Audio Preamp Headache!!!

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ArtemisGoldfish
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Audio Preamp Headache!!!

Post by ArtemisGoldfish » Sat Aug 26, 2006 12:50 am

Okay, since I'm relitively new with electronics, I decided to ask here, just in case someone here knows about audio preamps. I got a few Ti RC4560's (Datasheet) and I can't quite figure out what I'm doing wrong.

I think that providing a schem of what I'm doing is kind of useless, so does anyone have any ideas? Do I have to use a resistor or pot to set the gain? How exactly do I do this? Thanks :lol:
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codeman
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Post by codeman » Sat Aug 26, 2006 9:24 am

there's nothing really special about that chip...it's just a dual op-amp they say can be used for audio applications. Do a google search on how to set up op-amps with negative feedback to control the gain. You'll have to use a fixed resistor and a pot if you want adjustable gain.
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ArtemisGoldfish
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Post by ArtemisGoldfish » Sun Aug 27, 2006 8:13 am

Alright: I looked it up and did it, but still no dice. This is what I used: http://colomar.com/Shavano/op-amp3.gif . I used 10k's on both R1 and R2, and I followed the schem exactly, except putting the inverting input on ground, which I put on -In. Arg, I must be stupid or something.

Just to make sure it's not stupidity, A dot on the side of an IC indicates the notched end, right? Just checking :oops:

Anyways, is there any specific problems I also have to tackle? Nothing can be simple. :roll:
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codeman
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Post by codeman » Sun Aug 27, 2006 4:39 pm

you set up the circuit exactly like the schematic you have there? If you did, and you used 10K for both resistors you should just have an output that's double what the input is. So you have a 10k resistor from In- to ground, and another 10K resistor from out to In-? And the dot on an IC indicates where pin 1 is.
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Post by ArtemisGoldfish » Sun Aug 27, 2006 5:34 pm

I set it up exactly like the non-inverting setup, 10k both resistors, but I'm getting about 0% output from my original signal. Though my speaker does output noise.
Logan Whitehurst, Musician Supreme
R.I.P. (Deceased Dec 3, 2006)
You are missed.

ArtemisGoldfish
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Post by ArtemisGoldfish » Sun Aug 27, 2006 5:53 pm

http://img201.imageshack.us/my.php?image=chiplm9.jpg

Sorry for the doublepost, but here's a diagram I drew up in Paint (Yuck)
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timmeh87
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Post by timmeh87 » Sun Aug 27, 2006 9:06 pm

shouldnt input-, output- and power- all be connected together?

also, if its direct form a wall wart, it might need to be filtered. (100uf cap)
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ArtemisGoldfish
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Post by ArtemisGoldfish » Mon Aug 28, 2006 5:13 am

timmeh87 wrote:shouldnt input-, output- and power- all be connected together?

also, if its direct form a wall wart, it might need to be filtered. (100uf cap)
I don't know if they should all be together, if I did and it worked, I wouldn't be asking for help here :-)

Alright, I'll use a cap for the power.
Logan Whitehurst, Musician Supreme
R.I.P. (Deceased Dec 3, 2006)
You are missed.

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