Something Wrong with Coupling Capacitor

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Leo Hathaway
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Something Wrong with Coupling Capacitor

Post by Leo Hathaway » Thu Jan 10, 2019 12:12 am

I bought a 5532 front tuning board, with two coupling capacitors on the output side of the tuner, another two resistors at the input end without coupling capacitors, and two coupling capacitors at the input end of the post-stage power amplifier. In this way, there are four coupling capacitors between the front tuning board and the post-stage power amplifier, and two input terminals at the output end of the front stage tuning board, it is useful or not to place them like that? Why not put the coupling capacitor on the input end of the front stage tuning board but put it on the output side?
How about I remove the two coupling capacitors from the front output and connect them to the input? :???:

Emma813

Re: Something Wrong with Coupling Capacitor

Post by Emma813 » Thu Jan 10, 2019 12:46 am

Hi,
As a coupling capacitor, its function is to allow the AC signal to pass through normally, and to cut off the DC current of the upper stage amplifier circuit, so that it will not affect the working point of the next stage amplifier circuit. It is necessary to figure out what the coupling capacitor works and its functions, you can check this link: https://www.kynix.com/Blog/17.html, as it mentioned in earily sections, you will know the coupling capacitor and its functions in audio circuit well.

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haklesup
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Re: Something Wrong with Coupling Capacitor

Post by haklesup » Thu Jan 10, 2019 11:31 am

https://www.aliexpress.com/item/Class-A ... 82970.html

Are you talking about those two big orange caps 3.3uF, 100V. Are you sure the are in series and used for decoupling. A schematic of the board and a block diagram of the preamp- to amplifier configuration you are describing would be helpful.

In any case, used in series, the decoupling cap is actually a high pass filter as in it cuts off low like DC and allows AC of a certain range to pass through relatively unimpeded. When you start to put multiple caps and resistors into a network, you may be building a filter with different response than you might really want. Since you are trying to configure a preamp to adjust your sound quality, this could become relevant. If the Cap value becomes too large, it will filter lows excessively, if too low, it may cut off the highs, if combined in a series parallel arrangement with other components and the inductance of a speaker, you may have a complex filter. So a block diagram would clear that up.

in any case, these modules often work out of the box but there is no guarantee that you will be impedance matched to actually get the Hi-Fi you want. The value of decoupling depends on if you are making a wide band or subwoofer. for the most part, you can emulate values you see in other example audio circuits you may find in image searches.

Anyway, you say they are not working, in what way are they not working? how did you confirm this, are you just attaching power and loads or are you using instrumentation (DMM, Oscilloscope, etc.)

searching around, it looked like there were some youtube tutorials on audio decoupling caps that seemed more intuitive than what I was seeing in text.

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Re: Something Wrong with Coupling Capacitor

Post by dyarker » Thu Jan 10, 2019 12:45 pm

With 5532 I find a TV tuner and a pre-amp IC.

Your description sounds more like a radio tuner (with maybe a 5532 on board?), that would make the setup stereo and there would two coupling capacitors between each stage, one for left and one for right.

With separate boards each could have capacitors on input AND output times number of channels. The count adds up fast. But as said they are needed to protect bias levels of the boards from each other and the boards from the "outside world".

I would not recommend removing any capacitors without seeing schematics.

What makes you think a capacitor is bad?
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Leo Hathaway
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Re: Something Wrong with Coupling Capacitor

Post by Leo Hathaway » Thu Jan 10, 2019 6:37 pm

Thank you all you advice at first.
I guess, this can be regarded as the equivalent series of stopping DC capacitor, so the capacity decreases, the low frequency impedance increases, and the bass becomes worse. If the combination of the front and back stages is not constant, any straight phase can be removed; the combination of the stages before and after the constant transformation can stop DC capacitance, the voltage is constant, and the capacity is doubled.

dyarker
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Re: Something Wrong with Coupling Capacitor

Post by dyarker » Thu Jan 10, 2019 7:48 pm

Series capacitors have less combined capacitance, not more. Two same value capactors in series are half the capacitance of one.

The amount of effect on bass depends on capacitance, source and load impedances.
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CeaSaR
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Re: Something Wrong with Coupling Capacitor

Post by CeaSaR » Thu Jan 10, 2019 9:16 pm

The role of a capacitor in the signal path is a complex one, but it can be most easily explained as the two roles of 1.) blocking DC and 2.) frequency control.

DC blocking is just that, the capacitor prevents DC from passing through the signal chain. If DC were to get through, it would further bias the succeeding amplification stage into saturation, which at the minimum would cause lots of distortion, or, at the worst, drive the next stage into run away and burn up components.

Frequency control is a product of the resistance and capacitance working together to allow just certain frequencies through, that is, form a low pass, high pass, or bandpass filter. Generally, the input stages are more on the high impedance side whereas the output stages are usually much lower impedance. Input stages can use anywhere from .001 microfarads up to 10 or more microfarads. Output stages that drive very low impedance devices, such as speakers, would generally have capacitors of anywhere from 220 microfarads up to 4700 microfarads. There are many tutorials out there that explain how to calculate frequency, so I'll let you discover them. Alternately, if you search under my name for mini power amp or microphone amplifier, I do believe the formula and a brief explanation is somewhere within one of those posts.

The 5532 is a low noise dual audio op amp. That being said, there are conditions where input and / or output capacitors should be used. If the system or op amp is being run from a single-ended power supply, meaning that ground for the output is not at 0 volts but rather some point above 0, then you would need blocking capacitors on the input and output stages. If the system or op amp is being run off of a dual power supply and ground is referenced to 0 volts, then you can get away without using a blocking capacitor. However it would be advisable to have a frequency limiting capacitor on the input to control just exactly what is being amplified.

Hope this helps.

CeaSaR
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Leo Hathaway
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Re: Something Wrong with Coupling Capacitor

Post by Leo Hathaway » Sun Jan 13, 2019 7:53 pm

I think whether this can be regarded as the equivalent series of stopping DC capacitor, so the capacity decreases, the low frequency impedance increases, and the bass becomes worse. If the combination of the front and back stages is not constant, any straight phase can be removed; the combination of the stages before and after the constant transformation can stop DC capacitance, the voltage is constant, and the capacity is doubled. :|

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terrymulhern
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Re: Something Wrong with Coupling Capacitor

Post by terrymulhern » Tue Jun 04, 2019 1:44 am

Posted by haklesup
https://www.aliexpress.com/item/Class-A ... tuning-by-dissertationwriter-poweramplifiers/82970.html

Are you talking about those two big orange caps 3.3uF, 100V. Are you sure the are in series and used for decoupling. A schematic of the board and a block diagram of the preamp- to amplifier configuration you are describing would be helpful.

In any case, used in series, the decoupling cap is actually a high pass filter as in it cuts off low like DC and allows AC of a certain range to pass through relatively unimpeded. When you start to put multiple caps and resistors into a network, you may be building a filter with different response than you might really want. Since you are trying to configure a preamp to adjust your sound quality, this could become relevant. If the Cap value becomes too large, it will filter lows excessively, if too low, it may cut off the highs, if combined in a series parallel arrangement with other components and the inductance of a speaker, you may have a complex filter. So a block diagram would clear that up.

in any case, these modules often work out of the box but there is no guarantee that you will be impedance matched to actually get the Hi-Fi you want. The value of decoupling depends on if you are making a wide band or subwoofer. for the most part, you can emulate values you see in other example audio circuits you may find in image searches.

Anyway, you say they are not working, in what way are they not working? how did you confirm this, are you just attaching power and loads or are you using instrumentation (DMM, Oscilloscope, etc.)

searching around, it looked like there were some youtube tutorials on audio decoupling caps that seemed more intuitive than what I was seeing in text.

Hello,

Could you please explain a bit more about a block diagram? I'm planning to configure a preamp, but I know practically nothing about the process. What are the good alternatives to NE5532 Pre-Amplifier board? Any experience? Thanks.

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CeaSaR
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Re: Something Wrong with Coupling Capacitor

Post by CeaSaR » Wed Jun 05, 2019 8:06 pm

These boards are designed to basically be "plug and play" and should work right out of the box. Are you trying to use it in a manner that is not described in the included paperwork? Again, is there a schematic or at least a link to the board you have purchased? Just how are you going to use the board? Provide answers to these questions and we'll be better able to help.
CeaSaR
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haklesup
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Re: Something Wrong with Coupling Capacitor

Post by haklesup » Thu Jun 06, 2019 1:05 pm

A block diagram is a simplified schematic where subcircuits or whole modules are represented by squares with labels and lines connect the blocks representing the important signals. you can find many examples searching on "electronic block diagram audio" its kind of like a flow chart.

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