Alpine HU output voltage tweaking.

[rrae]

I am looking at two headunit specs. 9853 have 2V outputs, 9855 have 4V.
By looking at service manual - higher output voltage is done with TDA7412? Because i cant see difference in part-level.
To reduce noise floor from amp, wanted to get 4V output from 9853.
9853 sm -
http://diagramasde.com/diagramas/otros2/CDA-9853R.pdf
9855 ALPINE CDA-9855R SM Service Manual free download, schematics, eeprom, repair info for electronics

 

[Perry Babin]

Do you have the 9853?

 

[jerluwoo]

I couldn't access the 9855 manual. If they both use the tda7412 there should be no difference in the output from it. Have a look at the resistor values used in the buffer amps following the 7412. The 9853 uses 24k and 22k to set gain to near unity. Perhaps the 9855 uses different values to increase gain here.

 

[Perry Babin]

http://www.bcae1.com/temp/alpine - SM - cda-9855r.pdf
http://www.bcae1.com/temp/alpine - SM - cda-9853R.pdf

 

[rrae]

Yes, friend of mine have 9853. He wanted the upgrade. I am just curious, if its possible.
They both use the same resistors for the opamp input.

 

[Perry Babin]

Drive a 0dBfs signal into the head unit and see what the input and output of the volume IC is.

Changing the value of the resistors as was suggested may be one way to boost the voltage.

 

[jerluwoo]

After having another look through the sheets I am now a little confused. The 9853 claims 6 volts out and the 9855 4 volts. The schematic sections are pretty much the same.

 

[rrae]

I was looking in users manual - http://www.alpine-europe.com/filead...istory_products/CDA-9853R/OM_CDA-9853R_EN.pdf
Maximum Pre-Output Voltage
4 V/10k ohms (CDA-9855R)
2V/10k ohms (CDA-9853R)