Audio splitter troubles

[audioguru]

Yesterday I spent most of the day removing my good speakers from my old car and putting back the original crappy ones. I had to break their plastic holders to get them out and therefore had to modify other holders to fit them back in. I traded the car for a new one yesterday.
Today I looked at the "name-brand" speakers in my new car. They have tiny magnets like the old car's crappy ones, and are only 2 ohms!
They sound like they have a "whizzer cone" instead of a tweeter and the radio has tonnes of power so I'll replace them with my good 4 ohms ones anyway. It looks like I'll have to take apart the whole back of the car to get them out, because they are screwed in from the top. I can screw in my good speakers from the bottom (in the boot, for Brits). The car came with a powerful sub-woofer back there.
I'll be driving along going boom, boom, tshhhh, tshhhh like I am a teenager again! :lol:

 

[Dr.EM]

This is a nice simple power amp for you:

**broken link removed**

The IC is available here for a very reasonable cost:

**broken link removed**

This does involve mains wiring (unless you can hack an old amp) and heatsinking (which I found to be very easy). So, its up to you.

 

[audioguru]

Thanks, Dr. EM, I forgot about that one. :lol:

A guy in the USA makes stereo amps with the LM3886 68W version and sells them for many thousands of dollars each. He can't make them quick enough since he is getting many orders.
All of us should be printing money like that. :lol:

 

[moody07747]

thanks for that amp circuit

ill be building that next


ive been wiring the parts i got today

i do have a question

how do i know what connects to what on the chip?
i didnt get any info with the chips (TL071CP)

 

[audioguru]

If you need a picture of an IC to identify its pins or any other info about it, look on its datasheet.

 

[moody07747]

ok im still confused how it gets wired by the chip

i did this in paint
the red numbers are the pin numbers

 

[audioguru]

Nice try, Moody.
Out of 5 pins you got one correct. The inputs of an opamp are at the left side and its power supply pins are at top and bottom like this:

 

[moody07747]

thanks for the help audioguru

you truly are an audioguru :lol:


anyways

ill start wiring the chip tomarrow
today i was wiring and soldering in the POTS, installing the phone connectors and installed some of the resistors into the bread board

now it just looks like a huge knot of wire :roll:

 

[audioguru]

On a breadboard instead of a Veroboard or pcb without a metal case connected to its 0V, the wiring between each pot and the IC will pickup all kinds of interference. I always use shielded wire to connect to input connectors and audio pots even if the whole project is in a metal box.

I have seen many very complicated circuits having millions of wires but I never have seen anything that looks like "a huge knot of wire". Can you post its pic?

 

[moody07747]

almost done

Jameco sent me the wrond audio jacks so im waiting for the swap
that should come in about a day or 2

but i wired everything i could without that and labled where the wires for the jacks will go

heres 2 pics

 

[audioguru]

Yep,
It will hum like mad unless you turn-off the mains breaker to your whole house, and maybe your neighbours' too.
Test it in the daytime so you can see what you're doing and so it doesn't pickup hum from streetlights.
Any AM radio station's transmitter nearby? You might need your big wire-cutters. :lol:

 

[moody07747]

wny would i get a huge hum?

this is on a breadboard in a metal case and 22? wire

how would i stop that hum?

 

[audioguru]

Pin2 of the opamp has a fairly high resistance in your circuit and the opamp has a gain of about 200,000.

If you can put the whole breadboard and pots in a metal case connected to 0V, it will be OK. :lol:

 

[Dr.EM]

Yeah, its a technique called shielding. It's pretty vital with lower level devices, although I had nearly a foor of unshielded cable with a mic once and it wasnt too bad :lol: . Love those control knobs btw, I used them on something, but they cost me a fair bit, tend to use those push-on 12p ones now.

 

[Nigel Goodwin]

Love those control knobs btw, I used them on something, but they cost me a fair bit, tend to use those push-on 12p ones now.

Like I said earlier, these days you can buy a ready built high performance mixer, for less than the controls and knobs would cost to build your own :lol:

 

[moody07747]

i was at the shack and decided to pick up those small knobs

only a total of $6
i dont think i can buy a mixer for that price :lol:

 

[moody07747]

If you can put the whole breadboard and pots in a metal case connected to 0V, it will be OK. :lol:

i have no problem putting the project in a metal box, infact thats what i have been planning from the start...

but whats OV?

 

[audioguru]

Zero Volts is the ground of the circuit. If I said to connect the box to ground, then I was afraid you might literally connect the darn thing to earth. :lol:

 

[moody07747]

LOL

na

ok ill put it in a metal box and ground it to the ground bar...not to earth

 

[moody07747]

update

i got the rest of the parts today and soldered them in

its all set for a test run later today

ill let you all know what happens.