TL  [Philips]  SA572N
HA  [Logo]     GGW1791
AN             9814nH
ID

Topmark decodes as (per 2000 Philips Quality Manual, repeated at https://www.dutchaudioclassics.nl/TDA1541-Product-manufacturing-codes-and-markings/):

• Commercial part number: SA572N (SA572, 16-pin dual in-line package)
• Diffusion lot GGW17, assembly sequence 91
• Date of manufacture 1998, week 14. Diffused at Philips Semiconductors Nijmegen (H), assembled in Bangkok (n)

Later parts carry the more recent (~2000) Philips line-3 topmark format of YYWWDAR – Year, Week, Diffusion, Assembly, (centre of) Responsibility. These later parts usually indicate “centre of responsibility” being Sunnyvale, i.e. Signetics. This matches up with the Philips datasheet indicating that this is a Signetics part.

Decap took three attempts.

• First: rosin decap left residue stuck to the die surface.
• Second: Blowtorch caused thermal damage to the die.
• Third: rosin decap with hotter boil successfully decapped the chip.

Brightfield, Olympus MSplan 20x

• Single (25376×21760, 97.3794MiB)

• The circuit is mirrored roughly down the centre.
• A 2.5V bandgap voltage reference is shared by both channels. This is likely the non-quite-symmetrical centre section.
• Bipolar process with extensive use of polysilicon resistors

The SA571 is a mono version of this chip. A SPICE model is available from jorg on the Mod Wiggler forums, including a transistor-level schematic. This may make it easier to follow the circuitry on the IC.