Headphone Output to GC amp - diyAudio
Go Back   Home > Forums > Amplifiers > Headphone Systems

Headphone Systems Everything to do with Headphones

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 20th March 2005, 12:35 AM   #1
StalfoS is offline StalfoS  Canada
diyAudio Member
 
Join Date: Jan 2005
Location: Vancouver, British Columbia
Default Headphone Output to GC amp

What is the best way to add a headphone output to a GC amp? Has anyone had any experience with this? Can the lm3875 chip be used to drive the phones directly, or would it be better to include a separate circuit?

I wouldnt mind including a switch to turn the headphone output on/off as well as a switch for the speaker output. I sometimes like to switch between listening through the phones and speakers when I am mixing music.
  Reply With Quote
Old 20th March 2005, 02:00 AM   #2
sek is offline sek  Germany
diyAudio Member
 
sek's Avatar
 
Join Date: May 2003
Location: Berlin
Using the chipamp to power headphones is a waste of sound quality (a headphone wants to be driven 'differently').

Technically speaking, you could add a voltage divider to the output in order to reduce the amp's output level, matching the headphones specified sensitivity (and max. power limit!). This is how it's done in most home stereos.

But this has many drawbacks, as the GC has:
- audible noise,
- output offset that could ruin the headphones,
- class A/B switching distortions that are audible via headphones,
- only average sound into good headphones, even a regular opamp could sound as good...

I've never tried connecting a headphone to a chipamp, because I always feared an otherwise unnoticed turn-on/-off thumb or the small-but-not-zero output DC offset could harm it.

Sooo, you could try it with inexpensive headphones, but to answer your actual question: The best way of switching between loudspeakers and headphones is to switch between loudspeaker amp and headphone amp.

Cheers,
Sebastian.

PS: Could even be powered from the GC supply and built into the same case.
  Reply With Quote
Old 20th March 2005, 04:12 PM   #3
Alcaid is offline Alcaid  Norway
diyAudio Member
 
Alcaid's Avatar
 
Join Date: Nov 2003
Location: Klepp
A small split supply Cmoy with regulators (to get +/-15V) won't take up much space
  Reply With Quote
Old 20th March 2005, 07:01 PM   #4
StalfoS is offline StalfoS  Canada
diyAudio Member
 
Join Date: Jan 2005
Location: Vancouver, British Columbia
Thanks for the detailed explanation... The case that I picked up for my GC amp is big enough that I should be able to fit a seperate headphone amp into it.

Any design suggestions?
  Reply With Quote
Old 20th March 2005, 07:13 PM   #5
Alcaid is offline Alcaid  Norway
diyAudio Member
 
Alcaid's Avatar
 
Join Date: Nov 2003
Location: Klepp
Quote:
Originally posted by StalfoS
Thanks for the detailed explanation... The case that I picked up for my GC amp is big enough that I should be able to fit a seperate headphone amp into it.

Any design suggestions?
Well, the easiest one:

Quote:
Originally posted by Alcaid
A small split supply Cmoy with regulators (to get +/-15V) won't take up much space
Just be shure that the regulators can handle the input voltage you are feeding them.
  Reply With Quote
Old 28th March 2005, 10:22 PM   #6
mourip is offline mourip  United States
diyAudio Member
 
Join Date: Apr 2004
Location: Washington, DC
Hi,

I have been driving headphones directly with my gainclone(Brian's boards) for about 6 months. It sounds absolutely great. I have used Beyerdynamic DT990's and Sennheiser HD650's with it. I simply wired a headphone jack with an ON-OFF-ON switch so that I could choose between speakers-mute-headphones. I also ended up using a voltage divider on the input to attenuate the volume somewhat. I use the amp almost entirely for headphone listening. The chipamp has lots of detail, a nice midrange, and great pace. It make me tap my foot!

I am not sure where all of the predjudice comes from against using power amps for headphone listening. If you already have one I say use it. I honestly believe that those who counsel against it have never tried it.

My project right now is a modified Sonic Impact Tripath amp which runs my AKG K-1000s. This is the best sound I have ever heard. Once you are happy with the gainclone give the SI amp a try as your next project. The Tripath chip is where the action is now :-)

Best,

Paul
  Reply With Quote
Old 29th March 2005, 04:31 AM   #7
StalfoS is offline StalfoS  Canada
diyAudio Member
 
Join Date: Jan 2005
Location: Vancouver, British Columbia
Thanks for the suggestions all, I still have not decided what I will go with. I wanted to design my amp with simplicity in mind, however it occured to me that not having a headphone jack will be a problem.

If I were to include simple headphone amp circuit what would be the best way to power it? Off of the rails or with a seperate transformer?

Simply putting a voltage divider on the output is looking more and morea apealing...
  Reply With Quote
Old 29th March 2005, 05:08 AM   #8
joensd is offline joensd  Germany
diyAudio Member
 
Join Date: Dec 2001
Location: Germany
Quote:
Simply putting a voltage divider on the output is looking more and morea apealing...
I just did exactly that in a GC for my brother.
Just put a 120Ohm resistors on the outputs and connected them + ground to the headphone jack.
I put an additional 220uF cap in series for to block DC that might occur with simplified GC.
Put in another switch for muting the main speakers as well.

Indeed itīs more noisy than a dedicated headphone amp but for occasional listening itīs more than adequate.

What are your voltage rails?
With <+-24V you could use a OPA604 or the like.

You could also buffer the input with BUF634 or discrete parts as most line signals have adequate voltage swing to power (at least low impedance <=32Ohm) headphones. Sonically an improvement for the main amp as well.
With the BUF634 and most headphone amps youīd need additional voltage regulators. If you donīt want those there are simple enough buffers that just need a fet or two and can cope with higher rails.

greets
__________________
jens
  Reply With Quote
Old 29th March 2005, 06:39 AM   #9
sek is offline sek  Germany
diyAudio Member
 
sek's Avatar
 
Join Date: May 2003
Location: Berlin
Hi,


Quote:
Originally posted by mourip
I am not sure where all of the predjudice comes from against using power amps for headphone listening. If you already have one I say use it. I honestly believe that those who counsel against it have never tried it.
I honestly have tried it.

In class A/B amps, the transision between class A (low distortion) and class B (higher distortion) mode happens when the output swing increases beyond 'background' listening levels (if biased appropriately). The gainclone chips are set up for this transition to happen at roughly 1W into a loudspeaker.

Due to the voltage divider, you could actually have to drive the amp into class B mode without actually requiring the power (but only the voltage).

Other than that, average (commercial) amps are usually bad sounding anyway.
But I have never tried it with a (good) gainclone.


Quote:
Originally posted by joensd
Indeed itīs more noisy than a dedicated headphone amp but for occasional listening itīs more than adequate.
That's what I meant

Ciao,
Sebastian.
  Reply With Quote
Old 29th March 2005, 10:52 AM   #10
breez is offline breez  Finland
diyAudio Member
 
Join Date: Jul 2004
Location: Finland
Output impedance should be considered for headphones too, as their impedance curve is seldom a straight line through the audio range. A significant amount of op impedance would emphasize the frequencies at which the headphone has an impedance peak (many have one at the bass area, hence the usual impression of a muddied bass from speaker amp's headphone socket).
  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
4 Pin Amp output to 3 Pin headphone jack? StrayS2k Headphone Systems 3 17th February 2009 04:46 PM
Aikidos Headphone with Output Transformers? wonsup Headphone Systems 4 15th April 2008 05:34 PM
Add headphone output to preamp whitelabrat Headphone Systems 2 24th January 2008 07:36 PM
How to connect 62 ohm headphone to 8 ohm output Sunsun22 Headphone Systems 15 16th June 2007 01:29 PM
What output Z for headphone amp? jeffreyj Headphone Systems 29 13th August 2003 10:28 PM


New To Site? Need Help?

All times are GMT. The time now is 09:47 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright Đ1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2