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VoidKeeper
New Member
4 Posts |
 Posted - Oct 30 2010 : 5:07:56 PM
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Hi, I recently built the Audio Mixer posted on this website and it is quite good, I made a few changes like the capacitor at the input that created a high-pass filter which would cause a bit of bass to roll off.
Anyways, the volume that is coming out is a bit low, not THAT much, it's ok, but I notice the difference and I have to turn the volume up a notch, I would like to add some kind of pre-amp inside the mixer, I was wondering if anyone could recommend some kind of schematic or something in special? |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Oct 30 2010 : 5:51:54 PM
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The FET audio mixer circuit is extremely simple so instead of gain, it has loss. The loss increases each time another input is added.
If you need a mixer that has no loss or that has gain then an inverting opamp should be used instead of the FET-follower. |
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VoidKeeper
New Member
4 Posts |
Posted - Oct 30 2010 : 7:26:24 PM
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So all I need to do is change the FET and everything after it with an inverting op-amp?
I think I got an op-amp lying around, just need to check what resistor values to use to get little to no gain, I want to keep the sound quality as intact as possible. |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Oct 30 2010 : 7:34:17 PM
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You must design the opamp circuit correctly so it is an inverting mixer not just an adding buffer like the FET was.
You should use an audio opamp like a TL071, not a lousy old 741 opamp. |
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VoidKeeper
New Member
4 Posts |
Posted - Oct 30 2010 : 7:49:52 PM
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| I got an NE5532P here, but I might take a look at the TL072, since I built this thing with separate channels for Left and Right. I guess I'll test them both out and see which sounds better, although the TL072 does consume less current, that would probably be a plus. |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Oct 30 2010 : 11:01:12 PM
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| The NE5532 and the TL071 and TL072 all sound the same: perfect. |
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VoidKeeper
New Member
4 Posts |
Posted - Oct 31 2010 : 06:52:12 AM
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| Awesome, I'll get right on it =P |
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Audio Mixer + Pre-amp?
