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Old 28th July 2010, 08:40 PM   #1
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Default 4580 JRC Add Line Out

I have a DVD Nav Headunit in my Lancer and i want to add aftermarket amps to the radio.. But as you know most factory radios dont have rca out.. line-level out.. So I opened up the unit found the AMP IC and followed the imput to some "4580" jrc chips two of them.. can i solder my rca wires to the output.. do i need diodes capacitors etc this is a car radio..

Thanks for the help..
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Old 28th July 2010, 10:48 PM   #2
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That's a NJM4580 dual op-amp. It's probably line level out (ie RCA in this case). Whether or not you need capacitors or other parts depends on the circuit surrounding the op-amp.

Given that it's used in a car environment, you should put a capacitor (try 22uF 50V electrolytic) in series with the output followed by a resistor (try ~22k ohm) to ground.
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Last edited by Redshift187; 28th July 2010 at 10:51 PM.
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Old 29th July 2010, 09:11 PM   #3
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Quote:
Originally Posted by Redshift187 View Post
That's a NJM4580 dual op-amp. It's probably line level out (ie RCA in this case). Whether or not you need capacitors or other parts depends on the circuit surrounding the op-amp.

Given that it's used in a car environment, you should put a capacitor (try 22uF 50V electrolytic) in series with the output followed by a resistor (try ~22k ohm) to ground.

It looks like it uses the NJM4580 as a line driver for the TDA7386 AMP.. I dont plan on using the built in power at all so the amp will not have speakers pluged in.. But i do want to use the NJM4580 to output to RCA.. I found pins 11, 12, 14, and 15 to be the Line-IN at that amp ic and pin13 sig ground.. I was just thinking of putting 4 rca cables on pin 11,12,14,15 and ground all of them to pin 13..

Here are some pics i took so you can see what im looking at.. I know the cap the brown ones near the amp run in serial with the am imput one for each they say 224

IMG_0406.jpg

IMG_0411.jpg

Thanks for the info..
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Old 29th July 2010, 10:24 PM   #4
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It looks to me like C107, C127, C147, C167 are all electrolytics in series with the output of the op-amps to block DC.

10uF series -> resistor to ground -> resistor series -> muting transistor -> resistor series -> capacitor to ground -> brown capacitors? (0.22uF)

It's a very typical line out circuit. You can certainly tie some RCA outputs to the TDA7386 input pins. You may be able to find a better (easy to solder) ground point than pin 13. Just probe around likely spots and check for continuity to pin 13.
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Last edited by Redshift187; 29th July 2010 at 10:28 PM.
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Old 30th July 2010, 12:32 AM   #5
Artie is offline Artie  United States
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Actually, those caps are probably on the input pins, as shown here:

The outputs are bridged.
Attached Images
File Type: gif tda7386.gif (16.3 KB, 149 views)
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Old 30th July 2010, 01:15 AM   #6
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Originally Posted by Artie View Post
Actually, those caps are probably on the input pins, as shown here:

The outputs are bridged.
Yes the brown capacitors @ c169, c129, c109 and c149 are on the inputs to the TDA7386 so get the signal after the caps or before?

if the -> in brown caps -> tda7386
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Old 30th July 2010, 03:03 AM   #7
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Everything I said was after the op-amps, before the TDA. So yes, get your signal on the input pins of the TDA.
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Old 31st July 2010, 12:48 PM   #8
Artie is offline Artie  United States
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Here's a thought too: If it was me, I'd prefer not to go into the internals of the head unit. Why not build a simple spkr-to-line-level convertor? With the right selection of resistors, you can keep the TDA7386 down in the 1-watt range, which keeps the THD below .05%. That would be fine in a car environment, and you can adjust the resistor values to get whatever output voltage level you prefer.

Here's one way: (Btw, you want to balance the two speaker-wire output loads since this device is "bridged".)

The two inputs are LF+/LF- speaker outputs. Obviously, you'ld need four of these circuits.
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File Type: png spkr-to-line-out.png (2.8 KB, 134 views)

Last edited by Artie; 31st July 2010 at 12:52 PM.
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Old 1st August 2010, 12:35 AM   #9
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I like that idea Artie.
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Old 2nd August 2010, 08:21 PM   #10
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Quote:
Originally Posted by Artie View Post
Here's a thought too: If it was me, I'd prefer not to go into the internals of the head unit. Why not build a simple spkr-to-line-level convertor? With the right selection of resistors, you can keep the TDA7386 down in the 1-watt range, which keeps the THD below .05%. That would be fine in a car environment, and you can adjust the resistor values to get whatever output voltage level you prefer.

Here's one way: (Btw, you want to balance the two speaker-wire output loads since this device is "bridged".)

The two inputs are LF+/LF- speaker outputs. Obviously, you'ld need four of these circuits.
That is what I had before a "low level converter" but past 1/2 volume we saw distortion on a scope.. plus to me it did not sound good.. i had pop and noise.


IMG_0419.JPG

IMG_0418.jpg

well its done now.. I just need to put it back in the car and see what it sounds like I wished I still had access to the scope to see what it does now.. I belive those opamp should be doing around 4volts.. so that should be perfect for my amps..
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