Dare to compare! Summary page.


Some comments from YH:
The square waves show spikes with some caps and no spikes with others. The ones with no spikes are to be much preferred. This means the BG can be considered non-audiophile approved for decoupling.
For spikes, you hv to look at the spectrum analysis of the output sq waves with the caps. The ones with least noise is best. I believe you can easily switch to spec analy mode on the scope.


Some comments from vt4c:
Perhaps the Black Gates need longer break-in?


Some comments from Thorsten Loesch:
I'd note that all the premium capacitors show a notably lower noise level (including even the Starget which really are no good above around 100KHz and are designed and made for low audio range distortion) than "generic" ones. Even the BG and worse looking Os-Cons show at 1MHz only the initial inductive spike but an overall much lower noise level. As ANY of these capacitors require further bypassing in high speed applications, using the right ceramic bypass would eliminate the spike. In addition, the 15MHz curves would look much cleaner, 15MHz is really crapshooting in the dark with electrlytics.


What I would say is that, it's EXTREMELY difficult to redo this test after breaking-in each cap for say, 300 hours. It'll take more than a month! That said, you can see why some caps are great in digital circuits and some are just crap.

To do better, for the technically inclined (and those great with the soldering iron), Thorsten has this to suggest:

> > It would be interesting if you could test equally a
> "tripplet" consisting > 1pcs 10nF 0805 X7R SMD Capacitor,
> 1pcs 100nF 0805 Z5U/Y5U SMD Capacitor > a SH Series Os-Con
> 10uF/6.3V (with 5V supply) plus a further 1,000uF
> > Panasonic FC capacitor.
> i don't have these capacitors.

Then MAYBE you should get some. The SMD ceramic Cap's are DIRT CHEAP (strip >of 100pcs for a buck or two), the Sanyo Os Con and Panasonic FC are pretty generic parts too with generic industrial prices.

I mention this arrangement as if you test it you will find the noise much lower even at much higher test frequencies than any of those capacitors you tested.

As you seem to modify and build a lot of Digital gear I'd just like to note that strategically placement of suchlike SMD Cap combos plus the Os-Con give a PSU node impedance that is almost non-reactive at the driven node point (sadly IC lead inductance somewhat spoils the very good effect) around 0.5 Ohm up to 30MHz (towards DC it's a question of how good your regulator is) and remains below 1 Ohm until way above 100MHz. The result is considerably better sonically AND in measurement than the sum of the parts and by far ahead of just fitting some fancy "boutique" capacitors.


More goodies suggested by YH:
3-terminal feedthru caps from Murata...


OK. Why the hell am I taking the trouble doing all this? It's meant to show you that, next time before you spend your big $$ on stuffs, know what you are buying. There's a marked difference between the capacitors above. The test was done at "clock frequencies", thus the best capacitor suited for such function is the Sanyo Oscon. You can definitely do better by following what Thorsten and YH suggested but pay particular attention to your layout, otherwise it's all moot.

For DIYers, if you build a clock circuit and it doesn't sound good, refrain from blaming the circuit. An oscilloscope tells the best story (of course, not everyone can afford them) but the plots shown here is a guide.

Next time I see some digital circuitry with generic caps, I'll duck! : )