[ferrari993000]

hello,

I recently built an amplifier and after i finished it, i noticed some hiss coming from the unit even when the unit is on and the source is off. I am assuming that it is interference because when tested with different audio sources it gave different levels of hiss. I am using line out for the audio source, if you have any suggestions on how to get rid of hiss please let me know. Thanks
I also would like to know, when using a dual potentiometer the volume at low levels seems to be muted a bit in one ear more than the other, but when used at higher volumes is seems to even out. This is really odd for me and have never experienced this before. If you have any suggestions i will be glad to hear them or if there is anything you suggest that i do to get rid of the hiss and lower volume in one ear.

Thanks
Corey

 

[JMT]

It would help knowing what amp you built. Pictures would be even better. Additionally knowing some particulars such as gain, headphones used, etc. would assist in making some recommendations.

Incidently, this question would get more responses in the DIY forum so I am going to move it there.

 

[ferrari993000]

well,
i have tested it with several different headphones and always come out to the same results
the amp can output almost 600mW and has a gain of about 22.
I have tried everything but nothing seems to fix this problem. Is it the IC im using? Does the IC have a really big factor in noise, interference? Im using 2 LM386 IC for this amp. Any help is appreciated

 

[drewd]

Chances are very good that the high gain is why you are hearing the hiss. Any hiss that is present at the input of the opamps is going to be tremendously amplified at the output. But it would be helpful to know what type of amp you've built - is it a CMoy? Is it something that you threw together based on a datasheet?

Some opamps are noisier than others, but a gain of 22 is going to reveal any hiss that is present at the input of the opamp - and there is always some.

But without knowing the topology of the amplifier, it's going to be difficult to help you out. Pictures or a schematic would really go a long way!

-Drew

 

[ferrari993000]

Thats helpful...so your saying to lower the gain to something like....lets say 10-13. This amplifier is my own design and im using the LM386 IC. Id like to know if there is some sort of circuit or potentiometer that would work as a true volume from 0 to full. Im using a dual potentiometer 20K ohms and its seems to be very sensitive at the beggining and then barely changes after that. The volume control i am using right now goes full but when turned to minimum volume you could still hear it, quite loud too. Any suggestions

 

[ferrari993000]

heres a pic of the amp...

 

[Garbz]

Is the metalic part of the pot grounded to the signal ground? If not it should be

Also the volume difference are because of poor tracking usually. You may need a different pot.

 

[ferrari993000]

i have grounded the body of the pot. You said i should use a different pot...what do you suggest.

 

[Megaptera]

The way you describe the pot makes me think you used a linear taper pot. Swap it for a log taper. You can do a search for the reasons why linear tapers are not appropriate for audio use, but it basically comes down to the fact that we don't hear things linearly.

Any pot you use will be a "true" volume control in the sense that you describe -- it'll go from no volume to full volume. The differences between pots basically come down to whether they attenuate in a linear or logarithmic fasion, how many channels they control and how well they keep them apart, and how closely they keep the channels relative volume. As long as you go with one that's described as dual or stereo, log taper or audio taper, you won't go wrong. It may not be a very good pot, but it won't be the incorrect part for the job.

 

[ferrari993000]

thanks that info was really helpful