The Shure SM7B may have a reputation for needing lots of gain, but if you’re already clipping your converters then a lack of gain is not the problem!I’m planning to get a Cloudlifter to plug into an iRig Pre HD, which I connect to an iPhone for recording my acoustic songs with a Shure SM7B mic. Right now, I have to set the iRig preamp almost at its maximum gain to get a clean sound, but then it clips very easily on loud songs. Someone said that with the Cloudlifter you only need the iRig Pre gain to be set about halfway, which is plenty. I looked it up and the Cloudlifter adds 25dB of gain or “clean gain” (though I’m not sure what that means). And the iRig Pre can add 40dB of gain (I guess that’s when it’s maxed). So that would mean the iRig would have to be almost all the way up to get to 60, right? But everywhere it says SM7B needs 60dB of clean gain to run at its best. How come everyone says that setup is perfectly fine? Should I get a Rane MS1 or something so I can get to 60dB without having to go up much on the iRig? Also, I was wondering if a Focusrite interface is the same thing as this iRig, or if it is better somehow.
SOS Forum post
SOS Technical Editor Hugh Robjohns replies: First, there isn’t any need here for a Cloudlifter or other preamp: the SM7B is a fine mic, and the iRig is capable of making clean recordings. The second thing to point out is that context is everything when you read advice on the Internet! In a professional studio setup, the A‑D converters typically need a huge signal level before clipping, and to get the signal from an SM7B to peak around ‑10dBFS at the converter you really will need at least 60dB of gain, and maybe more, depending on how loud the source is. However, your recording system is very different, being based around an iPhone and iRig, which has a much more sensitive A‑D converter. Consequently, it needs a much lower input level to reach ‑10dBFS and it’s clear from what you say that the available 40dB in the iRig is more than enough in that context.
There isn’t any need here for a Cloudlifter or other preamp: the SM7B is a fine mic, and the iRig is capable of making clean recordings.
Note that clipping occurs when the signal level is too high for the electronics to handle. This might be because the signal coming into the preamp is too big, or it might be because the preamp is boosting the signal too much (the gain is too high) and it is either overloading itself, or the subsequent element in the signal path (such as the A‑D converter in the iRig, which turns your recording into the 1s and 0s needed for digital recording). If there’s no clipping with a low gain setting, the input signal is not too high. If it clips when you turn the gain up, the clipping is being caused by setting the preamp gain too high — you’re sending too much signal into the A‑D converter.
If you have enough gain on hand in the preamp to drive the signal into clipping — and you clearly do — then you don’t need to boost the input signal any further with a Cloudlifter (or any similar device). All that will happen if you add a Cloudlifter is that you’ll get clipping when you turn the iRig preamp gain to 5 (for example) instead of 10. And you will turn it to 5 because the signal still won’t be loud enough in your headphones!
You say that “the thing is it will not clip if I keep the gain lower around 8 or 7” so you already know how to make a good, clean recording: just set the gain to 7 or 8 (there’s no need to spend money on a Cloudlifter). The real problems that remain are that: (1) the mic signal doesn’t sound loud enough to you through your local monitoring while recording at a sensible level; and (2) neither does it sound as loud as commercial recordings to your friends when they play the files. It’s important to understand that these are separate issues which need to be addressed separately.
To improve your local monitoring volume, you either need more sensitive headphones, or an external headphone amplifier of some kind. That way, you’ll be able to hear yourself at your preferred headphone level when the iRig preamp gain is set to 7 or 8, and the mic signal is peaking at ‑10dBFS or so in your clean recording.
To make the recording sound like other commercial files, for your audience, you need to process the raw recording like commercial recording companies do. Basically, that means it needs to be compressed, and possibly limited, and you do that using Digital Audio Workstation (DAW) software of some kind. Most people do that in a computer, but there are phone apps that can help too. GarageBand or Cubasis might be good places to start, for example, though there are plenty of other options for the iPhone.
Start by setting the compressor ratio at 2:1 or 3:1, with a medium attack, 300ms (or auto) release, and adjust the threshold until you’re seeing up to 4‑6 dB of compression on the meter at the louder points in your recording. This will make the loudest bits quieter, and you can then adjust the makeup gain to raise the overall level to just below 0dBFS. A limiter is just a very assertive compressor, and after initial compression one of these can help you bring the average level up a bit higher — though if you push it too far you’ll start to hear side‑effects.