hiss

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Reduce the gain! preferably by reducing the size of the feedback resistor, not by increasing the input resistor (smaller resistors make less noise!).

Also try adding a single 0.1 uF or so cap directly across the V+ and V- supply pins of each '3886 (not to ground). Make sure that it is rated at an appropriate voltage (100 V will do).
 
macboy said:
Reduce the gain! preferably by reducing the size of the feedback resistor, not by increasing the input resistor (smaller resistors make less noise!).

Also try adding a single 0.1 uF or so cap directly across the V+ and V- supply pins of each '3886 (not to ground). Make sure that it is rated at an appropriate voltage (100 V will do).


The feedback resistors are allen-bradley .1%,that I have very few of.

Thanks for the suggestion.
 
jaudio said:
I plan to change the input resistor to 8k but first I would like to get the hiss as low as possible

You have no hum, right?
You did a good job with the grounds.
You have hiss because you have a high gain on the amp.
These chips were made for power amps, the noise specs are naturally much higher than a signal op-amp.
Don't think you can use them with the gain you want without a pre.
You should bring the gain down on the output stage and use a gainstage with a gain of 2~2.5x.
 
carlosfm said:


You have no hum, right?
You did a good job with the grounds.
You have hiss because you have a high gain on the amp.
These chips were made for power amps, the noise specs are naturally much higher than a signal op-amp.
Don't think you can use them with the gain you want without a pre.
You should bring the gain down on the output stage and use a gainstage with a gain of 2~2.5x.

There is no hum with nothing connected. with a preamp connected there is hum in one channel(when I switch them, the hum changes channel), so I think it a source problem

I have some gain in the preamp
 
jaudio said:
There is no hum with nothing connected. with a preamp connected there is hum in one channel(when I switch them, the hum changes channel), so I think it a source problem

I have some gain in the preamp

Hum is one thing, hiss is another.
So you have a DRV134 on the input, which has a gain of 2x.
So... that amp has a huge gain...:hot:
You need to reduce the gain on the output (LM3886 chips).
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.