Fortunately or unfortunately, the PCM63 datasheet on page 9 says below which necessitates op-amps. Can probably be replaced by tubes also or discrete transistors.
"APPLICATIONS
The most common application for the PCM63P is in highperformance
and professional digital audio playback, such
as in CD and DAT players. The circuit in Figure 6 shows the
PCM63P in a typical combination with a digital interface
format receiver chip (Yamaha YM3623), an 8x interpolating
digital filter (Burr-Brown DF1700P), and two third-order
low-pass anti-imaging filters (implemented using Burr-Brown
OPA2604APs).
Using an 8x digital filter increases the number of samples to
the DAC by a factor of 8, thereby reducing the need for a
higher order reconstruction or anti-imaging analog filter on
the DAC output. An analog filter can now be constructed
using a simple phase-linear GIC (generalized immittance
converter) architecture. Excellent sonic performance is
achieved using a digital filter in the design, while reducing
overall circuit complexity at the same time.
Because of its superior low-level performance, the PCM63P
is also ideally suited for other high-performance applications
such as direct digital synthesis (DDS)."