@@gammaboost Ageing, that's what is happening... I took a professional test as a kid, and I could hear up to 20khz. Now, at 25, I can hear up to 18 maybe 19 if I sit in complete silence...
I couldn't: my hearing in late teens cut off at no more than 16 kHz. Anyway, there were no FM stations anywhere around (but we did quite a lot of electronics DIY). Then, at 24 years, I was struck by pneumonia and lost hearing, almost completely. And then a very competent postdoc medic used me as a guinea pig for her studies... and brought my hearing sensitivity to norm and frequency range up to 26 kHz. Yes, I could hear quite a lot above 20 kHz - but then, it only showed up on test tones. The "opening" did not reveal any "previously unheard" sounds, natural or man-made. It did not last long though, and in one year frequency response fell back to around same 16 kHz. 30+ years later I can barely hear 10 kHz in the morning (much worse later in the day).
Be careful with headphones and avoid loud noises, I find that the ears response is not always constant and varies slightly from day to day so dont panic 😸
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.
I recently found some 70s and 80s air checks on RUclips. The ones featuring Z-100 and WPLJ really gave me the chills. Damn, how I miss those times (I was born in 1970). And those old tapes reflect those times perfectly. Especially the ads included in them.
Same. My tapes were mostly Austrian broadcasts from the 1980s, but recently I acquired a crate of used Sony Fe-Cr tapes from Japan, recorded off Japanese FM in the 1970s. Sweet. Great music of all sorts, no Dolby, no hiss.
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.
I was hoping somebody would comment on this, because it saves me the trouble of doing it. Also noteworthy is that the equalization of FM broadcasts depends on the region. Some tuners have a switch to deal with this.
The difference is clearly audible, and I was surprised because RUclips'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.
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.
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
Never fully understood the purpose of the MPX filter switch until your video. Thanks for your excellent explanation. Always look forward to your videos.
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.
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
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.
Love that picture @10:45 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'm all for dunking on over the top audiophiles, but I think vwestlife's hearing might not be what it used to be. I could hear a pretty strong difference between both, and considering YT audio is like 128kbs, the uncompressed one might be even more noticeable 🤷♂
13:30 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.). :)
1:00 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. :)
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!
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.
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.
@@seacampal1425 That makes sense. I assumed there was some ultrasonic content there, I guess it wasn't ultrasonic to everyone! Maybe it did to your ears what it did to my tapes. I could hear a TV horizontal back in the day (15750 Hz) but never could hear the FM pilot (19000 Hz).
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.
4:08 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.
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.
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 RUclips today and saw this video. Thank you!
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.
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.
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. 😊
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 :)
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 👍
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.
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?
No, I was too young back then (I'm younger than every Backstreet Boy except Nick Carter). I think I first learned about the pilot tone when I recorded FM radio into my Sound Blaster 16 card and wondered why there was a spike at 19 kHz on the spectrum analyzer display of my audio player program.
@ vwestlife I asked my brother last night about the MPX button and he actually knew it was recording off FM radio. He didn't know the details of why, but I was amazed he knew the function at least and apparently had used it for his own recordings. The reason I suspected he might know is because he used to sell A/V gear back in the 80s at some boutique stereo store, and he's a nerd so he certainly read all the manuals.
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?
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 :)
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.
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.
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 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!
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
Thank you Sankyo, I can now use Ferri-Chrome Type 3 tapes for years to come. Also thank you for such an easy transport design to rebelt (I have done a Pioneer, Technics and Yamaha that had that same angled design...not fun).
So awesome to see the SHIT-FM pic at 8:03. 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.
@@vwestlife You're missing the point. There is bleed into the lower frequencies that are audible to a lot of people. You also have to take the quality of the equipment into consideration as well. Perhaps your ears are not able to pick up on that bleed on your low quality consumer grade equipment. But better equipment and better ears will pick up on that bleed.
@@mirkomusanic Not on his equipment it can't. But audiophiles wouldn't go near this stuff. So blaming them for the MPX filter feature is just plain ridiculous as they never would have bought this anyway.
@@SSJfraz FM radio stations have to lowpass filter their audio at 15 or 16 kHz to prevent interfering with the pilot tone, so anything above 17 kHz on an FM broadcast is just noise and the pilot tone. There is no audio content that high in the signal.
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... ;-)
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.
Now I'm curious whether my tape deck has an MPX filter or a button to turn it on and off. Although chances are I'll never need it, so probably not worth me digging through my storage unit to find out. Actually, I'm really curious whether my DAT deck would have it. Considering how much higher fidelity the DAT format is, it might actually make a noticeable difference if you accidentally leave it activated for recording off a well mixed CD.
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.
The Soundesign has one too... and neither of them use LEDs! It's just an incandescent bulb with a spinning disc in front of it that alternately blocks and lets through the light.
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 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 the video but feel I need to clarify a couple of points. Firstly you say that engaging Dolby turns on the MPX Filter as you can see the level of the pilot tone reduce. This is probably not the case as when Dolby in engaged on playback the high frequencies are attenuated by hopefully the same amount as they were boosted during record. This is the basis of the Dolby B noise reduction. C/DBX are of course subtly different. When I was younger I had good hearing which of course decays with age as a main factor. But I could never really hear 19k. The 15.6k timebase from TVs was clearly audible. But the main purpose of the MPX filter / Beat Cut switch was to remove the pilot tone as much as possible so it didn't "Heterodyne" with audio signals to be recorded OR the bias erase oscillator on the tape unit. Some cheep beat cut systems just shifted the bias/erase oscillator frequency slightly.
Think of this as an example... If the pilot tone is at 19k and the bias oscillator is running at 25k then the sum and differences of these would be 19+25= 44k (Inaudible) and 25-19=6k (very audible). The same could theoretically occur with audio signals but on a well designed FM tuner the output after the decoder and de-emphasis should have removed the pilot tone and the L-R sideband along with RDS and other data signals. Cheers..
As I mentioned in the video, the filter does not affect playback. It is only engaged during recording. And cassette decks use bias frequencies much higher than 25 kHz. A bias frequency of around 80 to 100 kHz is typical.
@@vwestlife Exactly... The figures I chose were just an example to make maths and understanding easy. But the 19k will have harmonics that could beat with the erase oscillator causing audible effects. I just saw a number of comments fixating on the hearing of the 19k signal and wanted to advise the other possiblilities. Please threat this as a positive comment and please keep up the great videos.
Watching the video for a 2nd time was wondering if you could tell me about your c.crane FM transmitter. I am in desperate need of a good FM transmitter that actually gets the job done acceptably and hopes you could tell me a little more about yours; What exact model is that, is it worth buying, or is there a better option you'd recommend? I'm assuming this must be a really good unit if it was good enough to set up for demonstration in the video! Any feedback would be hugely awesome! And: Thank you for clearing up that ambiguously obscure MPX mystery. Love the channel, longtime viewer & supporter, I loves your content!! 🥰
HobbyBroadcaster has a detailed review of it. The current version is the C.Crane FM Transmitter 3. There's also the Whole House FM Transmitter 3.0, which you can also find a detailed review of on RUclips.
I ahem Sheritone brand AM/FM transistor radio and it has a special MPX red light that tells you when an FM Stereo channel is using MPX and most do, but a few do not, for whatever reason. You can hear the difference in superior warmth and clarity.
I've been recording FM audio to train an AI audio enhancement model, and I can definitely vouch for the 19khz stereo pilot-it sticks out on the spectrogram. Like you said, some radios filter it out by default, so the level varies.
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!
"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!
I figured it was something to do with radio, since MPX decoders exist for TVs (at least those that have the option from the 80s). Had no idea it was directly for the pilot light though, very interesting! Also didn’t know that the pilot light used high frequency to turn it on, but it does make sense considering it’s radio. Great video!
The 19KHz tone does a lot more than turn on the light. Inside the stereo decoder it get doubled to allow demodulation of the L-R audio information which is centred on 38KHz. Turning on the light is just a bonus.
Can't recall seeing an MPX filter switch on my Yamaha K-960... only a dbx switch.But, I did see one on my parent's dual 8-track Capehart compact stereo. Also: I have a Wollensak 8-track deck with an FM Decode switch... so, for all I know, that may be the same thing.
MPX filter also helps with CD players with lack of signal filtering above 22kHz (at least in my case) when recording with Dolby, can be useful with other type of DAC's.
It shouldn't. This is likely just the result of not being able to properly bais the tape for the specific formulation and the additional highs are over biasing. This is what HXPro fixed.
@@dewdudeWhat I was referring to is noise due to interference with bias frequency - mpx is cutting anything above 19KHz so problem solved. Try to look at signal from some DAC's on oscilloscope. The simples test you can do is to record CD or put PCM/WAV file with zeros and play it back - then record it, and then record with disconnected CD/DAC - if there is different noise level then you are dealing with unwanted frequencies (or bad shielding). Sadly in some decks MPX works only with Dolby enabled (maybe on all of them?)
@@xenon2Merchant biasing is a different can of worms all together. My rule is if you are not using a three-head deck and you are not calibrating the bias for that tape using a pink noise generator, then anything you do is moot. In a properly designed deck, the bias isn't anywhere in the dolby chain; mpx filtering would occur to the audio before it's sent through the Dolby encoder/compressor. Now the 19khz carrier can cause some degree of self-biasing, which can cause the tape to over-bias; but even the audio you're recording does this. That's where HX Pro comes in to play...which is...again...a different can of worms. There is some inherent advantage to using the mpx filter to prevent self-biasing..but then you add the complication of dolby to the mix. The MPX filter is very much a Dolby thing; it's entire system is based on accurately tracking the high frequencies. Given the fact that most consumer decks were lousy playback machines that rarely had proper azimuth and...Dolby is a bad idea. I think most of the things you're noticing have more to do with the self-biasing factor of the MPX carrier rather than anything related to the dolby circuit.
In my teens I could hear the 19 kHz tone, so audiophiles aren't exactly wrong. But most of them are older than that. :)
Same thing, but now i cant hear 19 kHz becouse of age
I'm a teen and my hearing barely goes above 17khz 😢. Used to be 18khz not long ago, dunno what happened because I look after my hearing.
@@gammaboost Ageing, that's what is happening... I took a professional test as a kid, and I could hear up to 20khz. Now, at 25, I can hear up to 18 maybe 19 if I sit in complete silence...
I couldn't: my hearing in late teens cut off at no more than 16 kHz. Anyway, there were no FM stations anywhere around (but we did quite a lot of electronics DIY).
Then, at 24 years, I was struck by pneumonia and lost hearing, almost completely. And then a very competent postdoc medic used me as a guinea pig for her studies... and brought my hearing sensitivity to norm and frequency range up to 26 kHz. Yes, I could hear quite a lot above 20 kHz - but then, it only showed up on test tones. The "opening" did not reveal any "previously unheard" sounds, natural or man-made. It did not last long though, and in one year frequency response fell back to around same 16 kHz. 30+ years later I can barely hear 10 kHz in the morning (much worse later in the day).
Be careful with headphones and avoid loud noises, I find that the ears response is not always constant and varies slightly from day to day so dont panic 😸
"Amazing dynamic range on CD's!"
Only to get absolutely destroyed by the loudness wars
Yup. That's what makes digital audio great. Garbage in, garbage out.@@truesoundchris
I appreciate you taking the time to incorporate every conceivable feature in your videos to assure long lasting state-of-the-art performance.
Keep these videos handy for future reference.
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.
I recently found some 70s and 80s air checks on RUclips. The ones featuring Z-100 and WPLJ really gave me the chills. Damn, how I miss those times (I was born in 1970). And those old tapes reflect those times perfectly. Especially the ads included in them.
Same. My tapes were mostly Austrian broadcasts from the 1980s, but recently I acquired a crate of used Sony Fe-Cr tapes from Japan, recorded off Japanese FM in the 1970s. Sweet. Great music of all sorts, no Dolby, no hiss.
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.
I guess the key point of the feature is being able to turn it off in case your batty ears can hear 19KHz tones recorded from a CD.
I was hoping somebody would comment on this, because it saves me the trouble of doing it. Also noteworthy is that the equalization of FM broadcasts depends on the region. Some tuners have a switch to deal with this.
congratulations on hitting 200K subscribers!
Your cassette deck vids are the best. Long may they continue and thanks!
I envy Kevin's collection of cassette decks.
The difference is clearly audible, and I was surprised because RUclips'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.
Watching VWestlife videos is NEVER a waste 😅
Apart from the MPX info, I adore your collection of decks - so nice !
Ya, I'm pretty jealous about his collection too!
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.
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
Never fully understood the purpose of the MPX filter switch until your video. Thanks for your excellent explanation. Always look forward to your videos.
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 ♥
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.
Only trashiest of sound cards generate any kind of ultrasonics, we're so past these problems its not even worth discussing.
@@VEC7ORltever heard of hi-res audio? Ultrasonic galore!
@@dlarge6502 Sure did, now demonstrate said ultrasonics.
My old FM tuner had MPX Filter stamped on the front, I often wondered what it meant. Cheers 👍
Wow. I had no idea what the MPX filter was for. I really appreciate the explanation!
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
I always learn something new from your videos ❤️👍🏻
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.
You were lucky, most teens can't even hear more then 17-18khz
You would not hear any difference if you recorded off a FM radio broadcast, which is 50 Hz -- 15 kHz only, by international agreement.
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😊
Love that picture @10:45 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 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
I'm all for dunking on over the top audiophiles, but I think vwestlife's hearing might not be what it used to be. I could hear a pretty strong difference between both, and considering YT audio is like 128kbs, the uncompressed one might be even more noticeable 🤷♂
13:30 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.). :)
1:00 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. :)
What an absolutely brilliant demo! Thank you!
1:08 The sound of the JVC deck brings me joy. I had a lower end model of the same generation, the TD-X335
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!
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.
HD exists outside the channel. It is literally extra sidebands within the adjacent frequency.
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.
The first CD version of "Octopus" was ultra agressive on highs; unlistenable.
@@seacampal1425 That makes sense. I assumed there was some ultrasonic content there, I guess it wasn't ultrasonic to everyone! Maybe it did to your ears what it did to my tapes. I could hear a TV horizontal back in the day (15750 Hz) but never could hear the FM pilot (19000 Hz).
@@davidg4288 I think "Octopus" was mixed and mastered for vinyl ( RIAA) and not for CD.
Mmmmmm! Denon. Nakamichi. Tapes. 1980's. Audible latching relay clacks. These are a few of my favorite things 😁
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.
WOW... great video. Please, keep up the good work.
4:08 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.
It is Mike Wallace.
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.
Yes!! I'm a "Wait, Wait, Don't Tell Me" fan!! Heard on KJZZ, in Phoenix, Arizona. Your friend, Jeff.
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 RUclips today and saw this video. Thank you!
Thank you, I never understand that switch before.
Thanks for comprehensive explanation with visual examples! Superb (as usual) 👍👍
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.
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.
Bless you Kev for answering questions I never had.
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. 😊
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 :)
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 👍
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.
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.
Good video. I've always wondered exactly what the MPX filter was for...
8:03 - Speaking of 'bad labeling'! :)
My sansui 7070 integrated amp from the late seventies has this filter although I don't ever remember using. Great explanation thank you!
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?
No, I was too young back then (I'm younger than every Backstreet Boy except Nick Carter). I think I first learned about the pilot tone when I recorded FM radio into my Sound Blaster 16 card and wondered why there was a spike at 19 kHz on the spectrum analyzer display of my audio player program.
@ vwestlife I asked my brother last night about the MPX button and he actually knew it was recording off FM radio. He didn't know the details of why, but I was amazed he knew the function at least and apparently had used it for his own recordings. The reason I suspected he might know is because he used to sell A/V gear back in the 80s at some boutique stereo store, and he's a nerd so he certainly read all the manuals.
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?
Too many.
@@vwestlifewrong, correct answer would be. Not enough. 😂😂😂😂😂
@@ralphreinhardt6020I like your way of thinking!
@@andriealinsangao613 great minds think alike ! 😎👍
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 :)
Nah, watching your videos can never be a waste!
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 very cool video there VW. 😎👍
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.
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.
I knew what MPX is and I knew what the filter does, but I didn't know it was because of Dolby. Interesting!
As always, great video. Never knew Sankyo existed👍🏻😉🏴
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!
Brilliant video, very educational.
Thank you.
My old Akai 1980 CMO2 has a ''Filter'' position setting on the Dolby B switch which is for ''FM recording''..sounds like MPX in use
Watching this video wasn't a waste, because I enjoyed learning about this while stuffing down a chimichanga.
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
VWestlife answering questions I've had for 30+ years.
Thank you Sankyo, I can now use Ferri-Chrome Type 3 tapes for years to come. Also thank you for such an easy transport design to rebelt (I have done a Pioneer, Technics and Yamaha that had that same angled design...not fun).
So awesome to see the SHIT-FM pic at 8:03. 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.
Watching the video was worthwhile just to see the picture of that "Hits Radio" van with the sliding doors 🙂
I never paid any attention but after watching this, I checked my Kenwood deck. It has Dolby B &C and has auto MPX.
13:10 - The problem is that MPX filter starts rolling off at around 17KHz, which is audible.
If you can't hear the 15.7 kHz flyback oscillator whine from a CRT TV or computer monitor anymore, then there's no way you can hear up to 17 kHz.
@@vwestlife You're missing the point. There is bleed into the lower frequencies that are audible to a lot of people. You also have to take the quality of the equipment into consideration as well. Perhaps your ears are not able to pick up on that bleed on your low quality consumer grade equipment. But better equipment and better ears will pick up on that bleed.
Impact of double mpx filter can be seen, that's for sure, but can it realy be heard? I doubt.
@@mirkomusanic Not on his equipment it can't. But audiophiles wouldn't go near this stuff. So blaming them for the MPX filter feature is just plain ridiculous as they never would have bought this anyway.
@@SSJfraz FM radio stations have to lowpass filter their audio at 15 or 16 kHz to prevent interfering with the pilot tone, so anything above 17 kHz on an FM broadcast is just noise and the pilot tone. There is no audio content that high in the signal.
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... ;-)
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.
The MPX filter does still have an effect on Dolby C, but not nearly as much as with Dolby B.
Oh nice a new video very interesting the mpx filter button 🔘.
Thank you. Finally the answer! :)
My Sony TC-K611S cassette deck does have an MPX switch/filter.
These videos are "comfort food", even though I do not actually "eat" them in any conventional sense
Now I'm curious whether my tape deck has an MPX filter or a button to turn it on and off. Although chances are I'll never need it, so probably not worth me digging through my storage unit to find out. Actually, I'm really curious whether my DAT deck would have it. Considering how much higher fidelity the DAT format is, it might actually make a noticeable difference if you accidentally leave it activated for recording off a well mixed CD.
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.
thanks for the well-explained issue
I like the "Tape Running" LED indicator or the Sankyo deck from the 70s 🙂
The Soundesign has one too... and neither of them use LEDs! It's just an incandescent bulb with a spinning disc in front of it that alternately blocks and lets through the light.
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 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…
incredible video as usual!
Thanks for the video but feel I need to clarify a couple of points.
Firstly you say that engaging Dolby turns on the MPX Filter as you can see the level of the pilot tone reduce. This is probably not the case as when Dolby in engaged on playback the high frequencies are attenuated by hopefully the same amount as they were boosted during record. This is the basis of the Dolby B noise reduction. C/DBX are of course subtly different.
When I was younger I had good hearing which of course decays with age as a main factor. But I could never really hear 19k. The 15.6k timebase from TVs was clearly audible. But the main purpose of the MPX filter / Beat Cut switch was to remove the pilot tone as much as possible so it didn't "Heterodyne" with audio signals to be recorded OR the bias erase oscillator on the tape unit. Some cheep beat cut systems just shifted the bias/erase oscillator frequency slightly.
Think of this as an example... If the pilot tone is at 19k and the bias oscillator is running at 25k then the sum and differences of these would be 19+25= 44k (Inaudible) and 25-19=6k (very audible). The same could theoretically occur with audio signals but on a well designed FM tuner the output after the decoder and de-emphasis should have removed the pilot tone and the L-R sideband along with RDS and other data signals.
Cheers..
As I mentioned in the video, the filter does not affect playback. It is only engaged during recording. And cassette decks use bias frequencies much higher than 25 kHz. A bias frequency of around 80 to 100 kHz is typical.
@@vwestlife Exactly... The figures I chose were just an example to make maths and understanding easy. But the 19k will have harmonics that could beat with the erase oscillator causing audible effects. I just saw a number of comments fixating on the hearing of the 19k signal and wanted to advise the other possiblilities. Please threat this as a positive comment and please keep up the great videos.
I recently got an early 90s Technics mid-high end tape deck that had this switch.
Watching the video for a 2nd time was wondering if you could tell me about your c.crane FM transmitter. I am in desperate need of a good FM transmitter that actually gets the job done acceptably and hopes you could tell me a little more about yours; What exact model is that, is it worth buying, or is there a better option you'd recommend? I'm assuming this must be a really good unit if it was good enough to set up for demonstration in the video! Any feedback would be hugely awesome!
And: Thank you for clearing up that ambiguously obscure MPX mystery. Love the channel, longtime viewer & supporter, I loves your content!! 🥰
HobbyBroadcaster has a detailed review of it. The current version is the C.Crane FM Transmitter 3. There's also the Whole House FM Transmitter 3.0, which you can also find a detailed review of on RUclips.
@@vwestlife nice, thanks man!!
I ahem Sheritone brand AM/FM transistor radio and it has a special MPX red light that tells you when an FM Stereo channel is using MPX and most do, but a few do not, for whatever reason. You can hear the difference in superior warmth and clarity.
@4:08 ~ is that Mike Wallace narrating that?
Yes!
I've been recording FM audio to train an AI audio enhancement model, and I can definitely vouch for the 19khz stereo pilot-it sticks out on the spectrogram. Like you said, some radios filter it out by default, so the level varies.
I have a Fisher 500-C vacuum tube receiver from 1964 with an MPX filter in it and a switch on the front
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!
"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!
MPX is also needed when recording from some VCRs, since HiFi VHS uses FM (and includes a pilot tone.)
I figured it was something to do with radio, since MPX decoders exist for TVs (at least those that have the option from the 80s). Had no idea it was directly for the pilot light though, very interesting! Also didn’t know that the pilot light used high frequency to turn it on, but it does make sense considering it’s radio. Great video!
The 19KHz tone does a lot more than turn on the light. Inside the stereo decoder it get doubled to allow demodulation of the L-R audio information which is centred on 38KHz. Turning on the light is just a bonus.
I guess I never really thought about the in depth details of how FM works. Always cool to learn more about audio!
Can't recall seeing an MPX filter switch on my Yamaha K-960... only a dbx switch.But, I did see one on my parent's dual 8-track Capehart compact stereo. Also: I have a Wollensak 8-track deck with an FM Decode switch... so, for all I know, that may be the same thing.
MPX filter also helps with CD players with lack of signal filtering above 22kHz (at least in my case) when recording with Dolby, can be useful with other type of DAC's.
It shouldn't. This is likely just the result of not being able to properly bais the tape for the specific formulation and the additional highs are over biasing.
This is what HXPro fixed.
@@dewdudeWhat I was referring to is noise due to interference with bias frequency - mpx is cutting anything above 19KHz so problem solved. Try to look at signal from some DAC's on oscilloscope. The simples test you can do is to record CD or put PCM/WAV file with zeros and play it back - then record it, and then record with disconnected CD/DAC - if there is different noise level then you are dealing with unwanted frequencies (or bad shielding).
Sadly in some decks MPX works only with Dolby enabled (maybe on all of them?)
@@xenon2Merchant biasing is a different can of worms all together. My rule is if you are not using a three-head deck and you are not calibrating the bias for that tape using a pink noise generator, then anything you do is moot. In a properly designed deck, the bias isn't anywhere in the dolby chain; mpx filtering would occur to the audio before it's sent through the Dolby encoder/compressor. Now the 19khz carrier can cause some degree of self-biasing, which can cause the tape to over-bias; but even the audio you're recording does this. That's where HX Pro comes in to play...which is...again...a different can of worms.
There is some inherent advantage to using the mpx filter to prevent self-biasing..but then you add the complication of dolby to the mix. The MPX filter is very much a Dolby thing; it's entire system is based on accurately tracking the high frequencies. Given the fact that most consumer decks were lousy playback machines that rarely had proper azimuth and...Dolby is a bad idea.
I think most of the things you're noticing have more to do with the self-biasing factor of the MPX carrier rather than anything related to the dolby circuit.
@@dewdude I did testing with signals above 30 KHz and it is creating extra noise.