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Old 21st August 2008, 10:17 PM   #1
joka22 is offline joka22  United Kingdom
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Default gainclone completed was working now screeching

Hi i have build my gainclone it was sounding perfect till i tried to wire up the rca cables in parrallel as i only have one channel from the computer sound card now the gainclone makes screeching sounds as song plays anybody know whats rong.
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Old 22nd August 2008, 12:20 AM   #2
joka22 is offline joka22  United Kingdom
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Anybody cum on plz guys i really need ur help experts ?
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Old 22nd August 2008, 01:07 AM   #3
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Quote:
Originally posted by joka22
Anybody cum on plz guys i really need ur help experts ?
Use 1uf or larger bipolar capacitors for input filter to block the entrance of DC at the input. Use one per each amplifier chip or 1 per each cable. This will be 2 capacitors.

EDIT: Don't parallel the signal, until safely at the opposite side of the two capacitors.
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Old 22nd August 2008, 01:09 AM   #4
lineup is offline lineup  Sweden
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It is no good
connect 2 left & right RCA to eachother.
To feed the input of amplifier.

What you can do is use two 1 kOhm resistors
going into amplifier input +connection.
Then you can attach left RCA + wire to one resistor
and the other, right channel RCA + pole to the other 1 kohm resistor.

Left RCA+ >>> 1 kOhm(R1) >>> Chip Amp + input terminal(J1)
Right RCA+ >>> 1 kOhm(R2) >>> Chip Amp +input terminal(J1)
Both channels GND wires (shield) go to the Amp Input GND, of course.

The resistors' value is not critical, as long as it is Not Too big.
You can use 470 Ohm or 2k2 resistors, too, for this MIXER Input trick.
But 1 kOhm resistors are what we often have in our DIY boox.
Isn't it
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Old 22nd August 2008, 02:40 AM   #5
joka22 is offline joka22  United Kingdom
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okay i connect r1 resistor + one right channel in series connection method and same with other channel.

but since i paralelled the signal wires together now when i connect just one signal input pair of wire to pc sound card the chip makes screeching sound it never did this before until i parelled the signal wires.
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Old 22nd August 2008, 05:51 AM   #6
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Does the PC sound card work correctly with only headphones?

Does the amplifier make a screech whilst there is no input?

Do you have a proper load (like a 20k resistor?) or a potentiometer on the input of the amplifier?

Is there a significant difference between the performance of the left or right channels?

Is a microphone connected to the PC sound card and also simultaneously nearby the speaker, and / or is there a webcam with an inbuilt microphone connected to the PC's USB ports?

Is there DC voltage present at the output of your PC sound card and/or is there voltage present at the input of your amplifier?
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Old 22nd August 2008, 12:00 PM   #7
joka22 is offline joka22  United Kingdom
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When i plug in the signal input wires to sound card on pc i select line out from the pc menu. I have no volume pot but i do turn down the gain on the media player.

the pc is 1 metre away from the gainclone amp.

I noticed when i connect the wire from the jack plug in on the pc sound card only one wires carries the sound to the signal input wire of the amp normally u need two wires to get sound but i can connect one and get sound. The amp hums every 10 seconds if no music playing.


20k resistor on the input i dont think so i jus connected the input straight to the pc sound card.
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Old 22nd August 2008, 12:36 PM   #8
lineup is offline lineup  Sweden
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and you have used my recommended
1 kohm resistors mixer

then i can not help you no more

maybe those other here, those 'more experienced and clever'
can give you some better advice

goodbye, have your way & your day
whatever you will listen to posted by members

me, you never see me post in tjhis topic no more

lineup
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Old 22nd August 2008, 12:38 PM   #9
joka22 is offline joka22  United Kingdom
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I just connected the sig to the psu ground pg and now the sound is fixed now.

Lineup i hope i havnt offended you man just that i find it hard to understand the electronic advice. This is not your fault this is my fault need to still learn more to understand. Thanks everyone you too lineup you always reply to my threads and i really appricate it. Thanks

view the gainclone playing music camera mic is **** so it sounds abit disorted. http://www.youtube.com/watch?v=MEqF3Yjb_T0
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