Adding a Headphone output to my amp. - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

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 11th February 2012, 08:08 AM   #11
diyAudio Member
 
aardvarkash10's Avatar
 
Join Date: Mar 2007
Location: Auckland, NZ
well, its flat at that scale...
__________________
"Folks, you can't prove truthiness with information. You prove truthiness with more truthiness. In a process known as truthinessiness." - Stephen Colbert, The Colbert Report
  Reply With Quote
Old 11th February 2012, 08:19 AM   #12
diyAudio Member
 
Join Date: Dec 2011
Location: Canberra, Australia
Man, thats flat. 32 ohms fromdc to daylight, as good as.
  Reply With Quote
Old 11th February 2012, 03:07 PM   #13
Sheldon is offline Sheldon  United States
diyAudio Member
 
Join Date: Dec 2003
Location: San Diego
Quote:
Originally Posted by Roulston View Post
Thanks all.

DB, that circuit seems to be spot on.
Yes, you probably want a resistive divider. And you want it to reduce the output level to the loudest listening level you want - with maybe a little extra margin. This, not just for protection, but unless your amp is designed specifically for very low residual hum (and many single ended DHT amps are not), you are likely to have objectionable hum at low listening levels.

Sheldon

Last edited by Sheldon; 11th February 2012 at 03:12 PM.
  Reply With Quote
Old 13th February 2012, 09:48 PM   #14
diyAudio Member
 
Vincent77's Avatar
 
Join Date: Jan 2011
Location: Bruxelles
Don't use Rod Elliott's circuit as-is! It was not meant for a tube amp.

It would load your OPT secondary at 120 ohm instead of 8... not good! The load line would become almost horizontal and negative half-waves could go over maximum allowed dissipation.

Your amp is 10 watt; your headphones can take a maximum of 0.2 watt. You need at least 10*log(10/0.2) = 17dB of attenuation. Let's say 20, to be safe.

Use this calculator: T-Pad / H-Pad Calculator - Resistor Values for Attenuation . Imput impedance 8 to 10 ohm, output impedance around 120 ohm, attenuation - 20-23dB.

I would use R1 = R2 = 5 ohm/10w and R3 = 120 ohm/0.5w.

I don't know if a fuse is really necessary, but if you want one, use a 80mA fast blow.
  Reply With Quote
Old 14th February 2012, 03:18 AM   #15
ChrisA is offline ChrisA  United States
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by Roulston View Post
I have a small and very nice SET value amplifier that with only about 10 watts gives me all the SQ I need in my DEN.

However ther are times that for reasons of family harmony I would like to be able to listen via heahones instead. My study ajoins the master bedroom and my wife can clear be kept awake.

What you need is a resistor network that will provide an 8 ohm load to the amp. Unless the amp also has taps on the transformer for 16 ohm

A single resistor in parallel likey will not provide enough attenuation. You need an "L-Pad". this is two resistors in the shape of an "L". With a l-pad you can choose the attenuation and impedance independent of each other. The single parrale 10R resister will give close to 8R but will not cut the sound much.

Read this. It's not hard to make
L pad - Wikipedia, the free encyclopedia

Then you want to limit the power so your headphones don't get blown out. You can buy a kind of diode called a Transient Voltage Surge Suppressors. These cost about 25 cents and are just a special kind of zenier diode. They will clip or "limit" the voltage across your headphones and do nothing to the sound if the volume is reasonable. They came on all voltage ratings.

You can put in a fuse but likely it will not be needed if you have the above diodes.


About the l-pad, you can adjust the attenuation to the volume sounds the same as the speakers. So when you plug in the headphones you do not have to adjust the volume control. But you will just have to test with you ears. Look of a calculator like this.
L pad calculator - attenuation dB damping impedance decibel loudspeaker speaker voltage divider - sengpielaudio Sengpiel Berlin
  Reply With Quote
Old 14th February 2012, 07:54 PM   #16
diyAudio Member
 
Vincent77's Avatar
 
Join Date: Jan 2011
Location: Bruxelles
Zeners or TVSS diodes would just clamp the output voltage to square waves, which can kill the headphones.
  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
Adding Subwoofer output to Sonic T-Amp HolyGhostFire20 Class D 4 23rd November 2011 07:33 PM
adding output tubes etc to pre amp pforeman Tubes / Valves 1 2nd February 2009 06:02 PM
adding a headphone jack Bama Slamma Headphone Systems 1 13th March 2007 01:36 PM
need help with adding headphone output to S5 Electronics kit / K501 kit Neville Headphone Systems 0 29th January 2007 09:23 PM
Adding 1/4" output to telephone handset RJSkypala Instruments and Amps 6 6th March 2006 08:08 AM


New To Site? Need Help?

All times are GMT. The time now is 11:01 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2