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GF-9494 - Convert Phono to Line In, simple mod


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#1 Line Out

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Posted 08 March 2018 - 08:38 PM

So, I just found out that my new 9494X doesn't make any sound from DIN or Mic input. So, a little bit of looking around for other model schematics and how they have made Line/Phono -inputs with a switch. After a while, I came to a conclusion that I just need to remove 4 caps and make two jump wires to the Phono switch and it should work.

 

So here is the schematics on how to do it. I will take some pictures and add more illustrations, but I'll rush a bit this time because I'm so stoked about this. The sensitivity of the input seems very fine and sound is clear!  :thumbsup: EDIT: And there isn't any noise either, very very good S/N ratio.

 

Attached File  Phono to Line In.png   89.83K   6 downloads



#2 caution

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Posted 09 March 2018 - 01:31 AM

Nice one! This would work for a lot of models.

I like the username/subject contrast. How to create line in, by Line Out.

"Hi, I'm a 35-year-old line out that likes long walks on the beach, not afraid of long-term attachment. Seeking a line in that's well-grounded and likes music. Turnons include normalization, balance and clarity. Phono conversion scars are not a dealbreaker. Turnoffs include hiss, interference, clipping and static."

 



#3 Northerner

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Posted 09 March 2018 - 02:16 AM

Nice one! This would work for a lot of models.
I like the username/subject contrast. How to create line in, by Line Out.
"Hi, I'm a 35-year-old line out that likes long walks on the beach, not afraid of long-term attachment. Seeking a line in that's well-grounded and likes music. Turnons include normalization, balance and clarity. Phono conversion scars are not a dealbreaker. Turnoffs include hiss, interference, clipping and static."

Lol you nutter :-) :-)

So, I just found out that my new 9494X doesn't make any sound from DIN or Mic input. So, a little bit of looking around for other model schematics and how they have made Line/Phono -inputs with a switch. After a while, I came to a conclusion that I just need to remove 4 caps and make two jump wires to the Phono switch and it should work.

So here is the schematics on how to do it. I will take some pictures and add more illustrations, but I'll rush a bit this time because I'm so stoked about this. The sensitivity of the input seems very fine and sound is clear! :thumbsup: EDIT: And there isn't any noise either, very very good S/N ratio.

Phono to Line In.png

Nice work! Some pics of the actual board would help me a lot :-)

#4 goodman

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Posted 09 March 2018 - 03:06 AM

Hello, I wrote about this mod before a year ago. look here:

 

https://boomboxery.c...n-mod/?p=330550

 

 



#5 metalhandbag

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Posted 11 March 2018 - 08:18 AM

Done this mod works well .

#6 Line Out

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Posted 11 March 2018 - 02:09 PM

Hello, I wrote about this mod before a year ago. look here:

 

https://boomboxery.c...n-mod/?p=330550

 
I just noticed your version a few moments after I posted mine. I noticed you didn't remove the caps, what is their function and how do they affect the signal? And of course, it probably is much smarter to remove the unneeded components altogether and my version was just a quick test but it seemed to work.

 

Here is how it looks on the PCB (illustration is from the top side)
Attached File  line-in-pcb.jpg   351.32K   6 downloads



#7 goodman

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Posted 13 March 2018 - 01:59 AM

Hi. I agree with you, that your method is very simple.
I don't have this boombox, and only want to help to another members.

My method is only theoretical. I don't test it.

Most important is, that this idea (to bypass phono amp) work in practice.
Have a nice day.



#8 Ceestarrs

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Posted 26 March 2018 - 04:33 PM

Here is how it looks on the PCB (illustration is from the top side)

 

I'm about to tackle this on my 9494- thanks for making things easier for me : )



#9 Superduper

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Posted 26 March 2018 - 08:17 PM

........I noticed you didn't remove the caps, what is their function and how do they affect the signal? And of course, it probably is much smarter to remove the unneeded components altogether and my version was just a quick test but it seemed to work.......

 

Wait, you have no clue what the purpose of the caps are for nor do you know how they affect the signal?  Double wait, and so you further concluded that because you don't know what they are for, IT'S SMARTER to just remove them because they must be unneeded and the manufacturers were just wasting money adding "unnecessary" components?   :blink:  :sadno:

 

Such caps are present throughout audio circuits and are essential components in amplifier circuits.  In simplistic explanation, they allow the desirable part of the signal to pass and block DC components which can introduce noise, distortion and possibly interfere with the succeeding amplifier stage's bias levels.  I think when I recapped a Marantz CRS-4000, I replaced about 120-something caps.  Caps are either the #1, or #2 most common component in audio circuits.  There is a reason for that.

 

In the future, if there's something you don't understand about the reason for the presence of something, remember that there's method to the madness, and the people who DO understand probably believes they are needed for good reason.