3-CHANNEL STEREO MIX EXPANDER

• Adds three stereo/dual-mono channels to Xcelon mixer (up to two supported)
• Two stereo FX sends and two stereo output mix busses selectable per-channel
• Variable input gain for both modular and line-level sources
• Long-travel volume faders with CV responsive LED indicators
• Balance controls with pan law curve and dual-mono crossfade mode
• Clickless mutes and VU meters on all channels
• Twelve discrete control voltage inputs
• Configurable jumpers for pre/post-fader FX and meters, plus volume VCA mode

Modular mixing expanded

Xcelon XP3 is a three-channel stereo expander for the Xcelon eurorack mixer. The module’s channels are identical to those found on the main mixer. Up to two XP3 can connect to Xcelon, expanding the total number of mixer channels to either nine or twelve.

Channel Expansion

The 22HP module has the same channel inputs, channel controls, direct outputs and rear jumpers as Xcelon. The primary difference is that the expander lacks the mix outputs and FX i/o section. This is because XP3 shares the two main mix busses and two FX sends busses with the main mixer.

XP3 is connected to the main Xcelon mixer using the supplied 16-pin ribbon cable, from the port labeled MIXER to one of the two expansion ports labeled EXPANDER 1 or EXPANDER 2. These expansion ports are found on the backs of both modules. Because the mixer supports up to two XP3, a set of channel labels with 10, 11, and 12 are included to update the front panel.

It may be possible to connect more than two channel expanders using a flying bus cable, but low noise performance cannot be guaranteed.

IMPORTANT: The expander ports should NOT be connected to a eurorack power bus or damage to the module(s) can occur.

Channel Inputs

Each of the three channels has a pair of audio input jacks (INPUT 7, INPUT 8, etc.) for left and right stereo signals. The jacks are normalled such that a single mono source in the left jack is simply copied to the right. Alternatively, two discrete mono sources can also share a channel (see XFADE). These AC-coupled coupled inputs accept typical eurorack-level audio signals, as well as line-level audio signals when boosted using the channel’s GAIN control.

The four jacks directly below each pair of audio inputs are CV inputs, which allow for voltage control of the channel parameters. VOL affects the volume within a range of 0 to +5V. By default, this control voltage input is biased by the fader position (summed), but in VCA mode it is attenuated by the fader (see Jumper Settings). BAL affects the channel balance within a range of -5V to 5V (even with XFADE enabled), while FX1 and FX2 affect their respective send levels within a range of 0 to +5V. These latter three control voltage inputs are all biased by their knob positions.

Channel Controls

The GAIN parameter is used to boost the channel’s input signal(s) up to +15 dB if necessary. Most eurorack audio sources may only need a small amount of gain, whereas line-level signals may require turning the knob up to the LINE position. The red PK (peak) indicator will illuminate just before either input signal becomes audibly distorted. For a clean mix, best practice is to set the GAIN such that only loud transients trigger the PK LED.

The BAL parameter adjusts the balance of the channel’s two input signals, and behaves much like a pan control, especially with a mono input signal. Control of the parameter is not linear, but instead implements a curve according to the -4.5 dB pan law. This yields a more natural sounding stereo panning.

When the blue XFADE button is engaged, the channel is configured in dual-mono mode. Both channel input signals are positioned to stereo center, and the BAL parameter acts as a mono crossfader balancing the two signal levels. Signals that do not need stereo panning can then be doubled-up on a single channel, such as kick and snare drum, two different bass sounds, etc.

The VOL parameter adjusts the channel volume, and is also commonly referred to as the channel fader. Its 45mm vertical slider has a linear volume response for smooth fade ins and outs, with an entirely usable range. The brightness of the white LED indicates the volume position, and is of course responsive to incoming CV.

Next to the volume control is a 5-segment VU METER to help visualize signal level and dynamics. The meter is affected by both left and right channel signals. And although it does behave according to a decibel scale, the meter is intentionally biased upward for better resolution when comparing relative channel levels. By default, the VU METER is post-fader, meaning it is affected by volume adjustments, but can optionally be configured pre-fader (see Jumper Settings).

The red MUTE button, when activated, will effectively silence the channel with up to -93 dB of normal signal attenuation. Its electronically latching circuit is completely VCA-based with a very fast on/off slew, eliminating any clicks or pops when muting or unmuting the channel.

The channel’s two gray knobs, FX1 and FX2, are independent stereo effects sends. Using these parameters, an adjustable amount of the channel signal can be sent to the two shared effects busses FX SND 1 and FX SND 2, which are commonly used for time-based effects such as delay and reverb. By default, both FX1 and FX2 are post-fader sends, meaning the amount of sent signal is also affected by the channel’s volume position. However, FX1 can be configured pre-fader (see Jumper Settings) to achieve a more than 50% wet mix of effect versus dry signal.

The AB switch assigns the channel output to one or both main output mix busses. In the leftmost and rightmost positions, the channel is routed to only one of the two busses, either A or B. In the middle position however, the channel is routed to both simultaneously, allowing for parallel processing, AFL monitoring (after fade listen), and other creative uses.

Direct Outputs

Just like the main mixer, XP3 is also equipped with several direct output ports to access individual channel signals for multi-track recording. Its bank of three stereo channels has two direct output ports, PRE and POST, to tap the channel signals either before or after the volume faders.

These groupings of six signals are connected using an 8-pin cable to the optional direct output modules, Xcelon TRS and Xcelon DB25 (TBA), for balanced line outputs. They can be mixed and matched in any order, and both the PRE and POST direct outputs for a bank of channels can be used simultaneously. This leaves the door open for future expansion such as dedicated cue monitoring and additional effects sends.

Jumper Settings

Each channel has three custom settings found on the back of the module, which are configured using one or more jumpers.