A  TDA1547-Based Tweak

The TDA1547 IC is an High Performances Single Bit Audio DAC of the past generation with the following features:

The Pin-Out of this unit is depicted in Fig. 1

Fig1

    The Switched Capacitor Network supplies out-of-phase charge-packets modulated by the One-Bit Input Block. The I/V conversion can be  obtained by the couple of OP-Amp embedded inside the IC. 

Fig2

To follow an "out-chip" low pass post-filtering  targets the design for a specific need.

For example the Fig3 shows a post-filter net for the mainstream 192fs application (f0=55kHz).

Fig3

AR and AL red-underlined blocks are charge-packets to voltage converters realized with the internal op-amps while BL and BR blue-underlined are the out-board post-filters for the 192fs application.

We can improve the sound of CD-Unit with the TDA1547 by a two-level of tweaking.

First Level
  • Remotion of  post-filtering blocks
  • Insertion of SOT1 m-metal core units as shown.

Note: Interface blocks represent to the interconnecting modalities of transformer  for 1:1 or 1:2  ratio and/or   balanced to unbalanced or balanced to balanced signal transfer (no additive components).

Second Level
  • By-passing of the embedded op-amps and rely on a passive charge-packet to voltage convertion (networks RC conncted to pins: 29, 22, 10, 11 respectively).
  • Inserction   of SOT1 m-metal core units as shown.

A tweak  on a Philips CD Units

Photo 1

 

Photo 2

                 Artworks by Alessandro Angelini

 

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