Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

Headphone amp with mixed-in telephone audio
Headphone amp with mixed-in telephone audio
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 10th March 2010, 03:47 AM   #1
krfjr1965 is offline krfjr1965  United States
diyAudio Member
Join Date: Feb 2007
Location: Illinois
Default Headphone amp with mixed-in telephone audio

Hi everybody.

This is something I would build. I have a job sitting at a desk. From time to time at work, I need to take and make telephone calls so I need to hear my desk phone ring. I would like to build an amplifier which will allow me to listen to an audio source such as an ipod or CD player, and has a 4-wire landline telephone connected to it, where both the audio source and both sides of the telephone conversation are mixed together, with possibly a buffer amplifier of some sort. I would also like to be able to talk on the telephone through this device, so I would need to know what kind of microphone I need for this.

Would anyone here have any ideas on how I could produce something like this?
Any help would be greatly appreciated.

  Reply With Quote
Old 10th March 2010, 04:11 AM   #2
wwenze is offline wwenze  Singapore
diyAudio Member
Join Date: Mar 2008
How about a computer with a modem?
  Reply With Quote
Old 10th March 2010, 10:13 AM   #3
Artie is offline Artie  United States
diyAudio Member
Join Date: Jul 2007
Location: Jax, FL
Check out how they do it in the Yamaha CA-400 integrated amp:

ca-400-s-corrected.jpg (jpg version - around 1.7M)
ca-400-s-corrected.png (png version - better - around 3M)

Check out on the far right. The mic preamp has a variable level that you can "mix" with the audio signal. The volume, or mix pot, also has the on/off switch built in. Shouldn't be too hard to duplicate this circuit.

(Or, you could just round up a nice old Yamaha CA-400.)

Edit: Ignore the few colored circles. Those were relevant to another post . . . somewhere else.
  Reply With Quote
Old 10th March 2010, 04:50 PM   #4
GPG is offline GPG  United States
diyAudio Member
Join Date: Dec 2004
Location: Indiana USA
Default Ducker?

I had a similar requirement a few years back. I tried some op-amp circuits with a jfet to reduce the gain of the music when the announcement came on. I never did get it quite right and resorted to just mixing the two signals together.

I came across this app note from THAT Corp that even gives the function a name.
Maybe this will do what you want.



  Reply With Quote


Headphone amp with mixed-in telephone audioHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Horn & mixed-order XOver. Please criticize! hasselbaink Multi-Way 17 21st December 2009 03:06 PM
Mixed cap & coil values in 12db/octave calvinhpk Multi-Way 2 10th October 2007 02:24 PM
Voltage amp mixed with current amp? kubeek Solid State 3 27th June 2006 08:36 PM
Adding 1/4" output to telephone handset RJSkypala Instruments and Amps 6 6th March 2006 09:08 AM
New mixed-device-type symmetrical folded cascode amp Mr Evil Solid State 31 15th August 2005 12:37 PM

New To Site? Need Help?

All times are GMT. The time now is 01:28 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio