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Scotch "Master" vs. "Classic"
I got a case of Scotch "Master" cartridges for cheap not long ago,
along with some of the older Scotch "Classics," so, of course, I had to test them to see what they'd do. "Classic" was marketed in the same time period when 3M's Wollensak division started selling its Japanese-made decks, including the top of the line 8075. The packaging of "Classic" even refers to using the "special" switch on the 8075, and the 8075 user's manual specifically states use of "Classic" for improved performance on this deck, so there was a deliberate marketing tie-in. "Master" came out a bit later, and there's no such tie-in, as the Wollensak line of recorders was already defunct by this time. The only other model to have this "special/normal" switch was the non-Dolby 8056. So what's the deal with this "special" switch, anyway? Not a lot, it turns out, and it's more or less a "quick fix" for tapes that require less bias than the Wollensak was able to provide in stock form. All this switch does is remove a ground from the equalization network for the record amp...that's it, nothing more. What the idea here is that, rather than cut the bias current to get flatter response, "fudge" the EQ curve to essentially do the same thing. What you wind up with is essentially (not exactly) the CCIR (later IEC) 3180/120 µS equalization that was adopted for ferric cassettes, which gives more boost to the top end starting more than an octave lower in frequency. This is interesting, as it shows that "Classic" doesn't need the same amount of bias current as does the old standby, 175, or its later replacement, "Dynarange," to get the same top end at the slow speed of 3¾ IPS. The oxide is definitely an improvement over both of these, and seems to be similar to that RTR favorite for years, Scotch 250. I remember when 250 came out, and I spent a lot of time rebiasing and equalizing Ampex machines to accommodate its better top end. I decided to set the bias on my modified 8075 to its stock current value and just use the "special" switch and see what happened. What I got was some great performance, markedly better than "Dynarange" or Ampex 381 in all areas. Top end was an easy 15 KHz at -3 dB, whereas "Dynarange" drops down around 12 KHz. "Classic" has a bit more headroom as well, as well as a lower noise floor...in other words, pretty much what I remember Scotch 250 gave on RTR machines. Thus, I'd bet that this is just basically Soctch 250 with the graphite back coating, much the same way that Ampex back coated its 406 and called it "Grand Master", catalog number 389. The EQ switch is obviously a good compromise; the fluxivity standard for 8 track is 185 nWb/m, so these machines can't really take advantage of a lot more headroom anyway, so rather than go through the exercise of rebiasing, simply peak up the record EQ to make it flat on playback using the standard 3180/50 µS NAB curve...and it works! Not being satisfied with that, of course, I had to twiddle with biasing using the stock record EQ to see what'd happen. As it turned out, rebiasing the deck didn't give me a lot, mainly because this format just isn't capable of exploring improvements in tape oxides made in the mid to late 1970s, that mainly being in the area of saturability. As earlier stated, this 8075 can handle a +5 VU before clipping its record stage, and when properly biased for flat record response, you can't get enough "ooomph" from the record stage to truly take advantage of the extra headroom afforded. So, you wind up where I was with Ampex 389, and to a lesser extent, TDK SD...there IS a limit to what 8 track recorders will hit the tape at, and any more than that's really kind of a waste of time and effort. What rebiasing for these tapes will give you, however, is ultra low third harmonic distortion while still giving good top end. This translates to a very high MOL, which to me is 2% THD operating level. All well and good, except, again, 8 track just can't take full advantage of it, and I'm sure 3M's engineers were fully aware of that when they designed the 8056 and 8075. So, they opted to just "fudge" the EQ on record, thus giving still-good distortion characteristics while giving oodles of top end without saturation. How does "Classic" sound? I like it better than TDK for magnetic reasons, mainly because it can eat up anything you can throw at it, incuding high level Dolby "B" encoding, with ease, probably moreso than can TDK. Recordings make with Dolby in the circuit come out with the same top end that goes in, for the most part, showing no hint of top end compression. However, the advantage of TDK SD...those finely designed and made cartridges...trumps Scotch yet again. Even after "limbering up" a "Classic" cartridge with five passes through the machine, I wasn't able to get anywhere down near what TDK could produce for wow and flutter readings. For that matter, neither could anyone else's cartridges. For serious music, TDK's still the best choice, based on that parameter alone. "Classic" shows some readable and listenable advantages when I hit the tape really hard, true, making it probably a better candidate for the car than TDK, but for home, I'd just about call it a wash. What's nice about TDK is that you don't really have to resort to re-equalization, either. Not doing this on "Classic" will yield and overly bright top end. On to "Master," probably the "last word" in 3M cartridges. This stuff came out later, and offers more of all that "Classic" offered...even lower noise, possibly even more headroom, and even more top end...in other words, more of everything that most 8 tracks can't really take advantage of due to the limitations of the format. This tape behaves and looks much like Scotch 306/307, a favored Scotch mastering and production tape from the '70s. Like Ampex's competing "Grand Master" 389, it's just TOO good for 8 track, making it something that only the recordist with epicurian tastes would lust after. I couldn't hit 2% THD on "Master" before the record amps on the 8075 and 8056 started clipping horridly, thus the tape has no limit on MOL; hit it as hard as you can, and obviously your machine starts to get in the way long before the tape does. Back off the bias, and distortion's STILL good, and noise goes down even further, but then you get the old problem of too much top end...LOTS of it. Even at 0 VU, I could get all the way out to 17 KHz on the 8075 using "Master." I learned when playing with the good Ampex tapes that I had to bypass the FM MPX pilot filter to get all the top end I wsa trying to get, since that 19 KHz filter will start to erode extreme top end when using good tape. Anyone with a good tuner wouldn't need such a filter anyway in their recoders; only cheapie tuner pass the 19 KHz through to its baseband output without at least trying to filter out most of it. So, "Classic" is good...really good...somewhat better than TDK is some areas, not as good when it comes to speed...and "Master" is the equal to Ampex's "Grand Master" when used on an 8 tracker. Only when you get into serious RTR machines will the differences between these two tapes become evident. To the 8 track recorder, both tapes make the tape "disappear" as an impediment to good saturation performance, and puts the onus directly on the machine's ability to exploit all that headroom and top end. Worth the effort to get? Only if you have really GOOD machines at home. For the car? If you're serious about fidelity in the car, sure, but who is? One thing about Scotch, a problem with ALL Scotch oxide binders from that era: They do NOT like water or humidity. Any Scotch tape stored in a humid or wet environment for any length of time will shed its oxide on the first play, making a mess out of your contacts, head and capstan in short order, and also destroying whatever's on the tape. As a desert dweller, I have no problems with Scotch, but friends of mine in LA who make their bread by digitizing old masters just about choke every time they have to deal with transcribing and old Scotch master tape. "Will it make it, or will it fall apart?", is the question they ask as they spend hours "baking" these tape to try to get them through an Ampex just ONE more time. Add the acetate backing of a reel of ancient Scotch 111 from the '50s, and it's "recording engineer CPR time." Ampex? NEVER a problem, even with the old Irish products. Next: Ampex's rare mid-line "20/20+" 388, and some "junk tapes," including the numbers on using old prerecorded carts as blanks. This'll be awhile, I'm sure, since I'm in the middle of rebuilding a very nice Ampex 440B-2 as my new 2 track machine for home. After that, I'm going to install a Nortronics head in the 8075 and see what happens with that. Happy tracking and watch out for flying "spaceballs!" dB |
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