Boulder Amplifiers 1012 DAC Preamplifier - Manual (Page 12)

CONNECTING AN UNBALANCED ANALOG SOURCE
Although the inputs are all of the 3 pin type, an unbalanced source
is easily accommodated by using a special cable. This cable has an RCA
phono type connector on the source end and a 3 pin connector for going
to an input on the 1012 DAC Preamplifier.
The minus input (pin 3) should be wired to ground only at the RCA
phono connector. This brings the minus input reference of the 1012 to the
unbalanced source ground, thus reducing ground loops.
Another option for accommodating unbalanced sources is that of the
Boulder ABL analog input adapter. It converts a balanced input into a
RCA phono input right at the rear of the 1012.
Like the above cable, the minus input of the 1012 is connected to
the ground of the RCA phono. However, this minus side will then share
the shield wire with the chassis ground and will not have the best hum
rejection.
GETTING
STARTED
1-6
UNBALANCED INPUT CABLE
3-NEG INPUT
2-POS INPUT
1-GROUND