Sony CFD-S47L auxiliary input

[jure8479]

Hi,

recently I decided to add an auxiliary input to my old Sony CFD-S47L radio.
I have connected an 3.5mm female audio jack to the TA2068N.
The inputs on the TA2068N coming from the tape deck gave my some very bad sound, so I decided to use the ones from the CD (pins 14 and 24).
When using this configuration there are two problems:

1. I need to play an "soundless" CD while I am using my improvised AUX input
2. The sound is still pretty bad, sounds like both stereo channels are playing on both speakers (or something similar)

How can I activate these TA2068N input pins without playing a CD (IE using an external switch).
Why is the sound still low quality?

Since I am not sure if it is allowed to post screenshots of Sony schematics so I will simply post a download link: **broken link removed**

 

[BradtheRad]

Assuming your player is compatible with what you're planning, I would make a 'silent' audio CD this way:

(a) Open a digital sound editing program. (Example, Audacity is free, and popular.)

(b) Generate several minutes of silence in L & R channels. 70-75 minutes is a reasonable maximum that will fit on an audio CD.

(c) Save as '.wav' file.

(d) Burn the wav file to CD. Your Mac and Windows OS can do this directly, if it's a recent version.

Not all CD's will be recognized in all players. The most reliable scenario is a CD-R, plain color.

Not so reliable is a CD-RW, or blue tinted.

 

[IANZACH]

From your Schematic it is clear to me that you are overdriving the inputs of the TA 2068N.
Typically a tape head delivers a signal of about 2 milivolts this would then be amplified a small amount by the volume sound control IC.
A aux input is typical in the region of 1volt this is why the sound is so bad.
you will need to make a voltage divider network to bring the voltage of the AUX input to the order of a few millivolts.

- - - Updated - - -

Looking at the datasheet for the TA 2068

Pin 15 = tape enable
Pin 17= Cd enable/ Radio enable ( when all inputs off radio is enabled)
pin 21 = rec/ PB enable

The enable can be anything from 4v to VCC of the IC.

Tape in = pin 8 left Pin 5 Right = 0.154mv input
Cd In = Pin 14 Left Pin 24 Right = 0.027mv input
Radio in = Pin 22 Left Pin 16 Right = 0.078 mv Input

 

[jure8479]

Assuming your player is compatible with what you're planning, I would make a 'silent' audio CD this way:

(a) Open a digital sound editing program. (Example, Audacity is free, and popular.)

(b) Generate several minutes of silence in L & R channels. 70-75 minutes is a reasonable maximum that will fit on an audio CD.

(c) Save as '.wav' file.

(d) Burn the wav file to CD. Your Mac and Windows OS can do this directly, if it's a recent version.

Not all CD's will be recognized in all players. The most reliable scenario is a CD-R, plain color.

Not so reliable is a CD-RW, or blue tinted.

BradtheRad thank you for your detailed instructions. I have previously used such a CD, but I was looking to avoid using the CD completely.

- - - Updated - - -

From your Schematic it is clear to me that you are overdriving the inputs of the TA 2068N.
Typically a tape head delivers a signal of about 2 milivolts this would then be amplified a small amount by the volume sound control IC.
A aux input is typical in the region of 1volt this is why the sound is so bad.
you will need to make a voltage divider network to bring the voltage of the AUX input to the order of a few millivolts.

- - - Updated - - -

Looking at the datasheet for the TA 2068

Pin 15 = tape enable
Pin 17= Cd enable/ Radio enable ( when all inputs off radio is enabled)
pin 21 = rec/ PB enable

The enable can be anything from 4v to VCC of the IC.

Tape in = pin 8 left Pin 5 Right = 0.154mv input
Cd In = Pin 14 Left Pin 24 Right = 0.027mv input
Radio in = Pin 22 Left Pin 16 Right = 0.078 mv Input

Thank you IANZACH. This explanation is what I was looking for. Will post my results here when I try this out.

 

[jure8479]

IANZACH are you sure Cd In voltage is 0.027mV and not 0.027V?

 

[IANZACH]

Hi Jure8479

I stand corrected all voltages are expressed in V and not mV

 

[jure8479]

Ok. Thanks a lot IANZACH.