Tube DIY Asylum

Do It Yourself (DIY) paradise for tube and SET project builders.

Return to Tube DIY Asylum

Message Sort: Post Order or Asylum Reverse Threaded

CCS loaded parafeed finals: how is parafeed cap value determined?

24.140.98.34
Posted on May 25, 2015 at 13:06:09
deathtube 667
 If you are using CCS loaded parafeed finals, how is the parafeed cap value determined?

The only things I have seen are formulas for choke loaded parafeed finals.

I am actively biamping from 800 cycles 4th order LR with my CCS loaded SE 45 parafeed amp.

Should I just pick the best quality small uF cap available since I am not concerned with the low end Hz rolling off?

 

Hide full thread outline!
    ...
RE: CCS loaded parafeed finals: how is parafeed cap value determined?, posted on May 25, 2015 at 14:51:22
drsx
Audiophile

Posts: 369
Location: around
Joined: September 11, 2005
 Basically you add the Z out from the plate to the impedance of the transformer primary, pick your rolloff frequency, and use

C = 1/(2 * pi * F * Z)

This will give you a good approximation.

 

RE: CCS loaded parafeed finals: how is parafeed cap value determined?, posted on May 25, 2015 at 15:36:21
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 The L and the C will form a tank circuit (with the R's contributing) and it will resonate.

You want to keep the frequency of that resonance below the lowest frequency of interest.

I don't have the formula right now but I bet you could find it.

Tre'


Have Fun and Enjoy the Music
"Still Working the Problem"

 

on line calculator, posted on May 25, 2015 at 16:16:39
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 .
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: on line calculator, posted on May 25, 2015 at 16:21:17
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 "Should I just pick the best quality small uF cap available since I am not concerned with the low end Hz rolling off?"

I would guess yes.

You're not going to excite the resonance so just a cap large enough to pass your lowest frequency of interest into the reactance of the load (reflected and inductance) should be fine.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

The problem is ..., posted on May 25, 2015 at 17:32:29
Paul Joppa
Industry Professional

Posts: 7296
Location: Seattle, WA
Joined: April 23, 2001
 ... the inductance of the output transformer primary varies over a wide range depending on frequency and signal level. The other problem is, the transformer losses (copper loss, eddy current loss, and core loss) are substantial enough that they must also be included if you are to calculate an accurate value for best bass extension.

For an active crossover, where you know there will be no deep bass, you can follow drsx's advice and set a first order highpass just low enough to not affect the crossover. You can even use that pole as part of the crossover.

 

RE: The problem is ..., posted on May 25, 2015 at 18:41:28
deathtube 667
 An octave below the crossover frequency should be OK.

I can check it with an RTA & mic , then tweak the parafeed cap value if needed.

Thanks to all.

 

Page processed in 0.022 seconds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]