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Author Topic: Oscillating ICS - ceramic cap  (Read 1152 times)

RMoore

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Oscillating ICS - ceramic cap
« on: April 12, 2005, 07:25:29 AM »

I bought some fader modules for a desk & in the course of service they got modded with
NE5534 ICS & I see the tech attached a 220 something ceramic cap to feet 1 & 4 of the ICS, I assume this helps stabilize the ICS / stops oscillation.

Looks easy enough to perform myself on other desk channels.

What does this actually do (cap between 1&4)?

What value is 220

Can I just use any ceramic cap from the local electronics supply or does it have to be 'audio grade'?

I would ask the tech but the one who did it has moved on & I have no way to contact..

Thnx!

Ryan
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Brian Roth

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Re: Oscillating ICS - ceramic cap
« Reply #1 on: April 12, 2005, 09:43:38 AM »

I hope you mean pins 5 and 8!!  Those are the compensation pins to make the 5534 stable at unity gain, and 22 pF is the value required under that condition.

At higher gains, a smaller/no cap can be used.

"220" is commonly used to mean 22 pF.  "221" would be 220 pF, etc.

Bri

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RMoore

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Re: Oscillating ICS - ceramic cap
« Reply #2 on: April 12, 2005, 11:27:48 AM »

Hi Brian - Thank You for the info!
It must be as you say re: the pin orientation, I  must have viewed it incorrectly, assuming pin 1 was the upper left hand..
So any old ceramic should do seeing as its not (I assume) in the audio path?
Thnx again!
Ryan
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By the end of today, another day is gone forever. You will never get it back.
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John Klett

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Re: Oscillating ICS - ceramic cap
« Reply #3 on: April 12, 2005, 01:25:20 PM »

more...

5534's are not stable at gains close to unity...  
or more specifically, at voltage gains less than 3

Pins 1, 5 and 8 are for dc balance and compensation.  

Typically the compensation cap would be connected between pins 5 and 8.  

Pin 1 is for dc balance.  

Pin 8 is the shared pin and is used for both balance and compensation.

Pin 5 is for compensation...  frequency response or slew rate depending on which app note you read...  "... frequency response can be optimized with an external compensation capacitor for various applications (unity gain amplifier, capacitive load, slew rate, low overshoot, etc.)"

220 would be 220 pF or picoFarads

a microFarad (
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Dan Kennedy

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Re: Oscillating ICS - ceramic cap
« Reply #4 on: April 12, 2005, 01:48:01 PM »

Actually the 220 is quite commonly 22pf, especially in the oriental parts marking.

221 being 220pf and so on.

But that is too big for compensation, unless you're looking for the sound of a 741 Smile
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John Klett

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Re: Oscillating ICS - ceramic cap
« Reply #5 on: April 12, 2005, 03:27:58 PM »

Dan Kennedy wrote on Tue, 12 April 2005 13:48

Actually the 220 is quite commonly 22pf, especially in the oriental parts marking.

221 being 220pf and so on.

But that is too big for compensation, unless you're looking for the sound of a 741 Smile


some people like that...  yeah U R quite correct...  220 would be 22pF and that is just fine...  I did NOT get enough sleep last night
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RMoore

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Re: Oscillating ICS - ceramic cap
« Reply #6 on: May 02, 2005, 03:13:45 PM »

OK - thanks again to John & all who responded,
This is a big help!
I am trying to breathe new life into an old console out in the boonies here & learning a bit about electronics as I trundle along,
Thnx,
Ryan
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People's Republic of Ryan

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By the end of today, another day is gone forever. You will never get it back.
We must never let up for a second. Work harder at every single thing - Terry Manning

 You miss 100 percent of the shots you never take - Wayne Gretzky
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