Stereomour II with Film Caps in PS

Jamier · 4212

0 Members and 1 Guest are viewing this topic.

Offline Jamier

  • Sr. Member
  • ****
    • Posts: 382
on: October 31, 2016, 10:10:20 AM
I'm building my second S II, this time with film caps in the PS. Since the films are so much larger than electrolytics, I had to build a taller base which took much longer than I had hoped.Then I built cradles for the caps which I suspended from the chassis using all-thread and nylon standoffs. As the amp nears completion I will need to connect the caps to the terminals with leads that will be about 4.5 inches long.So, my question is, should I twist the leads of each cap before connecting to the terminal or just run them directly to the terminal ( or does it matter)? I'll try to attach photos.

James Robbins


Offline Paul Joppa

  • Global Moderator
  • Hero Member
  • *****
    • Posts: 5751
Reply #1 on: October 31, 2016, 01:34:35 PM
Yes, I would recommend twisting the wires together. The objective is to minimize the loop area, so that local magnetic fields (from the power transformer mainly) do not induce hum currents. Twisting also reverses the direction of sensitivity with each turn, cancelling out much of the residual pickup.

Paul Joppa


Offline Jamier

  • Sr. Member
  • ****
    • Posts: 382
Reply #2 on: October 31, 2016, 01:58:56 PM
Thanks PJ,

Should I make the same number of turns per inch as the manual advises with the heater leads?

           
Jamie

James Robbins


Offline Paul Joppa

  • Global Moderator
  • Hero Member
  • *****
    • Posts: 5751
Reply #3 on: October 31, 2016, 06:07:34 PM
That's a reasonable goal, but not critical.

Paul Joppa


Offline Jamier

  • Sr. Member
  • ****
    • Posts: 382
Reply #4 on: December 07, 2016, 10:36:28 AM
I am almost ready to voltage test the amp. I have built it in the stock configuration and included all the required tests to be certain that it functions as intended before I begin the film cap substitutions. Is it safer to replace the caps one stage at a time,beginning with the last stage and working back? I feel like this approach will have greatest chance of success. I am concerned that if I change all the caps at once there could issues at the end of the PS that might be a problem, like increased B+  Voltage. Given that the film caps should have lower ESR, is this a possibility? If so I guess I will need to increase the values of the 130 ohm resistors that seperate the caps(?).

Jamie

James Robbins


Offline adeep42

  • Full Member
  • ***
    • Posts: 211
Reply #5 on: December 07, 2016, 12:47:55 PM
Some of you guys really blow my mind. Your Skills are just off the charts. That's just beautiful!!!!!!!!!!

Alan



Offline corndog71

  • Sr. Member
  • ****
    • Posts: 593
Reply #6 on: December 07, 2016, 02:28:16 PM
I've used Clarity Cap TC film caps in several projects from my Bottlehead Reduction to my VTA ST120 and they do a great job.  I don't believe you need to change resistors.  Another great feature is they discharge within a few minutes of turning off.
« Last Edit: December 07, 2016, 02:33:16 PM by corndog71 »

The world was made for those not cursed with self-awareness.

Rob


Offline mcandmar

  • Hero Member
  • *****
    • Posts: 1599
  • Not all engineers are civil
Reply #7 on: December 07, 2016, 11:20:35 PM
Fancy mounting brackets, how did you make them?

M.McCandless


Offline Jamier

  • Sr. Member
  • ****
    • Posts: 382
Reply #8 on: December 08, 2016, 03:03:59 AM
Hi Mark. This is the reason I haven't finished my F4. I'll be getting back to you for some more advice when I pick that up again. The cradles for the caps are made from 3/4 inch pine. I started by routing holes that are the same as the diameter of the caps. Then I cut those in half creating the cradles. Those half pieces are then placed back to back with about 1 inch of space between them and screwed down to a piece of 1/8 inch aluminum that has holes in it to allow zip ties to pass through it to hold the  individual caps. Some end pieces of the same 3/4 inch pine completes the cradle.They hang from the chassis on All-Thread, washers and nuts. I sprayed them with rubber paint (Plastidip). It's all gotten from Home Depot (well, actually Lowes).MDF might work but the end pieces are screwed to cradles and screws just don't hold well in MDF.

James Robbins


Offline mcandmar

  • Hero Member
  • *****
    • Posts: 1599
  • Not all engineers are civil
Reply #9 on: December 08, 2016, 04:47:02 AM
Nicely done, looking forward to seeing it finished :)

The F4 isn't as much fun to build, but its a wonderful pairing with a tube preamp.  You get the best of both worlds without the compromises.

M.McCandless


Offline JamieMcC

  • Hero Member
  • *****
    • Posts: 1167
Reply #10 on: December 08, 2016, 06:46:29 AM
Super effort I bet its going to sound just epic.

Shoot for the moon if you miss you will still be amongst the stars!


Offline Jamier

  • Sr. Member
  • ****
    • Posts: 382
Reply #11 on: December 08, 2016, 06:09:22 PM
Thanks to Alan, Rob, Mark and Jamie for the words of encouragement. I really hope this works out. If it does I will post all the construction details so anyone can duplicate and/or improve it.

Jamie

James Robbins


Offline Jamier

  • Sr. Member
  • ****
    • Posts: 382
Reply #12 on: December 08, 2016, 06:27:54 PM
And, to PJ, for the words of wisdom.

Jamie

James Robbins


Offline BNAL

  • Sr. Member
  • ****
    • Posts: 354
Reply #13 on: December 09, 2016, 02:15:00 AM
That is some great work. I wish I had good woodworking skills like that.

Brad Nalitt
Iron Upgraded S.E.X. Amp 2.0
Foreplay III
Quickie w/PJCCS
Eros Phono
Blumenstein Orca Speakers, Baby Benthic Subs
S.E.X.y Speakers W/FT17H Horn Tweeters
Thorens TD 125 MkII W/ Shure M97xE JICO SAS Stylus


Offline Jamier

  • Sr. Member
  • ****
    • Posts: 382
Reply #14 on: December 26, 2016, 08:04:14 PM
I finished the stock build, resistance checked, voltage checked and now listening to the stock configuration. I will let this run for a 10-20 hrs to be sure there are no problems and then I will replace the last stage ( the last 100 uF caps) with Mundorf 100uF M tube caps. If that goes well I will change the second stage, listen for a while and then move on to the 220uF caps in the first stage. The second stage will also be the Mundorfs, the first stage will be replaced with Cornell-Dubilier 947C series 230uF / 1KV caps. I chose these particular capacitors for a few reasons. They meet the required specs, have good reputations and, while physically large, still fit under the new base that I built for the amp with enough clearance to remain well below the warmer components of the amp. I created adequate ventillation in the base (I hope) and suspended the new caps below this level feeling that air will enter above the caps to keep the rest of the components cool, carrying the heat out the top leaving the area around the new caps relatively cool. The replacement film caps also have screw terminals which made this process much easier with all the in and out that comes with fitting, etc. Originally the plan was to use ASC PP in oil but I could only find 50 uFs which required 8 of them. I tried several configurations but I just couldn't get them under this base with enough room to spare so I had to go with Mundorfs. So as this process moves forward I will compare each change to the stock SII that I built a few months ago and make progress reports.

Jamie

James Robbins