Refurbishing the Revox A-77 Tape Deck

A month ago, Curt Palme posted about a Revox A-77 that he had just completed. I contemplated purchasing it for a few hours and then decided to see if he would take my unrestored Revox A-77 Mark IV in trade. After a quick back and forth, we agreed on $800 including shipping both ways and my Revox in trade for his restored A-77 Mark IV. I have a friend who’s lusted after one of my A-77s for a couple of years, so I sold him my other deck for the pretty standard price of $500 for an unrestored sample.

Before the new deck arrived, I fired up my old unrestored A-77 to see how well it was performing. I have over 50 pre-recorded commercial tapes to choose from. I pulled out the old fave, Belafonte at Carnegie Hall at 7½ips. Frankly, it sounded pretty bad. Although Belafonte’s voice was infused with a rich euphonic timbre, during louder passages there was noticeable hash and distortion on the left channel that occurred in direct relationship to his vocal’s volume level. Hiss was also present, but at a fairly low level. Spatial relationships in the mix were still clearly audible, with the band located well behind the solo vocals. The overall harmonic balance was good, with perhaps a bit more midbass relative to the low bass. How much of the distortion was caused by the tape as opposed to the tape machine? When the new unit arrived, I’d know the answer.

This is a good time to touch on the fact that while we audiophiles point to a “flat” response as the ideal, no tape deck is actually a flat-response device. All tape decks have an EQ curve like LPs, but it’s a different kind of EQ. Most contemporary professional and European tape decks use the IEC curve, while older units and consumer units made for U.S. sale use the NAB curve. At 3¾ips, all consumer decks record with the NAB curve. The IEC curve is used primarily on tapes recorded or played back at 7½ips or higher. If you ordered a new Revox PR99, you could designate either curve, but not both. The A-77 records using the NAB curve, but it has provisions via a front-panel knob to play back both IEC and NAB tapes.

Even after using the correct EQ curve for a particular recording, a tape deck’s output is not flat. Most decks have some non-linearity in the regions below 200Hz. Some also have rising top ends. Mastering engineer Jack Endino has measured the EQ curves for a number of decks on his site (endino.com). Some, such as the Studer A80 Mark II, have a serious bass bump around 40Hz and then roll off sharply.

All tape decks have something going on in the bass that is not flat. Plangent Processes, which I have written about in The Absolute Sound, uses a special multi-tone calibration file, which is then recorded onto a particular tape deck. When the tape is sent back to Plangent, they develop a filter set to correct the non-linearities of that particular deck. Plangent can then utilize this filter set when transferring a tape made on that deck. The results can be heard on most of the newest Grateful Dead re-releases such as Mars Hotel and on Erroll Garner’s The Complete Concert by the Sea.

Jonathan Valin has written extensively in these pages about new high-performance reel-to-reel decks, some of which are specifically designed for playback only. He has also produced an excellent reference about sources for new “mastertape” tape recordings. The prices for these new releases run from a low of $90 to over $1000 for an individual album. Old, pre-recorded tapes are much less expensive, but your artist choices will be limited to what was available back then. You’ll find far more Percy Faith and Romantic Moods than Beatles and Rolling Stones. Also, you run the risk of getting a bad sample that could have been damaged by a poorly maintained machine or stored in such a way that when you play it, it sheds bits of tape everywhere, squeals, or in extreme cases sticks to its backing, rendering it unplayable. You can bake some old tape formulations to reduce their stickiness, but that is best left to those whose lives depend on being able to restore old tapes. Most standard commercial tapes from the 70s and 80s will not need baking, but they will probably shed far more than newer tape formulations.

The New Deck Arrives

Buying any audio component that weighs above 50 pounds and requires shipping presents a dilemma: Will it arrive in the same condition as when it left the shipper? When it is something as heavy as a Revox A-77, the packing must be up to the task. With most new components in their original packing, this is not a major issue, but with an older component, where the original packaging is either long gone or sufficiently deteriorated to not withstand another trip, new packing must be employed. Since Curt Palme was packing my new A-77, I wasn’t too worried about how well it would be packed. He has several pages on his site devoted solely to how to properly pack a tape deck for shipping. He even employs a drop sensor on his packages! I plan to reuse his packaging to send my trade-in deck back to him.

Along with the tape deck Curt included a 10″ reel of his own tape brand, sourced from China, which I wanted to compare to the ATR Master Tape I purchased for the project. My plan was to record tracks from my live concert recordings on both tape formulations and compare them. But that would come, once I was familiar with all the deck’s quirks. Along with the reel of tape and the A-77, I found a bright red 10″ metal take-up reel and an authentic Reel-to-Reel-Tape-Recorders coffee mug, from which I’m drinking as I write this.

Although Curt Palme is located in Canada, he ships via USPS from the United States. The new A-77 came in a big box, even larger than I expected, due in large part to the fact that it was double boxed, with a layer of hard packing foam encircling the inner box. The A-77 itself was bubble-wrapped, with hard foam protecting the hubs and heads. Examining the deck after unpacking, it looked nearly perfect, except for a few minor rub marks on the front panel and a couple of scrapes on the wood side panels.

After connecting the new Revox to my Schiit Freya S, I was all set to begin listening. The first thing I put on was that Harry Belafonte tape that had sounded so groady on my old Revox A-77. When I pushed play, nothing happened. Bummer. I called Curt, whose first question was: “Was the drop tag on the outside of the box red, indicating it had been dropped?” The answer was, of course, yes. Curt instructed me to remove the A-77 from its case and find the three relays that had most likely been knocked out of their sockets by the drop. Once open, I discovered that, indeed, all the relays had been jolted from their sockets. I reseated them, reassembled the A-77, connected it up and pushed play, and it worked. Whew…

I put the Belafonte tape back on and listened. To say it sounded better would be an understatement. Now, the dynamic peaks weren’t distorted on “Darling Cory,” and the guitar and bongo accompaniment had a clarity that was missing from playback with my unrestored A-77. Was the sound “great”? No, it was listenable but lacked the resolution of the 96/24 version on Qobuz. Belafonte’s vocals had more sibilance on the tape than on the hi-res digital version, and the instrument’s locations in the soundstage weren’t as clearly defined as on the digital version. How many of the sonic issues were a result of the age of the tape? Probably a lot. Next, I played a recording of Mahler’s 1^st performed by Kiril Kondrashin and the Moscow Philharmonic on Melodyia 7½ips tape. It had an “antique” sound that was distant, murky, and thin. Again, I lay the faults to the tape, not the machine.

The most listenable old tape in my collection was a recording of Baroque music of two guitars on Mercury by Presti and Lagoya. It was also the least challenging, with just two guitars, moderate volume, and little else. While the timbres were accurate, I could hear a bit of flutter. It was subtle, but compared to a real guitar or a digital recording of a guitar the sound had an underlying micro-speed instability. Again, I suspect this was a result of high-speed copying, not the machine itself.

After working through my collection of old tapes and coming away largely unsatisfied, it was time to transfer one of my own recordings made in DSD 128 onto the A-77 to hear what it could sound like with new, well-recorded material and fresh tape. I used a seven-inch reel of ATR Master Grade tape for my first recording. I chose one tune from my recording of the Mr. Sun band at the Salina School House, as well as a tune from my Deadly Gentlemen recording from the same venue. I also recorded one movement of A Women’s Life performed by the Boulder Philharmonic in Mackie Auditorium. I recorded all the tracks at 7½ips directly from the single-ended RCA analog outputs of a Teac UD-507 DAC to the A-77. The recording level was adjusted by the Revox.

My tests were delayed one-half hour by another problem that involved taking the A-77 out of its case twice, following Curt’s instructions to make sure everything inside was connected correctly. After that, I was finally ready to make a recording. Mr. Sun’s tune “Danny Barnes” was the first file I copied. Wow, what a difference from the borderline quality of ancient pre-recorded tapes! This sounded almost identical to my original recording except for a slight bit of additional midbass energy. I also noticed that same slight midbass augmentation on my recording of The Deadly Gentlemen from Salina Schoolhouse. It was subtle, but the acoustic bass had a hair more fullness and weight. On My Boulder Philharmonic recording of “A Women’s Life,” only the hiss during the quiet passages gave away the fact that I was listening to tape rather than my original digital recording. The overall harmonic character of the Revox A-77 recordings was basically the same as the original tracks except for that wee bit of midbass hump.

So now that I’ve got it, what will I really use the Revox A-77 for? I suppose I could use it to “analogize” some of my digital recordings, but I probably will use it to primarily to play back tapes. Which tapes? Given its sound quality, I think I’ll pass on acquiring more old, pre-recorded tapes and concentrate on a few select new ones…I saw John Coltrane’s Blue Train on one of the tape sites priced under $200…now that I know my tape deck is up to snuff, I just might bite. In the meantime, I think I’ll put on that bright red 10″ take-up reel, admire how good it looks, and just smile.

Contact Curt Palme

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(604) 515-5500