Wiring For Optimal Performance
Regardless if you already have a fully functioning V2 board or are just starting your V2 preamp project, the single most important element of a successful V2 preamp build is the proper wiring of the audio, power and ground. We’ve learned much about the V2 since its introduction in May 2014; much of it through feedback from our growing DIY customer base. We advise careful review of, and adherence to, the diagrams and info below in the planning and execution of your V2 project.
There’s an abundance of info available online regarding audio and grounding. Why? Because poor grounding can bugger up any audio system and it’s all too easy to get it wrong. The most reliable approach to grounding is to use “star grounding”. In simple terms, star grounding means everything that needs to be grounded gets its own dedicated connection to one single common ground point. No daisy-chaining of ground connections. This is clearly illustrated in the diagrams below. Can you spot the daisy-chained violator?
Correct Audio Signal Grounding for AutoCal Operation
The diagrams below show both the left and right (unbalanced) and the + and – (balanced) audio signal grounds each being individually tied to star ground. These connections are absolutely essential to the proper functioning of Auto Calibration. Moreover, power ground must also be connected to the same star ground point regardless of whether you’re using an external DC power supply or bringing in a 3 wire AC main to power an internal power supply unit.
Single Ended Wiring
Single ended (or “unbalanced”) audio consists of single left and right channel audio signals which are each referenced relative to ground. The left channel input and output are terminated to J1L-Input (or LI) and J1L-Output (or LO) respectively. Similarly, the right channel input and output are terminated to J1R-Input (or RI) and J1R-Output (or RO) respectively.
Input, output and ground for both the left and right channels can be terminated via the J1L and J2L screw terminals respectively. A more permanent and maintenance free alternative to using the screw terminals is to solder the audio input, output and ground via the solder pads adjacent to the screw terminals. These are marked as LI, LO, and LG for the left channel and similarly RI, RO, and RG for the right channel.
Balanced Audio Wiring
Two (2) V2 boards are required for balanced audio. The Master handles the right stereo channel and the Slave handles the left stereo channel. The Master handles all communication with the user including command inputs from the remote or encoder and output to the display module etc. There is no user interface directly with the Slave board.
Designating the Slave Board (Left Channel)
All V2 boards operate in Master mode unless told otherwise. To designate a V2 board as a Slave, the pins of jumper JP1 must be connected together. A 2 pin shunt is provided for this. JP1 is circled in red in the second board above.
The V2 Master conveys necessary information to the Slave via a 2 wire serial data link and a single wire slave select command line between the 2 boards. These connections are shown in the red circles and arrows in the picture above. Please pay close attention to notes 1 through 4 in the picture above. Note that T-J13 on Master connects to R-J13 on Slave and likewise R-J13 on Master connects to T-J13 on Slave.
For balanced audio, you will need a pair of V2 boards. The master board is designated for the right channel and the slave board handles the left channel. The + channel terminates in J1L and the – channel terminates in J1R. This is arbitrary but it helps to be consistent to both avoid and help diagnose any problems. We recommend the XLR Pin 1 shields be connected together as “pass through” so that the whole “Pin 1 problem” is dealt with at your source and amp and not also at the preamp. A great article on the Pin 1 problem can be found here.