Upgrade: BRING THE NOISE (Hearing Assist & Fan Upgrade)

A Short Novel (and apparently my 50th post!)

I'm trying to remember how this rebuild began, but I think it started when I bought my blower fans a few months ago. I bought them while I was working on my initial fan system for the bucket, but since the build was almost complete, I decided to store them for later.

During one of my troops a couple of months ago, in a hotel no less, I had issues with the helmet fogging due to humidity. The small fans I originally started with just couldn't move enough air to fight the humidity. Eventually it got better as the event went on, but for the first few minutes I had a bad fogging issue.

I messed around with the blower fans and discovered that, in my bucket, they were way louder than my little fans. I wouldn't be able to use them without some sort of hearing assist system.

Then a few weeks ago I discovered the Velleman Super Ear Amplifier Kit - MK-136, a solution which apparently many troopers use for hearing assist, namely because it has two microphones that feed into one stereo headphone jack. It was pretty cheap at the local Fry's ($8), so I picked one up along with some replacement soldering components.

Finally, I wanted to ditch the 4x AA batteries the old fan system used, since they didn't have as long of an operating window as a rechargeable USB battery bank.

So my goal was threefold: replace the old 30mm fans with blower fans, assemble and install the hearing assist system, and run everything off of a USB power bank.

This was supposed to be a moderate bit of work, but it turned into a trek - no pun intended. What I expected to take a few hours ended up taking over a week to do. Hopefully some of my knowledge could help someone in a similar situation avoid some pitfalls for a smoother build. Overall it came out great, but it took some extra time to get there.

Phase 1

I didn't want to start this project until after I was done with a troop for BlizzCon. Once that was done, it was time to break out the soldering iron and carefully assemble the MK-136. Below are the results.

I made the following modifications:

• Instead of soldering the mics directly to the boards, I would obviously need them on the bucket, so I soldered them onto some lead wires recovered from an old DC power supply.
• I eventually cut these wires to insert some 3-pin quick connectors in-line in order to make bucket maintenance easier.
• I soldered a lead wire with a a 3-pin connector where the battery box would be connected, to prep the module for USB power. 
• Before I did this, I temp connected the battery box to the module to test it. It worked the first time. This is a big deal for me because I usually mess something up on the first try, but this just worked. Everything had been soldered together correctly.
• I added the 3-pin female connector to the battery box for testing. Later I'd use a lead wire connected to a USB-A male connector for the USB power bank. 

I used 3-pin connectors, as opposed to 2-pin connectors, in order to better keep track of polarity. The 3-pin connectors can only connect one way, making it impossible to accidentally flip the connector.

After soldering and testing, I cleaned the excess flux from the board with rubbing alcohol. Once cleaned, I used some 2" wide shrink wrap to protect the entire assembly. To shrink the wrap, I used my gas stove range and some tongs, carefully warming the wrap over the flame until it was inform and tight.

With the soldering for the module done, it was time to mount the microphones. Taking a page from UKSWrath and other troopers, I placed the mics under each ear piece (after ensuring the left mic was on the left side and vice versa) after drilling out a large hole for each mic, and miniature holes on the black stripe on the earpiece in order to help with the mic's pickup. The mic was secured on either side with low-temp hot glue.

To mount the mics, I had to remove the foam and screws as originally installed by ANOVOS (and reinstalled by me after I blacked out the interior of the bucket). Since I'd need some room behind the mics for the lead wires, I had to redesign this part. I decided, instead of mounting the eye visor to H&L tape attached to the foam, that I would instead mount it to the screws used to attach the ear pieces. To do this, I needed to replace the existing screws (which I'd already replaced with the correct screw types) with the same screw types - but with a longer length of 1" (twice as long as the screws I previously installed).

After cutting the new screws to length, I installed them with washers and bolts. I then placed the visor in the helmet and marked points on the visor (using permanent marker) to drill holes for mounting each side of the visor. This was tricky and I had to adjust the bottom holes since the visor was a little high at first, but it worked out. I then used these holes to put holes into the ANOVOS helmet foam so that I could use it to help cushion the mics from the visor.

On the screws, the order of parts is: earpiece, bucket halves, washer, bolt, foam, visor, washer, vinyl locking washer.

Phase 2

A few things happened after this. I wired the new blower fans to a USB cable (black for ground, red for +) and a switch, which I mounted into the helmet using H&L tape. I then connected the fans and the hearing assist to my power source, an Antec LifeBar 3.

Originally, I was hoping to use 2x smaller USB banks, mounted on each side of the bucket similar to what I had done with the AA packs I originally used. However, this meant I'd have to double up on charging the banks and remove the harness to get to the batteries. In addition, the original banks I tried didn't have any LED power indicators to let me know how much charge remained. They were also defective. So I returned them for something better.

Running both the hearing assist and fans from the same bank, however, presented a new problem: EM noise. While running the fans, EM noise created from the fans' electronic oscillation would create electrical feedback into the hearing assist module, and into the headphones.

Now I needed a low-pass filter. This is basically a capacitor and resistor in-line with the circuit, which acts as a settling pool for the current to reduce or remove EM noise. They're not hard to make, but knowing the capacitance and resistance needed can be tricky, especially with a module that can have a variable output for speakers/ headphones.

I thought hard about this roadblock, about creating a low-pass filter that would filter out any noise not within a normal hearing range. Then, with the help of my IT and ISP knowledge, it dawned on me: just use a DSL filter.

For those unfamiliar, a DSL filter is used between analog phone equipment, like a phone or fax machine, and a phone system that also has a DSL modem/ router. DSL equipment uses higher frequencies, which can impact regular voice traffic under the 5KHz range. The filter keeps the DSL frequencies off of analog gear.

I grabbed a spare DSL filter and decided to test in in-line between the USB power bank and the hearing assist module, with the module acting as the "phone" side and USB bank as the "line" side. I started by cutting the phone lead in half so I could strip some bare metal for testing by holding the leads in-place.

I connected everything, started the fans, and then connected the hearing assist module.

And it worked. I tested it at varying volume levels and, although not perfect, it cut out almost all the EM fan noise.

Now that I know it worked, it was time to remove the casing (to better fit it into the bucket) and integrate it with the hearing assist module.

EDIT: For my EU friends and others who just want to piece something form components, as far as circuit diagrams go, a full DSL filter will look something like this (click to enlarge):

The basic DSL filters I'm sourcing, which work fine, looks something like this (although it's hard to tell the exact component values as they're not well labeled on my components):

(END OF EDIT)

With the casing removed, I de-soldered the telephone lines and RJ11 jack. Then, I cut the pinned lead from the hearing assist module in half, and soldered the filter in-line.

I wrapped the module in 3/4" shrink wrap the same way I wrapped the audio module, although the wrap was barely big enough to fit over the big caps used on the filter.

Phase 3

More things happened after this.

Even with the hearing assist system and the low-pass filter, I was still picking up a lot of mechanical noise from the blower fans with everything mounted in the bucket. I was at another impasse.

After much thought, I decided two things:

• The tiny fans did a decent job on most days and were quiet, but couldn't move enough air around when things got hot and humid.
• The blower fans would move a lot of air, but at the cost of being able to hear easily.

So I decided to use both fan systems - a low-speed system and a high-speed system. I moved the blower fans from where I had mounted them (behind the Hovi tips) to my forehead (which I can do since I'm using the ANOVOS harness system instead of helmet pads). The original fans would stay in place on the existing fan harness, and I would run lead wires up the inner top of the helmet to power the blower fans (I used a bit of 4-conductor scrap USB cable for this, with red & black wires for one fan and green & white for the other). Both fans would use the same USB-A jack for power (since the 2nd port on the power bank would be for the hearing assist system) but would use two separate slider switches I already had available.

To get the hearing assist module and filter ready for mounting, I put H&L tape on them, along with the corresponding point on the fan mounting bracket. I did have to remove the wire between the module and low-pass filter and replace it with a longer wire so the filter could be installed on the back of the harness (with the wiring) and the module on the front (so I could have easy access to the power and gain while wearing the bucket).

I got both fan systems wired to the same USB-A cable, and installed two switches. Everything worked... for a bit.

Phase 4 (Final Phase)

The wiring with this installation was a mess; too many wires were soldered together, the USB-A cables were too stressed, and the thin 24-gauge wire in those cables wasn't up to the task. This caused both fan systems to loose power. Instead if having two working fan systems in the bucket, I now had no working fans in the bucket. The design was sound, but the implementation needed work.

I started over with the wiring with the following modifications:

• I installed screw-down terminal blocks onto the mounting bracket to help keep wiring clean and make installation easier. This would reduce the amount of soldering, cold solder joints, and wire stress.
• I used three blocks total: 2x 2-terminal blocks as positive blocks for the low (radial) and high (blower) speed fans, respectively; and a 1x 4-terminal block as a grounding block for everything.
• I spent $8 on an on-off-on 3-position toggle switch that would be used for both fan systems. There wasn't really a need to have both systems on simultaneously, and using one switch for both systems would reduce the amount of wiring.
• I replaced the stiffer USB-A cable I was using with thinner, more pose-able cables in order to make connecting the system to the power bank inside the helmet easier. Thankfully, the wire gauge for the red and black power leads was of a similar gauge to the old wires, but would still require reinforcement.
• I used solid-core copper lead wires between components and the screw-down terminals. I soldered tinned stranded wire from the fans and USB-A wires to solid core wires, and then screwed those down into the terminals. Solid core is more resilient and easier to screw down, and would overall improve the life of the wiring through wear and tear. It's also stiffer and easier to cable manage.
• I installed plastic anchors for the USB-A cables to eliminate stress at the solder joints (fastened with spare Chicago screws I picked up to fix a missing screw from my holster). I also installed more tie-down anchors to help with cable management.
• I re-did all the quick connected for uniformity, and added quick connects on the hearing assist module for the mic leads, to make work and maintenance easier.

Finally, everything worked, although I have to be careful when I put the bucket on to leave enough room for the blowers to work. I may add some stiff foam to the forehead as a spacer between my head harness and the fans.

Mounted, everything looks clean, and works great. You can see the blowers near the forehead, the hearing assist module and controls on the left side of the bucket (right side when it's inverted) and the LifeBar wedged between the back of the bucket and the back of the head harness (secured with H&L tape). In the top of the bucket I installed more H&L tape to have more mounting options for the LifeBar, blower fan cables, and other possible future hardware.

Earphones for the hearing assist can be tricky. With all the holiday shopping I don't have time to pick up a good pair of helmet speakers (as used by motorcyclists and skiers) as recommended by squad mates, but I was also recommended an inexpensive pair of RCA headphones (only $5 from my local Fry's) that work in a pinch. Of course, this means I have to put on the headphones before I get the bucket on, and then tuck the spare cabling into the bucket's chin, but until I have a chance to research and perhaps install some helmet speakers, they'll do for now.

Other mods (aka H&L Tape Is Our Friend)

In addition, I recently acquired a wireless microphone and receiver on sale at Amazon. I used H&L tape on the fan bracket and the mic to install the mic into the bucket, but have it easily removable for charging and storing.

For the personal PA, mounting the wireless receiver directly onto the PA makes it stick straight up, putting pressure on the 3.5mm jack due to the curvature of the chest piece. Instead, I used H&L tape to mount the receiver to the plate, and then used a small 3.5mm extension wire to connect it to my Pyle Pro.

Update 30 Nov 2016: after some advice from a fellow ANOVOS Builder FB group member and additional testing, the 2.4GHz feed used by the wireless mic creates RF noise on the hearing assist, which causes a mild to moderate radio buzz on my headphones, even with my head between the mic and the hearing assist module. I may try to create an RF shield for the hearing assist module, or may just revert to a wired mic int the meantime. Any further mods will be covered in a future blog post.

I also added more H&L tape to the inside of the chest piece for my elastic shoulder straps. I've been having issues with the back of the ABS shoulder straps popping out of the elastic loops, and realized that ti was because there was too much space between the chest and back piece at the shoulders. the extra H&L tape allows my to pull the elastic shoulder straps in to close the space off and keep the ABS shoulder straps in their elastic loops on the back plate side.

I might also fasten a holiday hat to my bucket using some magnets from the build :D

I still need new hand guards, new Hovi tip mesh, some thermal detonator modification, and a frown repaint on my bucket before I submit for Centurion, but I'm thinking about finally submitting for EIB this month or next. In any case, any work done to the armor will be documented here for reference. If I don't have any updates before year's end (I don't foresee any happening), then to my readers:

Happy Holidays

and a

Happy New Year!

Until my next update...