Splitting Power Supply Choke Question - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 24th January 2016, 07:54 PM   #1
diyAudio Member
 
blueglow's Avatar
 
Join Date: Nov 2012
Location: Winston-Salem NC
Default Splitting Power Supply Choke Question

I'm working on a SE KT88 amplifier design and wanted to get the groups thoughts on splitting the B+ feed after the first cap (following the 5U4G or similar) into a choke per channel.
I've seen some high end designs that deploy such a topology but its typically a full LC filter followed by two additional LC filters, one per channel.
My main reason for considering this approach is to keep the choke size to 100ma per channel thus smaller in size and being able to fit them under the chassis. I'm trying to avoid an above chassis choke, more for cosmetics of the design.
I know it would be a slightly more complex design but that's acceptable to me.

Thoughts? Pros/Cons?

Thanks,
Mark
  Reply With Quote
Old 25th January 2016, 04:32 AM   #2
DAK808 is offline DAK808  United States
diyAudio Member
 
Join Date: May 2012
Sure, that is not a problem, except similarly specified chokes are not exact. So, the B+ of both channels will probably be slightly off. I did a similar thing with a power supply that was L1 C1 L2A/L2B C2A/C2B.
  Reply With Quote
Old 25th January 2016, 07:36 AM   #3
diyAudio Member
 
Miles Prower's Avatar
 
Join Date: May 2005
Location: USA
Blog Entries: 7
You mean something like this (attached)?

For the Vixen, I split the filtering of the positive rail, as shown in the schemo, since this is a passive filter. I didn't split the negative rail since the current demand is very much lower, and this includes an active decoupler that has a much lower impedance.

There really is no need for common LC filtering followed by separate LC filters, at least not these days since high value, high voltage, capacitors are now available. 8H and 220uF gives a cutoff of about 4.0Hz (4.91 octaves) and more than enough ripple suppression. Not like back in "the day" when 20uF was about as large a capacitor you could find, so you needed to cascade LC filters to reject that AC ripple.

I considered doing away with LC filtering altogether, but since the PTX is a Hammond "Classic", not too sure how it would appreciate the much larger isurge of Si diodes operating into huge capacitors. Even so, the 47uF reservoir capacitor would bust the Isurge spec of the 5U4GB.
Attached Images
File Type: gif Vixen-PS.gif (17.4 KB, 243 views)
__________________
There are no foxes in atheistholes
www.dolphin-hsl.com
  Reply With Quote
Old 25th January 2016, 11:01 AM   #4
Ketje is offline Ketje  Belgium
diyAudio Member
 
Ketje's Avatar
 
Join Date: Dec 2012
Location: Flanders
Before someone make the same mistake, little adjustements
Mona
Attached Images
File Type: png vxn.png (52.4 KB, 213 views)
  Reply With Quote
Old 25th January 2016, 11:30 AM   #5
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
in my amp i use two forward biased diodes to split the B+ into left and right channels...
__________________
the best advertisement for a good audio design is the number of diy'ers wanting to build it after all the years....never the say so of so called gurus....
  Reply With Quote
Old 27th January 2016, 07:53 PM   #6
diyAudio Member
 
Miles Prower's Avatar
 
Join Date: May 2005
Location: USA
Blog Entries: 7
Quote:
Originally Posted by Ketje View Post
Before someone make the same mistake, little adjustements
Mona
That's not a mistake, and those "adjustments" aren't necessary. That schemo is exactly like how I built it. You definitely don't need those extra diodes with the LEDs: they're redundant. Also, don't screw around with the ground breaker either. The connection shown parallels two diodes in "69" fashion. Breaking that connection as shown cuts the current handling capacity in half.
__________________
There are no foxes in atheistholes
www.dolphin-hsl.com
  Reply With Quote
Old 28th January 2016, 09:04 AM   #7
12E1 is offline 12E1  United Kingdom
diyAudio Member
 
12E1's Avatar
 
Join Date: May 2012
Location: Near Huntingdon, Cambridgeshire, UK
Agree with not disturbing the grounding.

The reverse diode on the LED is generally good practice when it is fed from AC. Most LEDs have reverse breakdown voltages in the region of just over 5 volts. If fed from an AC with a limiting resistor they will work, but they may degrade over time and fail later. The reverse diode limits the reverse voltage on the LED to less than a volt, at the price of increased dissipation in the resistor.

If the AC voltage is low, the extra diode can be omitted, but I always put one in. It costs almost nothing, and saves the LED. Note that the diode can be any low voltage type - it only sees the LED forward voltage as its reverse voltage.

This is generally a better solution than a series diode, because the voltages are controlled. In the series case, the additional diode and LED share the reverse voltage but not in a controlled way and so the LED can still be stressed.
  Reply With Quote
Old 28th January 2016, 04:02 PM   #8
Ketje is offline Ketje  Belgium
diyAudio Member
 
Ketje's Avatar
 
Join Date: Dec 2012
Location: Flanders
Quote:
Originally Posted by Miles Prower View Post
That's not a mistake, and those "adjustments" aren't necessary. That schemo is exactly like how I built it. You definitely don't need those extra diodes with the LEDs: they're redundant. Also, don't screw around with the ground breaker either. The connection shown parallels two diodes in "69" fashion. Breaking that connection as shown cuts the current handling capacity in half.
The way you do it is just two diodes back to back, no need for a bridge.
Like I changed it gives two diodes in series back to back.That gives a liberty of 1.2V before there is a ground current, in your version it's only 0.6V.
Mona
Attached Images
File Type: png dddd.png (10.1 KB, 98 views)
  Reply With Quote
Old 28th January 2016, 09:46 PM   #9
diyAudio Member
 
Miles Prower's Avatar
 
Join Date: May 2005
Location: USA
Blog Entries: 7
Quote:
Originally Posted by 12E1 View Post
Agree with not disturbing the grounding.

The reverse diode on the LED is generally good practice when it is fed from AC. Most LEDs have reverse breakdown voltages in the region of just over 5 volts. If fed from an AC with a limiting resistor they will work, but they may degrade over time and fail later..
"Over time" means ten years now (I completed the Vixen in Dec, '05) of almost daily use for a couple hours or more, and "later" has yet to occur.

Quote:
The way you do it is just two diodes back to back, no need for a bridge.
Like I changed it gives two diodes in series back to back.That gives a liberty of 1.2V before there is a ground current, in your version it's only 0.6V.
Mona
You're still cutting the current carrying capability in half, and that's what's important: in the case of a catastrophic failure that makes the chassis live, you want the fuse to poof before the diode bridge. Low PRV, high current integrated bridges aren't that expensive, and are cheap insurance against a dangerously live chassis.
__________________
There are no foxes in atheistholes
www.dolphin-hsl.com
  Reply With Quote
Old 29th January 2016, 01:12 PM   #10
Ketje is offline Ketje  Belgium
diyAudio Member
 
Ketje's Avatar
 
Join Date: Dec 2012
Location: Flanders
Yeh, and there are 90 year old's smoking and no cancer )
Mona
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Using Choke in Choke Input Power Supply ? HP8903B Tubes / Valves 16 24th January 2014 05:01 AM
Power supply question:twin choke input? gtrmkr Tubes / Valves 8 2nd November 2013 09:54 AM
Choke input supply. Cap question. deicide67 Tubes / Valves 16 15th August 2013 08:16 PM
Splitting up power supply inductance boywonder Tubes / Valves 3 9th February 2009 11:00 PM
power supply choke question dorkus Everything Else 2 17th May 2002 12:35 PM


New To Site? Need Help?

All times are GMT. The time now is 09:34 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright 1999-2016 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki