Use only half of OPT secondary? - 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
Thread Tools Search this Thread
Old 14th January 2013, 02:25 PM   #1
diyAudio Member
Join Date: Mar 2010
Default Use only half of OPT secondary?

I've built a headphone amp with pencil tubes and use tiny OPT with CT secondary (2500:400+400 turns). It sounds much better when 32-ohm headphones are connected between one side and CT rather than between the two sides (reflects 1.25K to the tube with 400:2500 turn ratio).
The question is whether I can leave one half of the secondary unloaded (B+ is only 29V and output tube is 1p24p @approx 4.5 mA) or should I connect some resistor across it and what value would be best (32 Ohm to equal the other side, or not relevant)
The amp was playing for several hours with one half of the secondary open with no ill effects and I also tried connecting CT and unused side with 47Ohm, which reduces the volume but no audible distortion is added.
  Reply With Quote
Old 14th January 2013, 02:28 PM   #2
TheGimp is offline TheGimp  United States
diyAudio Member
TheGimp's Avatar
Join Date: Aug 2009
Location: Johnson City, TN
You can leave it open. This is the same as putting an 8 ohm speaker on a multi-tap output with 4/8/16 ohm taps.
  Reply With Quote
Old 14th January 2013, 03:08 PM   #3
diyAudio Member
Join Date: Mar 2010
Thanks, Gimp
Very simple answer once you think of it properly
  Reply With Quote


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
opt primary inductance and secondary load regal Tubes / Valves 4 5th February 2012 03:19 PM
cathode bypass on opt secondary alexg Tubes / Valves 4 2nd August 2011 01:54 PM
Single secondary -- dual half wave jmar Chip Amps 2 19th October 2009 01:19 PM
half bridge SMPS secondary voltage drop problem ? alexclaire Power Supplies 6 10th November 2006 03:19 PM
Why a Zobel network across OPT primary or secondary? ray_moth Tubes / Valves 6 4th March 2005 10:26 PM

New To Site? Need Help?

All times are GMT. The time now is 07:53 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2