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-   -   Use OS-CON in Vcc? (http://www.diyaudio.com/forums/digital-source/15020-use-os-con-vcc.html)

Marlowe 11th May 2003 04:38 PM

Use OS-CON in Vcc?
 
Hello everybody,

I am planning to modify my CD-Player. There are some electrolyte capacities around DAC chip, Burr-Brown PCM1716, for bypass or decouple. I want to upgrade them but I have doubt that can I use OS-CON as bypass caps to the power supply of Vcc of the DAC chip?
I think OS-CON are good things in digital circiut but use in Vcc also good?

jean-paul 11th May 2003 05:36 PM

Hi Marlowe, I think BG NX HiQ is a better choice there.

Petter 11th May 2003 05:52 PM

The way I read the original post there are a couple of questions:

1. Can I use OsCon's? Yes
2. Should I use OsCon's? Well that depends. OsCon's are high quality units with several advantages such as low impedance, extremely long life etc. Disadvantages include cost, and other types reportedly are even higher performing.
3. There are analog and digital power pins in the DAC chip. The analog power pins are of course the most sensitive, but use high quality parts and techniques for both.
4. If you do decide to replace the electrolytics which is probably a very good idea, consider adding a film or ceramic (depending on where you are) bypass. There has been several threads on the benefits of different types of bypassing which you should easily find if you search the forum.

Petter

Marlowe 11th May 2003 06:02 PM

Hi! pual,

Ok, I will try to use BG N for Vcc and FK for output stage. :cool:
Thanks!

Marlowe 11th May 2003 06:17 PM

Quote:

Originally posted by Petter
The way I read the original post there are a couple of questions:

1. Can I use OsCon's? Yes
2. Should I use OsCon's? Well that depends. OsCon's are high quality units with several advantages such as low impedance, extremely long life etc. Disadvantages include cost, and other types reportedly are even higher performing.
3. There are analog and digital power pins in the DAC chip. The analog power pins are of course the most sensitive, but use high quality parts and techniques for both.
4. If you do decide to replace the electrolytics which is probably a very good idea, consider adding a film or ceramic (depending on where you are) bypass. There has been several threads on the benefits of different types of bypassing which you should easily find if you search the forum.

Petter

Hi Petter,

Someone tell me that the high quality electrolytic capacities need no to add small cap bypass but I am confused.
Should I add film or ceramic caps to bypass for BG N TYPE?

jwb 11th May 2003 06:24 PM

That depends on the demands of the circuit being powered. For digital circuitry with fast rise times, it is almost certain that you need low-inductance capacitors on the Vcc line near the package. Usually you need two ceramic capacitors of decreasing value, as well as the bulk capacitor.

For fast analog circuits, you probably need a single ceramic capacitor near the package, such as .1µF, in addition to the bulk capacitor.

For audio frequency analog circuitry, a bulk capacitor (electrolytic, OS-CON, ...) on the Vcc is plenty.

Fred Dieckmann 11th May 2003 08:37 PM

caution
 
"Should I add film or ceramic caps to bypass for BG N TYPE?"

Black gate caps usually sound bad with bypass caps. Try about 47uf to 200uF as close to the chip as you can get it with low inductance traces. The standard type work fine for this and more black gates for a given budget would be a better bet. Try them close to the input terminals on you regulators. I have paralleled similar value Black gates with good results before.

Petter 11th May 2003 09:41 PM

What many people seem to consider the standard for decoupling these days is:

Digital circuits: Ceramic capacitors
Analog circuits: Film capacitors

Whether they are needed or not is another matter. It is still good practice to use decoupling capacitors in addition to the bulk capacitances you have already identified. I always use additional decoupling.

The reason for using small caps in parallel with larger ones is that smaller units typically have far lower inductance than larger ones. The problem with bypass capacitors (if you are unlucky) is that the wrong combination can lead to resonant effects. This is typically more of a problem in digital circuits than analog circuits, though. If in doubt bypass the analog section with .1uF or 1/10th the value of the other cap using film, and the digital section with 1/10th to 1/100th the value of the unit being bypassed.

Don't worry too much. It is very unlikely that the addition of bypass and improved quality of caps will have any negative influence whatsoever on the sound.

To give some pushback, I personally like OsCon's :)

Your mileage may vary.

Petter

jean-paul 11th May 2003 10:17 PM

I like OSCON too but not in analog. Did various experiments with them and they are not optimal for decoupling in this area. In digital however I prefer them over BG with BG NX Hi Q as an exception.

Fred Dieckmann 11th May 2003 10:38 PM

some advice ........
 
"Don't worry too much. It is very unlikely that the addition of bypass and improved quality of caps will have any negative influence whatsoever on the sound. "

It is not hard to real screw up the sound with the wrong type and value of bypass cap. The low ESR of some of the conductive electrolyte can make for a very high Q resonance. I had to try dozens of combinations of polypropylene caps and low ESR electrolytic caps of the to get the sound right for a video amp passing an SPDIF digital signal. A 680 uF cap sounded a lot better than 1000 uF or 470 uF. The form factor electrolytic made a big difference. Same value, voltage, manufacturer, and type cap, the skinnier taller cap sounded much better. The bandwidth of this video amp wasn't as fast as some of op amps people are using for analog stages now. Digital circuits are sensitive to bypassing also. It pays to experiment with this stuff. I would worry about it, but then I have a lot of experience with this. I never cease to be amazed by some of the "advice" I read here. Oh well ..........


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