Cyrus 2, does anybody know the voltage of the bipolar capacitors? - diyAudio
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Old 9th January 2009, 09:30 PM   #1
cchean is offline cchean  United States
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Default Cyrus 2, does anybody know the voltage of the bipolar capacitors?

Hello everyone,

I am recapping my Cyrus 2 and pretty much all the electrolytic capacitors are either 35 or 50V. There are 2 bipolar capacitors under the ribbon cable which are RDE and they are marked as 470/6. Does that mean they are 6V only? I am attaching a picture, hope that helps. Any input will be appreciated. Thanks.
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Old 9th January 2009, 10:21 PM   #2
mjf is offline mjf  Austria
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hello.
i presume it is 470uf/6volt.
6volt=max.suppy voltage for use.
i would take 35v or 50v like the others or so............
greetings.............
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Old 1st March 2016, 08:30 AM   #3
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Nice picture. How did it go? Im planning on the same project.
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Old 1st March 2016, 12:10 PM   #4
AndrewT is offline AndrewT  Scotland
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Bi-polar electrolytics are usually specified where the signal is AC.

That could be input signal. The maximum input signal going into a power amplifier is usually from a CDP and that is ~2Vac to 2.4Vac.
6V rating is plenty for that.
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Old 1st March 2016, 12:48 PM   #5
Cortez is offline Cortez  Hungary
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And what about the "quasi bipolar" caps when there is 2 normal electrolyt used in series with "mirrored" polarity?
How much DC can they bear in both polarity?
And what's the max voltage they can withstand in AC?
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Old 1st March 2016, 01:00 PM   #6
AndrewT is offline AndrewT  Scotland
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The voltage rating of the correctly oriented electrolytic limits the leakage and thus helps prevent the other electrolytic from failing.

Many electrolytic manufacturers tell us that they are capable of short term reverse voltage of upto around 1Vdc to 1.5Vdc.
If the leakage and the AC reverse component cannot generate more than that limiting reverse voltage, then the reversed capacitor should never fail at up the full rating of the non reversed capacitor.

If I slow reform two 10uF 25V electrolytics and then series connect them front to front, I expect I have created an effective bi-polar 5uF 25V that nearly matches the performance of a true bi-polar. There are (filter duty) tests showing that series connected bi-polars are better than series connected polars.

I have not seen any tests comparing performance of coupling capacitors.
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Old 1st March 2016, 01:02 PM   #7
AndrewT is offline AndrewT  Scotland
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470uF is an unusually high value of coupling capacitor.
Do you know why that value is used?
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Old 1st March 2016, 01:44 PM   #8
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The "usual" place for a 470uF 6v would be in series to ground with the gain setting resistor. Almost no DC across it.
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Old 1st March 2016, 04:33 PM   #9
roclite is offline roclite  United Kingdom
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According to my Cyrus 1 and 2 circuit diagrams, the feedback bipolar capacitor is first and the 1k resistor (3k6 in parallel for Cyrus 2) to ground, 470uF for Cyrus 1 and 680u for Cyrus 2. However, last few Cyrus 2 that I recapped were 470uF. This sets the lower -3dB frequency rather optimistically at well below 1 Hz!. I believe D. Self/Cordell recommended using higher value feedback capacitors e.g 1000uF to reduce capacitor-related distortion. With a Cyrus PSX providing the heavy bass current, you should get that characteristic Cyrus low bass delivery
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Old 1st March 2016, 04:48 PM   #10
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Looking at a service manual will avoid most of the guesswork - that's what they're for. The feedback network electrolytics C41,42 are indeed 470uF 6V. Note though, whilst there are at least 7 issues of the Cyrus 2 design, there are no other caps of 470uF/6V in the amplifier shown in the issues covered here: Cyrus 2 Manual - Stereo Integrated Amplifier - HiFi Engine
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