Cloud Microphones CL-Z Cloudlifter Z Variable Impedance Mic Activator

Phantom powered variable impedance gain booster for ribbon and dynamic microphones

by Phil O'Keefe

Ribbon microphones have seen a tremendous resurgence in popularity over the last ten or fifteen years as more and more engineers and recordists have discovered how well they work with modern digital recording systems. However, ribbon mikes (and to a lesser extent, moving-coil dynamic microphones) are not without their problems; several of which the Cloudlifter Z (Figure 1) was intended to address.

I CAN'T HEAR YOU

One of the biggest issues with ribbon mikes that the average home recordist is likely to run into right away is their low output levels. Most moving-coil dynamic mikes are a little "hotter" in overall output, but some of them could occasionally use a little help too. Both tend to provide much lower levels than the typical condenser mic, and ribbons in particular tend to need a LOT of gain. With some microphones, you could easily need 70dB or more of clean gain from your microphone preamp in order to get sufficient levels into your DAW. This will be less of an issue with louder sources and relatively close mic-to-source placement, but if you're trying to mic a soft sound source, or have the mic back a bit from the instrument, you're going to need a lot of gain. The problem is, most affordable mixing boards and audio interfaces don't have sufficient clean gain to really do the job properly. For example, while the built-in preamps on my Yamaha 01V96 digital mixer (Figure 2) sound good, they only provide up to 60dB of gain, which is not enough for some tasks. Plus, when pushed near or to their limits, many of the preamps that are built into mixing boards and audio interfaces start to get fairly noisy, so it's better not to turn them all the way up if you can avoid it.  

Cloud Microphones has been selling their popular single channel CL-1 ($179 MSRP / $149 street) and dual mono CL-2 ($299 MSRP / $249 street) Cloudlifters for a while now. These phantom powered direct-coupled discrete JFET preamps are similar to the internal preamplifiers built into the Cloud JRS-34 active ribbon microphone, which was designed by Stephen Sank in collaboration with Cloud. "Active ribbons", like FET condenser microphones, use a phantom powered onboard preamplifier and other electronics to bring the signal level up and to optimize the output impedance. While these earlier Cloudlifter units serve a similar function and provide up to 25dB of additional gain and a nice fixed 3kOhm load for the microphone's transformer to match up with, the Cloudlifter Z takes the basic concept to the next level.  

FIRST, THE BASICS

I was fortunate to be able to get my hands on one of the very first Cloudlifter Z units for this review. While it is functionally and internally identical to the units that are shipping out to customers, some of the graphics displayed in the article photos may vary slightly from what you see on the units in the store. Rather than wait on the final graphics, we wanted to get the info out to you as soon as possible.

Designed to be connected inline between the microphone and mic preamp, the CL-Z is a fairly simple unit, with XLR inputs and outputs mounted on either side of the sturdy steel enclosure. Compared to the sparse CL-1, which only has XLR inputs and outputs and no other connections or controls, there have been a few changes made. The case is a bit larger at approximately 5 3/8" L x 3.5" W x 2.5" H, and you'll immediately notice that on the top panel, a large knob labeled "Z" has been added, along with two toggle switches, which we'll get to in a moment.

"Z" is the symbol for impedance. In order to avoid any confusion, I'll be referring to the "Z knob" (Figure 3) as the "impedance knob" throughout the review. The basic purpose of this control is to allow the user to vary the impedance load that is presented to the microphone. Cloud recommends that the impedance value be five to ten times the output impedance of the microphone or greater. In other words, if you're working with a Beyerdynamic M160 ribbon mic, which has an output impedance of 200 ohms, then ideally you'd want to have the impedance dial set to 1-2k or higher on the CL-Z. This will help prevent the mic from being loaded down by being connected to a low impedance input. This kind of "loading" can result in increased noise, drastically reduced output level and significant changes to the frequency response of the microphone. And while these are generally things to be avoided, sometimes they're exactly what you're looking for.

SUPER FLEXIBLE HIGH PASS FILTER

The first of the two switches kicks in the CL-Z's high pass filter, and it's a doozy! The impedance knob and high pass filter switch are interactive, and the amount of bass rolloff and the rolloff frequency of the high pass filter change depending on where you have the impedance knob set. I tried to demonstrate the effect of this in the attached audio clips, because hearing it and understanding it is the key to "getting" the benefits the filter brings to the table.

Cloud recommends stating with the impedance control knob set to the midway point - 3k on the dial - and then adjusting to taste from there. For readers who are familiar with the CL-1 and CL2, this is the same impedance as you have on those units.  As you turn the knob higher, the sound opens up and deepens at the same time, becoming larger, louder and fuller as it becomes unconstrained by the effects of being loaded down. This is not always a good thing with a ribbon mic - sometimes when you have it placed in close to the sound source, there can be too much bottom end, and by varying the impedance dial, you can really make some drastic - or subtle - changes to the sound.

For example, when you turn the impedance knob down below 3k towards 150 ohm and the lows drop off in the bass, the sound becomes smaller and the level drops dramatically as it loads down. You can absolutely strangle a mic if you load it down too much, especially if you also have the high pass filter (HPF) engaged. If you want to get a really old-school lo-fi sound, this is a good way to do it. The high pass filter ranges from 20Hz to about 250Hz, so you can take a lot of bottom off… but for those who want to just tame the mic a bit and get the bottom end in check so they can have that silky ribbon midrange and softened top without the booming bottom, this can be a very powerful control. It allows the user to tailor the loading to suit the mic and the application at hand, while, if you want, simultaneously controlling the range of the high pass filter at the same time.

MORE OR MAX OUTPUT

The second switch is labeled "More / Max." This switch allows you to adjust the output gain. The gain is dependent on the impedance loading of what you have connected to the CL-Z, and will vary depending on the impedance knob and highpass filter settings. Up to 25 dB of gain is available with the Max setting, and about half of that with the More setting.

In order to optimize the signal to noise ratio of the signal path, Cloud recommends using the Max switch position and lowering your mic preamp's gain knob, but if you have the preamp turned all the way down and the gain from the CL-Z is still too hot (more likely to happen with "hot" sources and close miking), you can switch to the "More" setting. Following these instructions generally led to very good to nearly astonishing results as I connected a variety of ribbon mikes (Beyerdynamic M160, Cascade Fathead II, Groove Tubes Velo-8, Shure 315) and experimented with various quiet and distant sound sources.  

USE A RIBBON? YOU MAY NOT KNOW IT YET, BUT YOU WANT THIS BOX

The sonic flexibility benefits of the design are obvious after only spending a few minutes with it. You can drastically change the overall sound of the microphone while compensating for its low output level at the same time. The beefed up output from the CL-Z drives long cable lines with ease and with much less risk of picking up hum and noise, and allows you to turn the microphone preamp's gain knob down to a much less noisy part of its range. While the cost of the unit isn't exactly inexpensive, compared to the cost of a high-quality, low-noise, very high gain mic preamp suitable for use with low-output ribbon microphones, it's quite reasonably priced, and when it's set optimally, it will provide enough additional clean gain to let you use even relatively low output preamps that max out in the 45-50dB gain range with your ribbon and moving coil dynamic microphones, and it will give you a whole new range of sounds and flexibility from them. For fans of ribbon and low-output dynamic mikes like the Shure SM-7b, this is simply a must-have accessory. Not only does it increase the output level of your low-output mikes, it gives you a wide range of new sounds. Definitely highly recommended.  

Resources

Cloud Microphones CL-Z Cloudlifter Variable Impedance Mic Activator ($369.00 MSRP, $299.00 "street")

Cloud Microphones product web page

You can purchase the Cloud Microphones CL-Z Cloudlifter from:

Sweetwater

B&H Photo Video

Musician's Friend

Guitar Center

Audio Examples:

The audio files are all spoken word. The first one was recorded without the Cloudlifter to demonstrate the sound of the mic (a Groove Tubes Velo-8) and mic preamp (Yamaha 01V96 board preamp) that were used in all of the clips. The rest of the clips use the same mic position and preamp, but with no changes made on any of their settings - however, the Cloudlifter controls are at different settings, and the other clips show how the sound changes with adjustment of the impedance control, as indicated by the file names and the narration in each clip.

And here are a couple more images for you, including an interior "gut shot" and one with the included Cloud-branded cloth storage bag.

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Phil O'Keefe is a multi-instrumentalist, recording engineer / producer and the Senior Editor of Harmony Central. He has engineered, produced and performed on countless recording sessions in a diverse range of styles, with artists such as Alien Ant Farm, Jules Day, Voodoo Glow Skulls, John McGill, Michael Knott and Alexa's Wish. He is a former featured monthly columnist for EQ magazine, and his articles and product reviews have also appeared in Keyboard, Electronic Musician and Guitar Player magazines.