Microphone Activator Series

Anyone who has dipped their toe in the world of above-average audio has almost certainly come across a microphone preamp (aka mic activator). These devices are often recommended to people using quiet microphones, such as the legendary Shure SM7B(Amazon). The Cloudlifter CL-1(Amazon) occupies the top spot as the most sought-after microphone activator in this category. So much so, the name Cloudlifter has become synonymous with “mic activator,” like Kleenex vs. tissues.

Over the past decade, adding a mic activator to your setup has been a mostly valid suggestion for those who could not afford more expensive audio interfaces. More recently, budget interfaces such as the 4th gen Focusrite Scarlett Solo(Amazon) and 2i2(Amazon) have raised the bar in terms of offering quiet gain powerful enough to successfully drive microphones like the Shure SM7B(Amazon).

Interestingly, in late 2023, Shure released the SM7dB(Amazon) microphone, which includes a built-in preamp that is apparently licensed from Cloud Microphones. Maybe a little late to the party, but kinda cool nonetheless.

Anyway, let’s dive into what all the fuss is about. Out of curiosity, I decided to take a peek inside a Cloudlifter CL-1(Amazon), which turned into a deep teardown and ultimately a custom build of one. Join me on this epic journey of audio amplification!

The KiCad design files for this project can be found on GitHub: https://github.com/MostlyBuilds/microphone-activator

Part 1: Cloudlifter CL-1 Teardown

I didn’t intend to go this deep on this project, but curiosity got the best of me. I was also really surprised by how simple the amplification circuit is. I need to give Cloud credit for their excellent build quality and tip my hat to their success. This thing is beautiful and built like a tank, surely allowing for years of use without issue.

I’m not an audio expert (I just play one on TV), but the components used appear to be high quality and appropriate for an audio circuit like this. The LSK389C JFETs are low noise and are explicitly designed to be used in audio circuits, according to the datasheet. Their use of plastic film capacitors over something more common like noisy ceramic caps is a solid choice for an audio circuit of this type. The XLR connectors are from a reputable manufacturer (Neutrik) and are used all over the audio industry. Nice job, Cloud!

Here is a breakdown of the components:

• LSK389C JFETs (2)
• 1.8nF 1206 PEN Film Capacitor (2)
• 3K 1206 Thin Film Resistor (1)
• 33K 1206 Thin Film Resistors (2)
• 22Ohm 1206 Thin Film Resistors (2)
• 39Ohm 1206 Thin Film Resistor (1)
• Neutrik NC3MD-L-1 3-Pin XLR Male Connector(Amazon) (1)
• Neutrik NC3FD-L-1 3-Pin XLR Female Connector(Amazon) (1)

My desoldering skills using my hot-air station in this video are pretty comical. The hot-air station(Amazon) that I use is actually a decent unit in the “just a little better than budget” category. My failures originated from somewhere between ignorance and user error! It’s true that I did destroy three Cloudlifters during this project, but you can’t make an omelet without breaking a few Cloudlifters, right? Bad joke… moving on.

Part 2: Cloudlifter CL-1 Schematic

After tearing down the Cloudlifter CL-1(Amazon), I thought it would be fun to create a schematic using the free open-source software KiCad (pronounced like key-cad). I’ve used KiCad for a few other hobby electronics projects and thought it would be cool to create a little schematic design tutorial that might inspire others to get into circuit design or just to try out KiCad.

I tried using Eagle years ago and found it pretty difficult to use (now it is subscription-based — hard pass!). I find KiCad to be pretty intuitive and easy to learn. Since it is open source, there are lots of great resources online for using it. It has also steadily gotten better and better over the years. KiCad is a pretty significant open-source project, attracting interest from the engineers over at CERN, who have helped fund its development.

Part 3: Designing a Custom PCB

This is really turning into a textbook “one thing leading to another” kind of situation. Since I went to the trouble to build out the schematic, I figured, why not design a custom PCB?

I decided to make a smaller version of the CL-1 and try to put it into some kind of off-the-shelf metal case that will shield the electronics and look appealing. I basically wanted to avoid having to fabricate anything custom or go with an inferior material like plastic.

After some searching, I found two options for a case that looked interesting:

• Neutrik NA-HOUSING(Amazon) (this is what I ended up using)
• PROCRAFT PB1-2X-BK Steel Project Box(eBay)

The Procraft project box design looks pretty much identical to the Cloudlifter CL-1(Amazon), but not as pretty as the CL-1. While it’s cool to find a match for the CL-1 enclosure, it wasn’t really what I was going for aesthetically.

Shortly after finding the Procraft enclosure, I discovered that Neutrik makes a nice little split design box called the NA-Housing(Amazon). The NA-Housing(Amazon) is explicitly designed to be used with Neutrik D-style connectors, which are the exact ones that I had planned to use for the XLR connectors for this project. I later discovered that Triton Audio appears to use this same housing for one of their Fethead preamps(Amazon).

Success! Now that we can define our target PCB size and build the layout to meet that specification.

Part 4: Building a Custom Mic Activator

I sent out my PCB design to be fabricated by Osh Park. I’ve tried a few other fabs in the past, and Osh Park is my favorite. Their website is really great at giving you a preview of what your board will look like. Since Osh Park is located in the USA, the turnaround time is pretty fast. You can always spot Osh Park boards a mile away with their signature purple color.

I always enjoy assembling surface mount PCBs because they come out with such a professional look when you bake them in a reflow oven. For larger boards, I usually order a custom laser-cut stainless steel stencil (from Osh Cut) that you can use to squeegee solder paste onto the board to perfectly deposit the paste on all the pads. This board is so small that it was easy enough to add the paste manually with this cool dispenser that I made (video).

Learning from my mistakes during the teardown of the CL-1, I bought low temp solder paste to reflow the PCB (chipquik part #TS391LT50). This allowed me to stay within the thermal limits of the plastic film capacitors that I destroyed with too much heat in Video 1.

For placing the components, I used a homemade foot-operated vacuum pickup tool made from a craft bead pickup tool(Amazon). I don’t have a build video for this yet, but I’ll probably make one in the future because I love this tool so much.

When it finally came time to reflow the board, I used a reflow oven that I built from a kit designed for modifying a toaster oven. I know it sounds a little crazy, but this reflow oven works really well and was super fun to build.

Soldering the header pins to the PCB and XLR connectors was a bit of a challenge and took some thought to get right. Rushing this part would have likely resulted in things not fitting well and a lot of frustration. Luckily I took my time, and it worked out really well.

Something that is really nice about the Neutrik NA-Housing(Amazon) is that because it is a split design, you can totally remove the PCB and connectors from the housing without desoldering anything. The Cloudlifter CL-1(Amazon) gets soldered into the case and cannot be removed without desoldering the connectors. This is totally fine for a production device like the CL-1, but is not super desirable for my custom hobbyist build.

After assembly was done, it just didn’t seem right to leave it with a generic all-black case. To give it some flair, I 3D printed a stencil and hit it with some white paint(Amazon) to leave my mark on the audio world. At this moment, the FETLIFTER was born. Or should I have called it a CloudHead??? Nah.

I’ll admit that when I first went to try it, I plugged in a cheap XLR microphone in case I got something horribly wrong and electrons decided to go places they shouldn’t. Thankfully, it worked, and nothing exploded. I finished off the project by recording all the audio for the YouTube video series using the world’s first FETLIFTER.

Final Thoughts

This was such a fun project. The Cloudlifter CL-1(Amazon) is a simple but well-made device. Some people may turn their nose up at the price tag in relation to the simplicity, but after making one myself, I think Cloud is charging a fair price for the CL-1. It’s a quality device in a premium case, and it’s made in the USA. Like anything else, if you add up the cost of the components, it is going to be less than what the product retails for, but it takes a lot to bring a product to market and run a business. I congratulate Cloud for earning the top spot in the microphone activator category.

Please don’t use my project as the basis to build a knockoff product to compete with Cloud. Doing that would be a waste of time anyway, in my opinion. The market is already saturated with preamps, and they are likely going to become a thing of the past with the rise of super affordable interfaces that are capable of driving quiet microphones.

I hope this project inspires someone out there to go build something. Don’t forget to like and subscribe! Catch ya in the next one.