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Old 9th July 2013, 06:39 AM   #2111
henryve is offline henryve  South Africa
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My problem is not with the quality of the decoupling caps to use. There my preference is usually for the Panasonic FC or FM caps because of their better temperature rating than the Muse caps.

However, how does one determine the best possible value for the decoupling cap? Using an oscilloscope on the rails to see which ones filter left over noise after the smoothing and rectification the best? Listening tests, or both? In other words, how does a designer like NP decide which value to use on a specific circuit, as I have seen values from 10uF to 470uF used for this purpose, and sometimes it is bypassed by another 100nF cap also, sometimes not.
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Old 9th July 2013, 07:06 AM   #2112
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The size of the caps will determine the frequency range at witch the caps have the lowest impedance.
The circuit topology determines the sensitivity of the circuit for power supply impedance as a function of frequency. Hence different circuits use different cap values.
Having looked at various NP designs I see the recurring use of standard component values like 10u and 220u caps. Wayne tends to bypass 220u caps in his designs with smaller caps in the signal and power path. NP tends to do that less.

Personally I favour ballanced designs and they have minimal ground currents as well as easy decoupling from rail to rail for signal current.
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Old 9th July 2013, 07:47 AM   #2113
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by henryve View Post
........................ I have seen values from 10uF to 470uF used for this purpose, and sometimes it is bypassed by another 100nF cap also, sometimes not.
the electrolytic is NOT BYPASSED.
The HF decoupling is in a different location from the MF decoupling.
These two decoupling types are separated by trace impedance.
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Old 9th July 2013, 09:30 AM   #2114
henryve is offline henryve  South Africa
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Yes Andrew, I understand what you are saying. BYPASSING is the wrong term technically to use. What I refer to is putting a smaller value cap in parallel to the the electrolytic, where each handles a different frequency band if one can put it that way. I was using layman's terminology, sorry for the confusion it caused.
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Old 9th July 2013, 12:24 PM   #2115
Einric is offline Einric  United States
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I actually did use "Bypass Caps" on my 220uF decoupling caps.
I used 220uF Panny FM's and each one got a Vishay 1837 .01uf.
I don't know what difference it makes but I figured it couldn't hurt.
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Old 9th July 2013, 03:00 PM   #2116
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Quote:
Originally Posted by henryve View Post
My problem is not with the quality of the decoupling caps to use. There my preference is usually for the Panasonic FC or FM caps because of their better temperature rating than the Muse caps.

However, how does one determine the best possible value for the decoupling cap? Using an oscilloscope on the rails to see which ones filter left over noise after the smoothing and rectification the best? Listening tests, or both? In other words, how does a designer like NP decide which value to use on a specific circuit, as I have seen values from 10uF to 470uF used for this purpose, and sometimes it is bypassed by another 100nF cap also, sometimes not.
Is heat that large a factor at the location in question. Well there is some data that the higher temp cap will live longer in the same application but for this one I felt not that big a factor.
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Old 9th July 2013, 03:18 PM   #2117
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by Einric View Post
I actually did use "Bypass Caps" on my 220uF decoupling caps.
I used 220uF Panny FM's and each one got a Vishay 1837 .01uf.
I don't know what difference it makes but I figured it couldn't hurt.
It might hurt a litlle or a lot.
You should test the supply rails for ripple or oscillation when subjected to reasonable step changing loadings.
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Old 9th July 2013, 04:10 PM   #2118
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Originally Posted by WalterW View Post
Haha, it's just because I didn't have room for them.
But it gives no problems, I have no hum at all.
But as you can see on the pictures I have made a shielding sub-chassis for the trafos. It is not, as the rest of the case of aluminum, but made of steel plate 2mm thick.
So the input section doesn't see the trafos.
The sub chassis with the trafos and rectifier diodes can be removed separately from the case and also prevents bending the bottom plate from the weight of the trafos.

Walter
Thank you

Same problem in my case not so much room for the trafos.
I will think about this solution... maybe i give it a try
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Old 13th July 2013, 04:06 AM   #2119
bcmbob is offline bcmbob  United States
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As promised, here is a link to the progress made on the liquid cooling project.
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Old 15th July 2013, 08:37 PM   #2120
12B4A is offline 12B4A  United States
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One last round of amateur graphic design...I did one with the FW logo that was suggested earlier by bcmbob. If I did decide to do the engraving I would do one of these two. However, it's possible I might not choose the F5 to be under the hood for good so maybe just printing it out on a plastic cling sheet would be best. Hell, I could just make sticky cling sheets for each Pass diy amp circuit.
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