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Are 8-track & 4-track cassettes compatible? Can the same calibration tape be used?

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I had a question recently from a viewer about whether he could purchase a calibration tape and expect it to work his 8 track cassette recorder. I just got a 488 that has been sitting in my projects pile for ages working , so I thought i'd take the opportunity to investigate exactly how Tascam's and Phillips' formats for 4 track and 8 track heads differ - Phillips in this case refers to the common, garden-variety commercial cassette format used in the sony walkman, car stereos, home stereos, etc.
tried playing back several tapes in my Tascam 488;- a 4 track recording made on a 244; a commercial tape my mum must have bought from woolworths or Tower records or some other long-defunct record store several decades ago, and a Teac MTT-122BN 1kHz level test tape .
To better visualise the way the 488's head was responding to the different cassettes, I colour coded a diagram from the 488's service manual using adobe Photoshop i.
I go into more detail in the video but here is a brief summary of my conclusions;-
The tracks on a 4 track head are narrower than those on a a phillips head, but they do line up, so you can playback a prerecorded tape intended for home entertainment on any four track, its just that side B will play backwards.
Tracks , 2, 3, and 4 recorded on a 4 track tascam unit will be played back clearly on tracks 1, 2, 7 and 8 respectively of an 8 track tascam. Some of the same information may also appear on other tape tracks due to partial overlap of regions.
The Teac test tape I have appears to be printed with a special head that puts signal accross the entire width of the tape, meaning it cna be used to set playback levels of any format of cassette recorder. But if you have a calibration tape recorded using a phillips or tascam 4 track head, you will not get reliable results when calibrating track 3 through 6 of a tascam 8 track cassette recorder.
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Опубликовано:

23 мар 2022

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Комментарии : 20

@Musinformation96 2 года назад

Brilliant visual explanation here, the photoshop layers... such a good idea.

@Tetrakan 2 года назад

Thanks, drawing overlays on schematics in photoshop has played a major role in developing my understanding of electronics, I'd recommend it.

@DiegoCarvacho 2 года назад

A few months ago I got a cassette with a 1khz signal. It was recorded with a head that records on the complete tape Width. It is very usefull for this kind of stuff. Its good for calibrating a 4 track or an 8 track machine. Until a few weeks ago I didn't even know these things existed. Interesting video, thanks!

@ordaleem 2 года назад

Excellent. Yes, I think this is what's meant by "full track" test tapes. I'm after one for head azimuth calibration. Where'd you get yours?

@DiegoCarvacho 2 года назад

@@ordaleem you can find them on ebay. The guy who sells them lives here in Germany. Cool guy!

@markbilyeu1129 2 года назад

I love this sort of thing. Well done, and thanks.

@DaveZula 2 года назад

I'm a bit surprised to find out that the 488 and 688 have the same heads. In my experience the 688 does sound incredibly good for an 8 track cassette machine. To my ears it sounds better than any 4 track or 2 track cassette machine I've heard. It seems to have a lower noise floor, greater dynamic range, everything. Maybe it's the preamps and built in mixer? Variance from one unit to the next? Placebo effect? I've used a lot of cassette machines over the years but certainly not as many as you. I'm also one of the few who actually likes and uses the built-in noise reduction, if that makes a difference. Anyway, I love your vids, man. Keep it up. ✌️

@Tetrakan 2 года назад

Hi David. Just checked the service manuals on both the 488 mark one nad 688 in case I was confabulating, but the transports in both units are identical, record playback head is part number 5378601600 in both units. Technically speaking, becasue ther egions of tape the signal occupies are narrower on a 488/688 than - for instance - a 424, the signal is being represented by fewer metallic crystals and the dynamic range should be meaurably worse on the 688 than the 424 (!). DBX dramtically increases the dynamic range, at the expense of changing the frequency response and adding some compression artefacts - like you, i actually prefer the sound of this and typically record with DBX on. So what accounts for your preference/perception of the 688? Is the performance of the record amplifiers and mixer much better? Or is your 688 much better calibrated and maintained than other units you have had access to? Or is there an element of confirmation bias? I don't really know. I do plan to start making a series of videos where I compare sections of schematics accross serveral makes and models of multitracker to identify common features and differences...for example comparing the headphone amplifier in a Teac 144, Tascam Porta 07, and Yamaha MT8x....so comparing the preamplifiers of several multitrackers including a 688 alongside other brands and cheaper models is something I will add to my holding pen of video ideas..thanks for watching :)

@DaveZula 2 года назад

@@Tetrakan Yeah it's totally illogical that a tiny sliver of an already narrow piece of tape would sound any good at all, let alone better than a wider format. I assumed there had to be some fancy engineering under the hood considering the 688 was a later model, and I believe the most expensive, high end cassette multitracker they ever made. (Some of that was to do with the midi capability and more complex routing options which I never used.) But the EQ alone on the 688 sounds excellent. I have had mine serviced by TEAC as well. 🤷‍♂️

@BlazeONEANdChill 2 года назад

Thank you

@wehappyfewmusic 2 года назад

Interesting video and your coloured version of the head diagram comparison really helps clarify things. I tried playing a tape back recorded on a 244 in a 488, and noticed how the different head spacing also threw the tracks out of sync a bit. Also it’s good to know that all the Tascam 8 tracks share the same heads. I’ve got two 488mk11’s which won’t record on one of the tracks, and fear I may need to start the quest to find replacement heads. 😬

@Tetrakan 2 года назад

Thanks. I've got a repair report on a 488 Mk 1 I'll be publishing next week. It ahd one channel not erasing, and initially I thought it was dead heads, but it turned out to be tape to head contact issue, perhaps that will rpove to be the case with your mark IIs? I'll eb going over testing heads for continuity and so on in that video so stay tuned...

@wehappyfewmusic 2 года назад

@@Tetrakan Brilliant, I hope that’s the case with my mk2’s then. Look forward to seeing your new video! Thanks, Calum.

@hkhjg1734 Год назад

Question: I want to normalize the playback levels of my own 488. I don't have a cassette test tape, but I have a 2 track 1/4in reel to reel mastering deck. Ive looked at how the heads would line up on this tape and know it would cover 4 of the 488's heads. If I record a few tones on my reel to reel, physically split the tape in half, load it into a cassette, Can I just look at the levels of all the channels, find the average, and from there adjust the playback so that they are all the same based off this arbitrary level coming from my franken-tape?

@Tetrakan Год назад

I havent tried that but I think that'd basically work? And it wouldn't do any harm...let us know?

@Lilliputian63 6 месяцев назад

Great, informative video. However, the fact that you can't get a signal on channels 1 and 2 make me wonder HOW compatible 4 channel tapes are on 8 channel recorders. Looking at your very diagram, the tape read/record head is only half as wide as the 4 channel. So how could it possibly read the tape in as high a quality was as a 4 channel head?

@eric8847 2 года назад

Aww, I wish I had seen this a couple days earlier. I set playback levels on my 488 mkii with a cheap test tape recorded on a stereo deck. Do I really have to pay for an original Teac test tape? They’re really expensive on eBay.

@Tetrakan 2 года назад

You're probably okay. The regions recorded by the IEC head are wider than thise recorded by a 4 track head so they're probably getting picked up better by tracks 3-6 of the 8 track head? So variance is probably in excess of factory specs, but not terrible? If you were worried, I have this untested theory that you could turn off noise reduction and use tape hiss from a blank tape in conjunction with a VOM or oscilloscope to ensure all the playback amps were set within a plus or minus 1 decibel range 🤔

@rundownrecording6073 2 года назад

Wow that diagram really blew my mind. Is it hopeless to try calibrating a 4 track portastudio with any tapes produced on an IEC machine? Any chance you would ever consider selling test tape duplicates from your calibrated 4 and 8 track machines? Thanks for continuing to make great videos, I just saved two cassette doors after learning to spin weld from you XD

@Tetrakan 2 года назад

Thats great the spin welding stuff has woroked out for you. Oh no, you can totally use IEC calibration tapes for a four track, the problem would be using that tape in an eight track machine, it'd work well for some tracks but not others. My attempts ot duplicate calibration tapes for friends by hooking up two portastudios have been plagued with problems, they all came out off-pitch or quieter than I intended due to some snafu with claibration ... maybe one day I'll look into getting some porperly duplicated, a form of channel merch, but I've got an overflowing inbox so it might be a while!