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Enclosure not stated · 1 knob

Revolution Deux

Dallas Rangemaster

Based on the Dallas Arbiter Rangemaster· 36 other boards clone it

Category
Boost
Controls
Boost
Price
see vendor
Read the post at Revolution Deux Schematic imageGeofex Rangemaster articleAnalogman Beano page

From the vendor

The 1960s germanium treble booster: a single PNP germanium transistor (OC44 or OC71) in common emitter, with a small 0.005uF input capacitor that sets the treble emphasis. Used to push dark British valve amps by Clapton, Brian May, Iommi, Blackmore and Gibbons. The post stresses precision metal film resistors and a well-regulated supply, since the circuit is prone to hiss.

Tuning (from R.G. Keen's Geofex article): temporarily replace the 68K (Rb1) with a 100K pot and the 3K9 (Re) with a 10K pot, adjust for -6.6 to -7.2V on the collector with a fresh battery, then fit the nearest standard values; if Rb1 ends up below 27K or above 82K, or Re below 2.7K or above 5.1K, use another transistor. The input capacitor (nominally 5n) may need to be as much as 6.8n for some transistors; smaller thins the sound, larger boosts lower notes, and around 150n boosts all notes for a full-range soft distortion that is not the original sound. Stay within about +/-50% of 5n for the original voice.

Schematic

The schematic is in the post. Open it at Revolution Deux. No KiCad fragment has been drawn for this circuit yet.

Parts list 9 rows

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RefValueNormalizedTypeNotes
Resistors 3
R1470K470kbias, to supply; read from the schematic by eye
R268K68kbias, to ground (Rb1); read from the schematic by eye
R33.9K3.9kemitter (Re); read from the schematic by eye
Capacitors 4
C15n5ninput; read from the schematic by eye
C247u47uelectrolytic, emitter bypass; read from the schematic by eye
C310n10noutput; read from the schematic by eye
C447u47uelectrolytic, supply; read from the schematic by eye
Transistors 1
Q1OC44OC44PNP germanium; or OC71; read from the schematic by eye
Potentiometers 1
Boost10K10kPotentiometerdrawn 10KA; read from the schematic by eye

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