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silentblackhat 15th June 2006 09:39 PM

Do i need a diode?
Below is the schematic of my amp that i made for my microphone. long story short i made a PA system. when the amp powers off, it makes that loud crack/click sound. im guessing thats a voltage spikewhen it turns off, correct? i remember reading that placing a didode between the + and - would correct that problem, since the voltage would go through that instead of the whole amp making that sound.

Also if I do need a didode, does it matter what kind i get? i have a 15/30 watt soldering iron that my brother ran over today. the reason y its 15/30 is that it has a switch. i saw how it works, the 15 watt setting is conencted through the didode so it only gets one half of the 60hz electrical AC cycle; the 30 watt setting gets all of the cycle. COuld I use that one thats in there? its broken so im going to throw it away anyways.

by the way thanks for all the help everyoneh as given me allready

AndrewT 16th June 2006 05:27 PM

is that a relation of Dido?

Sorry couldn't restrain myself;)


Have another bash at posting your schematic, remember to compress it using one of the accepted formats.

silentblackhat 18th June 2006 06:29 PM

I was thinking of either connecting 6 and 4 or 6 and 2 since 6 is the main power and 2/4 are grounds.

darkfenriz 18th June 2006 06:33 PM

You will need an output relay

clem_o 19th June 2006 12:35 AM

Replace S1 with a DPDT switch. Wire the other half of the switch so that when you turn the power off, the speaker gets disconnected as well.


ps: I don't think wiring up a diode is going to help...

anatech 19th June 2006 12:42 AM

Hi Clem,
You are correct. That circuit is a natural thumper.

Even with the switch, you may get a turn on click or thump. One problem is the charge / discharge current through the cap (C3). Depending on grounding and lead dress, you could be picking up a surge current through the wiring.


clem_o 19th June 2006 12:48 AM

Hi Chris,

Well, he did say "turn off".... :-) I felt the switch would be a cheaper solution (and less current drain) than a relay..



ps: is your home network up?

anatech 19th June 2006 12:52 AM

Hi Clem,

Well, he did say "turn off".... :-) I felt the switch would be a cheaper solution (and less current drain) than a relay..
That is very true, however you are possibly introducing another variable. Just thought I'd cover that. ;)

The home network is sort of up. I'll explain via PM.


silentblackhat 19th June 2006 08:31 AM

the way that i have this hooked up is the S1 is hooked up through a SPST relay in my car. the "speaker" output is converted into a pair of RCAs that go into my cars cd player(it has aux inputs on the back).

i have all my speakers hooked up to spdt relays . i have all 4 speakers insde hooked to "30" and "87a" so when the 12v switch i have powers on, it turns all the relays inside to 87(which turns the speakers off) and turns a SPST relay "on" that connects a PA speaker that i have under my hood of the car. also it feeds the 12v to my microphone amp. So when i turn on that switch, it turns off all the inside speakers, turns on the mic amp and the speaker outside so i can have a PA system.

when i turn off/on the 'network', i get half of hte crack on the inside speakers nad half on the outside PA speaker since it switches the cd players output fro the inside speakers to the outside.

so a didode would not work at all?

anatech 19th June 2006 12:49 PM

Hi silentblackhat,
I think you are talking about a diode across the relay coil. You should always put one across DC coils. Orient so the diode is reversed biased under energized coil conditions.

I don't think it will help with this problem, but it should be there.


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