JBL 300.4 amp upgrade/mods

ahmisuhairi · 11th September 2007, 05:31 AM

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?

ppia600 · 12th September 2007, 12:01 AM

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

ahmisuhairi · 12th September 2007, 05:03 AM

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

1moreamp · 12th September 2007, 07:02 AM

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.

ahmisuhairi · 13th September 2007, 04:12 AM

thanks
i do hv the service manual does it help?
should i replace the cap inside?

1moreamp · 13th September 2007, 06:18 AM

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..

ahmisuhairi · 26th September 2007, 06:34 AM

whats the options that i have if i would like to upgrade the op amps in terms of sq and audiophile quality?

11th September 2007, 05:31 AM	#1
ahmisuhairi diyAudio Member Join Date: Sep 2007	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?

12th September 2007, 12:01 AM	#2
ppia600 diyAudio Member 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 __________________ Don't worry... you can always turn the gain down!

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12th September 2007, 05:03 AM	#3
ahmisuhairi diyAudio Member 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

12th September 2007, 07:02 AM	#4
1moreamp diyAudio Member 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.

13th September 2007, 04:12 AM	#5
ahmisuhairi diyAudio Member Join Date: Sep 2007	thanks i do hv the service manual does it help? should i replace the cap inside?

13th September 2007, 06:18 AM	#6
1moreamp 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..

26th September 2007, 06:34 AM	#7
ahmisuhairi diyAudio Member 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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