MPX Filter - What does it actually filter? 

In my teens I could hear the 19 kHz tone, so audiophiles aren't exactly wrong. But most of them are older than that. :)

I appreciate you taking the time to incorporate every conceivable feature in your videos to assure long lasting state-of-the-art performance.

"Amazing dynamic range on CD's!" Only to get absolutely destroyed by the loudness wars

Watching the entire video has not been a waste. It’s fascinating and entertaining.

You're right! <a href="#" class="seekto" data-time="499">8:19</a> 'Shweddy balls' is the best example of dynamic range you could have given us. Thank you for this hidden festive gift. 👍😎🇦🇺

Speaking of recording off of FM, that was routine back in the 80s. I still have several tapes recorded off the radio here in NYC from 85-88, featuring stuff from Z-100, WPLJ/WWPR and even WAPP. 35 years on, they still sound great.

Watching VWestlife videos is NEVER a waste 😅

You've presented yet another fine video. Point of information: The FM (Stereo) broadcast standard specifies that transmitted audio must be between 50 Hz and 15 KHz. The absence or presence of a MPX filter would have no effect on the frequency range of a recording from FM radio, as most MPX filters didn't start their rolloff until 17 KHz.

My friends and I recorded a very popular techno/dance/trance radio show every Saturday in the 90s and we reminded each other after stepping out of the school bus, to put the right dolby system on (mostly we used B, because everybody had that setting on his deck) and MPX on, only knowing, it's needed for a better radio recording 🙂 After moving more and more to MD at the mid of the 90s, the settings were gone, and the days of "still knowing nothing and get a better result" had started.

congratulations on hitting 200K subscribers!

Your cassette deck vids are the best. Long may they continue and thanks!

I could hear a difference on the test at the end. It doesn't look or sound like a 19k notch filter, it's a lowpass shelf around 15k

A modern use for the MPX button - is recording from a modern hi-res sound card that has noise shaping. Some of these generate significant ultrasonics and these ultrasonics completely confuse dolby encoding. Its yet another reason people "don't like dolby" without actually understanding what's gone wrong. Whilst the MXP filter is centered at 19khz, it's wider than that and actually starts just above 15khz and goes well above 30khz in order to remove the entire stereo carrier. As such its perfect for cleaning up a noisy sound card.

Apart from the MPX info, I adore your collection of decks - so nice !

My old FM tuner had MPX Filter stamped on the front, I often wondered what it meant. Cheers 👍

Mmmmmm! Denon. Nakamichi. Tapes. 1980's. Audible latching relay clacks. These are a few of my favorite things 😁

That Laser tape is a true warrior, lasting for so long, also thank you for your amazing videos, my dinner is way better when I can watch you, Kevin ♥

I had a high end Yamaha deck when I was 20 or so, and at the time, I could hear up to 20K, according to tests. It could record up to that frequency, or higher on Metal tapes. Having the switch for MPX was necessary in that case. With it on, I could hear the loss in those high frequencies on some songs, like Owner of a Lonely Heart by Yes, which has hi-hats that do produce very high frequencies. Unfortunately, I can barely hear the hi-hats in that song at all anymore. I never checked with a spectrum analyzer, but with the MPX on, I could hear those hi-hats lose some zing back then. Today, I miss those frequencies. I can remember what they sounded or felt like back then, and now they're gone.

I must remember to tell my 15 year old self to use the MPX filter when recording on my TDK DC-90 tapes, on my older brother’s Panasonic slab music centre, from London pirate radio stations when I go back in time 40 years. Thanks for the heads up!

Watching new videos and learning things from you is never a waste! thank you for teaching me something that I didn't know or would have never known about my Kenwood stack that I now have

VWestlife answering questions I've had for 30+ years.

I found another use for the MPX filter years ago, I found certain albums and definitely certain CD's that would produce distortion on the cymbals on the tape recording. I fooled with bias and levels which was little help. I tried using Dolby it it's various forms or no Dolby at all. It was still distorted. I tried another cassette deck, that one did it too. I tried a reel to reel deck, that still had the cymbal distortion to a lesser degree. I finally tried the MPX filter, and that almost completely eliminated the problem. Apparently there were high frequency signals(s) in the audio that became nonlinear on tape. The cassette decks were a Sony and a Sansui, the reel to reel was an Akai. I *think* the CD was "Octopus" by Gentle Giant but there were others. Some vinyl LP's had the problem too to a lesser extent. I can''t set this up for testing as none of my tape machines actually work any more.

I was about to write how much I love these meticulous show and tells even though I'm familiar with most old world technology before the ending so no, absolutely no time wasted

Wow. I had no idea what the MPX filter was for. I really appreciate the explanation!

Thanks for explaining this little known feature, I always wondered what it was for and just ignored it. Now that I'm finally educated on the subject...…I guess I'll continue ignoring it.

This is great! I might have to put together a deeper dive on how FM multiplexing works and why you can still run HD Radio even if you have an additional SCA program.

<a href="#" class="seekto" data-time="60">1:00</a> I knew that the tape deck on top had to be made by Philips because I have a matching Philips 5-disc carousel CD player deck with the same industrial design with buttons jutting out from underneath. I also like the "bubble" or "pill" windows of your Philips cassette deck which give it a distinctive look. :)

<a href="#" class="seekto" data-time="483">8:03</a> - Speaking of 'bad labeling'! :)

Never fully understood the purpose of the MPX filter switch until your video. Thanks for your excellent explanation. Always look forward to your videos.

All my cassettes were recorded on mpx + dolby C on the hi-fi stack on my parents because manual said (and my teen brain understood) that best results were obtained with that combination. Then all my own integrated hi-fi and subsequent walkmans sported only dolby B, so genius move.

This was so awesome. Thanks for the thorough explanation amd demonstration. I do have to ask, did you know about the 19khz pilot tone and MPX filter back in the 80s as well?

Bless you Kev for answering questions I never had.

I knew what MPX is and I knew what the filter does, but I didn't know it was because of Dolby. Interesting!

Thank you, I never understand that switch before.

Yesterday I saw a tape recorder and wondered what MPX filter meant, and I was hoping you would do a video on one, I opened RU-vid today and saw this video. Thank you!

I always enjoy your posts, especially the ones about lesser known features on audio equipment. That brings me to the question: how many component tape decks do you have?

Yes!! I'm a "Wait, Wait, Don't Tell Me" fan!! Heard on KJZZ, in Phoenix, Arizona. Your friend, Jeff.

And the crazy thing is: You only demonstrated Dolby & MPX filtering on Dolby B. I'd imagine it'd sound unbelievably good (possibly near CD quality) with Dolby C & MPX filtering.

What an absolutely brilliant demo! Thank you!

<a href="#" class="seekto" data-time="68">1:08</a> The sound of the JVC deck brings me joy. I had a lower end model of the same generation, the TD-X335

1. Worrying about 19khz on a standard FM transmission 2. Worrying about 19khz on a cassette. Audiofools. Next, I'll be hearing about 19khz on vinyl! Appreciate the videos vwest

The difference is clearly audible, and I was surprised because RU-vid's audio should not, under any circumstances, reproduce 19 kHz. But the MPX filter is not of the 14th order; it's already a lot if it's a 2nd order, so it kills high frequencies long before reaching 19 kHz. In fact, even with my eyes closed, I guessed when the filter was activated in the video. Anyway, congratulations on the video, beautiful as always.

Not sure I ever owned a deck with MPX filter, thanks for the video, happy belated thanksgiving Kevin 😸🥂

Thank goodness we have our lord and savior - digital audio - its so damn near perfect its amazing - no mucking with filters, tape bias, types, hiss, or even figuring out what which dolby type is and how to use it. Interesting material you got there - lets us peek into ways ppl tried to squeeze the last drops of performance.

When the MPX was turned on when playing the CD it made the volume sound lower to me anybody else also think SO? Great video I always wanted to know what that was for.

Thanks for comprehensive explanation with visual examples! Superb (as usual) 👍👍

Watching this video wasn't a waste, because I enjoyed learning about this while stuffing down a chimichanga.

it's never a waste watching your videos kevin....you have taught me and others I'm sure about alot of things we did not know....thanks kevin😊

Next, you'll do a video on the many systems that were proposed for FM Stereo. I've had several decks and tuners that had MPX filtering, but some of them had Hi Cut which seemed to take a lot more of the HF away than the MPX filter did and likely was meant for noise reduction more than anything. Those were usually on the amp side anyway.

<a href="#" class="seekto" data-time="810">13:30</a> Time well-wasted, VWestlife. Haha! Thanks for the info regarding MPX filters because I never knew what it actually filtered and whenever I pressed the button, I couldn't hear any discernible difference. The best part was seeing a number of your cassette decks by various brands and I also acquired quite a substantial cassette deck collection thanks to eBay sellers and numerous thrift store finds (Bang & Olufsen, Nakamichi, Harman/Kardon, Tascam, Pioneer, Sony, Sansui, Technics, Toshiba, Hitachi, Akai, Aiwa, Nikko, Scott, etc.). :)

Your videos are interesting and awesome, so it's never a waste! Even if all I have is an old cheap soviet cassette deck.

Great explanation. SACD recorded on a good tape deck can triggered the Dolby circuit to if the MPX filter is not engaged. I have some bad experiences with a Rush SACD ( Conterparts) recorded with Dolby C on chrome tape in my Nakamichi BX-300: The 3 head monitoring make it so clear. The sound was extremely dull without MPX... Like a non Dolby recording decoded with Dolby. When i turn on MPX filter and Dolby B or C on monitor mode, differences are minimal. Without any Dolby encoding on SACD's no MPX filter is needed and the sound is so close to the original source but hiss can be heard on quiet passages.

These videos are "comfort food", even though I do not actually "eat" them in any conventional sense

Good video. I've always wondered exactly what the MPX filter was for...

I like how Mike Wallace was narrating for Zenith.

Love that picture @<a href="#" class="seekto" data-time="645">10:45</a> lol! I still have all that stuff. Always wondered about the MPX filter button, knew it had something to do with filtering out the carrier signal but I never heard the difference. FM stereo is too noisy and hissy anyway, even with a good rotating roof antenna. I usually end up recording FM in mono mode to cut the noise level if I’m recording off the radio.

I always learn something new from your videos ❤️👍🏻

Nah, watching your videos can never be a waste!

<a href="#" class="seekto" data-time="836">13:56</a> Damn it!

Brilliant video, very educational. Thank you.

Granted, this confused me a LOT back then too. Until i used a 3 head tapedeck and did a FM Stereo recording with Dolby C and enabled MPX filter. I was switching between MPX off and ON and realized the sound was so much better with MPX filter on. Resulting in a crystal clear tape recording of my FM Radio program i was recording. So clear, it almost made me believe i had a DAT recording. With MPX off it sounded a lot more muffled since the Dolby Noise reduction circuit thought the high pitch FM Stereo Pilot tone was a noise that was supposed to be removed. Which of course had a profound negative effect on the sound quality. Once you knew the benefit of the MPX Filter, Dolby NR recordings from Radio became a LOT more fun :)

Interesting! And cool that you showed a Sankyo tape deck. Not many even mention Sankyo. I had a Sankyo STD-3000 back in the day.

<a href="#" class="seekto" data-time="248">4:08</a> That voice sure sounds like Mike Wallace. For me FM radio back in the early '70s was great, and we had WVUD from The University of Dayton to enjoy. Ran by collage kids who were probably stoned at the time, we heard music you would never hear on commercial stations. Oh yeah, learning something new is never a waste.

Watching the video was worthwhile just to see the picture of that "Hits Radio" van with the sliding doors 🙂

Thanks 😊 for the Dolby-MPX noise reduction system, which I remember some years ago. I remember a friend who had a Marantz Stereo FM receiver that had a Dolby filter for FM reception if the station had it installed to reduce noise on FM, which never really caught on in use. 😊

Thanks, no doubt this feature has been a mystery to many audio enthusiasts over the years and decades. From what you have explained and by what we can see on the spec ann, the MPX feature is a simple notch filter to notch out 19KHz, as what is present in all FM stereo broadcasts and the MPX filter simply notches that out when engaged. 19K is indeed within the audible spectrum range of healthy human hearing so it doesn't come as a surprise to me that some folks with good to exceptionally good hearing could actually hear the stereo MPX pilot tone in FM radio stations that are indeed broadcasting in stereo, nevertheless FM broadcasters are required to brickwall the high end fo their programme audio at 15K so as to prevent audio frequencies in the broadcast from interfering with the station's transmitted 19K pilot tone. The MPX filter is indeed handy to further notch out the 19K spike that might otherwise get reproduced and amplified on a high-end receiver and set of speakers.

There's actually a little difference in airyness if you ask me. But Im not starting discussions about it. Your vids are never a waste of time, no arguing about that either 👍

Great video, I appreciate the effort and level of detail you've put in. I knew the MPX filter removes some "service" FM signal, but I had no idea that signal defeats Dolby NR.

While neither of my Kenwood decks or my JVC deck have the MPX filter switch, watching the video was certainly not a waste of time! That was very educational and interesting!

Ignoring the topic just for a moment, how many functioning cassette decks do you own? There's a very impressive collection just in this video.

When I see that stack of cassette decks (and I know, many are missing in that video) and then I turn around to see my pile of 8 decks that are next to me (plus the 5 others I have elsewhere), I feel better about myself.... Though I should really start shrinking that pile... ;-)

I've worked in radio and television broadcasting on and off since the mid 90s, and I never knew the MPX filter on a cassette deck was related to stereo MPX. I always assumed it was a filter for some other Dolby system... 😂

My sansui 7070 integrated amp from the late seventies has this filter although I don't ever remember using. Great explanation thank you!

Good tuners actually often contain a better way to cancel the 19 kHz pilot tone than cassette decks. The cheapest way to implement that is by a low-pass filter. The problem is that these filters often are not steep enough and thus cut into the audible frequency range way below 19 kHz. A better way is to instead cancel out the pilot tone by literally adding another 19 kHz signal that has its phase inverted w.r.t. the original pilot tone. This is the same principle as used in active noise reduction. If done correctly, this only affects the pilot tone (not even any music signal, although FM broadcast does not reach such high frequencies).

I never paid any attention but after watching this, I checked my Kenwood deck. It has Dolby B &C and has auto MPX.

thanks for the well-explained issue

WOW... great video. Please, keep up the good work.

Watching your videos is never a waste. You could entertain a group of claustrophobics in a tunnel...and I do have several MPX filter buttons, as I have a cassette deck collecting problem sadly :)

I've allways been curious about what that actually does. A quick google search I did many moons ago didn't bring up much in the way of usefull information. Untill now all I could tell was that it was a button that seemingly does nothing.

Fascinating, thanks!

Oh nice a new video very interesting the mpx filter button 🔘.

As always, great video. Never knew Sankyo existed👍🏻😉🏴󠁧󠁢󠁳󠁣󠁴󠁿

A very cool video there VW. 😎👍

I’d challenge anyone to pick out the effects of a 19k filter in a double-blind test. This is why we in the pro audio industry find audiophiles to be so incredibly insufferable. They’ll even argue against null tests 😂😂

lol after hearing some of old stories from fellow broadcast engineers, many hack stations back in the day would just air the pilot to fool radios while remaining mono.

Thanks for your videos, very usefull.

I recently got an early 90s Technics mid-high end tape deck that had this switch.

Thank you. Finally the answer! :)

So awesome to see the SHIT-FM pic at <a href="#" class="seekto" data-time="483">8:03</a>. There’s a story behind that. At the time, CKIX flipped from KIXX Country to top 40 with no notice. As you can imagine, people were pissed and that snafu resonated with so many people at the time. The Country moved over to 590 VOCM and eventually to 103.9 KIXX after its transition from 560AM.

I have a Fisher 500-C vacuum tube receiver from 1964 with an MPX filter in it and a switch on the front

An MPX filter on a tape deck is, at least, a notch filter that will block the 19 kHz pilot tone, and possibly higher frequencies in the 23-53kHz and 63-75kHz bands. The difference can be heard when recording from an FM stereo source and engaging and disengaging the MPX filter switch. On a three-head deck with monitoring, this can be heard while recording. The filter should not be engaged when recording from other sources, such as Compact Disc. The setting of the switch has no effect during playback. Decks with no MPX filter switch typically have a non-defeatable MPX filter incorporated in their design, which limits the overall (i.e. record to playback) frequency response to about 15-16 kHz.

A few years ago, I bought a couple broken tape decks(with the intention of fixing them) solely because I was enamored with how cool they look with those little reel-to-reel tapes running in them. They're collecting dust now. It was a bit of the TechMoan effect and a dash of VWestlife syndrome.

that Nakamichi cassette deck is really nice! have you done a video on that one specifically ? If so I would like to view it.

i could hear that 19khz tone (and the whine of a CRT) up through my early 20s. now i'm lucky to hit 15khz at 39... hopefully we get a fix for this sometime in the future!

Finally! Thanks.

I am 18 years old and can still hear the full frequency range (it won’t last long). To me, there is a clear cut in the high frequencies when the MPX filter is engaged when it shouldn’t. I am probably going to be fine after my mid 20’s tough…

Thanks for waiting until the end of the video to confirm that you've wasted my time. (You haven't. None of my equipment has this switch, but I've always been curious what it does.) Great video, just as good as the beat cut one. Looking forward to the next dorky video about obscure audio switches!

I like the "Tape Running" LED indicator or the Sankyo deck from the 70s 🙂

My Nakamichi CR-1A does indeed have one of these doohickeys, so luckily this was time well spent 😂

"Sankyo" reads like what a German would say if he thanked you. I should know 😅. Anyway, very nice video, learned something again I didn't even notice on decks before. Cheers!