ER-100 Eurorack 8 Channel Stereo Transformer Balanced Out Summing Mixer


ARREL Audio Eurorack Stereo Summing Mixer is the answer to all stream mixing needs for EURORACK synthesizers. Its features set it apart from other similar products on the market due to a very high fidelity approach used for the design of the electronics together with the use of line transformers to drive the L and R outputs. The circuit used in the ER-100 are directly derived from our line of professional audio units in order to obtain the best sonic performances.

The use of line transformers means a higher voltage output level (about 10 dB over the competitors), suitable to drive all modern audio converters. Output transformers mean also a very reliable connection in terms of unbalancing and ground loops problems. The ER-100 is characterized by 8 input channels and a stereo output.

Each channel is characterized by a pan pot control, a volume control and a solo in place button. A stereo insert controllable by a switch is available on the output bus. The monitor section is characterized by a volume control and a monitor out. An auxiliary input is available (push button selection), suitable for monitoring DAC or general external inputs such us a CD. Two LED VU meters are available on the output bus.

Number of Channels: 8 Inputs, L/R Outputs
Power Supply Eurorack Standard
Power Consumption 3.5 W
Input Unbalanced, Level 0 dBu max +20 dBu Impedance > 5 KΩ
Master Output Transformer balanced and floating, Output Impedance optimum load impedance > 5KΩ
Master Level Level +4dBu, Max +26 dBu
AUX Input (DAC) Stereo. Level -6dBu, Imp. 10kΩ, unbalanced
Bandwidth 5 - 60.000 Hz -1dB, perfect square wave up to 20 KHz
Distortion + Noise <0.005% ( typical 0.001%).
Front Panel Controls Master Section, Monitor Section: Rotary volume control, Input Section:level and pan control, Solo button,Insert Section: Stereo insert on Left and Right Selected by a button
Front Panel Input Connectors 8 x 3.5 mm jack for the input , 4 x 3.5 mm jack for the stereo insert 1 x 1/4” stereo jack for headphones Imp. >50Ω 2 x 3.5 mm jack for the output 2 x 3.5 mm jack for the AUX input 2 x 3.5 mm jack for the monitor out
Front Panel Indicators L/R 10-LED Bargraph Level Indicator (7 x green, 3 x red), 1.5dB step, Solo LED, AUX in LED,
Rear Panel Connectors Eurorack power supply connector
Construction 28U TE Units (142mm)
Dimensions W 142 mm, H 128 mm
Weight 500 g

    ER-100 Key-Technologies


    High quality output line transformers means a lot of advantages especially when used in the Eurorack environment such as: increase in the signal output level over the Eurorack standard level that is limited by the low supply voltages (+12V/-12V), no problems with ground loops (transformer galvanic isolation), no problems when the output will be unbalanced. Transformer galvanic isolation assure that the output signals are floating with respect to the ground so you can unbalance without problems. The possibility to unbalance the L and R output signals can be very useful in a lot of live situations.

    Large Bandwidth (LB) means a very fast transient response able to represent the original sound with the maximum temporal resolution. LB is required to improve the perception of a “real sound” and to represent the details of the original sound.

    Large bandwidth plus very low total harmonic distortion means a perfect square wave reproduction.

    Ultra Low Noise (ULN) active and passive components and ULN design techniques. This requirement is especially important when the audio bandwidth is large as in the case of ARREL Audio products.

    High Dynamic Range (HDR) means that the saturation probability of the output stages is very low. This is obtained by using a step up transformer in the output stage.

    Electro-mechanical tolerance means that electromechanical components are doubled in every situation in which maximum reliability it is important due to a frequent use (switches, push buttons, potentiometers).

    Through Hole technology means the maximum reliability in terms of thermal and mechanical stresses especially for connectors and electromechanical components.

    FAQ 1: Why the ER-100 is equipped with transformers on the line out L and R channels?

    The two high quality (large bandwidth and high output level) output transformers are fundamentals in order to:
    1. Increase the signal output level over the Eurorack standard level that is limited by the low power supply voltages (+12V/-12V).
    2. Avoid any problem with ground loops due to the transformer galvanic isolation.
    3. Avoid any problem when the output will be unbalanced. Transformer galvanic isolation assure that the output signals are floating with respect to the ground so you can unbalance without problems. The possibility to unbalance the L and R output signals can be very useful in a lot of live situations.

    FAQ 2: Why the ER-100 is not a cheap equipment ?

    The ER-100 is a high quality 8 channel mixer in a very compact format. The cost of the unit is high due to the following reasons:
    1. ER-100 uses two high quality audio line transformers on the L and R line outputs, high quality transformers are very expensive.
    2. The ER-100 is extremely compact. Please take into account that we offer, 8 channels, solo in place function, pan-pot, monitor out with high quality headphone amplifier supporting 50 ohm headphones, insert point, auxiliary input, and a flexible and accurate VU metering system. Implementing all these functions in the 28U format in about 40 mm of depth is a real engineering challenge. The unit is composed by 6 boards mounted over a motherboard so 7 boards in total so very compact and complex.
    3. The ER-100 is based on high quality integrated circuits for audio applications. We have applied our experience in very high quality audio units for recording and live into the Eurorack world...
    4. All the electromechanical components (potentiometers, switches, push buttons and jacks) used in the ER-100 are of top quality. We know very well that these components are the most critical for reliability. Moreover whenever possible we use the concept of "Electromechanical Fault Tolerance (see KEY-TECNOLOGIES link ) to ensure very high reliability to our units.

    FAQ 3: What is the function of the auxiliary input (AUX IN)?

    The ER-100 AUX IN has exactly the same role as in a traditional mixer it is conceived as an auxiliary input on the Monitor Bus. This input is not added to the 8 channels. When you select the AUX IN you disconnect the monitor bus from the summing bus and connect the auxiliary in to the monitor bus in order to hear only the signals connected to this input. The typical situation is when you have to monitor a recording. If you want easily check the song recorded with your Eurorack synth you can connect the recorder output to the AUX IN and easily check "on the fly" the recorded song just by switching the aux in on position. At the same time, on the main out you can hear the mixed channels.

    FAQ 4: What is the function of the solo button?

    1. The solo button permits to listen only the channels corresponding to the SOLO button switched in ON position all the others channels are muted. So if you want to listen only channel four you have to select SOLO ON on channel 4. If you want to listen the mix of channels 2 and four you have to select SOLO ON also on channel 2.
    2. If you want to emulate the MUTE function (on the main L/R outputs) you can easily use the solo buttons. For example if you want to mute channel 4 you have to select SOLO ON on all channels excluding channel 4

    FAQ 5: Why there are no Control Voltages (CV) on the ER-100 ?

    Because ER-100 is a very high quality traditional mixer in the Eurorack format. It is characterized by the maximum transparency and linearity with very low distorsion in order to reproduce with maximum fidelity your sounds. The implementation of an amplifier or a pan pot controlled by a voltage means the use of VCAs (Voltage Controlled Amplifiers) or similar technologies that inevitably deteriorate the sound quality. ER-100 has not been conceived to be a "creative" mixer (in the sense of CV). ER-100 viceversa permits to the Eurorack user to have in his Eurorack case the power of a very high quality traditional mixer able to preserve all the sounds generated by the artist.

    FAQ 6: How the ER-100 INSERT works ?

    The stereo INSERT point of the ER-100 is connected to the main summing bus before the main L/R volume controls. You can easily use this stereo insert to connect whatever effect you want (compressors, EQs etc.) that works at line level. The insert can also be used for "on the fly" monitoring of a different signal source. To do this, connect the signal source output to the RETURN jack (the SEND jack is not used). The jack insertion disconnects the mixing bus from the L/R outputs and connects the alternative signal source to the L/R bus so can monitor whatever you want just by a jack insertion in the RETURN plug.