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guruji
Apprentece
8 Posts |
 Posted - Jul 06 2016 : 10:11:43 AM
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Hi Aaron I've built your mic mixer with two741.
The thing is that it's sounding distorted.
Is maybe cause I used only one 9v battery to both op amps?
Thanks
Andrew. |
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Aaron Cake
Administrator
Canada
6718 Posts |
Posted - Jul 07 2016 : 09:06:03 AM
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| The 741 is a fairly crappy op-amp audio wise, but yes, a large part of that is going to be the lack of -9V. You need two 9V in series, ground is center, +9V is +, -9V is -. |
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guruji
Apprentece
8 Posts |
Posted - Jul 08 2016 : 02:56:00 AM
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quote:
Originally posted by Aaron Cake
The 741 is a fairly crappy op-amp audio wise, but yes, a large part of that is going to be the lack of -9V. You need two 9V in series, ground is center, +9V is +, -9V is -.
Thanks fors response. If I use a powerful transformer and hook both connections in parallel will solve the problem?
Thanks. |
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Aaron Cake
Administrator
Canada
6718 Posts |
Posted - Jul 09 2016 : 10:17:37 AM
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I'm not quite sure what you are asking referring to the transformer.
But the fundamental problem is that the 741 requires a dual polarity power supply when used as an amplifier. |
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guruji
Apprentece
8 Posts |
Posted - Jul 10 2016 : 03:42:46 AM
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I meant that if I find a transformer center tapped +9v-0v-9v will this work? or a power supply?
Thanks |
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Aaron Cake
Administrator
Canada
6718 Posts |
Posted - Jul 10 2016 : 10:15:38 AM
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| Oh, yes. If you check the circuits page you will find a dual polarity power supply which will give you the basic circuit. |
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guruji
Apprentece
8 Posts |
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Aaron Cake
Administrator
Canada
6718 Posts |
Posted - Jul 13 2016 : 09:47:16 AM
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Just keep in mind that the unregulated power supply will produce about 13V as the load of the op-amp is so low. Also, you will likely find the need to add additional filter capacitors to remove line noise.
Connect Vout+ to +9V on the mixer, and Vout- to -9V. The arrow pointing down (ground) connects to the ground plane of the mixer.
Honestly, two 9V batteries do the job very easily and last for years with the minimal power draw of the 741. |
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guruji
Apprentece
8 Posts |
Posted - Jul 15 2016 : 09:45:38 AM
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Last time I disconnected the ops seperately I mean from pin 7 brought two wires out to a 9v battery and it sounded ok.
Maybe with a one pole trafo this will still work ok. |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Jul 15 2016 : 12:46:19 PM
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| The output of the opamp must swing positive and swing negative to produce clear audio. Without the negative polarity supply it cannot swing negative and instead it acts like a rectifier and chops off all the negative going output swings which causes severe distortion. |
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Aaron Cake
Administrator
Canada
6718 Posts |
Posted - Jul 16 2016 : 10:39:28 AM
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What he said.
If you don't want to line power it, nor carry two batteries, then there are several circuits on the circuits page designed to produce a negative voltage from a positive. Listed under "Voltage Inverter". |
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guruji
Apprentece
8 Posts |
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Topic |
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mic mixer
