Microphone preamplifiers are essential for electrical recording. Microphones output mic level signals [60 dBV (0.001 volt) to -40 dBV (0.010 volt)]. Electrical analog (and analog's conversion to digital) recordings run at line level [0 dBV (1 volt)]. Therefore, in order to properly record, mix, and ultimately use microphones, we need microphone preamplifiers that amplify mic levels signals to line level signals.
Microphone preamplifiers work by taking electrical energy from an external power source and using that electrical energy to amplify an inputted mic level signal. Mic Preamps also provide common-mode rejection for balanced audio signals from microphones, and sometimes offer phantom powering, phase flip switches, filters, pads, and other beneficial signal processors.
Choosing the right microphone preamp depends on your situation. However, with that said, I will recommend what I believe to be the top 3 microphone preamps for the situations I see the most often. They are:
- Cloud Microphones Cloudlifter CL-Z: The Cloud Microphones Cloudlifter CL-Z (link to check the price on Amazon) is the single channel mic preamplifier from Cloud Microphone's Cloudlifter line. This simple preamp looks more like a DI box than a typical
preamp, but works extremely well by delivering up to 25 dB of clean gain. The CL-Z is phantom powered, though it doesn't pass phantom to its microphone. CL-Zs are ideal for bringing quiet signals from low-sensitivity dynamic and ribbon mics up to workable levels before an audio interface or even another preamplifier. - True Systems Precision 8: The True Systems Precision 8 (discontinued) is an 8-channel preamp design with incredible transparency. Each of the Precision 8's preamps features full phantom power, phase invert, and 16 – 64 dB of gain for mic inputs or -4 – 44 dB of gain for direct inputs. I recommend the True Precision 8 for its sonic purity and amazing price.
- ART TubeOpto 8: The ART TubeOpto8 (link to check the price on Amazon) is an excellent jack-of-all-trades tube preamp at a very affordable price. This unit features 8 high-quality discrete Class-A vacuum tube mic preamps in one compact unit with an integrated 8-channel 24-bit digital I/O. Each of the preamps also features up to 64 dB of clean gain for mic input and up to 36 dB for instrument input. They also feature an adjustable output level, pad, high-pass filter, and phase invert options. At an affordable price, the TubeOpto 8 by ART gets a top recommendation from me as a microphone preamplifier.
Before getting into each of the above microphone preamplifiers, let's talk about the specs that make for a great mic preamp.
Related reading:
• What Is Microphone Gain And How Does It Affect Mic Signals?
• What Is A Microphone Audio Signal, Electrically Speaking?
• Do Microphones Output Mic, Line, Or Instrument Level Signals?
• How To Connect A Microphone To A Computer.
What Makes A Great Microphone Preamplifier?
- Clean gain: Clean gain is by far the most important criterion when choosing a mic preamplifier. Mic signals are low in level and require a lot of amplification for use with mixing consoles and digital audio workstations. Choose a mic preamp that will provide enough gain to boost mic signals properly and that will no add noise to or overly colour the mic signal.
- Number and type of inputs: Select a preamplifier with enough inputs (both mic and line) to effectively do the job it's required to do.
- High input impedance: Pick a mic preamp with a high enough input impedance. The input (load) impedance of a mic preamp must be much higher (at least 5-10 times) than the output (source) impedance of the microphone that feeds it.
- Phantom power: Pick a preamp that is able to supply full professional phantom power (48 volts DC) to its connected active microphones.
- Pads: Though not necessary, it's a benefit to have passive attenuation devices in a mic preamp to help control input levels that are a bit too strong.
- Filters: Again, a nice benefit to filter (especially high-pass filter) signals that require filtration in a preamp before amplification.
- Phase Flip: Sometimes audio signals need to be flipped in order to become phase coherent with the other signals in a mix. Doing so at the preamp level will help to “print” a more cohesive mix with less post-preamp processing.
- Internal A-D converter: It is sometimes a nice bonus to have an interface built-into the mic preamp (or a preamp built-into an audio interface). This combination eliminates an extra piece of gear from the DAW recording setup. When choosing a preamp/interface combo, picking an A-D converter with professional specs in bit depth, sample rate, and latency is important.
So this is a good quick “buyer's guide” for mic preamps. Let's see how each of my recommendations stacks up against the above criteria.
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The Cloud Microphones Cloudlifter CL-Z
The Cloud Microphones Cloudlifter CL-Z Mic Activator is a high-quality single channel mic preamp and part of Cloud Microphones' flagship product line of Cloudlifters. Unlike the other Cloudlifter models, the CL-Z features very useful variable input impedance and an optional high-pass filter switch.
This “mic preamp” is designed as an in-line amplification device between moving coil and ribbon dynamic mics and their mixers, interfaces, or preamps. It simply boosts the input mic level signal and outputs an clean and clear amplified signal.
The CL-Z really is simple. One mic input and one mic output (XLR). The Cloudlifter CL-Z adds gain to the signal with its phantom powered patented Class A, discrete JFET circuitry. Sending full phantom power to the Cloudlifter will result in 25 dB of beautifully clean signal gain.
Let's talk a bit more about this somewhat unorthodox mic preamp recommendation.
Gain Of The Cloud Microphones Cloudlifter CL-Z
There are two gain options with the Cloud Microphones Cloudlifter CL-Z: “more” (+12 dB) and “max” (+25 dB). These gain values are achieved by supplying its internal JFET amplifier with full 48V phantom power. The gain of the CL-Z is super clean and clear.
Most quality phantom power sources will supply the full 48 volts DC, which will allow the CL-Z to boost its mic signal by the full 12 or 25 dB. Less phantom power would mean less gain.
I'll mention here that phantom power will power the internal circuitry of the CL-Z but will not be sent through to the microphone on the other end. The CL-Z is designed for use with dynamic mics that do not require phantom power and can even suffer from applied +48V.
Inputs Of The Cloud Microphones Cloudlifter CL-Z
The Cloudlifter CL-Z has only one input.
The Cloud Microphones Cloudlifter line features the CL-1, CL-2, and CL-4, which feature 1, 2, and 4 inputs respectively. However, the variable input impedance version (CL-Z) only comes with a single input.
Input Impedance Of The Cloud Microphones Cloudlifter CL-Z
The Cloudlifter CL-Z features variable input impedance. One knob will continuously vary the input impedance from as low as 150 Ω all the way up to 15 kΩ.
With the CL-Z's variable input impedance, we are able to properly bridge any dynamic mic with its manufacturer-recommended load impedance. On top of that, we may get creative with the input impedances to alter the sound of our microphones in new and musical ways.
Changing the input impedance will shape the sound of the mic signal at the most basic electrical level. Lower load impedances yield a thinner sound (more current, less voltage) while higher load impedances yield a thicker sound (more voltage, less current).
Phantom Power Supply Of The Cloud Microphones Cloudlifter CL-Z
The Cloudlifter CL-Z does not supply phantom power as it is designed for low-level passive dynamic microphones that do not require phantom power.
However, the CL-Z does require phantom power in order to power its patented Class A, discrete JFET amplification circuitry.
Pads Of The Cloud Microphones Cloudlifter CL-Z
The Cloudlifter CL-1 does not feature any pads. That being said, there are two gain options (+12 dB and +25 dB), and so we could think of the CL-Z as having a 13 dB “pad switch.”
Filters Of The Cloud Microphones Cloudlifter CL-Z
The Cloudlifter-Z has a switchable -6dB per octave high-pass filter. When engaged, the HPF's cutoff works continuously in tandem with the variable impedance control for even greater tonal shaping. The cutoff frequency is variable from below 20 Hz to well above 200 Hz.
For more info on high-pass filters, check out the following My New Microphone articles:
• What Is A Microphone High-Pass Filter And Why Use One?
• Audio EQ: What Is A High-Pass Filter & How Do HPFs Work?
Phase Flip Of The Cloud Microphones Cloudlifter CL-Z
The CL-Z does not feature a phase flip switch.
Does The Cloud Microphones Cloudlifter CL-Z Have An Internal A-D Converter?
The Cloud Microphones CL-Z is a purely analog device with no A-D or D-A converters.
The True Systems Precision 8
The True Systems Precision 8 microphone preamplifier unit is my personal favourite and the one I'm the most familiar with. This analog preamp 8-channel preamp unit has extraordinarily clean gain all the way up to 64 dB and really allows any microphone to shine. Each of the 8 preamp channels features independent 48V phantom power, continuous gain control, and phase flip as well as excellent metering.
True Systems is featured in My New Microphone's Top Best Microphone Preamplifier Brands In The World.
One feature that I really like about the Precision 8 is the mid-side encoding on channels 1-2. This really helps in capturing the mid-side technique at the source rather than waiting until after recording to process the signals properly.
Let's talk about some of the specs that make the Precision 8 so great.
Gain Of The True Systems Precision 8
As mentioned, the Precision 8 preamps offer up to 64 dB of clean gain.
Each of the 8 mic preamps will boost their mic signals anywhere from 15.5 to 64 dB. The gain knobs allow for continuous but accurate gain application.
As for the DI options (in channels 7 and 8), the Precision 8 offer -4 to 44 dB of clean gain.
This is more than enough gain to boost both low-out passive mics and high-output active mics up to line level for further processing. The True Systems Precision 8 does so with minimal colouration to the signal and barely any noticeable noise.
Inputs Of The True Systems Precision 8
The True Systems Precision 8 features 8 mic XLR inputs.
Channels 1-6 are purely XLR mic inputs (pin 2 is positive, pin 3 is negative, pin 1 is shield).
Channels 7-8 have dual-purpose inputs. Inserting XLR microphone connectors makes for normal operation of channels 7-8. Inserting 1/4″ phone plugs (tip-sleeve) causes channels 7-8 to act as direct-input “instrument” preamps. DI-1 and DI-2 are controlled by the gain and phase controls for channels 7 and 8, respectively.
A Note On Outputs
The Precision 8 features 8-channel DB25 and 8 individual TRS outputs. Both output types are electrically equivalent and may be used simultaneously to connect to Line Inputs on mixing consoles, recorders, etc.
Input Impedance Of The True Systems Precision 8
The input impedance in each of the True Systems Precision 8's mic preamps is 5.5 kΩ. This is fairly universal rating for a microphone preamp input impedance. The vast majority of professional microphones will fair well and sound great with this load impedance.
The DI input impedance (if we so choose to use channels 7-8 as DI) is given as 2.5 MΩ, which is perfectly appropriate for those signal types.
Phantom Power Supply Of The True Systems Precision 8
Each of the 8 preamps in the True Systems Precision 8 is capable of individually providing full +48V phantom power. 48 volts DC is the ideal standard for phantom power and will run most professional active microphones (and the aforementioned Cloudlifter CL-Z).
Pads Of The True Systems Precision 8
The True Systems Precision 8 does not feature any passive attenuation devices (pads).
Filters Of The True Systems Precision 8
The True Systems Precision 8 does not feature any switchable filters.
Phase Flip Of The True Systems Precision 8
Every channel of the True Systems Precision 8 has a phase inversion switch. This helps tremendously in capturing phase coherent recordings at the source.
Does The True Systems Precision 8 Have An Internal A-D Converter?
The True Systems Precision 8 is an analog device and does not feature any analog-digital or digital-analog converters.
The ART TubeOpto 8
The Applied Research and Technology (ART) TubeOpto 8 gets a top recommendation from me because of its beautiful tube sound and excellent A-D/D-A conversion at a very reasonable price. The TubeOpto 8 features 8 high-quality 2nd gen discrete Class-A vacuum tube microphone preamps in a single rack space unit with eight channel 24-bit digital I/O.
ART is featured in My New Microphone's Top Best Microphone Preamplifier Brands In The World.
The TubeOpto 8 features mic, line, and instrument level inputs. It also has 8 balanced outputs on 6.3 mm jacks (switchable +4 dBm / -10 dBV). Additionally, it has 8 inputs / outputs on ADAT optical ports (44.1 kHz or 48 kHz at 24-Bit).
All-in-all, this “preamp” sounds great and is very versatile. There's a lot going on with this unit, so I'll stick to the short list of criteria we've been discussing thus far.
Gain Of The ART TubeOpto 8
The ART TubeOpto 8 has 8 fully featured class-A vacuum tube mic preamps with input gain and output level control on each of these 8 channels.
The max preamp gain for mic level signals is given as 64 dB while the max preamp gain for instrument level signals is 36 dB.
The “tube” gain of the ART TubeOpto 8 does not overly saturate or colour the signal at higher gain values, though it does add that “tube sound” that is often sought after in audio equipment.
Inputs Of The ART TubeOpto 8
The ART TubeOpto features the following inputs:
- Mic/Line combo jacks 1-8
- Hi-Z instrument input options in channels 1-2
Each of the inputs features the following options:
- Gain control
- Pad
- High-pass filter
- Phase flip
- Output level control
Input Impedance Of The ART TubeOpto 8
The input impedance of each of the ART TubeOpto 8 inputs depends on the signal they are expecting. Here are the given input impedance values:
- Mic (XLR input in combo jack 1-8): 6.4 kΩ
- Line (TRS input in combo jack 1-8): 20 kΩ
- Instrument (TS input on front jacks 1-2): 2.5 MΩ
Each of these values provides more than enough load impedance for the vast majority of the professional equipment (at mic, line, and instrument level).
Phantom Power Supply Of The ART TubeOpto 8
The ART TubeOpto 8 does supply full 48V phantom power though it does send it through individual channels. Instead, this unit has two phantom power switches, which engage or disengage phantom power on channels 1-4 and 5-8.
Pads Of The ART TubeOpto 8
Every channel of the ART TubeOpto 8 has a pad. These pads will affect the mic and line inputs but not the instrument inputs. Though there is no specified attenuation value, I believe the pads attenuate 20 dB.
For more information on passive attenuation devices, check out my article What Is A Microphone Attenuation Pad And What Does It Do?
Filters Of The ART TubeOpto 8
Each channel of the ART TubeOpto 8 has a high-pass filter. These HPFs are set at an 80 Hz cutoff frequency and filter sound at -6 dB/octave.
Engaging these HPF helps to rid of low-end rumble and electromagnetic interference without overly thinning the audio signal.
Phase Flip Of The ART TubeOpto 8
Every channel of the ART TubeOpto 8 has a phase inversion switch. This helps tremendously in capturing phase coherent recordings at the source.
Does The ART TubeOpto 8 Have An Internal A-D Converter?
The ART TubeOpto 8 is the only preamplifier on this list that has internal analog-to-digital and digital-to-analog converters.
I was initially hesitant to add A-D preamps on this list as we're bordering on “audio interfaces” here. However, the ART TubeOpto 8 isn't a simply plug-n-play interface with a computer, so I figured I'd list it here.
The ART TubeOpto 8 features 8 channels of ADAT lightpipe digital 24-bit audio I/O at 44.1 or 48kHz. It is an ideal 8-channel input / output expander for any ADAT lightpipe equipped audio interface, direct-to-disc recorder or digital audio workstation.
It also has word clock input and passage.
As for latency, we're looking at the following specs for the TubeOpto 8:
- A/D Latency: 0.667ms(48KHz), 0.725ms(44.1KHz), 32 samples
- D/A Latency: 0.458ms(48KHz), 0.500ms(44.1KHz), 22 samples
The Recap
So if you're using microphones to record, you'll need some sort of microphone preamp. My top recommendations are universal preamps that work wonderfully with professional microphones and I think you should consider them for your audio recording or live sound reinforcement applications. Once again, my top 3 microphone preamplifiers are:
- Cloudlifter CL-Z: Recommended in-line single channel microphone preamplifier.
- True Systems Precision 8: Top recommended multi-channel analog microphone preamplifer.
- ART TubeOpto 8: Recommended due to its great price point, tube preamps, and analog-digital capabilities.
For all the My New Microphone mic/gear recommendations, please check out my page Recommended Microphones And Accessories.