MPX Filters - diyAudio
Go Back   Home > Forums > General Interest > Everything Else

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

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 27th August 2001, 08:33 PM   #1
diyAudio Member
 
Join Date: Aug 2001
Location: Cheshire, UK
I wonder if anyone can help me with the following conundrum, which is driving me CRAZY:
I play a Yamaha PSR-9000 keyboard, purely for my own entertainment. When I record any of my tunes to my Technics cassette deck, on playback the sections containing certain instrument sounds (notably sounds with lots of attack, and rich in harmonics, such as trumpet and saxophone etc.) have a peculiar "gargling" effect. I can record to the cassette deck from any other source (CDís, vinyl LPís, FM radio etc.) and the results are perfect. I can record to my PC from the PSR-9000 and then burn a CD from the captured recordings, and this plays perfectly. However, if I then record this CD to cassette tape, the "gargling" is still present.
Having bought a copy of the service manual for the cassette deck, and spent a fruitless 2 weeks tweaking adjustments, and even building a complete new power supply, I still havenít nailed this problem.
Iím now inclined to believe that the root cause of the problem is probably detritis left on the analogue waveform by the digital method of sound generation used by the PSR-9000. Iíve noticed that the more recent cassette decks have a facility called "MPX Filter", which, I imagine, addresses this particular issue.
The question is : Does anyone out there have a circuit diagram, or know where I can obtain a circuit diagram, for such a filter ??

Fingers crossed ÖÖÖ.


__________________
Alec L
  Reply With Quote
Old 28th August 2001, 01:17 PM   #2
diyAudio Member
 
Join Date: Jun 2001
Location: Alexandria, VA USA
Default MPX filter

na thats not what it is for. It is for recording off air FM. In order to get a stereo signal, it uses a pilot carrier at around 19kz (there are more added for SCA)..(multiplexing, thus the MPX) This is usually not heard, and is filtered out in the reciever anyhow. BUT <p>

when recording to tape, it is possible that this noise will rise to the level that it could be recorded, thus adding to the overall signal level, and causing distortion (especially intermod). Turning on the MPX filter just slams everything above some freq so that the 19kz is notched filtered out. So while it might take of your immediate problem, the reality is that a notch filter period might help since it sounds like this is an intermodulation or beat freq problem. <p>

You can build one of these using a simple op-amp.

  Reply With Quote
Old 30th August 2001, 10:49 PM   #3
diyAudio Member
 
Join Date: Aug 2001
Location: Cheshire, UK
Many thanks for your thoughts on this one, Sawzall.
I am familiar with op-amp-based active filters.
I was hoping that someone else had experienced similar problems and had developed a "killer" fix, complete with tried and tested component values.
Looks like it's going to be down to some happy hours of experimentation.

Alec L
__________________
Alec L
  Reply With Quote
Old 31st August 2001, 03:22 PM   #4
diyAudio Member
 
Join Date: Jun 2001
Location: Alexandria, VA USA
Default take a look at TI and AD sites

Both I think give sample applications with values for using op-amps as filters. It sounds like your keyboard's analog outputs are pretty trashy. If it has MIDI or other digital outs, I might think about building/buying a better digital to analog interface to solve the problem as opposed to just filtering the problem.
  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
RC filters Sch3mat1c Parts 1 29th April 2011 08:34 PM
FM IF Filters Juergen Knoop Analogue Source 4 30th October 2008 02:35 AM
PSU filters kyrochan Power Supplies 1 2nd April 2005 04:05 PM
PI filters Prune Tubes / Valves 3 26th September 2004 09:16 PM
Filters Mr. Bungle Solid State 2 31st July 2004 05:08 PM


New To Site? Need Help?

All times are GMT. The time now is 07:09 PM.


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