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The Lavry DA-924 and Sansui TU-X1 are on separate equipment legs/chains and only come together at inputs to the amplifier.  They also are on separate uninterruptible power supplies that are on separate legs of our wall supplies.  Also, amplifier has internal pre-amplifier section.

Leg/chain A.

Digital source #1 feeds the DD-2 processor.
DD-2 processor feeds the Lavry DA-924 (AES-1).

Digital source #2 feeds the Lavry DA-924 (AES-2).
Lavry DA-924 feeds analog output to the amplifier (inputs pair #1).
Amplifier feeds speaker arrays.

Leg/chain B.

AM tuner system (aerial, rotator and fine tuner) feeds the Sansui TU-X1.
FM tuner system (aerial array and rotator) feeds the Sansui TU-X1.
Sansui TU-X1 feeds analog output (OUTPUT-1 VARIABLE FM) to the amplifier (inputs pair #2).
Sansui TU-X1 feeds analog output (OUTPUT-2 VARIABLE AM) to the amplifier (inputs pair #3).
Sansui TU-X1 feeds analog output (OUTPUT-3 FIXED FM) to the amplifier (inputs pair #4).
Amplifier feeds speaker arrays.

Leg/chain C.

Microphones feed analog output to the Lavry 4496 (pre-amplifier + clock + ADC).
Lavry 4496 feeds digital output to the hard disc recorder.
Hard disc recorder (inbuilt DAC) feeds analog output to the amplifier (inputs pair #5).
Hard disc recorder (digital source #3) feeds digital output to backup DAC.
Backup DAC feeds analog output to the amplifier (inputs pair #6).
Amplifier feeds speaker arrays.

Thoughts:

1.  Lavry performs a power supply upgrade for DA-924 units marked as 'db technologies'.  Have you done that upgrade?  I wonder if that upgrade would help mask some of the noise/interference you are receiving.

2.  Does your Sansui TU-X1 have the AM section active or did you disconnect/remove it?  I assume that your Sansui TU-X1 has the AM section operational and that, as standard, the TU-X1 is supplying AM and FM output simultaneously.

3.  Do you have an external AM aerial attached to the Sansui TU-X1 or are you relying on the inbuilt AM aerial (which I found unusable in our location)?  In my case, I was able to use my powerful AM antenna system to clearly identify one of the noise sources as a very distant AM broadcast even though the amplifier was switched to amplify the Sansui TU-X1's OUTPUT-1 VARIABLE FM or the OUTPUT-3 FIXED FM.  Weird.

4.  Regardless of the above, there is still a source of noise/interference that the Lavry DA-924 generates on my system when it cycles looking for digital sources, i.e., AES1 -> AES2 -> IEC -> MUTE -> AES1 ... at 95.7 MHz through 96.0 MHz.

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