Unity Gain Operation (or low gain)

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
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
 

Attachments

  • stuff.gif
    stuff.gif
    12.5 KB · Views: 669
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.
 
Hi,

I don't want to be limited by the guidelines. Besides according to this schematics, you can have it operating at UNITY gain.

I want to know how the snubber connected across the inputs will bring stability to opamp which isn't unity gain stable.

Tomo
 
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
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.