Digital Input DC filtering on the DIO
Aug 2, 2002 at 2:24 AM Thread Starter Post #1 of 6

taoster

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i recently received a modded ART DIO, one of the mod was the removal of a small mica cap from the digital input for sound purity.

however, because of the removal, the DIO can not lock with the Arcam cdp, though it does works flawlessly with the pioneer DVD player!

i tried with much success, adding a ceramic cap. valued 331, 1000pf and 0.1uf. all three worked as expected. I also noticed a dramatic drop in loudness(and maybe quality, not sure)

questions:

1. would it br correct to assume that the lower the capacitance the less effect it would have on the signal quality??

2. are there any difference between the large disc cap, small disc cap and the squarish ceramic type?

3. where do i get quality caps in Sydney, Australia!
mad.gif

i only know jaycar, dicksmith..
 
Aug 3, 2002 at 2:09 PM Post #2 of 6

Tomo

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Hello,

Digital signal doesn't work like analog signals. Cap swapping won't change much. Signal purity means very little here. It is more important to prevent noise pick up by coupling correctly. I suggest get the original capacitors and put them back.

Ceramic isn't good for coupling of any kinds. (Bypassing power supply is whole another matter, do not confuse.)

Tomo
 
Aug 3, 2002 at 2:37 PM Post #3 of 6

taoster

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thanks for replying..

i dont have the original cap so ive replaced it with a similar rated 0.01uf ceramic cap. ill try giving it a good listen.. what kind of would you recommend trying for this situation?
 
Aug 3, 2002 at 5:00 PM Post #4 of 6

aos

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It's not a good idea to have that cap removed unless isolation transformer is used to separate coax line from the receiver chip. Also, mica caps are very high quality and stable.

Value of cap will have influence even on digital signal because it will act as high pass filter. If the cap is too small device will stop working as the base frequency starts getting attenuated and signal loses shape. I found that it stopped working somewhere between 100pF and 1nF but it depends on input resistance of the chip.

Anyhow, datasheets for the receiver chip always show recommended input schematics.
 
Aug 4, 2002 at 2:43 AM Post #5 of 6

taoster

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i received this modded ART DIO with the caps removed already. Although lock can be established with the Pioneer DVD player, it couldnt with the Sony and the Arcam CD player.

To remedy this, i added the ceramic cap.

I tried caps ranging from 100pF to 10uF and I couldnt perceive any noticable difference. I also tried 3 different ceramic caps valued at 0.01uF with slight difference in sound characteristic.

where would i be able to obtain mica caps? I dont think i was able to found it at the local electronic store?

ps: i am not a DIYer.. i am just trying to get my ART DIO to lock with as little interference as possible.
 
Aug 8, 2002 at 7:25 AM Post #6 of 6

aos

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Use 0.01uF NPO ceramic capacitor or film (polypropylene for example) capacitor, as long as they are small in size (i.e. a boutique polypropylene will be likely too large in size to be a proper choice for SPD/IF signal).
 

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