2012 – Richard L Hess—Audio Tape Restoration Tips & Notes

Studer A80 RC modifications for 1/2-inch two track and other modifications

2018-03-112012-01-20

In a discussion on 2012-01-20 in the New Studer list, Todor Dimitrov posted the differences between the record and repro boards between a 1/4-inch and a 1/2-inch two-track A80RC repro cards. Here are the changed components for the 1/2-inch version. There are five different oscillator versions in the manual, including one for 1/2-inch.

RECORD: C34=68pF
REPRO: R1=100K; R21=330

Note that the mechanical modifications between 1/4 and 1/2-inch tape handling may be substantially more complex in terms of tuning the transport. I know of no definitive notes on this subject. [Added 2013-10-09]

CBC A80RC Repro capacitor mod

I had previously posted in the original (and now reconstituted) Studer List on 2008-04-24 that there were other extant and possible modifications. Here is a slightly edited and reformatted version of that post:

Playing full-track mono tapes

2018-03-022012-01-06

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.

Source for D5 (Decamethylcyclopentasiloxane)

2018-03-022012-10-09

I have recently been looking to replenish my supply of D5 (Decamethylcyclopentasiloxane) and did not have much luck receiving replies to my email. Others have reported difficulty finding this in quantities smaller than a 55-gallon drum.

I found a promising listing for cyclopentasiloxane and when I queried the supplier, he indicated that the analysis was 97.5% decamethylcyclopentasiloxane and the balance being octomethylcyclopentasiloxane. I suspect that is more than good enough for tape work.

Playing a squealing reel of Sony PR-150 tape using D5 (Decamethylcyclopentasiloxane)

2018-03-022012-10-01

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.

Speed variation with unmatched reels

2018-03-022012-09-20

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.

DTRS (DA-88) Transfers now available through TASCAM

2018-03-022012-07-20

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.

Gap Length

2018-03-022012-03-06

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.

Agfa PEM-469 success

2018-03-022012-02-26

We had success transferring two reels of one-inch Agfa PEM-469 tape that was shedding and leaving a waxy clear-to-yellow exudate on everything. We were happy to get through these and recover the content. This is discussed in more detail towards the bottom of our Degrading Tapes page—hopefully the most up-to-date resource on the Web about problem tapes. Please let me know if you would like to help me add anything to the page. It is there for everyone struggling with old degrading tapes. If you haven’t looked already, please look at my paper on the subject.

Capturing both directions of a half-track mono tape

2018-03-022012-01-06

It is possible to capture both directions of a two-sided half-track mono tape in one pass.

The critical factors are:

Azimuth
Direction
Polarity

The Phone Plug—Uses and Misuses

2018-03-022012-12-12

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.

The Digital Cliff and HDMI

2018-03-022012-12-12

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. There were issues with the application of a TRS phone plug (another story).

The church had a PC and two 60-inch diagonal video monitors plus a smaller monitor for the choir. There appeared to be a powered splitter/amplifier at the balcony console to split the HDMI to the two big monitors, with one cable running down each side of the church. I believe there must have been a second two-way splitter (hopefully another powered splitter/amplifier) to tap off the feed from the right main monitor for the choir monitor.

When I arrived, the PC was set up for 1024 x 768 display with the HDMI output mirroring the laptop built-in display. The laptop built-in display was capable of 1366 x 768. The slide show was a 16:9 WMV file. I tried expanding the display to the widescreen resolution and it was fine on the PC, but the monitors would not sync.