Questions about switching cathode bypass cap.

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psychepool
Posts: 260
Joined: Fri Apr 18, 2014 8:29 am

Questions about switching cathode bypass cap.

Post by psychepool »

I want to switch the cathode bypass cap.
I planed to add/remove the 22uF cap in parallel to the 1.5K / 1uF combination with the push-pull pot.

I know that the capacitor needs to be charged with current, so plug one resistor like the link below link instead of short the circuit completely when switching.
Http://i643.photobucket.com/albums/uu15 ... n1cath.jpg
I have a question here.

1. In this case, does the 100K resistor connected in series below the capacitor have any influence on the bias?
2. Why is the resistance value 100K? For example, what happens if it replace with 47K or 1M?
3. What is this resistor called? I wonder the name of this.



Thank you for always providing good information here. Please answer.
Stevem
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Re: Questions about switching cathode bypass cap.

Post by Stevem »

On 3 of my own amps I use a rotory switch to select between 3 different caps ,and yes there is a slight pop when switching but its loudness will depend on where in the signal chain your shuffling caps around.

If it's on the first gain stage then you may need the resistor to null the addition of a larger caps charge up cycle.
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pdf64
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Re: Questions about switching cathode bypass cap.

Post by pdf64 »

1 No, no dc can pass through the cap so the dc conditions / bias can't be affected.
2 On a log scale 100k lies midway between 10k (caps would still have a slight bypass effect) and 1M (may get a switching thump/pop, especially soon after power up).
3 Not aware of a textbook name; how about a de-popping resistor?
psychepool
Posts: 260
Joined: Fri Apr 18, 2014 8:29 am

Re: Questions about switching cathode bypass cap.

Post by psychepool »

In fact, I don't mind to popping noise occurs. What I worry about is that the capacitor is not charging instantly, and I worry that the desired effect will not be applied immediately when switching.

If put a resistor in series like this, is the effect works immediately when switching?

To summarize: 1. Because the direct current passes through the cap, no matter what the value of the resistor in series with the cap is, it has nothing to do with the bias. 2. Therefore, the resistance value can be determined only by considering the degree of the papping noise.

Can I understand like this?
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