Hi,
I am thinking about using LM1875 or equivalent power opamps to drive Grado headphones. I am hoping that it might well be operating in Class-A at ear-splitting volume.
The main concern is that it might blow the cans. But what if I operated the opamp at fairly low gain such as 1 ~ 3. I found a following schematics in LM675 specs.
I am wondering if I can use this with LM1875. Also, I am wondering if I were to attack another resistor to the feedback resistor to fix up gain other than 1.
Thanks,
Tomo
I am thinking about using LM1875 or equivalent power opamps to drive Grado headphones. I am hoping that it might well be operating in Class-A at ear-splitting volume.
The main concern is that it might blow the cans. But what if I operated the opamp at fairly low gain such as 1 ~ 3. I found a following schematics in LM675 specs.
I am wondering if I can use this with LM1875. Also, I am wondering if I were to attack another resistor to the feedback resistor to fix up gain other than 1.
Thanks,
Tomo
Attachments
1) Per the datasheet, the minimum gain for LM1875 & LM3886 is 10. Then the fastest and easiest way to drop power is to use resistor in series with headphones. For 8 ohms, use 330.
There may be a more "correct" or eligant way, I don't know of one.
1) It may "technically" screw up the damping.
2) Try it, and let us know if it does.
There may be a more "correct" or eligant way, I don't know of one.
1) It may "technically" screw up the damping.
2) Try it, and let us know if it does.
Tomo said:Hi,
I am thinking about using LM1875 or equivalent power opamps to drive Grado headphones. I am hoping that it might well be operating in Class-A at ear-splitting volume.
The main concern is that it might blow the cans. But what if I operated the opamp at fairly low gain such as 1 ~ 3. I found a following schematics in LM675 specs.
I am wondering if I can use this with LM1875. Also, I am wondering if I were to attack another resistor to the feedback resistor to fix up gain other than 1.
Thanks,
Tomo
It should work. You can add a res between -In and GND to change the gain. R2/R1 should be bigger than 10 (so that LM1875 is stable). The cap, use someting like 1uF.
Tomo said:Hi,
I want to know how the snubber connected across the inputs will bring stability to opamp which isn't unity gain stable.
Tomo
http://www.diyaudio.com/forums/showthread.php?s=&threadid=25515
Hi,
I read the paper and I realized something. Appearently, this method reduce the actual "signal" gain to unity, however, noise gain stays at the minimum gain within some certain bandwidth.
That means G=10 applied to noise, but the signal goes through without gain. I am worried that such increase in noise level may be very bad ...
Help me, oh so great ones of the hall of wise!
Tomo
I read the paper and I realized something. Appearently, this method reduce the actual "signal" gain to unity, however, noise gain stays at the minimum gain within some certain bandwidth.
That means G=10 applied to noise, but the signal goes through without gain. I am worried that such increase in noise level may be very bad ...
Help me, oh so great ones of the hall of wise!
Tomo
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