What input impedance do you aim for?
The NE5532 has 300k input impedance. This is already not very high for guitar input. The total input impedance is this in parallel with your bias resistor (wich isn't there at the moment) and the 470k resistor.
The NE5532 has 300k input impedance. This is already not very high for guitar input. The total input impedance is this in parallel with your bias resistor (wich isn't there at the moment) and the 470k resistor.
Whatever you have connected to "bias" is effectively in parallel with the 470 kohm.
That's open loop. Its closed loop input impedance is much higher. Nonetheless, FET input op-amps are more suitable for high impedance sources because of their smaller equivalent input noise current.
you mean ESD protection diodes to prevent voltage spikes above the maximum input voltage ?
Yeah. Again, I am not skilled in musical instruments nor am musician and their habbits, buy always it's good to be safe.
There is an issue with my TDA7267 op amp.
If I connect a 10 ohm load the sine wave has a weird shape and there is distortion. Without load the sine wave looks fine.
Did anybody have a similar issue? The TDA is a power amp and should handle that load easily.
Any ideas?
The schematic is according to the data sheet.
without load
with 10 ohm load
If I connect a 10 ohm load the sine wave has a weird shape and there is distortion. Without load the sine wave looks fine.
Did anybody have a similar issue? The TDA is a power amp and should handle that load easily.
Any ideas?
The schematic is according to the data sheet.
without load
with 10 ohm load
here is the setup
1 input cap
2 output cap
3 load 10 ohm
I tried four identical chips, all the same.
1 input cap
2 output cap
3 load 10 ohm
I tried four identical chips, all the same.
The supply decoupling must be far away, as it isn't on the photo. Does adding decoupling right next to the chip improve anything?
It could also be that the cooling of the chip is worse on a solderless breadboard than on a normal PCB. Does it distort immediately when the 10 ohm is connected or does it take a few seconds?
It could also be that the cooling of the chip is worse on a solderless breadboard than on a normal PCB. Does it distort immediately when the 10 ohm is connected or does it take a few seconds?
Waveform is not horrible and must not sound that bad, (except to those who listen with their eyes 😉 ), any low or no feedback single ended tube amp can easily show a similar shaped one.
Or even a PP one when one power tube is weaker/more worn than the other.
But here we have a very high feedback power "Op Amp" which by definition must be way more linear and symmetrical, so we DO have a problem.
No sharp clipping, apparently top half is more current limited than the lower one, which shouldn´t happen, chip designers will make both equally capable, at least within frated specs.
2 possibilities (may be others, of course)
1) the resist or is not 10 ohm but lower, measure it.
2) you have a serious wiring/grounding problem
If the input ground reference is taken along the speaker return path, any somewhat resistive return path (I do NOT trust much protoboard contacts with more than a few mA) will develop an Audio signal.
In some cases it adds to input signal (since input ground is not really ground but an AC point) and one half becomes larger, the other smaller.
Don´t ask how I found out 🙄
Plagued many breadboard prototypes and poor early PCB designs.
I suggest speaker return goes on its own cable straight to power supply negative, not even approaching the Protoboard.
By the way, what is the value of the supply main capacitor?
Add, say, 2200 or 4700uF in parallel with supply output, any change?
My point being: probably you have nothing broken there, just poor layout/grounding.
Which no simulation will show, of course.
Or even a PP one when one power tube is weaker/more worn than the other.
But here we have a very high feedback power "Op Amp" which by definition must be way more linear and symmetrical, so we DO have a problem.
No sharp clipping, apparently top half is more current limited than the lower one, which shouldn´t happen, chip designers will make both equally capable, at least within frated specs.
2 possibilities (may be others, of course)
1) the resist or is not 10 ohm but lower, measure it.
2) you have a serious wiring/grounding problem
If the input ground reference is taken along the speaker return path, any somewhat resistive return path (I do NOT trust much protoboard contacts with more than a few mA) will develop an Audio signal.
In some cases it adds to input signal (since input ground is not really ground but an AC point) and one half becomes larger, the other smaller.
Don´t ask how I found out 🙄
Plagued many breadboard prototypes and poor early PCB designs.
I suggest speaker return goes on its own cable straight to power supply negative, not even approaching the Protoboard.
By the way, what is the value of the supply main capacitor?
Add, say, 2200 or 4700uF in parallel with supply output, any change?
My point being: probably you have nothing broken there, just poor layout/grounding.
Which no simulation will show, of course.