adding buf634t to op amp questions

crippledchicken · 9th November 2005, 03:06 PM

hi there, i thought about trying the circuit as it is in fig 5 of the buf634t data sheet. i have the njm4556 op amp alone, driving the headphones of 60 ohms impeadance. i thought about replacing the njm4556 with the opa2132 and adding the buffer as it is in figure 5. my question is, should i duplicate all resistors as is in the schematic including, the ones on the op amp it's self? i think the gain now, is less than the stated +21 gain as in the schematic. i'm trying to get around building an outboard headphone amp if possible. i will be driving the phones with the Adcom GFP 565 preamp. thanks for any help http://focus.ti.com/lit/ds/symlink/buf634.pdf

jaudio · 9th November 2005, 04:12 PM

You can leave the gain as it is now,just add the opa634 to the feedback loop.

Nisbeth · 9th November 2005, 04:18 PM

A gain of 21 is way too much for 60Ohm headphones. I suggest replacing the 10k resistor in the feedback loop with on that is 3k3-4k7 for a gain of app. 4-6. Leave the rest as it is

/U.

9th November 2005, 03:06 PM	#1
crippledchicken diyAudio Member Join Date: Dec 2003 Location: south east mo.	adding buf634t to op amp questions hi there, i thought about trying the circuit as it is in fig 5 of the buf634t data sheet. i have the njm4556 op amp alone, driving the headphones of 60 ohms impeadance. i thought about replacing the njm4556 with the opa2132 and adding the buffer as it is in figure 5. my question is, should i duplicate all resistors as is in the schematic including, the ones on the op amp it's self? i think the gain now, is less than the stated +21 gain as in the schematic. i'm trying to get around building an outboard headphone amp if possible. i will be driving the phones with the Adcom GFP 565 preamp. thanks for any help http://focus.ti.com/lit/ds/symlink/buf634.pdf

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9th November 2005, 04:12 PM	#2
jaudio diyAudio Member Join Date: Oct 2004	You can leave the gain as it is now,just add the opa634 to the feedback loop.

9th November 2005, 04:18 PM	#3
Nisbeth diyAudio Member Join Date: Jan 2001 Location: Denmark	A gain of 21 is way too much for 60Ohm headphones. I suggest replacing the 10k resistor in the feedback loop with on that is 3k3-4k7 for a gain of app. 4-6. Leave the rest as it is /U.

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