Hello People I have Pot Arcing and Soft input issues . - diyAudio
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Old 15th March 2011, 04:33 PM   #1
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Default Hello People I have Pot Arcing and Soft input issues .

This is my pre amp :
Click the image to open in full size.
With a 100k pot going out after the 470uf cap .
Yes , there is sound , but my strat IS acoustically louder then it .
And with this power amp :
http://www.futurekit.com/2009/manual...6/FK604E-2.pdf
It's hooked up to a 12Wrms 4ohm load .
But when i tried it with a line output ... the preamp pot smokes and arcs .
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Old 15th March 2011, 05:21 PM   #2
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Does the FUTURE KIT work by itself? Which pot is it that arc's? is it the one on the FUTURE KIT? You will need to give us a more detailed discription befor we can understand.
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Old 15th March 2011, 05:29 PM   #3
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Originally Posted by firechief View Post
Does the FUTURE KIT work by itself? Which pot is it that arc's? is it the one on the FUTURE KIT? You will need to give us a more detailed discription befor we can understand.
It does , if i just use the line in from something else , but it won't work as a guitar amp by itself , so i made this preamp , the 100k on the output of the preamp is smoking .
1 is to ground 2 is output 3 is input .
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Old 15th March 2011, 07:38 PM   #4
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Ok well I have looked at the data sheet for the LM386 and it is able to put out 350 milli watts of power, so it may be that you are dumping that into the pot. You have a blocking capacitor between pin 5 and the pot so that means its not a DC problem, asuming it is wired just like the diagram. Really, the right answer is that you shouldnt use the LM386 as a pre-amp. You can do what you need with an op amp. It should be one with a high input impeadance to match your guitar (say 500K to 1M ohm) and the gain will be something on the order of X10. or mabe a little more. Look around for a Op amp pre-amp design. The parts should be realllllllly cheap.

Last edited by firechief; 15th March 2011 at 07:54 PM. Reason: checked my facts
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Old 15th March 2011, 07:58 PM   #5
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You know what, on second thought this is probally a incorrect connection. double check your wiring.
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Old 15th March 2011, 08:00 PM   #6
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Originally Posted by firechief View Post
You know what, on second thought this is probally a incorrect connection. double check your wiring.
It's been checked , with magnifiying glasses , nothing is incorrect .
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Old 16th March 2011, 08:58 PM   #7
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Quote:
Originally Posted by DJDestiny View Post
This is my pre amp :
Click the image to open in full size.
With a 100k pot going out after the 470uf cap .
Yes , there is sound , but my strat IS acoustically louder then it .
And with this power amp :
http://www.futurekit.com/2009/manual...6/FK604E-2.pdf
It's hooked up to a 12Wrms 4ohm load .
But when i tried it with a line output ... the preamp pot smokes and arcs .
Sorry, that's not a preamp, it's a small power amp - and you don't put a 100K potentiometer on the output of a power amp, even a small one.

Trying to feed a speaker from it means the pot has to be fully at one end, or VERY, VERY close to it. This means it burns the pot out.

The pot needs to be at the input of the little power amp, not the output - but what's wrong with the pot already in your guitar?.
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Old 17th March 2011, 08:30 AM   #8
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Originally Posted by Nigel Goodwin View Post
Sorry, that's not a preamp, it's a small power amp - and you don't put a 100K potentiometer on the output of a power amp, even a small one.

Trying to feed a speaker from it means the pot has to be fully at one end, or VERY, VERY close to it. This means it burns the pot out.

The pot needs to be at the input of the little power amp, not the output - but what's wrong with the pot already in your guitar?.
it's feeding the power amp , who has a input impedance of 50k
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Old 17th March 2011, 09:14 AM   #9
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Originally Posted by DJDestiny View Post
it's feeding the power amp , who has a input impedance of 50k
Exactly, so you don't need another one.
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Old 17th March 2011, 09:17 AM   #10
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Originally Posted by Nigel Goodwin View Post
Exactly, so you don't need another one.
The issue is about overdriving the power amp ...
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