Output Coupling Capacitors

[Laudanum]

I appreciate the Reply.  Eventhough I did know about the parallel resistance I still added the output impedance to the headphone impedance to use as, what was, a very bad example and would logically elicit a lesson in parallel resistance like you gave.  So my fault all around for not thinking or explaining what I was getting at.  Im not very good at being succinct when typing and it was a brain fart on my part to boot.

Thanks for the effort.

 

[Paul Joppa]

Laudanum - in spite of the opioid implication :^) - has it correct. The source impedance (120 ohms resistive approximately) is in series with the load impedance (32 ohm headphones for instance) so the current loop consists of the output capacitor in series with the total impedance (152 ohms resistive in this case).

This analysis is based on a voltage source (zero impedance) in series with the source resistance, the output capacitance, and the load resistance.

 

[Laudanum]

Thank you once again, Paul.

 

[tvr2500m]

Hope this discussion is still alive...

I just bought and built a Crack. LOVE it already. Same old, same old. Massdrop x Sennheiser HD-6XX and experimenting with coupling these with an OTL.

I have, but haven't installed, the Speedball upgrade. I'm acclimating myself to the stock Crack, and shaking it down. Sounds lovely like it is. Have ventured into some tube rolling. From previous tube lives, I have a cosmos of 12AU7s to select from, but the 6080 is a new one for me. (I really like the 6SN7 and 6CG7. I have a lot of them and reading through the Crack discussions it seems that the Crack can easily accommodate these tubes for the 12AU7 position.)

Pretty much two changes I'm considering. A different potentiometer and film output coupling caps. I see that Mouser has some Kemet film caps in the same value as the Lelon aluminum electrolytics my kit came with - 100mfd/160V. They're small, affordable. I'm considering giving these a try.

Question I have is that the three Nichicon power supply electrolytics and the two output coupling caps are all polarized. The film cap, AFAIK, isn't polarized. Does this matter? How? Why? Do I have to consider worry about polarized/non-polarized? Guidance here would be appreciated.

Thanks!

 

[mudvin]

I see that Mouser has some Kemet film caps in the same value as the Lelon aluminum electrolytics my kit came with - 100mfd/160V. They're small, affordable. I'm considering giving these a try.

I'm not sure which caps at on mouser (could you post a link) however, the caps that come with the crack are 100uF/160V. The only caps that size and brand that I could find on mouser are polyester film.

The film caps that others are installing are mostly polypropylene film, not small and not overly affordable, and should offer much better audio performance. I would double check that the caps you are considering are the correct value and would actually improve performance over the stock (A lot of people dislike polyester caps in the audio path).

Question I have is that the three Nichicon power supply electrolytics and the two output coupling caps are all polarized. The film cap, AFAIK, isn't polarized. Does this matter? How? Why? Do I have to consider worry about polarized/non-polarized? Guidance here would be appreciated.

Most electrolytic are polarized, most polymer caps are not (Some have a preferred direction). You can install either (in this application), however if the cap is polarised, pay attention to install direction.

 

[L0rdGwyn]

Can someone who has experience rolling different output capacitors on the Crack/Crackatwoa comment on the significance and audibility of these changes?  On my Crackatwoa, I have a pair of Mundorf Evo Aluminum in Oil, basically bought the highest quality output caps I could fit without too much trouble, and admittedly, did not do a lengthy A-B comparison versus stock since I was strapped for time when building.  I haven't attempted to swap them out since finishing the build a year ago, and probably never will, but just curious for those who have swapped several caps, what is the magnitude of the difference in sound?

For example, many people call the Mundorfs "warm" vs. other caps.  Are we talking a slight warm tilt, or a night-and-day difference?  Thanks.