Audio

Our AV setup joins a couple different worlds together. This article focuses on the AV itself, networking documentation belongs to Netbox.

Some quick guidelines for new users:

• NEVER push the 48V buttons; YOU WILL BE LIABLE FOR DAMAGED EQUIPMENT
• The gain knob should NEVER be used as a volume knob; see the next heading
• Faders go from -Infinity dB to -0 dB; think of this as 0% and 100%, with everything above BOOSTING the audio
• The master fader will limit all your other channels; set the master to the max you want for this listening session, then gradually use the channel fader to introduce your audio onto
• The mute buttons cuts a single channel off; DO use mute buttons, and DO check them (pressed == muted, depressed == unmuted)
• The solo buttons cuts all OTHER channels off; DO NOT use solo buttons (pressed == solo, depressed == normal)
• Does the top right of the mixer blink red? Solo is on somewhere; turn all channels down, find the active solo buttons, and unpush them.

Your gain may be wrong.

The gain knob works differently depending on the channel:

• For stereo channels (9 through 16): 12 o'clock is 0 dB, all the way to the left is -20 dB, all the way to the right is +20 dB
• For XLR/jack channles (1 through 8): TL;DR all the way to the left is 0 dB and all the way to the right is +40/60 dB

Check the list above, then do the following:

1. Turn all the channel faders down
2. Move the gain knob to the 0 dB position
3. Put your audio source to 100%
4. Play music on your audio source if possible. Other audio will do but it's not optimal
5. Move the master slowly to 0 dB
6. Move the channel fader(s) slowly to 0 dB, up until the reasonable max you'd expect for “a party vibe”
   1. If it becomes too loud for comfort: Stop, turn down a bit, go to next step
7. If it becomes too loud TOO QUICKLY (e.g. -40 dB or below) then adjust the gain DOWN
8. If you reach 0 dB and still think the audio is too low, then adjust the gain UP

The amps and parametric EQ have currently been adjusted using multiple reference songs such that the bass response vs. the mid/highs should be as close to flat as possible across the entire room. This will also be tripple-checked using measurement microphones.

If you still think your source isn't entirely flat, check the EQ/normalization settings on your source.

If you still experience that the balance is off, use the EQ knobs on the MIXER to adjust your balance. DO NOT adjust the amplifiers/parametric EQ.

The following channels are currently in use:

• Ch. 3-4: TG:HACK Dante
• Ch. 9-10: Hack-Radio project pi
• Ch. 13-14: TV
• Ch. 15-16: Chromecast

We have a borrowed set of professional audio Dante receivers that are hooked up in the audio rack. These are owned by skandix from TG:HACK and labelled as such.

These are occasionally used during parties, or when we're lending out the Matelight for use in e.g. Flerbruksen.

Hackeriet does not own any source devices. You are free to map sources onto these from the Dante control software, however the receivers themselves MUST be left untouched in the rack.

The same goes for the audio channels: Do NOT adjust the gain (should be NO GAIN) nor the EQ.

For more details on Dante, see dante.

An older Chromecast Audio dongle is connected to the mixer. The dongle is in the bottom of the audio rack, and is regularly prone to unplugging due to short cables.

Chromecast Audio dongles are sensitive to its power source and may easily leak the USB clock onto the audio circuit as noise when powered by certain power sources.

The Chromecast Audio dongles output low audio levels, and must be gained up on the mixer NO MORE THAN 12 o'clock on the gain knob.

The PC in the audio rack is hooked up to aux out 1+2 on the mixer. Specific audio channels can be forwarded raw to LedFX as desired, without affecting the master output.

This lets us e.g. receive audio from Flerbruksen and analyze it on our end, without (or with) playing the audio on our speakers

1. Turn the aux send knobs to max for the channels that should be sent
   1. For stereo channel pairs: Send the left-panned channel to Aux1, and the right-panned channel to Aux2.
   2. For combined stereo channels: Send to both Aux1 and Aux2. The mixer fixes levels for us.
2. Ensure the aux return is set to infinity for all knobs
3. Ensure return to aux1 (between level & return knobs) is de-pressed
4. Align the levels so that we do not redline the audio card in the mix rack (ring around the gain knobs on the Focusrite, see image below)
   1. The level knobs on the mixer should be used if possible
   2. If those are maxed out, adjust the gain knobs on the audio card

There are two switches in the rack, for powering AV-related escapades:

• 1x 48 port 1 Gbps switch (lydrack-sw2), for high-throughput applications (video, etc.) with uplink to hackeriet-sw
• 1x 24 port 100 Mbps switch (lydrack-sw), for low-throughput PoE applications (audio, DMX, etc.) with uplink to lydrack-sw2

See netbox for further information.

There is one PC in the audio rack, aimed at powering AV projects: https://ip.hackeriet.no/dcim/devices/77/

It has the following AV-related connections:

• 1x Dedicated USB audio-card (Focusrite top-of-rack) connected to Aux send 1+2 on the mixer, for audio processing (e.g. LedFX)
• 1x HDMI connection pulled to the projector in the roof
• 3x UNUSED MiniDP ports for further projection units

For display capabilities, see the project ndi.

The PC runs the following software:

• LedFX
• TODO: music player daemon
• TODO: shairport-sync (AirPlay)
• TODO: Materix controller
• TODO: Chromecast-MQTT bridge

Anything marked “TODO” is currently running on the “hack-radio” project pi. It is supposed to be moved to the lydrack-PC; please reach out to 404'd if you want to help.