UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > Components and Circuits

Notices

Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

Closed Thread
 
Thread Tools
Old 22nd Jul 2017, 11:03 am   #1
els1967
Pentode
 
Join Date: Aug 2016
Location: Dunstable, Bedfordshire, UK.
Posts: 139
Default DAA ic

I put a post up about buying a DAA chip a few days ago which, with a little help (thanks all) I located and purchased. It's a good chip and has worked out well for what I need it for and has interfaced perfectly with the Arduino. One thing I just can't work out though, is the little ctt. that comes with the chip. It's a simple circuit that converts two wire to four wire using a couple of op amps (Wheatstone bridge principle I think) and boosts the signal slightly to compensate for loss through the chip. I've bread boarded it out but when I take the audio output into my Focusrite A/d box it comes out very low and very distorted. Sending works fine, very well in fact. I can shove internet radio down it and get quite good reproduction on the phone handset.

I've been over and over the diagram and my breadboard so I'm pretty confident I've not made an build mistakes but I'm not an electronics expert so I'm at a bit of a loss where to start to find out what the problem is. If I plug in directly to the line1 out of the DAA it works perfectly and gives an nice, clear output signal, but acts like a two wire.

I've set r3 at 350 ohms (as per UK value on the chart) but I've not used a cap c3 as the documentation doesn't say what to use. I've tried a few different value caps but it makes little difference any way.

http://www.ixysic.com/home/pdfs.nsf/www/AN-122.pdf/$file/AN-122.pdf

The ctt. I've made is on page 5.

If anyone has any clues I would be very grateful.

Thanks
els1967 is offline  
Old 22nd Jul 2017, 1:32 pm   #2
els1967
Pentode
 
Join Date: Aug 2016
Location: Dunstable, Bedfordshire, UK.
Posts: 139
Default Re: DAA ic

Um I've just realised that the op-amp is tied to -5v, I have mine to ground. I expect it's that.
els1967 is offline  
Old 26th Jul 2017, 11:35 pm   #3
els1967
Pentode
 
Join Date: Aug 2016
Location: Dunstable, Bedfordshire, UK.
Posts: 139
Default Re: DAA ic

Quote:
Originally Posted by els1967 View Post
Um I've just realised that the op-amp is tied to -5v, I have mine to ground. I expect it's that.
It was.

Bit of a mono-post this but I think writing it up helped me think it through properly.
els1967 is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 2:44 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.