diytube.com

Can you use a polypropylene cap instead of a electolytic in a power supply?

I found a 100uf polypropylene rated @ 630/800 vdc

If not , I more than likely will go with:

(3) 100uf + 100uf electrolytics (by FT)

(1) 50uf electrolytics (by FT)

This means I would have and extra 100uf section left over. This is because I cannot find a sigle section 100uf 550/600 vdc Caps.

What would you do with this spare? Not use it or parallel it in with another section?

JW34 wrote:I found a 100uf polypropylene rated @ 630/800 vdc

Cool! Where are these monsters?

http://www.die-wuestens.de/eindex.htm

Follow this link and then click on the words "Our High grade audio caps....."

Scroll down until you see 100uf in the middle colum and then click on the Acrobat link. It is in German.

Would these "Polypropylene" work for the Power supply?

JW34 wrote:

Would these "Polypropylene" work for the
Power supply?

Yes.

I did not look at your link, but I'll bet those
caps are pricey.

The schematic below uses a Solen 10uf
polypropylene in the power supply.

http://diyaudioprojects.com/Tubes/KT88/ ... Supply.png

I'm modifying my Poseidon / MK III right now, it has an SDS Mk III board that worked out to be 50/50/50/50 @ 800 VDC, I kept that, but added a JJ 50/50 mfd @ 560VDC (it will fit inside the chassis) .

Currently connected as 50 / 150 / 50 / 50 with the JJ 560VDC being the last 2 50 mfd sections.

My logic was the 800 VDC rating on the first 2 sections would allow me to use solid state rectifiers without any worries and I wanted more than 50 MFD on the 2nd section B+ for good bass. In general, I find that about 2 mfd per watt of output on the B+ is a good figure for most amps.

BTW, I believe the FT 600vdc surge, 550vdc operating caps mentioned earlier (40/80/32/20 mfd) are the same as those offered by Dynakit Parts. A close look at the construction and the labeling of the two appear to be the same. The Dynakit Parts cap is 600 surge/ 550 operating on the 40, 80 and 20 mfd sections, the 30 mfd is rated for 575 surge, 525 operating.

Add my 2 cents to the pile.

Ed

EdStiles wrote:

Currently connected as 50 / 150 / 50 / 50 with
the JJ 560VDC being the last 2 50 mfd
sections.

Where did you get these JJ 560VDC caps?

The 50/50 mfd @ 560 vdc are JJs, they were purchased while back from Eurotubes.com. I just went to their site and don't see these anymore, I do see a 32/32 @ 560 vdc, which would still be a reasonable solution for the last 2 sections as the Dynaco originals were 20/20. The JJs are rated at 560vdc, but that is an absolute rating; the surge and operating are the same as I understand it (which is why I use them in the last sections, startup with the 5AR4 may exceed 560 vdc). I installed them under the chassis to shield them from the heat of the 6550s and 5AR4.

The site listed above for FT caps has a 20/20/40/40 at 550 wkg / 600 surge vdc, that might be an option, especially as it is a twist lock (if used with an under-chassis board like the SDS.

One other option that I am considering for my amp is to use only 3 sections of the SDS board to make a 100 mfd B+ section, then adding a second small (20 ma, 10 Hy) choke and isolating the driver board from the B+ tap: the configuration would be 50 mfd -> C354 _> 100mfd for the B+, the first 50 mfd section would be shared so the driver supply would be 50 mfd -> small choke -> 50 mfd (4th section of SDS) -> 6.8K -> 50 mfd (JJ)-> 2nd resistor -> 50 mfd (JJ)

You might want to call Eurotubes and see if they can special order the 560V cap.

Ed