Quite a while back, Larry Toy (astrotoy) was kind enough to give me his Ampex ATR700. I was curious to see just how good a machine it was and planned to go through it and get it up to snuff.
A couple of years passed and it sat on my bench gathering dust waiting for me to whittle down my backlog of projects.
A month or two ago, I was flipping through the pages of Ampex offerings on eBay (alway in search of that ATR102 that nobody wants) when I spied a full track mono headblock for an ATR700. It was cheap enough so I picked it up and quickly forgot about the '700 once again.
I should say that for whatever reason (can't rightly say!), I started collecting very old tapes in every format you could think of and some of them are full track and 1/2 track mono.
Once the headblock arrived and it looked to be in decent shape, I started to look for a full service manual. Luckily, I found one and started to think about what I wanted to do with the machine.
Seeing that I had the full track head and the stock 1/2 track could be used for 1/2 track mono, making this into a dedicated 'odd format' machine seemed like a natural.
Of course, all those old tapes are early acetate which can be very fragile. Keeping that in mind, once I did the usual cleaning/lube and voltage checks, I adjusted the machine to factory spec's. Once I was satisfied that all was working correctly I lowered the tension bit by bit until I started to lose signal level (home made multiband test tape) then I increased the tension a hair and put the machine through it's paces for a day or two and tested it again.
Then I did the same for the brakes making sure that they would stop the reels precisely with the least amount of tension for 7" reels only (not far off of the specs actually).
Then, it was time to actually play some of my weird format tapes. Using Y connectors, I listened to a number of my mono tapes and they sounded way better than I had hoped. Except for having to change the headblock, it was fantastic to finally hear the full track tapes as they were meant to be played (instead of using a 1/2 track head). They seem to sound fuller with the full track head.
But now came the real test.
The ATR700 is a 1/2 track record and playback machine. Some come with a 4th 1/4 track head like my Technics or some Otari's (this one didn't), but it's also one which the record head can be switched to sync for 2 track overdubbing. I'd heard that some machines with this feature have the correct distance from the gap of the record head to the gap of the playback head to listen to the old "staggered heads" stereo tapes.
So, I put a staggered head tape (Atlantic AT 7-8 BN) on my Technics regular 1/2 track stereo machine and recorded it into some digital editing software. In that software I'm able to zoom onto a transient and line up the two channels visually as well as by ear.
Once I was satisfied that I'd lined the two channels as it was originally recorded, I put the same tape on the Ampex, put the left channel of the record head on sync (playback), and let 'er rip.
A/B comparisons revealed just a tiny bit of smearing and I adjusted the sync head by ear as well as adjusted the balance till it sounded about right.
I was more than pleased! Even though the sync channel doesn't have the same frequency extension or as nice a curve, the stereo image was killer!
I then recorded the playback from the Ampex into the editing software and took a look. It was pretty much spot on.
I've heard that one of the selling points of the staggered head stereo format was "no crosstalk". I haven't really sat down to see if that makes any real world difference and at this point I don't think my excitement would allow me to make any objective opinions on the sound.
All I know is that even with a less than optimum set up (sync rather than a second 1/2 track repro head) it sound like music to me and I'm really happy with the results.
Fun little project and I have to thank Larry and that eBay guy that sold me the mono headblock for helping me get a "swiss army knife" reel to reel up and running.
Now, about that home brewed electrostatic headphone amp,..