CXA2570 Sony Corporation, CXA2570 Datasheet - Page 15

• Manufacturer Part Number: CXA2570
• Description: RF Matrix Amplifier
• Manufacturer: Sony Corporation

Notes on Operation
Stabilizing the RFAC signal
The RFAC system (RFSUM + EQ) is comprised entirely of non-inverted function blocks.
This is in order to support pickups with built-in RFSUM.
Therefore, if the voltage gain of each block is increased, a feedback loop is formed over the entire RFAC
system causing the RFAC signal to become unstable (oscillate).
In these cases, it is recommended to lower the EQ frequency response and the boost gain. This has a large
effect on the board (power supply, I/O signal cross talk, etc.) loop. The RFAC signal easily becomes unstable if
the VCA gain is increased, the EQ boost frequency is set to a high frequency, the EQ boost amount is
increased, etc.
The VCA gain is low in ROM mode, so the RFAC signal is stable. Also, when not using RFSUM, the RFAC
signal is stabilized because the overall gain is low.
The area where the RFAC signal becomes unstable is thought to vary for each set, as this is greatly affected
by the board loop as noted above.
Proposed stabilization measures
The board and other loop characteristics can be changed by adding external capacitance as noted below.
This has a particularly large effect on the stabilization when using RFSUM.
RF
SUM
ACSUM
Add capacitance of 10pF to 20pF.
0.1
EQI
– 15 –
VCA
EQ
AMP
CXA2570N