Bottlehead Forum

General Category => Technical topics => Topic started by: Jim R. on March 19, 2012, 10:57:35 AM

Title: Basic parafeed plate choke calculations?
Post by: Jim R. on March 19, 2012, 10:57:35 AM: I'm tackling my first parafeed design project -- a SE 12b4a amp using MQ exo-45s and I would like to know how one goes about calculating the values for the PF choke and cap.

Any guidance appreciated.

Thanks,

Jim
Title: Re: Basic parafeed plate choke calculations?
Post by: nullspace on March 20, 2012, 04:48:36 AM: Hi Jim,

Here's Paul Joppa's Rule of Thumb crica Dec. 2007:
Parafeed cap: C = 2*L/(RL squared). C is the capacitance in microfarads (uF), L is the plate choke inductance in henries, RL is the nominal load resistance in kOhms. Example: for the Paramour upgrade, L=40 henries, RL=3K, C=8.9uF. Usually half to twice that value is reasonable, i.e. 4.5 to 18uF; we use 10uF.

In terms of choosing a choke, the other Paul lays out some thoughts on choosing a choke interspersed with other interesting stuff here: Parafeed Fun (http://www.siteswithstyle.com/VoltSecond/Parafeed_fun/Parafeed_fun.html). In short, minimum 8-10H/1kOhms of nominal load. So, for EXO-45, at least 40-50H.

Hope that helps.

John
Title: Re: Basic parafeed plate choke calculations?
Post by: Jim R. on March 20, 2012, 10:03:03 AM: Thanks, John -- helps a lot. I also bookmarked VS's page.

Thanks again,

Jim
Title: Re: Basic parafeed plate choke calculations?
Post by: jazbo8 on April 23, 2015, 08:29:14 PM: Bumping an old topic... but does anyone still have the image files that go with VoltSecond's Parafeed Fun article? I tried archive.org, but all the image files were missing.

TIA,
jaz
Title: Re: Basic parafeed plate choke calculations?
Post by: Paul Birkeland on April 24, 2015, 06:12:22 AM: Try this spreadsheet.

-PB
Title: Re: Basic parafeed plate choke calculations?
Post by: jazbo8 on April 24, 2015, 11:14:43 AM: Quote from: Caucasian Blackplate on April 24, 2015, 06:12:22 AM
Try this spreadsheet.

-PB
I already have the spreadsheet, but would like to see the whole article, I think the images were from the PSpice simulations...
Title: Re: Basic parafeed plate choke calculations?
Post by: jazbo8 on September 21, 2015, 10:10:12 PM: Bumping the thread in the hope that someone has saved the image files from VoltSeconds' parafeed page...