What was this test tone?

[Rick Sutton]

I was working on an archiving project today and ran across a test tone on a 15ips 2t r/r tape that I didn't recognize. The tape had multiple 1k and 10k tones of random length as if the original engineer (1980) was adjusting them as they ran. After these tones came the tone that i didn't recognize, about 10 seconds of what sounded like a twin tone and the kicker is it looked just like a perfect square on the phase scope. Obviously had both in and out of phase signals. The tape sounded great and had no obvious signs of noise reduction (nor were there any hint in the notes of any NR being used) .
What was that tone?

[Time Tech]

Probably Telcom C4 (ANT) NR alignment tone

Does it alternate between 550 and 650hz at one second intervals?

Was it a european recording or from a home recording (possibly AKAI Hi Comp format)?

Cheers,

Bruce Maddocks
Cups 'n Strings LLC

CUPS 'N STRINGS are experts in digitizing, restoration and preservation of audio recordings. audio analog to digital transfer specialists, Los Angeles

[johnlink]

Could you post an audio file?

John Link

[Waltz Mastering]

Could have been FSK? used a lot in the late 80's.

[Rick Sutton]

Thanks for the replies. I'm not worried about the tone as the tape transferred beautifully and I'm thinking the tone was a mistake.
Anyway, here's an update after further investigation.

The tone is 7.48 seconds long and stereo. The tone does not alternate but is a twin, continuous tone that is different on L/R channels.
The left channel is 850 Hz and smooth in tone.
The right channel is 890 Hz and pulses at .663 second increments.

How's that for a mysterious test tone? I'm thinking it's a non issue as all the test tones at the head of this tape are so random that it appears that someone was a little confused or was having some troubles with the alignment. In addition, this tape contains songs from sessions that were a year apart and clearly from different studios/machines.
Oh well, audio archeology at its finest.

[dcollins]

Originally Posted by Rick Sutton

Thanks for the replies. I'm not worried about the tone as the tape transferred beautifully and I'm thinking the tone was a mistake.
Anyway, here's an update after further investigation.

The tone is 7.48 seconds long and stereo. The tone does not alternate but is a twin, continuous tone that is different on L/R channels.
The left channel is 850 Hz and smooth in tone.
The right channel is 890 Hz and pulses at .663 second increments.

How's that for a mysterious test tone? I'm thinking it's a non issue as all the test tones at the head of this tape are so random that it appears that someone was a little confused or was having some troubles with the alignment. In addition, this tape contains songs from sessions that were a year apart and clearly from different studios/machines.
Oh well, audio archeology at its finest.

That's a Dolby A alignment tone.

Are you decoding the noise reduction?

Also, you may be aligning to the record section of the tones if you see them moving around like that. There should be a section where they are either steady or it may be separately leadered.

DC

[Bob Olhsson]

I'm feeling old Dave...

[Rick Sutton]

Originally Posted by dcollins

That's a Dolby A alignment tone.

Are you decoding the noise reduction?

Also, you may be aligning to the record section of the tones if you see them moving around like that. There should be a section where they are either steady or it may be separately leadered.

DC

Thanks for the info Dave. These tones are at the head of the tape and are the only tones available. I am not even sure that this tape is on its original reel but I am sure that it is its correct box as the song titles match. No tech info is written on the box other than session dates and the notes on which songs are stereo and which mono. These are songs of a deceased songwriter and the family is trying to catalog all of his material.
I have heard undecoded NR many times and have always been able to detect the compression and eq pre-emphasis in the loud areas and obvious uprush of room noise etc. in the quiet areas but I can't for the life of me detect any signs of that here. Also, as I noted before, there are two different sessions a year apart on this reel and the second one is actually in mono and distinctly different sounding.
Is Dolby A so subtle as to avoid my detection on a simple voice and acoustic guitar recording? (OK, I know that begs the question of whether I'm deaf or not!). I own and have used many times Dolby SR, Dolby B, C (cassette of course) and DBX type 1 and can spot them . Never owned A but I have heard it many years ago on multitrack tape and recognized that a NR was involved.
I am transferring these old tapes to 96/24 wave files, with regular CD copies for the family, and will make the appropriate notes on the documentation as to the test tones (which I am also transferring). I don't have an A decoder here and since these are 5 songs out of hundreds I am transferring (mostly from low quality home decks at slow speed which definitely don't have any NR) I will probably send these out to get another transfer with Dolby A before the project is done. These 5 songs sound so good that if it is indeed Dolby A encoded I can see how it could have been used as an "enhancer" back in the day!
Cheers, Rick

[glassmaster]

Originally Posted by Bob Olhsson

I'm feeling old Dave...

You're only old if you:
• always refer to Dolby encoded tapes as 'stretched'
• feel there's no need to specify the type or brand of NR
• have a drawer full of yellow Dolby stickers

[Greg Reierson]

Or you feel the need to yell "Speed" before each take.


GR

[Bob Olhsson]

Originally Posted by Greg Reierson

Or you feel the need to yell "Speed" before each take.

Now THAT'S esoteric! :-)

[Thomas W. Bethe]

Originally Posted by glassmaster

You're only old if you:
• always refer to Dolby encoded tapes as 'stretched'
• feel there's no need to specify the type or brand of NR
• have a drawer full of yellow Dolby stickers

I got about 200 Dolby stickers if anyone wants them and around here the correct term use to be "rolling" and not "speed" as there are too many crackheads that think you are advertising their favorite product <GRIN>