Internet forums are filled with threads discussing the compatibility of the Shure SM7B with regular computer audio interfaces. Many claim that the mic preamps in most audio interfaces may not offer enough gain to amplify the SM7B to an adequate recording level. Musical equipment retailers have also latched onto this idea, with many offering the mic in bundles with small phantom powered JFET-amps that bump up the Shure SM7B’s output level by 20 or 30 dB. Products often mentioned in this context are the Cloud Cloudlifter, the Triton FetHead or the Thomann FetAmp to name only a few.
I decided to test how my Focusrite Saffire 6 USB got to grips with the SM7B’s output level, by first recording a bit of acoustic guitar strumming using the interface’s own mic preamp, after which I recorded the same passage using Thomann’s FetAmp between the Shure and the Focusrite.
I found that I really had to add a lot of gain on the Focusrite’s mic preamp (around 90% of the available gain) to get a healthy recording level out of the SM7B without the additional in-line amplifier. Despite the hefty gain level the recording sounded very good and wasn’t hissy or distorted in any way.
Inserting the Thomann FetAmp in the signal chain did make it much easier to get a good recording level out of the Shure SM7B. I only had to add approximately 25 to 30 percent of the Focusrite’s own mic preamp’s gain reserves. In terms of sound I could hardly make out any difference between using only the audio interface and adding the in-line amplifier.
To sum things up, I’d say that a decent audio interface should offer enough gain to work smoothly with the Shure SM7B. On the other hand, the signal boost that one of the relatively affordable in-line amps will bring to the table will make recording the SM7B noticeably easier.