You don't want to bypass these transformers.
Standard mixer design for consoles of that era was to use transformer inputs set for 600 ohms to match the typical output impedance of equipment such as tape recorders, cart machines as well as incoming lines from the telephone company.
Most of this equipment, and especially the telco lines, were balanced outputs and were happiest into the 600 ohm load.
If you look at an over-all schematic these 600 ohm inputs would then go to step attenuators, which would then feed a common program buss. The impedance of this buss would vary depending upon the number of inputs that were turned on at any one time. So this buss was designed to be a low impedance, hence switching faders in or out would not change the impedance of the buss that much. Otherwise, the signal levels would change as sources would be switched in and out. So the faders were designed to match 150 ohms. Hence 600 ohm to 150 ohm transformers.
Soooooo....how do you match high impedance devices such as CD players? You use a device like this (twin-match):
http://www.broadcasttools.com/view_product.php?pid=109#
which are made by a variety of manufacturers, but can easily built using TLO-72's & a bi-polar power supply.
The circuit takes the unbalanced -10 db output from the consumer style device, and creates a +4 balanced output that the board wants to see. Also clearing up level and frequency response problems.
48 ohm to 8 ohm transformers are cheap, they are commonly used in PA installations. Look for someone in your area who does this kind of work, the PA folks call them "70 volt Line" transformers (although that's a higher impedance, but many have both primary and secondary taps). Here's a sheet from a Canadian manufacturer:
http://www.hammondmfg.com/117.htm
