freestompboxes.org

PDF:

A frequency doubler for electric guitar
The device, the diagram
of which is shown in figure
1, raises the frequency
of the signal applied to the
input by one octave, i.e.
doubles its frequency, and can
be used to modify the timbre
of a electric guitar.
The signal taken from
the guitar sensor (of the order
of 50 mV) is amplified by
the operational amplifier nel
A₁, so as to obtain at the
input of C₂ a voltage of
approximately 4 V (the necessary
gain is adjusted by the
variable resistor R,), and
applied to the input of a
second operational amplifier
(A₂) through the diodes D,
and D2. In this way, the alter
positive nances of the signal
arrive on the non-inverting
input (through D2), and
the negative alternations
on the inverting input (through
D₁). At the output of A2
a voltage is obtained, the
frequency of which is twice
that of the input signal.
The output voltage, dosed
by Rs, contains a high level
of HF harmonics, the level
of which can be reduced
by shunting R. with a 22
to 33 nF capacitor.
The two integrated circuits
are 741 μA741CA or
CV (Signetics), SN72741P
or N (Texas), LM741CN
(National), MC1741CG or CP
(Motorola), etc. The diodes
D, and D₂ are any
germanium HF (OA90, OA95,
OA73 etc.).

“Radio, television,
electronica”>,
(Bulgaria),
N° 11-1979.

As indicated below the article, this was taken from a Bulgarian magazine 'Radio Televisio Elektronika' which goes back to 1952 and is available from this dodgy site in djvu format...





Here it is in PDF:
I thought people around here would love this cover. Brutalist architecture at its best.

But then the Bulgarian article seems to reference this one in Amaterske Radio:

Somewhere amongst my earliest builds was Escobedo's Simple Square Wave Shaper made Simpler with sockets for the diodes.
I remember that the next effect I built after finishing it was a noise gate

I hardly ever use the SSWSmS anymore but have always thought of it as a design block that I should incorporate into a larger design with an envelope follower and eq, maybe a lfo...

I haven't seen the Polyphony article that he references yet.

Good job on consolidating a few things to paint a bigger picture of history and diy cross pollination modman. Cheers.

cspar wrote: ↑25 Oct 2022, 11:02I haven't seen the Polyphony article that he references yet.

pg. 24
http://www.muzines.co.uk/images_mag/pdf/pl/pl_82_01.pdf

cspar wrote: ↑25 Oct 2022, 11:02 Good job on consolidating a few things to paint a bigger picture of history and diy cross pollination modman. Cheers.

Hey thanks, that is really the idea behind posting all this stuff... More and more archives are emerging and it is clear that circuits were never considered to be proprietary. If you are a cool guy, you credit the source. If you don't want to do that, publish the article anonymously.
I did have to resort to Google Lens to transate the texts, it works great. There is supposed to be a desktop version, but haven't tried that...

1978-06 Czech version with transistors
1979-11 Bulgarian version with IC
1981-02 French version with IC
1982- Bobby Beausoleil - English version in Polyphony
2003-03 Tim Escobedo version


But, thinking Bobby Beausoleil (=Beautiful Sun) is a fake name, I looked him up:
https://en.wikipedia.org/wiki/Bobby_Beausoleil

The french article, same as bulgarian, points out some adjustments that should be done. Rough translation: use the trimmer R1 (Ra) to adjust the gain, so for 50mV signal at the input, we get around 4V at the output on the first gain stage (at capacitor C2 according to the schematic in the french article). Output signal is rich with HF harmonics and if you want to reduce them add a 22n (22n-33n in the french article) capacitor in parallel with the Rb potentiometer. Two 9V batteries are needed.

hello. I tested the Doubleur de fréquence circuit on a breadboard. Supports dual power supply using 7660 chip. I wired it according to the circuit diagram and it worked. It produces an octave fuzz that sounds a lot like an octave up sick box. In addition to germanium diodes, I have tried 1n4148 LEDs, etc., but they all produce octave sounds. I personally like the rough feel of 1n4148. 　
I
hf I connected a capacitor in parallel to the last pot as a countermeasure against high frequency (noise?), but there is almost no change. Please let me know if you have any ideas.