Why the MixPre is the Best Microphone Preamplifier for the SM7B

Shure’s SM7B is an iconic microphone that has been used for voice over and vocals since its introduction in 1973. This classic microphone has experienced a popularity surge in the past few years due to its distinctive sound and look. Serious podcasters, in particular, love the SM7B. The SM7B exhibits a smooth, warm frequency response, good pop protection for close-talking, and like most dynamic microphones it can handle extremely hot signals. However, its output level is very low (-59dBV a 94 dB SPL).  With low level speech, the SM7B quickly reveals the limitations of many microphone preamplifiers. 

Noise

Enter the MixPre II Series. The compact MixPre recorders have some of the best microphone preamplifiers built into any gear, whether portable or studio. The MixPre’s ultra-low thermal noise of -130 dBV introduces very little added noise to a signal when used with an SM7B, or any other microphone. The extreme low noise of the MixPre preamp is one reason that it sounds so transparent.

Gain

The microphone preamplifiers in the MixPre provide a generous, and necessary, 76 dB of gain. When used with the SM7B, there is enough gain for any situation. There is no need to use ‘lifter’ type devices to add gain. In fact, these types of devices add more self-noise and degrade sound quality.

Frequency Response

The MixPre II Series has an extended frequency response, flat from 10 Hz to 80 kHz. This frequency linearity ensures that the sound of the SM7B is not changed at all, whether the microphone’s presence boost is engaged or the low cut is activated. Additionally, the low cut filter in the MixPre’s preamp can be used along with the microphone’s low cut to create a sharper, more dramatic reduction of low frequencies.

Headroom

The MixPre II Series can handle input levels up to +14 dBu, which equates to a signal level of 165 dB SPL at the SM7B capsule. This would be the equivalent of having the SM7B a foot away from a jet engine. Even with this extremely hot signal, it is impossible to clip the preamplifier of the MixPre. When set to 32-bit float mode, the MixPre II’s patented input and analog-to-digital converter topology has up to 142 dB of dynamic range, effectively the entire dynamic range of the microphone.

Limiters

For 16 and 24 bit recording and streaming, input limiters are helpful to prevent signal overload. The MixPre has analog limiters to prevent hot input signals from overloading a recording or USB signal. In live stream applications in particular, getting a high enough level from speech is important. If the signal is occasionally activating the limiter, it is just about right.

Recording or Streaming – Your Choice

The MixPre II Series can record internally to an SD card, so you can record with the SM7B without using a computer. This lightweight setup is a great option for recording on-location.  In addition to being a capable recorder, the MixPre is a flexible multi-channel USB audio interface. An SM7B connected to a MixPre is a great setup for podcasts and live stream productions. 

Headphone Amp

If a recording cannot be monitored and heard accurately, then it is hard to get the best sound out of a recording or a stream. The MixPre’s powerful and low-distortion headphone amp is one of the best-sounding headphone amps available on any piece of gear, and will drive any pair of headphones so you can hear the SM7B perfectly.

Size/Powering

The MixPre-3 II is incredibly compact and lightweight, measuring just 5.7” x 4.4” x 1.4” and weighing only a pound. It can be powered from USB, AA batteries, Li-Ion batteries, or AC power. The size and portability of the MixPre make it perfect for any mobile applications as well as studio work.

Conclusion

The MixPre II is the ideal all-in-one solution for driving an SM7B due to its ultra-low noise, transparent preamps. Although cheap preamplifiers are available, these will sacrifice the quality of the SM7B’s signal in the form of too much noise or not enough gain. Add in all of the other features a MixPre II offers — including recording, USB streaming, and a killer headphone amp — and you can see why the MixPre II Series is the perfect companion piece to the SM7B.