Silver Mica for Crystal?

[dj_holmes]

I have read a few forums stating that silver mica made a big difference to clock performance! Is this true does anyone has experience in this that they can share please?

 

[rayma]

I have read a few forums stating that silver mica made a big difference to clock performance!

They have low inductance and losses, are stable and accurate, and are good for high frequencies.

 

[Tiido]

I would imagine surface mounted NP0/C0G is going to be better, simply because of the smaller physical size (less proximity to unrelated things, less chance of any interferences which might cause changes in timing, plus even lower inductances).

 

[Henderson]

PEN smd capacitor (but if the inductance matter in serie ?) = better behavior than Ceramic Class 1 ?


Silvred Mican in smd package (choice in frequency above few hundred pF ?)


bulk polystyren capacitor ?

 

[DF96]

There are no magic bullets in oscillator design.

 

[Henderson]

what is the best bullet cap for it ? List of looked for behavior in a cap for oscilator design ?

 

[DF96]

Stability. Linearity.

 

[Henderson]

Thanks,


So PEN dielectric should be better than ceramic for NPO/COG : flater and higher linearity !


But Better than silver Mica ?

 

[DF96]

I seem to recall reading somewhere that silver mica caps can sometimes suffer from small random step changes in capacitance, which can be noticeable (but only just!) when used in an LC VFO. The effect would be much smaller in a crystal oscillator so perhaps no problem for audio. I don't know.

 

[dj_holmes]

Thanks for all the input!

Rayma that's exactly what I read about silver mica. So it made sense since it has excellent frequency abilities it some how has a better effect on the crystal and made it sound better. Someone actually posted that it was as good as a clock mod by up to 50-60% the quality! And a lot cheaper and simpler

I am not confident in doing clock mods but caps yes I can do. Now the question is some caps used are not bipolar for clocks but I guess can be bypassed with silver mica?!?

I have a Teac Pd-h500i (currently not working) that uses electrolytic capacitors that I thought about bypassing but is the value of the cap important.

I don't know anything about clocks or the required caps or even type of cap. I just trying to get some professional advice / tried and tested opinion of the best caps to use.

thanks

 

[jcx]

PEN was only resorted to for a smt soldering compatible Mylar substitute

it has higher TC than NP0/C0G by an order of magnitude, MHz DF way worse too

the only place I'd use PEN caps near a oscillator would be DC blocking or PS bypass

 

[dj_holmes]

What is a PEN cap? has no one tried silver mica or going to try it? Or does it have to polarised for crystals?

 

[Henderson]

Siver Mica is OK

PEN is a dielectric : WIMA SMD-PEN Capacitors with Polyethylene-Naphthalate Dielectric which has few capacitance changes at highs frequencies VS some others dielectric as ceramic class I like X7R for instance: its capacitance curve stays flat at higher frequencies than many dielectric but Silver Mica and C0G/NP0. (jcx member's inputt at the post above)


Conclusion of this thread is you can both use for HF signal path Silver Mica cap or Ceramic class I cap (a.k.a: C0G/NP0).


Silver Mica is maybe more consistant (aging) in time & less fragile, but I'm even not sure of that ! I Just readed the datasheets.


regards

 

[phase]

Wouldn’t a solid polymer be better for power supply to an oscillator?
Or a network of C ferrite C R?

 

[Henderson]

To prevent oscillation you meant?


OP should ask perhaps about the purpose of the cap in his circuit...

 

[DF96]

Mention of silver mica in connection with oscillators causes me to assume that the OP is asking about the low value caps connected to the crystal, not supply rail decoupling etc. However, he hasn't said.

 

[dj_holmes]

Basically most crystals have 2 caps connected to it. Not Power caps. For example look at pics of my broken Teac cd player 500i. it has electrolytic caps. front is 47 middle 0.1 and back 47 how could this I use silver mica? Can only polarised caps be used?

 

[Henderson]

C354 & C353 are not the caps you asked for ?

 

[DF96]

Electrolytics used as supply rail decouplers may require some ESR to dampen resonances. If so, they cannot be replaced by 'better' film caps. I can think of no good reason to replace an electrolytic with a silver mica cap (or vice versa).

 

[cbdb]

Excuse my ignorance, what do these caps do? At first I thought they were replacing the crystal, but that dosnt make sense. Anyone lead me to a schematic?