![]() ![]() ![]() In all cases where Darlington transistors are used as the output devices it is essential that the sensing transistor (Q4) should be in as close thermal contact with the output transistors as possible.C4 value can be varied from 100nF to 470nF to suit your treble-enhancement preferences.When SW1 slider is connected to C4 the treble-enhancer is enabled.When SW1 slider is connected to C5 the overdrive feature is enabled.SW1 and related capacitors C4 & C5 are optional.SPKR – One or more speakers wired in series or in parallel, Total resulting impedance: 8 or 4 Ohm, Minimum power handling: 20W T1 – 220V Primary, 48V Center-tapped Secondary 20 to 30VA Mains transformer SW1 – 1 pole 3 ways rotary switch (Optional, see Notes) Q6 – BDX54A 60V 8A PNP Darlington Transistor Q5 – BDX53A 60V 8A NPN Darlington Transistor Q4 – BD135 45V 1.5A NPN Transistor (See Notes) Q1,Q2 – 2N3819 General-purpose N-Channel FETs It also features a two-FET preamplifier, two inputs with different sensitivity, a treble-cut control and an optional switch allowing overdrive or powerful treble-enhancement.Ĭ4 – 220nF 63V Polyester Capacitor (Optional, see Notes)Ĭ5 – 47♟ 25V Electrolytic Capacitor (Optional, see Notes)Ĭ7,C8,C9,C10 – 47♟ 25V Electrolytic Capacitors The present circuit can deliver 10W of output power when driving an 8 Ohm load, or about 18W at 4 Ohm. Furthermore, nowadays we can do without the old-fashioned Vib-Trem feature frequently included in those designs. 5W power output was a common feature of these widespread devices due to the general adoption of a class A single-tube output stage (see the Vox AC-4 model). It is well suited as a guitar amplifier but it will do a good job with any kind of electronic musical instrument or microphone. The aim of this design was to reproduce a Combo amplifier of the type very common in the ‘sixties and the ‘seventies of the past century. ![]() It is well suited as a guitar amplifier but it will do a good job with any kind of electronic musical instrument or microphone.ġ0W Old-Style ultra-compact Combo, Two inputs – Overdrive – Treble-enhancement ![]()
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