bsteinbach

Indeed, no hf oscillator, instead it looks like it uses DC bias via R12. It's also neat to see all the circuitry re-used identically for amplifying the tape in playback, or amplifying the microphone input to record to tape. Was that a standard and obvious plan for the engineers of the time?

I'm also curious if R22, the thermistor, would have been just for thermal protection, or if it was actually used to set the operating point for the output transistors in normal operation? Would it have switched on loud and angry before the transistors warmed up and the bias point cooled down, the opposite of a tube amp?

The power vs voltage thing I think comes from the historical connection of dB to sensing waves. Because you can change impedance to match any sensor, but power is conserved, power was just more often more important to discuss than voltage. I still have to look it up every time whether 10x is 10 or 20 dB.

In defense of sliding windows of time series, if not clustering, the principal components analysis of the matrix on page 1 is one robust way to extract a linear model for the system producing the time series. It's useful for finding frequencies of closely spaced oscillators in a time series when least squares fitting would be arduous to parameterize and convergence a battle.

Not only similar, it's identical to Newton Raphson in ideal arithmetic!

The nth order product approximation for the reciprocal of d = 1 - x is y_n = product_{i=1}{n} (1 + x^{2^(i-1)}) = sum_{i=0}^{2^n - 1} x^i = (1 - x^(2 n)) / (1 - x).

The Newton-Raphson iteration for the reciprocal of d is z_{n+1} = z_n * (2 - (1-x) * z_n).

Induction with the base case z_0 = 1 = y_0 shows the sequences are equal by inserting y_n for z_n in the Newton Raphson iteration: z_{n+1} = (1 - x^(2 n)) * (2 - (1 - x^(2 n))) / (1 - x) = ( 1 - x^(4 n) ) / ( 1 - x) = y_{n+1}.

So I guess you could call it an explicit product formula for the Newton Raphson reciprocal.