The Dock6: A CV controlled VCA Mixer

A six input to stereo output mixer for ‘Eurorack’. Each channel is VCA based affording a fantastic sounding signal path.

VCA channel features:

2 CV inputs each with a control knob: A large range of flexible control is available by controlling the VCA with envelopes, LFO’s, step sequencers, and random source generators.

Initial Gain Control: Essential for balancing the channel against the others into the mix.

Mute Switch: Bi-colour LED Red: Muted / Green: On. A reasonable amount of time was spent choosing the right switches with a good tactile blend that gave a satisfying engagement but did not hinder live performance rhythmic muting.

A large bipolar notched slider for panorama control.  The slider features an LED which reflects the input signal of the channel. Very useful for clarification when working with complex signal topologies. An often wildly underestimated feature of this mixer is the pan control. The world of the modular synthesiser is plagued by mono signals. Take the time to build up a pleasing stereo image with layers and width tricks.

Signal Indicator: The LED on the PAN control indicates the signal at the input. Sometimes it is just great to see the reassuring glow of your stereo signal

Name Inspiration

The inspiration for naming the DOCK6 came from this article: 

DOCK 6: Combining techniques to model RNA–small molecule complexes

The CV control input buffering system: 

Short Version: The first socket on both CVA and CVB are normalled to all the consecutive inputs.

Long Version: If a CV is connected to the top channel’s CVA input then this CV is electronically buffered to the remaining 5 channel’s CVA inputs.

Plugging a CV into the top channel’s CVB input will result in a buffered copy being sent to the other 5 channels CVB input.  This way you can control all channels with a single control voltage source.

Each channel can have its own CVA and CVB controls as plugging in to channels 2- 6 CV inputs will override the buffered inputs.

The design philosophy…

….for this mixer was to utilise the THAT 2162 Blackmer VCA IC’s.  These chips are similar to those found in classic hardware compressors such as the SSL Bus Compressor.

Current vs Voltage Summing.

The output from the Blackmer VCA’s are a Current Source. This is a provides a great sounding alternative to the usual voltage summing found in most other mixers.

 

 

Specifications:

Dimensions
EuroWidth 45HP
 
Width  228 mm
Height 128.5 mm
Depth 30mm (with the IDC power connected but without the extra cable relief)
 
Power
Requires +/-12v to operate
Current Draw ~400 ma
A 4 layer PCB construction
 
Construction
A reflow oven was used for the SMT, whilst sockets and pots are traditionally soldered.