Do you mean function generators or circuits built into recording consoles, or analog oscillators?
Analog oscillators, and indeed function generators, from that period could be tuned to very precise
frequencies, and high quality ones like HP, for instance, wouldn't drift. Frequency counters of high
accuracy had been available for quite some time, so it was very easy to check and re-tune whenever
desired. As for the built-in oscillators in some tape machines and some consoles, that's another
matter. I've seen a lot of varience in so-called "1kHz" and "10kHz" tones, where the following music
was in tune to a trained ear but the tone frequency was obviously and measurably off. I assume the
reason for this is drift in component values in the oscillator circuits built into the console,
which weren't of the highest quality in most cases. I recall early ADM consoles have a separate
slate-tone module, and there were trimmers to tune the tone frequency. I think by the time this all
was on a single IC, it wasn't as adjustable. What probably goes out of value are carbon resistors or
other passive components around the IC, probably used to set the oscillation frequency. Just a
-- Tom Fine
----- Original Message -----
From: "Jim Sam" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, January 27, 2011 1:40 PM
Subject: [ARSCLIST] Test tones circa 1978
> Does anyone know how much test tone generators varied circa 1978?
> I know not to expect digital accuracy. For example, I would not
> expect a 10.00 kHz tone, but how much leeway was there? +/- 0.25kHz,
> +/-0.5 kHz, +/-1.0 kHz, etc.?