A general question regarding the biasing.
I cannot get the op amp to work if I bias the negative terminal. Do I have to bias the negative terminal differently to the positive one?
I cannot get the op amp to work if I bias the negative terminal. Do I have to bias the negative terminal differently to the positive one?
Bias is always at non inverting (+) input. Inverting (-) is for feedback purposes generally speaking in audio uses.
You can feedback to NI to make a Schmitt Trigger, not usual in audio gear.
You can feedback to NI to make a Schmitt Trigger, not usual in audio gear.
Ltspice models offer internal bias all the time.Whether you offer it or not externally to an op amp , it assumes the input has a bias anyway.That's why some simulations can't be done properly.Op07 is a jfet anyway.If you place film caps at the input, the only bias current would be the internal leakage current if there is one.If you place an electrolitic cap you don't need resistor bias, it will bias the op amp with the cap's leakage current.
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The OP-07 is an op-amp with bipolar input, but with base current compensation.
Yes, this is a general practical Problem with single supply, half bridge Power stages. I had same problems with TDA2003
EVEN IF signed by TI themselves, the example you circled DOES NOT WORK.
The + input NEEDS a DC path to some reference voltage, as shown it has none (the capacitor blocks DC).
Not even TI can disregard the Laws of Physics.
The schematic now looks like this.
A few of you suggested a FET input stage. Since it will be both an audio and a guitar amp I want to stick to the NE5532.
In the first stage (buffer) the signal is transformed from high impedance to low impedance output. The 1k input resistor helps to reduce the fizzle. The sound loses a tiny bit of the high frequencies but to me it sounds more pleasant.
In the pre amp stage there is a simple low pass filter, the gain control and the volume control.
Please feel free to comment.
And a general question regarding the connection of a tone pot. You can but you don't have to connect lug 1 ?
Electronically it does not make a difference, right?
A few of you suggested a FET input stage. Since it will be both an audio and a guitar amp I want to stick to the NE5532.
In the first stage (buffer) the signal is transformed from high impedance to low impedance output. The 1k input resistor helps to reduce the fizzle. The sound loses a tiny bit of the high frequencies but to me it sounds more pleasant.
In the pre amp stage there is a simple low pass filter, the gain control and the volume control.
Please feel free to comment.
And a general question regarding the connection of a tone pot. You can but you don't have to connect lug 1 ?
Electronically it does not make a difference, right?
I don't really see the point of the buffer circuit. It has about the same input impedance as the clipping amplifier, right?
C3 and C9 seems severely exagerated in their values. 1mF and 10K make a 10second time constant, that is, will take about this time to get the 63% of its final voltage value, which is tremendously high. 1uf suffices.
I guess no time constants or highpass frequencies were calculated, values were chosen "because they were seen somewhere else"
Similar with 100 ohm in series with power amp output.
This design is a collage.
The input impedance is still way too low, unless you only want to use it with active guitars. Guitar pickups are inductive so have a much higher impedance at the frequencies where the harmonics and the 'tone' happen. You can expect a very dull, lifeless tone with low impedance input. Why not configure the input stage as non-inverting? You could then make R1 1M (though this might be a bit high for the 5532, I'd use a 072) and Rimpedance1 10M.
That 100 ohm at the power amp output needs to go.
edit: I misssed that!
That 100 ohm at the power amp output needs to go.
edit: I misssed that!
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