Audio Ideas: Open Reel Wow and Flutter? It May Be The Pinch Roller!

      Date posted: July 8, 2013

Here’s a story for you that befits an aging audiophile. Some months ago, I was looking for a used 1/4-track reel-to-reel recorder, and though it wasn’t a prime requirement, the capability of handling big (10 1/2″) reels was one criterion. That narrowed the field quite considerably, and after looking at a number of Akai, Otari, ReVox, Tandberg, TEAC and other recorders available, I finally found what I was looking for at a decent price, and more important, close enough geographically for pickup. This latter consideration is important when dealing with these large, heavy recorders, because they are very expensive to ship, that cost often exceeding the actual selling price, especially from US or overseas locations. TC-755-upperVw

What I settled upon was a 1974-vintage Sony TC-755, from the days just before the yen and manufacturing costs rose steeply, leading to much cheaper build quality (or much higher prices) for such components. Now this situation also ultimately resulted in better manufacturing techniques that led to a quality that is today often unsurpassed, but it also marked the end of an era, and the build quality of this 70s Sony recorder was quite remarkable. It’s a dual capstan design, with a nominally closed-loop system, the capstans and pinch rollers flanking the record and play heads, with the erase head outside the loop at left. This is an excellent design for smooth tape handling, and though the transport is still pre-logic, it works well if you don’t get too quick with the buttons. There is a mechanical pushbutton interface/interlock that can be confused that way.

TC-755-Front View I overbought in tape stock a few years ago when it was quite inexpensive, mostly on 7″ reels, as well as 5″ types for my Nagra and previous Stellavox machines. Since that time, I’ve been buying up 10 1/2″ empty reels, mostly metal, but a few plastic ones as well, the latter generally the clear NAB-hub variety. But I also have hundreds of 7″ and smaller recorded reels dating back to my undergraduate days, with all kinds of stuff on them. Mono from the various radio stations I worked at during Summers (CHVC, Niagara Falls; CFOR, Orillia) and the Queen’s University stations CFRC, AM and FM, at which I cut my microphone and technical teeth, so to speak, and later managed between 1968 and ‘74 before freelancing my way into Toronto (CJRT-FM, CKFM, and CBC Radio AM/FM), while later recording, producing and hosting concert broadcasts with the Hamilton Philharmonic and Kitchener/Waterloo Symphony orchestras for Toronto Classical station CFMX. And then, there were 3000 3-minute AUDIO IDEAS programs over 13 years for CKFM up to 1986. I became very familiar with analog, and then, digital tape formats, during my radio days.

That year, new CKFM management fired us all, from program director Jerry Good, through to the very popular morning man, Don Daynard. Of course, Don, “The Dazz”, TO’s leading morning voice, immediately departed to competitor CHFI, and took enough audience with him to catapult ‘FI over ‘FM to #1 FM station in the ratings, while CKFM, now become THE MIX, went from a 10% overall ratings share to 4% within 6 months. And that was during a heavy growth period for FM, but well before it pretty much ran AM off the dial, except for chatterbox broadcasting.

Dating from my first professional encounters with pro tape recorders (PT-6 Magnecorders, AMPEXes and Scullys), and my own first amateur 1/4-track, a Sony TC-250A, Sony TC-250A recorder to my current machines (aside from the new/old Sony that’s the focus of this ramble), which are a TASCAM 34B and 32, Nagra IV-S-TC, this augmented for up to 12″ reels by a Lyrec FRED play-only deck, I’ve had a long and pleasurable experience with reel-to-reel recorders. Along the way there have been other Sonys, a Concertone, a legendary Technics (thereby hangs another tape tale), a Fostex, a Uher, and several TEACs, and the TASCAMs, ranging from 2 tracks through 3 (the Fostex) to 4 (the 34B). There may be others I have blocked from memory, but that’s just as well.

They all had their individual personalities, like cats, I suppose, and perhaps some of the same annoying habits, friendly traits, and varying levels of reliability. Some ate tape like it was Puss n’ Boots, too, or spewed it out like a chewed mouse. However, I never had one that hid anything dead under the bed. What they all had in common were varying degrees of speed variations, usually categorized as wow (slow), and flutter (fast). Each had its own noise floor, 1/4-tracks being less quiet than 2-tracks because of the narrower tape track, but also carried more audio information at any given speed. To increase S/N ratio (and dynamic range, not quite the same thing, but I may explain that another time), noise reduction could be employed, and perhaps at some later date, I’ll elaborate on why I ultimately hated them all, from Dolby B through ANRS to dbx.

The speeds that were usually employed for home decks were 7 1/2 and 3 3/4 IPS, while some that had professional pretensions. like my TEAC 3300S, TEAC 3300S recorderran at 7 1/2 and 15 IPS, which ate tape pretty fast, but sounded best of all. And I won’t descend into the bathos of an analog vs digital recording comparison here, but leave that for another cat barf confession. I’ve never owned a Tandberg or ReVox (though I’ve worked with Studers, the latter’s professional siblings), but may yet, and there are other recorder brands I’ll probably never experience, such as Otari or Telefunken, not to forget Philips. Some of the European machines were touted for their extended low-speed/high-frequency performance, and low noise and speed variances, but also tended to be somewhat cranky, while the Japanese decks were more robust and less fussy. I’m not so sure those generalizations really always apply, from my fairly limited experience, except for the bad one with the Uher Report Stereo portable, more a dog than a cat.

But the most recent Sony has been especially interesting, with its dual-capstan drive system. There may be something to be said for the very simple tape paths of the Eurodecks, like the also legendary A-77, since less head, guide and roller/capstan contact should mean lower friction, hence lower wow and flutter (or “flow and wutter”, as I sometimes call them). And this leads me to a story I thought I’d leave for later, but does seem apropos now. I did many of my CKFM SuperSound shows at 15 IPS on a 2-track Technics RS-1500, these two-hour monthly programs of a Sunday afternoon, playing and commenting on audiophile LPs, mostly, and early CDs, the few among commercial and audiophile releases that I actually felt sounded decent enough to present on the program. As an aside, I thought the transfer to high-speed analog tape of most CDs actually improved their sound, taking of a bit off that 44.1/16-bit edge that was then prevalent.

But with the almost-suppressed analog tape shedding scandal that affected several tape brands in the late 70s and early 80s, many machines with these tapes from Scotch, AMPEX, BASF, and others became quickly clogged up, and the Technics would actually stop after the sound turned to mud, which was basically what the heads were covered with, ferric, or iron, dirt. The cause was a manufacturer run of poor adhesives, or binders (the gluey stuff that keeps the oxide which records the music permanently stuck to the tape), so the tapes started to leave their oxide coatings all through the tape path, gumming up not just the heads, but all guides, rollers and capstans, too, and the long U-shaped tape path of the 1500 series machines (which of course, made them unique) gummed up even more than most other recorders, including my more basic TEACs of the time. I don’t think I’ve ever used so many Q-Tips and alcohol so often as then, the tape path having to be cleaned every few minutes of record or play use. Luckily most of that problem was soon avoided, in my case, by using mostly Maxell and other Japanese tapes (TDK, Fuji), which never suffered from this oxide shedding problem. But it did lead me to simpler transports than that of the Technics in later years. Luckily, the then Maxell distributor was an Audio Ideas radio (and magazine) sponsor, so I had enough superb, pristine tape stock available. Maxell 10

And this anecdote only underlines my point (at last!) for this particular diatribe, which is that if your home tape recorder (and this includes cassette decks, too) starts to sound muffled and wavering in pitch, it’s probably clogged with rubbed-off tape oxide. Even more insidiously, the pinch roller may also be fouled and slicked up by either the oxide, or lubricants applied to the back side of many tapes (sometimes to excess) that make this rubber roller very slippery, so it can’t properly grab and pull the tape past the heads. Before the final clogging takes place, you may notice an annoying increase in wow and flutter, which, of course, is both a warning, and the point of this particular essay. Once you hear consistent speed variations coming form your tape machine, it’s time to remove the head cover and get out a Q-Tip or equivalent, and preferably, a dedicated brand of head cleaner, like the SR-Audio stuff that I buy online through e-Bay.

But cleaning the heads and tape path is one exercise that requires a fluid that is often alcohol-based with added small amounts of a special detergent, but there is yet another challenge and approach to the dreaded fouled and slippery pinch roller. Alcohol-based cleaners, as well as other formulations of head cleaner should not be used on rubber parts, because they tend to degrade the rubber surface over time. Therefore, a special pinch-roller cleaner fluid is necessary, also available from SR-Audio and many tape deck manufacturers, like TEAC/TASCAM. These will remove the tape lubricants and oxide buildup, as well as helping renew the rubber surface to its necessary tackiness, so it can effectively combine under pressure with the capstan to accurately and smoothly carry the tape past the heads in record and play.

Hopefully, this process will not be required too often, though in the halcyon days of analog tape in the pro world, such as at the CBC, when so many programs, including my own there, were packaged on tape, the technicians cleaned all the studio tape recorders almost every morning as a part of their daily routine. It will always be the case that cleanliness is next to good sound where analog tape reproduction is concerned. And, finally, always follow the instructions, especially with respect to letting the capstan and its pinch roller dry for sufficient time after cleaning before using the deck, for optimum performance from your clean machine.

How The Dual Capstan TC-755 Got A Slight Re-Design TC-755-OrigRollers

I had successfully cleaned this recorder up, and was still not happy with its wow and flutter performance at either speed, and it seemed to me that the key lay in insufficient pulling power from the dual capstan/pinch roller system. This was especially evident aurally near the end of tapes, where the tension was simply too high due to the smaller diameter of the tape supply reel’s remaining contents. I thought about this problem for a day or so, and decided to look in my electronic goodie box, with all its little plastic drawers full of various parts and partially finished projects. There I found several pinch rollers from old TEACs, and a pair of unused Nagra rollers that I’d ordered years ago on the expectation that the one on my IV-S would eventually wear out and need replacing. As it turned out, it never did, always responding to a good cleaning and drying cycle to work perfectly again.

So, here were these two rubber rollers, which looked to be about the same size, maybe a bit bigger around, with what looked like exactly the same diameter hole in the centre; they were also a bit wider. However, it occurred to me that they might solve the problem I faced with the Sony, and I knew Sony had liquidated their parts stock years ago, so exact replacements were not in the cards. Well, worth a try… TC-755-Nagra-1roller

A few minutes later I’d replaced the tired Sony roller with one of the Nagras, on the right side of the tape path, cleaning the shaft and applying a little light oil to it before putting on the roller. And, voila, when I fired up the deck in play first, and then record with some guitar and piano music, the flutter and accompanying graininess were completely gone, even at 3 3/4 IPS. The slightly larger diameter of the new Nagra pinch roller improved the contact pressure even further, so that when I turned the reels around to provide a worst-case/end-of-reel pulling situation, everything was still clean and pure in pitch, and smooth in tape flow.

The Sony roller at the rear of the tape path was still in place, and I thought, “Well, maybe replacing this one with the other Nagra roller will make for even more of a good thing!” TC-755,Nagra-2rollers But it was not to be. The contact had never been as strong with the Sony roller at that end of the tape path just after the erase head, and everything seemed fine for a few minutes with the two Nagras, but somehow the tape started to wobble as it went past the play head, in what we call “tape skew”, causing the sound to drop out. Obviously there were tape tension conflicts with the stronger pressure from the slightly larger-diameter Nagra roller. Removing that left-side roller altogether fixed this problem completely, so I found ultimately that the best situation, and perhaps the most accurate mechanical performance this recorder has ever had, came from having just one really good capstan/pinch roller system smoothly pulling the tape through the heads from the take-up side (as shown above right), the way all my other recorders do.

A major contributor to the success of this almost accidental re-design has to be the exceptional quality and durability of the rubber used by Nagra for their pinch rollers, which, as I recall, were not all that cheap. And having to use only one of them at a time, meant that I now have a spare for the long term (see it on the editing block at the bottom of the full recorders photos above). So, coming full circle to where we began, the TC-755 is so well built, that I expect it will continue to operate at optimum for a good long time to come. And the near-perfect pinch-roller internal and external size match from the old to the new is just an extreme example of incredible luck!

Well, all this is a little more rambling than I would have done on radio, so that’s it for now. As I used to say on air at the end of every show, “For Audio Ideas, I’m Andrew Marshall.”

Andrew Marshall

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2 Responses to “Audio Ideas: Open Reel Wow and Flutter? It May Be The Pinch Roller!”

  1. James Reid c-unknown Says:

    This guy does repairs, and has some stock.

    “Terry’s Rubber Rollers & Wheels”
    “Send me your old roller, I will remove all old rubber and replace it with new. It will be perfectly flat, or rounded depending on your style of roller. It will be perfectly round. No thumping, no wobbling, no humming, no more tape slippage. When I’m done, it will work as good as new.”

    I have bought 2 Studer/Revox P99 rollers from him.
    Just perfect.

  2. Andrew Marshall c-unknown Says:

    Hi James,
    I, too, have been a customer of Terry’s over the years, and am currently awaiting a rebuilt Nagra IV series roller, which detached from its steel centre and became erratic in rotation. Terry invoices only when he has done the work, and works promptly, with swift Air Mail return of rollers from his Michigan headquarters.

    Previously, several years back, he restored a Stellavox SP-8 roller for me, and I highly recommend his unique service, which is easily Googled. All analog tape freaks (and former broadcasters) like us should now know about Terry, if they did not already.

    And, finally, I cannot overemphasize the importance of the pinch roller’s operation in ensuring smooth tape motion, low wow and flutter, and reduction of audible modulation noise in recorder performance. This latter improvement actually increases the apparent S/N ratio of any recorder thusly upgraded.

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