Problems with LM4562 Opamp in Tjoeb '99 cd-player - Page 2 - diyAudio
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Old 19th November 2007, 08:49 PM   #11
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Don't use ceramic caps here!
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Old 19th November 2007, 08:55 PM   #12
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Hi,

Quote:
Don't use ceramic caps here!
Please explain your comment.

Cheers,

Jon
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Old 19th November 2007, 09:10 PM   #13
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I know it works, I just don't like ceramic caps anywhere near analog signal path. It usually makes the sound hard, metallic, and can induce microphony.
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Old 19th November 2007, 09:22 PM   #14
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Hi,

You want something with good HF properties (low ESR at HF and low ESL) so a surface mount ceramic would be better than a leaded film cap in this respect.

What about a combination, ceramics from + and - to GND and poly between + and - ?

Cheers,

Jon
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Old 19th November 2007, 09:23 PM   #15
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Quote:
I just don't like ceramic caps anywhere near analog signal path.
Use C0G/NP0 caps and you will be fine.
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Old 19th November 2007, 09:29 PM   #16
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Quote:
Originally posted by BrianDonegan


Use C0G/NP0 caps and you will be fine.
I agree, those are better...
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Old 19th November 2007, 09:57 PM   #17
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Quote:
Originally posted by Bassivus
Don't use ceramic caps here!

Ceramic caps on the power supply pins are the preferred caps to use. They will snuff out any RF oscillation as was previous stated. Also use some nice Panasonic FC caps. low ESR, as bypasses for PS pins.

Ceramic caps as SIGNAL caps are to be avoided at all costs. This is probably what you might have heard about ceramics.

Regards, Marcus
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Old 19th November 2007, 10:07 PM   #18
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Quote:
Originally posted by jrockhead



Ceramic caps on the power supply pins are the preferred caps to use. They will snuff out any RF oscillation as was previous stated. Also use some nice Panasonic FC caps. low ESR, as bypasses for PS pins.

Ceramic caps as SIGNAL caps are to be avoided at all costs. This is probably what you might have heard about ceramics.

Regards, Marcus
Hello, Marcus - jrockhead and welcome

I've beliveve only what I have heard with my two ears

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Old 19th November 2007, 10:16 PM   #19
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Quote:
I haven't soldered a ceramic capacitor (0,001uF) right across the power supply leads but soldered it underneath an 8 pin dip socket in wich i put the opamp itself. Could this have a bad influence on the functioning of the the capacitor?
To decouple HF you need low inductance - a cap with short (preferably no) leads. So solder the cap directly across the pins, the dip socket pin effectively extends the lead of the cap and increases the inductance.

Quote:
What else can be done? If i use a 0,01uF cap instead of the 0,001uF, could it make a difference?
Use 0.1uF (100nF).
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Old 19th November 2007, 10:31 PM   #20
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To decouple a supply you need caps with'*some* esr. The idea of 'damping' is to take energy from the system to prevent it from ringing or oscillating. You can't do that with pure C (or L, for that matter).

Using audiophile (read: almost zero esr) caps for supply decoupling may even make the problem worse. Those ceramics with their losses are excellent for the purpose. If you read data sheets for low-drop-out regs (where you need the same caps to prevent oscillation) they even specify a MINIMUM esr, certainly not the lowest possible.

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