JBL 300.4 amp upgrade/mods - diyAudio
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Old 11th September 2007, 05:31 AM   #1
diyAudio Member
 
Join Date: Sep 2007
Default JBL 300.4 amp upgrade/mods

Im new here and wondering if u guys can help me with the options that I have.

MAIN PCB

ICO-00-00022
I.C PWM IC "DIP 14"
TL494CN
U1

ICO-00-00109
I.C QUAD OP AMP "DIP 14"
NJM2058D
U101,102,103,104,105,108,109,110

ICO-00-00003
I.C DUAL OP AMP "DIP 08"
TL072
U111,112,113,114

ICO-00-00095
I.C DUAL COMPARATOR "DIP08"
KIA393P
U801

What about power cap, is it advisable to change it too?
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Old 12th September 2007, 12:01 AM   #2
ppia600 is offline ppia600  United States
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Join Date: Jun 2007
Location: Louis y ana
You need to specify what you are hoping to achieve by trying to "upgrade", maybe that will clarify it for the people here who might know if its possible
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Don't worry... you can always turn the gain down!
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Old 12th September 2007, 05:03 AM   #3
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Join Date: Sep 2007
i would like to tweak the amp to be used specifically for midrange and tweeter usage. (better in mid n highs)
i hope i can get more transparent in the sound n less floor noise
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Old 12th September 2007, 07:02 AM   #4
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Join Date: Dec 2005
Location: Northern California
Easy, Bypass the entire IC frontend, and run straight input to the main amplifiers on the board. Most of your troubles will be generated by all the IC's in the frontend.


PS leave the 494 and 393 IC's alone, they are power supply control chips, No audio there.
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Old 13th September 2007, 04:12 AM   #5
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Join Date: Sep 2007
thanks
i do hv the service manual does it help?
should i replace the cap inside?
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Old 13th September 2007, 06:18 AM   #6
diyAudio Member
 
Join Date: Dec 2005
Location: Northern California
Only if its defective , If you store excessive power inside the amp it could actually cause noise on shutdown unless the amp is muted properly.
Please remember if its not broken it does not need fixing.
Armed with this you will save yourself tons of money and time and effort..
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Old 26th September 2007, 06:34 AM   #7
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Join Date: Sep 2007
whats the options that i have if i would like to upgrade the op amps in terms of sq and audiophile quality?
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