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δ2 dual bus configurations - zone or loop

PostPosted: March 8th, 2018, 9:27 am
by HSEAlark271
I was planning the configuration of a pair of d2 selectors for a passive use case that required use of only one of the busses. the d2 layout has some interesting flexibility and I came up with several options to use the second bus that others may find useful in their use cases. Please note that deviating from the intent of the original designer risks losing certain features incorporated in the base product, such as the shunting of outputs on power on/off and integration into the alpha preamps. The primary assumption in the following examples is that load impedances are high enough to be "bridging" for all source impedances. Buffers may be required if this condition is not true in your system. No trace cuts or software modifications are required to implement these configurations.

The diagrams illustrate only half of a d2 board and I have removed ground circuits along with other distracting details to highlight the "HOT" audio path. I have also tried to use terms consistently:
SEND = output bus to processor or recorder to which input sources are connected as in the usual d2 board configuration
RETURN = bus to which external processor outputs connect that serves as final output to MONITOR as in the usual d2 board configuration
INPUT = from sources
MONITOR = final output to speaker or headphone amplifiers

First is independent selection of sources for two zones:

Dual-Bus_2-zone_selector.gif


Use Outputs in toggle mode to select 1 input per zone. Up to 4 inputs can be shared in both zones or dedicate some inputs to each zone with fewer inputs shared. Shunt resistors mean sources always drive a pair of parallel loads. Of course you could enable multiple zone outputs in the usual d2 configuration, but sharing only a single selected source in all zones.

Modifying this configuration slightly enables a loop configuration to insert a processor or recorder using standard configuration of each IO port:

Dual-Bus_loop_selector_A.gif


The SEND output is always live and parallels the MONITOR output when the SEND bus is selected for MONITOR out. Toggling outputs operates like a processor insertion loop. If you want to isolate the SEND outputs when inactive, try this alternative:

Dual-Bus_loop_selector_B.gif


This configuration uses the shunt resistor pad to jumper the MONITOR output IO relay ground leg to the alternate bus, making the relay an output selector between the 2 busses. The ground shunt resistors are not used in this output configuration, as the output is always connected to a source. This neat trick allows up to 7 inputs if necessary - the external processor loop uses the OBUS connection as the RETURN port. Even more interesting options may be the use of IO ports/relays to activate SEND outputs. With one additional IO port, the loop may be toggled as outputs in software configuration. Multi-output enables separate activation of SEND output to the processor or recorder and selection of the MONITOR output - SEND bus or processor RETURN. The independent selection of MONITOR output operates more like the old tape monitor function. You should notice that additional SEND and MONITOR outputs can be configured using multi-output operation until you utilized all the available IO ports.

I an not sure yet if I will use Configuration B in my deployment, but find the flexibility of the d2 quite interesting and hope others find this informaiton useful.