Do you what know the greatest innovation on inline headset controls is?
The microphone mute switch. Sure you could have a volume knob that controls the audio volume, but you can get keyboards with that, or even a hardware mute knob.

But when it comes to microphone mutes, there aren’t really any solutions (that I know of) out that are simply just “plug and play”.

There exists software solutions (i.e. AutoHotkey) or perhaps a macro keyboard - but a software microphone mute only works if the audio capture program respects those audio levels. For example, OBS captures the output audio streams regardless of the audio level or mute setting (though I haven’t actually tested it for input audio…)

So I opted to looking for hardware solutions - something like an inline push to talk / push to mute device.

Now unfortunately when you invest in pro-audio gear, you consequently pay pro…spectively more money for everything. Being a sound engineer and wannabe musician, my microphone setup at home uses a microphone with an XLR output into my Steinberg UR44 audio interface. So I wouldn’t be able to just buy some generic 3.5mm headset extension cable, which go for like $5.

Now I could have probably made my own mute switch by grabbing a pair of XLR connectors, finding a push switch and bridging pins 2 and 3 together when I wanted to mute… But I also wanted the finished product to be quite sturdy. Since I don’t have the facilities to manufacture a metal chassis or anything of that quality, I bit the bullet and paid a 5720% premium for the Sennheiser MAT 133-S which set me back by AU$286.

Product Description

The MAT 133-S is a sturdy, wired table stand that provides a stable base for XLR-3 gooseneck microphones. It has a user-friendly microphone button with a two-color status display that provides quick visual feedback on whether the microphone is active or muted. The TTL logic output on the underside can be used to activate a camera or media control system. The model is available in black color.
Source: https://en-au.sennheiser.com/mat-133-s

As you can see, the MAT 133-S is an XLR table stand designed for gooseneck microphones for boardrooms or conferences, etcetera. The -S model has a push button on the front to toggle/momentarily toggle the mute. The above image was legitimately the only picture I could find of the unit, so I had little to no idea about where the ports or switches were located

What’s In The Box

Considering a standard consumer wouldn’t really purchase this model (more for bulk corporate deals I guess), the unit comes in a completely plain cardboard box affixed with a single product label.
Inside we see a general usage manual and the obligatory health and safety notice.

The rest of the box is empty apart from the main unit, which came in a nylon drawstring bag.
I’m not really sure why Sennheiser thought this was a good idea to include a bag for a product that will probably never move around - but hey that’s what makes this $286…

The unit is nice and sturdy, weighting roughly around 1.2kg. The finish on the metal is quite nice, and gives the product quite a premium vibe.

On the underside we can see the mode switches, which affect how the unit operates when the push button is pressed.

• ON / OFF - (Un)latch when the button is pressed
• PTM - Push to Mute
• PTT - Push to Talk
• ON - Always On

We also see the TTL outputs for remote control of the device / of other devices

At the back we have the male XLR socket

What’s In The Box

So what did I get for AU$286?

• Phantom power extraction
• AQV252G - Solid State Relay
• 74HCT109D - JK Flip-flop ([truth table])
• And the rest, eh.

Realistically, there’s not too much going on.
Honestly I was expecting there to be a tad more circuitry - more on this later.

Usage

When the light is green, the input is unmuted; and conversely when the light is red, the input is muted.
Simple!

Popping

Often mute switches will cause an audible ‘pop’ noise as the mute is toggled, due to the imbalanced circuit configuration or electrical DC biases.
Unfortunately this unit is also susceptible to these issues, which is a bit of a letdown for the price.

Geek Stuff

The MAT 133-S seems to draw around 10V on its own (not really an issue, phantom power is high voltage low current).
When the mute is toggled the output voltage drops by around 5V, which attenuates the microphone by about 40 dB.
It’s not a true mute, but 40 dB is still substantial

Since there’s still a voltage still being applied during mute, we know that the mute functionality doesn’t just disconnect pins 2 and 3 from ground (pin 1) - which a good thing.
So, our popping must come from some circuit imbalances.

There are a few ways that Sennheiser could address this, from gradually applying the attenuation, or perhaps just fixing up the circuit balance…
Maybe a future model might resolve this (unlikely though!)

Conclusion

In any case, despite the popping issue (which though apparent, isn’t that annoying), I’m pretty happy with the unit.
Here’s to hearing me cough less often during the countless meetings I need to attend 🥂