We are currently working on some un-published tapes for a major Canadian folk artist. We have a 7.5 in/s 2-track stereo recording that was one of (if not the) first studio recording of this artist from circa 1972.
At some point, this tape was played on a 1/4-track machine that injected hum onto the left channel. Here’s what the magnetic viewer showed:
Here’s some info that might be useful concerning which batches of Ampex 456 are good and which have sticky shed problems.
I recently unearthed 26 brand new 10 1/2-inch reels of 456 from 8 different batches. I checked one reel from each batch by playing them back and forth at 15ips (I only played the bad reels in one direction – that was enough!). The following batches were bad:
Note: This information has been incorporated into this page which contains a more in-depth discussion.
I received an urgent phone call yesterday from a man who had digitized several reels of 2″ 24-track analog recordings that he wished to re-mix.
The tapes were originally recorded in about 1978-1979 and he said that he needed them to have Dolby C noise-reduction processing applied to the files.
I did a bit of research, as that did not sound correct from an historic point of view.
Here is an approximate chronology of the major noise-reduction systems and their dates of introduction:
There has been much discussion on some web fora about the differences between different brands’ cassette equalization standards.
As I stated here in 2006, there is a 4 dB ambiguity at 16 kHz.
Many things conspire to make this 4 dB ambiguity essentially meaningless in a generally low-fi medium. The only reason I’m mentioning this now is that I’ve been bombarded with email from more than one participant in this discussion and apparently there may be some editorial judgment attached to what is posted.
Jay McKnight has graciously permitted my posting of his comments to me:
The International Association of Sound and Audiovisual Archives (IASA) has released their landmark Guidelines on the Production and Preservation of Digital Audio Objects as a free web (HTML) edition, available here.
I provided some information for the listing of tape equalizations, and I find the compiled table (here) most useful.
Thanks to Kevin Bradley and the IASA team for their work in making this available. If you want a PDF copy, join IASA and it’s available.
I added a Track Configuration page to the resources hierarchy in the sidebar at the right. This points to other resources on the web to provide further insight into the various analog audio track configurations. There is also a brief note there about the variation in the two-track, half-inch format. These differences are minor, but they could be a source of some problems under some extraordinary circumstances.
This page was updated 2012-01-05 to provide track widths on higher-density audio multi-track formats.
A link to the Studer track dimensions page was added 2012-01-06.
I remain a fan of the Sigma MV-95 magnetic viewer despite its slowness at times. I discussed it at length here in June of 2007. It has helped analyze many problematic tapes and has helped me understand the issues enough to apply the correct solution to transfer damaged tapes.
An example is here.
In several articles on magnetic viewers, we have discussed the spray-on Kyread product.
GOOD NEWS! The company is back! I received a phone call from Ryan Blackwell this afternoon and he pointed me to their new website. The company name is now Kyros Technologies LLC.
Note their jump into the 21st century with a real website and great domain name: magneticdeveloper.com — they even have a shopping cart for online ordering. This is apparently the same product I’ve been using for the last eight years.
This is a reminder that data formats come and go just like audio and video formats. On this, the 48th anniversary of the JFK assassination, this article was posted at the Library of Congress website. It talks about first locating and then converting research data held on IBM 80-column punch cards. I remember working with those my first summer job back in 1967! I guess I have a penchant for obsolete formats, as I learned a good deal about IBM’s unit record equipment, including the amazing 407 (introduced in 1949). That certainly was not as useful as knowing about analog tape now.
The punch cards were found and converted. This is a much happier fate than that suffered by the original IRIG 14-track 1-inch tapes of the Apollo Moon Walk from 1969! In 2011, I digitized 14-track 1-inch seismic tapes surrounding the Mount St. Helens eruption in 1980, and am working on another confidential project in 2018.
About ten years ago, when I transferred the oldest tapes in the United States as part of the Mullin-Palmer collection, my good friend Don Ososke pressured me to use a full-track head for the project. I had started transferring these full-track tapes with a Woelke NAB stereo (two 80 mil (2 mm) tracks) head and recording both channels. When I obtained a Nortronics full-track head, the difference was night-and-day. The full-track reproduction sounded fuller, smoother, and quieter. There were no tracking problems to speak of that would cause azimuth wander large enough to create a “flanging” or “phasing” effect of in-and-out high-frequency loss.
It is possible to capture both directions of a two-sided half-track mono tape in one pass.
The critical factors are:
This page provides a table of signal wavelengths for different speeds and frequencies. It is sometimes useful in understanding bandwidth limitations at the high end for a particular head. The first null occurs when the wavelength of the signal is about 112% of the optically measured length of the gap. A common place to set the gap length is for a 4 dB loss at the highest frequency of interest. This corresponds to the half wavelength indicated in the table below. See Mallinson, John C., The Foundations of Magnetic Recording, Academic Press, San Diego, 1993. pp 95–96.
TASCAM has set up a very reasonably priced transfer service for multiple-cassette projects recorded in the DTRS format (DA88, etc.).
For more information, click here.
I cannot warrant this service, but what could be better than having it attached to the service facility. I have listed other resources on my format page.
I received an interesting question from a European tape user with whom I frequently correspond:
“Is there any speed variation when playing a tape with different hubs on the supply reel and take-up reel?”
And I replied:
You raise an interesting question. The easiest answer to this is simple:
There is a risk of speed variations throughout the reel if the tape tension varies throughout the reel.
followed by the corollary:
This effect is made worse if the condition of the capstan / pinch-roller system is degraded.
and
Some capstan / pinch-roller / constant-torque systems handle this better than others.
Today I worked on a batch of five Sony PR-150 7-inch reels recorded at 3.75 in/s in one direction, two-track mono. One of the five reels showed marked shedding during fast-wind/rewind (to get the original reel as takeup and to check the tape pack). Four of the five reels played fine. This one squealed horribly. I ran the tape up and back over the dispenser and then fixed it in position for running the tape over it during the playback session. Once again, D5, Decamethylcyclopentasiloxane, CAS Number 541-02-6 comes to the rescue. The lovely thing about D5 is that it evaporates.
Is this better than cold playback? I don’t honestly know. Both work. This is easier if there is no reel machine standing by for cold playback (which there was not today). I keep a Nakamichi MR-1 in the refrigerator so it is ready to go when I need it. The Studer A810 I put in the fridge did not like it. The capstan motor seized up AND the heat output overwhelmed the refrigerator’s capacity to cool. I suspect the APR would also overwhelm the refrigerator’s capacity. Also, it is much easier to lubricate a reel than a cassette.
I have made a variety of static pages for my tape restoration Web site, but thought it was time to add a more user-friendly, article-based location to discuss various topics, tools, tricks, and techniques that I have come across in various ways.
What is easier to use than ready-made BLOG software, so I guess Richard is finally Blogging!
I hope you like this and find it of interest. Please let me know of any changes or topics you might like addressed.
Enjoy!
Note: This post has been put in every top-level category because it appears that a post is needed in each top-level category if the sub-categories are to be visible.
Note 2: The Tips & Notes blog and the Formats & Resources static pages of this sub-site replace the Tips and Resources static pages on the Web site. And, there is integrated searching across both the blog articles and the static pages.
The 2 mm hex head screws that hold panel modules and blanks on Studer A810s are easily stripped by slightly worn hex drivers. Studer used 2.5 mm hex head screws in the later A807, perhaps aware of this issue. Using PB drivers from the start will reduce the possiblity of this happening.
There are essentially two choices when this happens:
When I was confronted with this situation recently and I didn’t have an EZ-out of the correct size to bite into the screw without drilling, I grabbed a T10 Torx driver and gently tapped it into the screw head. I pushed in hard while starting to turn and the screw came out.
The ubiquitous phone plug, especially in the 1/4 inch (6.3 mm) size, is extremely confusing to the uninitiated. I was at a church today where I struggled to get a video to play properly in advance of an event in a few days.
The church had a PC and two 60-inch diagonal video monitors (another story). The audio was fed to the good-quality 16-input mixer (Allen and Heath, I think) from the PC’s headphone output.
In the video, there are two places where there is speech and the music is faded into the background. When played in the church, the voice disappeared! This created some angst coupled with erroneous assumptions. I hope this post will perhaps help solve this problem for others.
I received an email requesting clarification on my 1980 AES Preprint about the use of voltage audio distribution vs. power matched audio distribution for analog audio signals.
The confusion seemed to be about equipment being rated for driving a 600 ohm load. Yes, most professional audio equipment will drive a 600 ohm load, but might (repeat might) lose a small amount of headroom doing so. The better reason to be able to drive a 600 ohm load is to drive long cables which might create slew-rate limiting if they load the output to the extent that they slow it down. It’s all about current. In fact, merely being able to drive a 600 ohm load may not provide enough current to drive very long cables.
In October, 2016, Jonathan Richardson of the Indiana University Media Digitization and Preservation Initiative contacted me and sent these two photos:
