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| Building a sound mixer within my guitar amp with line IN & mic input |
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| dazz:
Thanks for the info on the LTSpice pot simulation. I'll take a look now. I modified an existing component to create my own pot with a parameter to pick the taper (1=linear, 2=logarithmic, 3=reverse log) But it seems to be rather inefficient and transient runs sometimes get stuck when I have one in circuit. Files attached |
| Zero999:
--- Quote from: dazz on June 15, 2019, 04:03:26 pm ---Thanks for the info on the LTSpice pot simulation. I'll take a look now. I modified an existing component to create my own pot with a parameter to pick the taper (1=linear, 2=logarithmic, 3=reverse log) But it seems to be rather inefficient and transient runs sometimes get stuck when I have one in circuit. Files attached --- End quote --- I'll have a look later. Did you look at the tutorial I linked to? Modelling a potentiometer from discrete resistors seems to result in a faster simulation and is more flexible, although the schematic doesn't look as nice with a symbol and it's a bit more clumsy to use. https://www.eevblog.com/forum/beginners/simulating-potentiometers-using-ltspice/ |
| Audioguru:
Your "Mic output" is a very low impedance from the output of a preamp opamp. When you connect it directly to the (-) input of the mixer opamp then the mixer opamp will have a gain of almost infinity for its high frequencies. You MUST include a series resistance to set its gain low. |
| dazz:
--- Quote from: Zero999 on June 15, 2019, 04:51:21 pm ---Did you look at the tutorial I linked to? Modelling a potentiometer from discrete resistors seems to result in a faster simulation and is more flexible, although the schematic doesn't look as nice with a symbol and it's a bit more clumsy to use. https://www.eevblog.com/forum/beginners/simulating-potentiometers-using-ltspice/ --- End quote --- I had a quick look, will test all those later today. The only reason I went with a custom pot is that it allows me to test different tapers simply by changing a parameter. --- Quote from: Audioguru on June 15, 2019, 05:30:07 pm ---Your "Mic output" is a very low impedance from the output of a preamp opamp. When you connect it directly to the (-) input of the mixer opamp then the mixer opamp will have a gain of almost infinity for its high frequencies. You MUST include a series resistance to set its gain low. --- End quote --- Yes, that was an incomplete schematic. The resistor is at the output of the mic preamp. It's of the same value Rin as in the other inputs |
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