Wiring to a BA3426AS Preamp

[Robotnik]

Hello, I have a CD/Dual cassette/AM/FM player from Sony (model: CFD-ZW700).

IT doesn't have audio inputs, and of course, I want some (to use it for
watching movies, computer games...et cetera).

I took it apart and found that it as the BA3426AS Preamp chip. I found some
reference info about this chip (
http://www.rohm.com/products/databook/audio/pdf/ba3426s.pdf <--- there's
what I found and looked at), and it says it has Mic Input (I think it's mono
though) CD in, dual cassette in, and Radio in. Now, I was
wondering....could I just wire my audio input connectors to an existing
input (just solder wires from the connectos directly to where the CD player
inputs are soldered to this chip) and then just turn it on and set it to CD,
and and start inputing audio? Or am I going to start a fire doing
this.....? And if so, where do I wire the ground to?

Hope someone can help

Thanks!

Nic

 

[Lizard Blizzard]

Robotnik wrote:

Hello, I have a CD/Dual cassette/AM/FM player from Sony (model: CFD-ZW700).

IT doesn't have audio inputs, and of course, I want some (to use it for
watching movies, computer games...et cetera).

I took it apart and found that it as the BA3426AS Preamp chip. I found some
reference info about this chip (
http://www.rohm.com/products/databook/audio/pdf/ba3426s.pdf <--- there's
what I found and looked at), and it says it has Mic Input (I think it's mono
though) CD in, dual cassette in, and Radio in. Now, I was
wondering....could I just wire my audio input connectors to an existing
input (just solder wires from the connectos directly to where the CD player
inputs are soldered to this chip) and then just turn it on and set it to CD,
and and start inputing audio? Or am I going to start a fire doing
this.....? And if so, where do I wire the ground to?

You have to drive the CD input with enough power to get the half volt or
so that's usually the line level at that point. If the CD's output is a
low impedance, it might need quite a bit of AC current from your
external device. It might be advisable to put a resistor between the CD
and the chip, to make sort of a passive mixer. The resistor might be
some value in the 1 to 100k range. It depends on how low the input
impedance of the chip is. If you get the value too high, you will have
to crank the volume control up too much to get average listening level.

Like so: (view with courier font)

Was: CD Player -->-------------o Chip

Change to:

CD -->--------+---------o Chip
|
|
|
o
from external device

OR:

CD -->--/\/\----+---------o Chip
|
|
|
o
from external device

OR:

CD -->--/\/\/\---+-------o Chip
|
\
/
\
/
|
o
from external device (if it's also low impedance output)

Resistors depend on the input impedance of the chip. They could be 10k,
or maybe 2.2k for best compromise in levels.

Hope someone can help
Thanks!
Nic

--
----------------(from OED Mini-Dictionary)-----------------
PUNCTUATION - Apostrophe
Incorrect uses: (i) the apostrophe must not be used with a plural
where there is no possessive sense, as in ~tea's are served here~;
(ii) there is no such word as ~her's, our's, their's, your's~.

Confusions: it's = it is or it has (not 'belonging to it'); correct
uses are ~it's here~ (= it is here); ~it's gone~ (= it has gone);
but ~the dog wagged its tail~ (no apostrophe).
----------------(For the Apostrophe challenged)----------------
From a fully deputized officer of the Apostrophe Police!

<<Spammers use Weapons of Mass Distraction!>>

I bought some batteries, but they weren't included,
so I had to buy them again.
-- Steven Wright

FOR SALE: Nice parachute: never opened - used once.

F
o
d
d
e
r

f
o
r

s
t
u
p
i
d

n
o
t

e
n
o
u
g
h

i
n
c
l
d
u
d
e
d

t
e
x
t

e
r
r
o
r

m
s
g
..

 

[Robotnik]

So do you think it might be wise to use some pots for temporal use until I
find proper resistances?

"Lizard Blizzard" <NOSPAM@rsccd.org> wrote in message
news:bgr3mh$3kedj$1@hades.csu.net...

Robotnik wrote:

Hello, I have a CD/Dual cassette/AM/FM player from Sony (model:
CFD-ZW700).

IT doesn't have audio inputs, and of course, I want some (to use it for
watching movies, computer games...et cetera).

I took it apart and found that it as the BA3426AS Preamp chip. I found
some
reference info about this chip (
http://www.rohm.com/products/databook/audio/pdf/ba3426s.pdf <--- there's
what I found and looked at), and it says it has Mic Input (I think it's
mono
though) CD in, dual cassette in, and Radio in. Now, I was
wondering....could I just wire my audio input connectors to an existing
input (just solder wires from the connectos directly to where the CD
player
inputs are soldered to this chip) and then just turn it on and set it to
CD,
and and start inputing audio? Or am I going to start a fire doing
this.....? And if so, where do I wire the ground to?

You have to drive the CD input with enough power to get the half volt or
so that's usually the line level at that point. If the CD's output is a
low impedance, it might need quite a bit of AC current from your
external device. It might be advisable to put a resistor between the CD
and the chip, to make sort of a passive mixer. The resistor might be
some value in the 1 to 100k range. It depends on how low the input
impedance of the chip is. If you get the value too high, you will have
to crank the volume control up too much to get average listening level.

Like so: (view with courier font)

Was: CD Player -->-------------o Chip

Change to:

CD -->--------+---------o Chip
|
|
|
o
from external device

OR:

CD -->--/\/\----+---------o Chip
|
|
|
o
from external device

OR:

CD -->--/\/\/\---+-------o Chip
|
\
/
\
/
|
o
from external device (if it's also low impedance output)

Resistors depend on the input impedance of the chip. They could be 10k,
or maybe 2.2k for best compromise in levels.


Hope someone can help
Thanks!
Nic



--
----------------(from OED Mini-Dictionary)-----------------
PUNCTUATION - Apostrophe
Incorrect uses: (i) the apostrophe must not be used with a plural
where there is no possessive sense, as in ~tea's are served here~;
(ii) there is no such word as ~her's, our's, their's, your's~.

Confusions: it's = it is or it has (not 'belonging to it'); correct
uses are ~it's here~ (= it is here); ~it's gone~ (= it has gone);
but ~the dog wagged its tail~ (no apostrophe).
----------------(For the Apostrophe challenged)----------------
From a fully deputized officer of the Apostrophe Police!

Spammers use Weapons of Mass Distraction!

I bought some batteries, but they weren't included,
so I had to buy them again.
-- Steven Wright

FOR SALE: Nice parachute: never opened - used once.

F
o
d
d
e
r

f
o
r

s
t
u
p
i
d

n
o
t

e
n
o
u
g
h

i
n
c
l
d
u
d
e
d

t
e
x
t

e
r
r
o
r

m
s
g
.

 

[Lizard Blizzard]

Robotnik wrote:

Maybe I should find some volume control pots then, since there are two
channels, just to keep them equal. Also, where do I attach the ground to?
Just whichever pin is
marked ground on the preamp chip? Or the post amp........or none of the
above.

Well, presumably the signal wire to the CD has a shield or ground.
That's as good a place as any.

[snip]


--
----------------(from OED Mini-Dictionary)-----------------
PUNCTUATION - Apostrophe
Incorrect uses: (i) the apostrophe must not be used with a plural
where there is no possessive sense, as in ~tea's are served here~;
(ii) there is no such word as ~her's, our's, their's, your's~.

Confusions: it's = it is or it has (not 'belonging to it'); correct
uses are ~it's here~ (= it is here); ~it's gone~ (= it has gone);
but ~the dog wagged its tail~ (no apostrophe).
----------------(For the Apostrophe challenged)----------------
From a fully deputized officer of the Apostrophe Police!

<<Spammers use Weapons of Mass Distraction!>>

I bought some batteries, but they weren't included,
so I had to buy them again.
-- Steven Wright

FOR SALE: Nice parachute: never opened - used once.

F
o
d
d
e
r

f
o
r

s
t
u
p
i
d

n
o
t

e
n
o
u
g
h

i
n
c
l
d
u
d
e
d

t
e
x
t

e
r
r
o
r

m
s
g
..