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Old 26th January 2005, 08:37 AM   #1
argo is offline argo  Estonia
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Default Question about cathode bypass capacitor

I am sorry if this has been already covered somewhere in the forum just couldnt find it during the quick search.
Is it OK to use one section of the power supply multi-section capacitor for cathode bypass or would it cause a problems?
If it's a bad idea, what type of separate capacitor would you recommend instead (except Black Gate) - some film cap like Solen metalized polyprop or just a decent electrolytic.

Thanks in ahead,

Argo
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Old 26th January 2005, 09:10 AM   #2
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It's been done in the past. Unfortunately, they also sucked on the value, using for instance 20uF across a 250 ohm cathode bias resistor - what the heck good is that!

As long as the capacitance is sufficient and voltage rating in range, it's fine. (Caps like to be ran near rated voltage, otherwise they degrade and capacitance changes. This can be temporarily (i.e., <5 years) recovered by reforming. Using a 450V rated cap at 20V is not using your brain or resources.)

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Old 26th January 2005, 09:31 AM   #3
argo is offline argo  Estonia
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Thanks for the input.
I was thinking to use the free section of 220+220uF/500V Elna Cerafine PS cap. I didnít thought about too high voltage rating though. Hmm, interesting point.
I was more worried about the common negative terminal of the multisection caps. As if one section will be used for PS smoothing and other section used for signal, probably both, very high and dirty currents and signal will flow through the same negative terminal tied to ground and will be mixed which could degrade the sound?
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Old 26th January 2005, 11:17 AM   #4
SY is offline SY  United States
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The ground currents could be an issue for an SE amp- a push-pull amp will have decent common mode rejection at the cathode. But if the lead to ground is short and thick, you're unlikely to have a problem.
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Old 26th January 2005, 07:20 PM   #5
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If you star ground to the ground terminal of the capacitor, the only place that can develop a voltage is the terminal between the star and the capacitor itself. Not a problem.

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Old 26th January 2005, 10:14 PM   #6
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Quote:
Using a 450V rated cap at 20V is not using your brain or resources
Oooou. I have done that in a cathode bypass cap!I have bypassed an electrolytic cap,range at 50V, with a MKP range at 400V.Is this wrong?How can I bypass an electrolytic cap at 470uF if I can't find a MKP at 4.7uF/50V?
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Old 26th January 2005, 10:21 PM   #7
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Hi,

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with a MKP range at 400V.Is this wrong?How can I bypass an electrolytic cap at 470uF if I can't find a MKP at 4.7uF/50V?
With filmcpas this isn't a problem.....
You can find 63VDC filmcaps though.

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Old 26th January 2005, 10:32 PM   #8
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Where can I find 4.7uF/63V MKP?
Until now I was using Audyn MKP at 400V to bypass the electrolytics at small voltages.
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Old 27th January 2005, 12:04 AM   #9
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Hi,

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Where can I find 4.7uF/63V MKP?
Not sure about MKP but any dealer carrying WIMA or Roederstein
filmcaps should have them in MKS or MKC @ 63VDC.

The lowest voltage MKP cap I have in my parts bin is 100VDC one.

The values should go up to about 10ĶF in these voltages and films.

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Old 27th January 2005, 06:54 AM   #10
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Hmmm....yes I know those Wima and Roederstein.I haven't use them because they're not MKP.And I believe that they're not so good as Audyn MKP are.
Are they?
Do you know the differences btw MKP,MKS and MKC?
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