How crucial C in LC filter? - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

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 8th July 2004, 10:05 AM   #1
rider is offline rider  Pakistan
diyAudio Member
 
Join Date: Jun 2004
Location: Islamabad
Default How crucial C in LC filter?

Hi!

I need help from the forum. Attached is the pic of a portion from a Delta Modulator card for speech applications (speech transmission over 1-bit). You can see the input is lablled as 300-3400 Hz , -3.5dBr/600 ohm. It means the input signal is expected to be in this range.

The input signal is received by a coupling transformer (V42231-s78-A from siemens in RM5 core , 5 pin former, faraday shield, ref# 605). The signal is then amplified by an Op-Amp.

What comes next is a bit confusing for me(606 and 607)...I guess this is a Low pass LC filter, but i cant guess of what kind (T, L or PI). This is made by feeding the op-Amp output to a coil wound on a former (with RM5 core again, Only one side of former pins are used 1,2,6) so it seems to me a "Centre Tap inductor" with 2 pin as common. Both 606 and 607 have similar construction but differ in some parameters (like DC resistance between 1-2, 6-2 and 1-6 pins and so too the inductance).

There are Styroflex caps shown below the coils (574-578). These are of extremely hi precision. Like 8.25n 1%, 7n 1/2.5%. These are very hard to find.

My question is :

1) If I replace 8.25nF 1% with 8.2 nF 5%, and 7n 1/2.5% with 6.8 nF 5%...how would it effect the filter response? Currently the filter is cutting at nearly 3.5Khz.

2) What if I replace two 7n, 1% parallel caps with a 14nF cap? Is it admissible?

Please Advice
Attached Images
File Type: jpg filter.jpg (56.4 KB, 35 views)
__________________
Rider
  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
need help wana change 60-Hz twin-T notch filter to 279 Hz filter prorms Solid State 0 10th February 2008 12:38 AM
active filter from rod elliot and sub filter questions wuffer Parts 0 2nd October 2005 02:12 PM
Crucial to match tubes when running PSE? G Tubes / Valves 25 25th September 2003 09:15 PM
chassis-mounted filter or IEC plug filter jarthel Solid State 7 11th March 2002 11:17 AM


New To Site? Need Help?

All times are GMT. The time now is 05:29 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