Question: I'm working with the following op-amps:

LM308AN
LM358P
UA741CP

I want to make a small box that will control the power to any string of christmas lights based off of music that is playing. I would like it to pulse with the base. I want the input to be the signal from the headphone jack of my computer and I want the output to be something that would operate any light that could be plugged into a wall outlet (120VAC?).

Answer: 
Sometimes, simply stating what you're trying to accomplish is better than asking the question you *think* you want to ask. This could very well be the case here. So, indulge me as I try to restate your situation and provide some sort of answer.

You have a headphone jack with some music on it, and you want that music to control some lights. You probably want the lights to blink or pulse with the music. Right?

This type of device is called a [Light Organ](http://en.wikipedia.org/wiki/Light_organ). There are many forms of light organs, but I assure you that none of them use an op-amp driving a relay. There are several reasons for this: 

1. Relays don't operate well from an audio signal. They really want a signal that stays on or off for a while and doesn't just oscillate like an audio signal does.
2. Relays can't dim a light. They can turn one on or off. Not so good at dimming.
3. Relays would make a lot of noise, chattering away with the music. Not a pleasant sound.

I would recommend that you Google for "Light Organ". When I did, I came up with 65 million pages. Some of them are selling completed units, some have kits, and some have schematics. 

I hope that helps!
**\* See important addition at end \*** 

You have not provided enough information to allow a good answer. Provide more information and I'll upgrade this answer progressively.

You don't explain what you are trying to do. Do you you want the relay to operate on sound peaks, or when sound is present at all, or to latch on when sound is detected , or ... . You **MUST** provide a clear explanation of your actual requirement.

Saying that you had the '308 working and that now it isn't is like saying that "My car was running but now it is broken, what's wrong with it?"

However:

* The LM308 is a nice opamp but far better than is needed here.
* The LM741 is an OK opamp but has characteristics that will make it VERY hard for you to use here.
* The LM358P is just what you want - once we know what it is that you want :-)

There is a 95% chance that we can tell you how to do what you want using an LM358 once you give us enough details. 

What are the relay's voltage and current ratings? They should be marked on it. Maybe also coil resistance, brand, model etc. The more we know the better.

Help us to help you - at present your question is unanswerable.
 An explanation of what you are trying to achieve is still needed.

[A catalog of the D2w203F and similar relays is here](http://www.crydom.com/en/Tech/crydom_us.pdf) 
and [the datasheet for the D2W203F relay is here](http://www.crydom.com/en/products/catalog/d_2w.pdf) 

This is a somewhat expensive SSR ("Solid State Relay") with 3-32 VDC control input **BUT** AC output using an internal TRIAC. It's rated for switching from 24VAC to 280 VAC at 0.06 to 3 Amps. It is not suitable for controlling DC.

It could control AC powered Christmas tree lights either by mains switching or at low voltage. The 2A rating should not be exceeded. 

This relay is made only for on/off operation. It may be able to be used to 
modulate" the lights in time with the music, if that is the aim BUT the TRIAC switch will always turn on for at least half an AC cycle so use as a "color organ" would be limited.

Tell us what you want and we'll tell you what you need. :-)