i have the njm4556 for headphone output on my adcom GFP 565 preamp which the manual states 100 ohm impeadance but, the radio shack phones i just purchased have 60 ohm impeadance? are there better choices for op amp? or maybe add buffers such as LT1010, or buf634t which i have both of? if buffers would be best, anyone know of any Links where i could find out how to apply the buffers? thanks, crippledchicken 
The BUF634 datasheet is very good and explains how to boost op-amps with it.
Any normal op-amp would be struggling to drive less than 600 ohms. I think OPA134 series will drive headphones OK directly. You'd have to check the datasheet for the NJM to confirm it's driving ability. You need to see what voltage the chip is running from then check the output current limit graphs.
Any normal op-amp would be struggling to drive less than 600 ohms. I think OPA134 series will drive headphones OK directly. You'd have to check the datasheet for the NJM to confirm it's driving ability. You need to see what voltage the chip is running from then check the output current limit graphs.
Hi crippledchicken,
You will find the 4556 is used in almost every product without an amplifier to drive headphones. It was designed for this.
If you want better performance, I would suggest building an outboard unit. There is only so much you can do with a single op amp to get rid of heat. Then you can build better power supplies and use the better op amps to full effect.
-Chris
You will find the 4556 is used in almost every product without an amplifier to drive headphones. It was designed for this.
If you want better performance, I would suggest building an outboard unit. There is only so much you can do with a single op amp to get rid of heat. Then you can build better power supplies and use the better op amps to full effect.
-Chris
hi Dominique, what i need are the DIP-8. i have, opa2132, opa2134, opa2604, lm6172,, AD826, LT1364, as well as the LT1010, and BUF634T buffers on hand if any of these could be implemented for better performance? thanks for any ideas, crippledchickenDominique said:There are certainly better performing op-amps out there... (ok, I didn't look at the NJM4556 datasheet yet
Do you need a DIP-8 or SO-8 package?
I had in mind to simply replace the op-amp for a stronger one, but after checking my gathered data, I couldn't find op-amps in a DIP package better than the NJM4556 (low impedance output), but only in SOIC and TO packages. Most of them are high speed, so it's not clear if they would work fine without tweaks in your existing circuit anyway.
Either you simply try your new headphones and listen if there's more distortion, build an outboard unit like anatech proposed, add a little pcb with a buffer in your preamp (then you could replace the NJM4556 for a weaker, but better op-amp), or use a SOIC op-amp with a SOIC to DIP adapter (but it's not guaranteed to work fine in your existing preamp (because all those strong SOICS on my list were high speed )
Sorry I couldn't be of much help!
Cheers,
Dominique
Either you simply try your new headphones and listen if there's more distortion, build an outboard unit like anatech proposed, add a little pcb with a buffer in your preamp (then you could replace the NJM4556 for a weaker, but better op-amp), or use a SOIC op-amp with a SOIC to DIP adapter (but it's not guaranteed to work fine in your existing preamp (because all those strong SOICS on my list were high speed
)Sorry I couldn't be of much help!
Cheers,
Dominique
Hi Dominique, i replaced the op amp with the opa2132p and added the buf634t buffers and the difference is amazing! no problems at all driving the phones sounds great, and no back ground hiss or any type of audible distortion. thanks very much for your help, crippledchickenDominique said:I had in mind to simply replace the op-amp for a stronger one, but after checking my gathered data, I couldn't find op-amps in a DIP package better than the NJM4556 (low impedance output), but only in SOIC and TO packages. Most of them are high speed, so it's not clear if they would work fine without tweaks in your existing circuit anyway.
Either you simply try your new headphones and listen if there's more distortion, build an outboard unit like anatech proposed, add a little pcb with a buffer in your preamp (then you could replace the NJM4556 for a weaker, but better op-amp), or use a SOIC op-amp with a SOIC to DIP adapter (but it's not guaranteed to work fine in your existing preamp (because all those strong SOICS on my list were high speed
Sorry I couldn't be of much help!
Cheers,
Dominique
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