Clarity TC film caps in the power supply

I've been itching to try the Clarity Cap TC film caps in the power supply of a ST-35 build - on a larger chassis of course. The original ST-35 used a 450Vdc rated electrolytic can cap on the power supply. I use a 550Vdc rated can cap with a 600Vdc surge rating.

Clarity Cap offers a 450, 600, and 700Vdc cap, among others. Is the 450Vdc enough - the original used it - or would the 600Vdc be a better solution, giving more headroom. I know that you shouldn't go too far beyond the voltage a cap "sees" in order for it to form properly, so I wonder if 600 is too large. The operating voltages are roughly 385-380-320 for the three stages of ST-35. I'll be using higher uF values by the way.

Thanks for any help

Captain Coconut wrote:I've been itching to try the Clarity Cap TC film caps in the power supply of a ST-35 build - on a larger chassis of course. The original ST-35 used a 450Vdc rated electrolytic can cap on the power supply. I use a 550Vdc rated can cap with a 600Vdc surge rating.

Clarity Cap offers a 450, 600, and 700Vdc cap, among others. Is the 450Vdc enough - the original used it - or would the 600Vdc be a better solution, giving more headroom. I know that you shouldn't go too far beyond the voltage a cap "sees" in order for it to form properly, so I wonder if 600 is too large. The operating voltages are roughly 385-380-320 for the three stages of ST-35. I'll be using higher uF values by the way.

Thanks for any help

Film caps do not "form", only electrolytics do. So you can discount that factor. You can use larger voltage film caps if you like and don't mind the expense and/or their size!

As far as the voltage rating - select the worst case voltage and add a bit to it. Don't neglect to figure you could easily experience a 5-10% high AC line voltage which would add about 30-35 volts to the B+. So if the B+ is 385 or so then worst case would be about 425. 450 should do just fine, but 600 would be fine as well.

The most readily available versions are the 600 and 700 volt TC caps from Partsconnexion.  It looks like all they have left of the 700V are 45uF.  I just picked up a bunch of them as they are on clearance.  The newer 600V versions are supposed to be slightly improved.  

In my original ST35 build I used Panasonic electrolytics in the power supply and it sounded really good.  When I rebuilt it with the TC caps a layer of haze vanished from the overall sound and clarity and transient speed improved.  Bass definition improved as well.  Since the ST35 uses just a CRCRC filter you could probably just go with 4 of those 45uF caps.  Parallel 2 of them for 90uF in the middle to better drive the output taps.

The trickiest part is figuring out how to mount them.

Thanks for the input Corn. Jim, thanks for the clarification. A couple of prominent contributors in another forum talked about higher voltage rated film caps being harder to "form". I just went along, seeing that they were more "qualified" than I.