

After I get some more experience with it, Mike, I will gladly report back. I will most likely start a new thread for it. Hopefully, sooner than later.