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umut1001 15th September 2008 07:59 AM

opamp mod
 
hi..i have an emu1212m sound card.it has very good audio specifications.there is njm2068opamps in this card...i want to replace a better high current dual opamps..i had a little look at the internet..LM4562 has 40ma output current max..njm4556 has70ma output current but its an old opamp..i want the card to be capable of driving low impedances(70-100)ohms and low noise low distortion..what do you prefer?..thanks

lineup 15th September 2008 11:06 AM

Re: opamp mod
 
Quote:

Originally posted by umut1001
hi..i have an emu1212m sound card.
it has very good audio specifications.
there is njm2068opamps in this card...
i want to replace a better high current dual opamps..

i had a little look at the internet..
LM4562 has 40ma output current max..
njm4556 has70ma output current but its an old opamp..
i want the card to be capable of driving low impedances(70-100)ohms and low noise low distortion..what do you prefer?..thanks

Guess the output voltage max will be ~2.0 V RMS ?
Would need 20 mA - 30 mA max output (100-70ohm)
20 mA x 100 ohm = 2.0 Volt
30 mA x 70 ohm = 2.1 Volt

Most standard opamps we use for audio can do this!

Here is one photo series article, when one guy replacing NJM4556
with one absolute killer perfromance Op-amp: LME49860
see this National OpAmp selector WIZARD
http://www.national.com/analog/amplifiers


This new super opamp, LME49860, has Minimum 30 mA output current.
Quote:

X-FI Op Amp and Cap Modification
http://www.esnips.com/profile/7e52f1...1-e66aa0b8ae45

- NJM4556 replaced with National Semiconductor LME49860 -
Jamicon 220uf @ 16vdc replaced with Panasonic FK series 1500uf @ 16vdc
Visitors: 2997
One budget Audio OPA2134 could do the job.
It is one normal dual opamp in 8 pin DIP8.
And can provide something like 35-40 mA.

umut1001 15th September 2008 11:54 AM

hehe hi lineup..i am using sennheiser hd25 dj headphone..i had m-audio 192 sound card(it has njm4556 +-70ma output for150ohms) it can drive these headphones.and now i have emu1212m(it has njm2068 it has lower distortion but lower output current too).i used lm4562 too..it was not enough for my headphones..i am sure it can drive little headphones not mine..it becomes distorted when i increase the level of the sound..i want to drive directly from sound card by opamps..not wanna use headphone amps..

TheSeekerr 15th September 2008 12:33 PM

I don't mean to ignore what you're saying, but realistically you're not going to find a high fidelity opamp that is suitable for your application and supplies a high current output. Building a small, separate, buffered headphone amplifier will allow you to use high quality opamps for the gain stages while leaving the current capacity to chips designed for the job.


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