I’ve never seen that, and i’m thinking something fairly low in frequency that was induced into the head could masquerade as bias — what frequency was it? Sony dictation machines were like 43kHz and that’s the best we’ve been able to see, did a job for an Atlanta outfit… The normal bias of like 100kHz doesn’t survive probably because of the thermal self-noise of the head.
And as I said in the post, I would more likely track the hum. which would rise in pitch on playback from 60 to something like possibly 240 for a 1/4 speed slowdown. The LF recording works fine regardless of how slow the tape is going. Tape can record DC.
I’d love to find a mechanism that would do 15/16IPS —— anybody know of a decent quality deck that will do that?
> On Feb 26, 2016, at 8:11 PM, Ellis Burman <[log in to unmask]> wrote:
> That might be quite challenging Jamie. I had one tape where the batteries
> were obviously dying - the audio sped up greatly and became distorted and
> very low level towards the end of the tape. Once I speed corrected it (by
> ear - just matching the voice tonality at the end with that at the
> beginning, and then determining the middle part (linear? or logarithmic?),
> the bias was clearly audible in the later portion of the tape. I guess the
> bias frequency was very dependent on the battery voltage and dropped down
> to well within audio range, even with the very slow tape speed. All I can
> say is "good luck with that one" as, at least in my case, the bias
> frequency was not constant.
> On Fri, Feb 26, 2016 at 9:26 AM, Jamie Howarth <[log in to unmask]> wrote:
>> Tyra - if you want them at fixed speed we can track the hum or room tone
>> and put them back in constant natural pitch. PM me at
>> [log in to unmask] if you like.
>> Jamie Howarth
>> Plangent Processes
>> Please pardon the mispellings and occassional insane word substitution I'm
>> on an iPhone
>>> On Feb 26, 2016, at 11:57 AM, Tom Fine <[log in to unmask]>
>>> Tyra, you could have cases where the recorder batteries were low, which
>> would cause recording speed to slow down and playback speed to increase.
>> I've run into that with oral histories. I usually don't even try to make
>> the result "pitch perfect." Rather, I determine a point where playback
>> speed has gotten so fast that the intelligability has decreased badly. I
>> then go back a bit before that, and select to the end of the field. Then I
>> pitch-alter it for the best overall audibility, again not worrying about
>> "perfect pitch" but rather best audibility of the words being spoken. It
>> depends on how fast and how clearly someone is speaking.
>>> -- Tom Fine
>>> ----- Original Message ----- From: "Grant, Tyra" <[log in to unmask]>
>>> To: <[log in to unmask]>
>>> Sent: Friday, February 26, 2016 11:42 AM
>>> Subject: [ARSCLIST] Cassettes that speed-up---what's up?
>>>> We're transferring a collection of personal
>> cassettes---interviews---mainly from the 90s.
>>>> A few start out okay then slowly speed-up so people sound like The
>>>> Then, some are okay on one side but the flip side is speeded-up.
>>>> What's up here?
>>>> We'd appreciate recommendations re: the best way to handle these in
>> order to get something listenable.
>>>> Tyra Grant
>>>> [log in to unmask]
>>>> University of Kansas Libraries
> [log in to unmask]