Hi guys,
What kind of ideas do you have for reducing this on an input of an amplifier (that has 1uf input caps on signal)? On one hand it's a bit tubey, but the positive affects appear they may shift around in the frequency they affect. Perhaps the reason is the chipamp is dependent on signal ground being connected to power ground; ANYTHING in-between so far has resulted is catastrophes noises.
One suggestions has been a 470pf to ground, for infrasonics.
Other thoughts?
What kind of ideas do you have for reducing this on an input of an amplifier (that has 1uf input caps on signal)? On one hand it's a bit tubey, but the positive affects appear they may shift around in the frequency they affect. Perhaps the reason is the chipamp is dependent on signal ground being connected to power ground; ANYTHING in-between so far has resulted is catastrophes noises.
One suggestions has been a 470pf to ground, for infrasonics.
Other thoughts?
You might get no or little answer if your question is not clear.
2nd order HD is determined by the amplifier overall design. The 1uF input cap is added to protect DC. This cap determines the lowest frequency the amplifier will be able to pass, and usually it is designed around a maximum of 10Hz (if you want to lower the frequency you can increase may be to 2uF).
Of course, cap has it's own distortion. To lower this you can use MKP, may be a good quality one. But Non-polar electrolytic is also fine.
470pF to ground is an input HF filter. It is usually needed to avoid oscillation. The better the amplifier design (and real implementation and usage) the lower capacitance you need here. For a good one, maximum is I think 270pF. You might need more if your amp is prone to oscillation due to (1) the amplifier design itself (2) PCB trace, cabling, etc (3) speaker cable capacitance.
Grounding is another complex issue. Usually it relates to hum. I don't understand what catastrophic noises you were talking about.
2nd order HD is determined by the amplifier overall design. The 1uF input cap is added to protect DC. This cap determines the lowest frequency the amplifier will be able to pass, and usually it is designed around a maximum of 10Hz (if you want to lower the frequency you can increase may be to 2uF).
Of course, cap has it's own distortion. To lower this you can use MKP, may be a good quality one. But Non-polar electrolytic is also fine.
470pF to ground is an input HF filter. It is usually needed to avoid oscillation. The better the amplifier design (and real implementation and usage) the lower capacitance you need here. For a good one, maximum is I think 270pF. You might need more if your amp is prone to oscillation due to (1) the amplifier design itself (2) PCB trace, cabling, etc (3) speaker cable capacitance.
Grounding is another complex issue. Usually it relates to hum. I don't understand what catastrophic noises you were talking about.
What do you mean by incoming distortion?
An amplifier has an input impedance (Zin). This Zin will affect distortion of the previous amplifier (preamp or CD player). The Zin is slightly affected by the input resistor. But this (Zin and input resistor) is part of the amplifier design. It could be also affected by potentiometer, depends on your implementation of the volume control (passively, or actively within a preamp).
You were talking about "noise". When did you hear the excessive noise? Is it not oscillation? Nor hum? You may also check the power supply, it may need more regulation or capacitance (some amplifiers need it more than others).
An amplifier has an input impedance (Zin). This Zin will affect distortion of the previous amplifier (preamp or CD player). The Zin is slightly affected by the input resistor. But this (Zin and input resistor) is part of the amplifier design. It could be also affected by potentiometer, depends on your implementation of the volume control (passively, or actively within a preamp).
You were talking about "noise". When did you hear the excessive noise? Is it not oscillation? Nor hum? You may also check the power supply, it may need more regulation or capacitance (some amplifiers need it more than others).
Separating signal ground from power ground creates massive noise, but may also be the link for problems with distortion from volume control pieces.
SMD resistor volume controls and digital ones interact just fine. Any resistors inline cause a total loss of balance and you end up with tons of bass and poor qualities otherwise. This occurs no matter what caps are used.
The worst is Dale resistors, but potentiometers seem to be bad, too.
SMD resistor volume controls and digital ones interact just fine. Any resistors inline cause a total loss of balance and you end up with tons of bass and poor qualities otherwise. This occurs no matter what caps are used.
The worst is Dale resistors, but potentiometers seem to be bad, too.
I think understand what you are posting, but I don't believe what you have posted.
Am I misunderstanding what you are concluding?
If you put a resistor in series with the input (i.e. you connect to the amp through a resistor) you have to make sure the resistance is correct. Too big, (in combination with cap connected to ground) it will pass low frequency more than expected.
Did you measure the resistance? You need to measure two resistors, one the series resistor, another the "shunt" resistor.
All we have so far is that the OP believes he hears something unpleasant when he makes some sort of change to the resistors between the source and the amp. We don't know it is 2nd. We don't know if it may be frequency response (due to significantly inappropriate resistor values). We don't know if the amp has a seriously non-linear input impedance.
All we have "I changed something, and I don't like it. Could someone tell me why?".
All we have "I changed something, and I don't like it. Could someone tell me why?".
Specifically changing volume attenuators. It's an issue with the TDA7297 that came up for me.
Resistors inline got worse with higher values. But digital and SMD resistors don't change anything when they provide volume control.
It's not a small difference. It's not a subjective change. It's more like having a 60hz buzz in a guitar amp or dead silent kind of difference; there's no level of subtlety.
Resistors inline got worse with higher values. But digital and SMD resistors don't change anything when they provide volume control.
It's not a small difference. It's not a subjective change. It's more like having a 60hz buzz in a guitar amp or dead silent kind of difference; there's no level of subtlety.
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Sounds plausible, depending what you mean by "higher values", where you put these resistors, and exactly what you are saying happened.
But then:
So resistors sound bad but SMD resistors don't? Digital what?
I think you should draw a schematic, show what you are doing, and clearly describe what happens in each case.
The SMD stepped attenuator doesn't cause the same effect. A dale resistor one does. If I put dale resistors inline before the capacitor or after that's the DC blocker, it equally causes problems, and seems related to the amount of resistance.
Potentiometers seem to have a similar affect to the Dale's as either an attenuator or inline.
Inline as in directly in the signal path. The attenuators are just thus minus the connection to pot shield, for volume.
It's very bizarre, but very real.
Potentiometers seem to have a similar affect to the Dale's as either an attenuator or inline.
Inline as in directly in the signal path. The attenuators are just thus minus the connection to pot shield, for volume.
It's very bizarre, but very real.
OK, so you put a stepped variable attenuator (I think you said 20K) in front of the amp and everything works, is that right? But you want to do something else involving fixed resistors, but that doesn't work. So that sounds like you are wiring the resistors incorrectly; let's see a schematic of what you are doing.
If the stepped attenuator works, why are you using something else that doesn't?
If the stepped attenuator works, why are you using something else that doesn't?
No.
Changing the variable attenuator between an SMD/Dale/pot/digital, causes the issue.
I don't want to do anything with resistors. I just have tried putting them inline with the signal to the amp, and got the same problem. The larger the value of through hole resistors, Dale RN55 in this case, the worse the issue becomes. There's something about that type of resistor and sliding potentiometers that introduces very problematic distortion and changes in volume in different frequency ranges. Basically it turns to mud the higher the value unless it's an SMD based attenuator or digital, and emphasizes bass extensively as the value goes up.
This explanation of change and effect is complete nonsense.
Draw your attenuator and how you connected it, pencil and paper are good enough . Post the details and a pic of the different installations.
You're non-sense. It's happening, deal with it. If you were an employee I'd fire you.
Here's the schematic (I'll post another of amplifier)
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