Thought you?d thunk enough today? Well think again! Here?s a think piece for you.
How do you know if your recorder is running at the correct speed? And who cares? Let?s leave the ?who cares? part for later. OK, I cared - this afternoon when I was trying to finish up tweaking my ?new? ASC 6002 recorder. Finished setting the tape tensions, then the instructions mentioned how to adjust the tape speed. Simple I thought, just record a high frequency tone and measure its frequency coming off the tape. But; wait a minute dummy ? the tone gets converted to a wavelength on the tape and as long as the tape is playing at the same velocity when I ?listen? to it, it will have to be the same frequency ? which is certainly the case if I listen off the third (playback) head. Even if I had a two head machine, as long as its capstan motor keeps turning at a constant speed, when playing back I?ll still measure whatever frequency I record.
OK, how to get the recorded wavelength "right"? Let?s see, I guess you need to get a tape with some "standard? frequency recorded on a deck that?s running EXACTLY at whatever speed you want to check your deck at, with low enough wow and flutter to be able to measure the frequency ?precisely?. Running to my trusty MRL Calibration Tape catalog, I find that these tapes certainly exist and are part of their 3150hz flutter and speed test tapes, which of course I don?t have as this test is not part of my ?standard? tapes (with level, azimuth and frequency sweeps only). The MRL flutter and speed tapes have specs better than +/- 0.1% which equates to +/- 3.15hz from a speed perspective. Oh great - another $100+ tape.
Then I remembered that the idlers on both sides of the Stellavox headblock have concentric marks which when viewed under a neon light (switching on and off at 60hz) create a stroboscopic effect that results in a non-rotating ?circle? when the tape speed is exactly ?on?. The circle starts rotating slowly clockwise if the speed is too slow and counter-clockwise if too fast (I might have gotten that backwards). Had an extra idler in my parts bin and was able to ?jury rig? a temporary mount on the deck; which enabled me to determine that the speed was a little slow. In the process I found that the pinch roller pressure also seemed low and that the tape was slipping due to a hardened roller. Oh well; Terry Witt gets another pinch roller to rebuild, and I?m dead in the water till after VSAC2008. More time to pack!
This also reminded me that back in the 60?s??!! these stroboscopic, speed measuring, wheel thingies were advertised in Allied and Lafayette catalogs.
Does correct speed matter? You tell me. Enough thinking; now where?s that aspirin bottle ? better yet, a cockatail. O yeah, PLEASE feel free to correct any missed-conceptions or outcomes mentioned above.
Charles