Looking for "textbook" FM receiver schematic - Page 4 - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 16th August 2011, 12:42 PM   #31
forr is offline forr  France
diyAudio Member
forr's Avatar
Join Date: Dec 2004
Location: Next door
Originally Posted by DF96 View Post
Sample and hold stereo decoders can run into problems with the sinc frequency response, which can give an HF rolloff.
That was EC8010 thought, see posts #15 and #17 :

Hybrid FM multiplex decoder?
  Reply With Quote
Old 16th August 2011, 01:19 PM   #32
DF96 is offline DF96  England
diyAudio Member
Join Date: May 2007
His original idea was a switching decoder, but then the conversation shifted to sample-and-hold. It is possible that some people thought they were the same thing - I'm not sure. Both decoders have problems, but different problems.

Sample-and-hold suffers from a sinc frequency response, which is phaseless. Unfortunately this means that any attempt to correct it will introduce phase errors. On balance, probably not too bad. I saw a circuit somewhere (probably Wireless World or HiFi News) which used this method without any correction. I suspect the author did not realise what was happening, and may not have realised that the 'smooth' sound he got was due to HF rolloff.

Switching decoders give incomplete separation, because a pi/4 creeps into the maths, so a bit of cross-mixing is needed to cancel out the error. Decoder chips will already include this, but some DIYers might not realise that it is needed. You get 19.4dB separation without the extra cross-mixing, which will sound reasonable but measure poorly.

Interestingly, you could make a half-and-half decoder which gates for 13.16us instead of 26.32us but still at 38kHz rate. This would give a little bit of both problems, but perhaps not enough of either to worry about?
  Reply With Quote
Old 3rd April 2013, 08:38 PM   #33
diyAudio Member
Join Date: Aug 2009
If you want to get into the nitty-gritty of fixing tuners, I hear good things about ""The Theory Of Servicing AM, FM, And FM Stereo Receivers" which is discussed in the thread by the same name:


You can DIY a very good chip-based FM decoder and use it with any number of tuners including tube units:

fm-mpx : FM Tuner MPX Kits

I have one and it works well and sounds good!
  Reply With Quote


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
31 Band Equalizer "the t.eq" "TQ-60" schematic wanted tiefbassuebertr Solid State 2 29th March 2010 03:45 PM
Looking for "good" fm tuner Jimmy154 Analogue Source 89 10th October 2008 02:44 PM
Schematics for "NAD Stereo Receiver 7130" tobias_svensk Solid State 1 24th March 2004 03:51 PM

New To Site? Need Help?

All times are GMT. The time now is 02:03 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2