Category Archives: Video

Guitar Amplifier

[b:900792506e] * 10W Old-Style ultra-compact Combo
* Two inputs – Overdrive – Treble-enhancement [/b:900792506e]
[b:900792506e]
Circuit description:[/b:900792506e]

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.
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).
Furthermore, nowadays we can do without the old-fashioned Vib-Trem feature frequently included in those designs.
The present circuit can deliver 10W of output power when driving an 8 Ohm load, or about 18W @ 4 Ohm.
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.
Technical data are quite impressive for so simple a design:

Sensitivity: 30mV input for 10W output
Frequency response: 40 to 20KHz -1dB
Total harmonic distortion @ 1KHz and 10KHz, 8 Ohm load: below 0.05% @ 1W, 0.08% @ 3.5W, 0.15% at the onset of clipping (about 10W).

[b:900792506e]Notes:[/b:900792506e]

* SW1 and related capacitors C4 & C5 are optional.
* When SW1 slider is connected to C5 the overdrive feature is enabled.
* When SW1 slider is connected to C4 the treble-enhancer is enabled.
* C4 value can be varied from 100nF to 470nF to suit your treble-enhancement preferences.
* 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. Therefore a TO126-case transistor type was chosen for easy bolting on the heatsink, very close to the output pair.
* To set quiescent current, remove temporarily the Fuse F1 and insert the probes of an Avo-meter in the two leads of the fuse holder.
* Set the volume control to the minimum and Trimmer R9 to its minimum resistance.
* Power-on the circuit and adjust R9 to read a current drawing of about 25 to 30mA.
* Wait about 15 minutes, watch if the current is varying and readjust if necessary.

Source: [url]http://www.redcircuits.com/Page52.htm[/url]

Copyright Flavio Dellepiane

A kit is available, mail to: info@redcircuits.com with subject [i:900792506e]10 Watt Guitar Amplifier Kit[/i:900792506e]Parts:P1______________4K7 Linear Potentiometer
P2_____________10K Log. Potentiometer

R1,R2__________68K 1/4W Resistors
R3____________220K 1/4W Resistor
R4,R6,R11_______4K7 1/4W Resistors
R5_____________27K 1/4W Resistor
R7______________1K 1/4W Resistor
R8______________3K3 1/2W Resistor
R9______________2K 1/2W Trimmer Cermet
R10___________470R 1/4W Resistor
R12_____________1K5 1/4W Resistor
R13___________470K 1/4W Resistor
R14____________33K 1/4W Resistor

C1____________100pF 63V Ceramic Capacitor
C2____________100nF 63V Polyester Capacitor
C3____________470µF 35V Electrolytic Capacitor
C4____________220nF 63V Polyester Capacitor (Optional, see Notes)
C5_____________47µF 25V Electrolytic Capacitor (Optional, see Notes)
C6______________1µF 63V Polyester Capacitor
C7,C8,C9,C10___47µF 25V Electrolytic Capacitors
C11____________47pF 63V Ceramic Capacitor
C12__________1000µF 35V Electrolytic Capacitor
C13__________2200µF 35V Electrolytic Capacitor

D1_____________5mm. Red LED
D2,D3________1N4004 400V 1A Diodes

Q1,Q2________2N3819 General-purpose N-Channel FETs
Q3____________BC182 50V 200mA NPN Transistor
Q4____________BD135 45V 1.5A NPN Transistor (See Notes)
Q5____________BDX53A 60V 8A NPN Darlington Transistor
Q6____________BDX54A 60V 8A PNP Darlington Transistor

J1,J2________6.3mm. Mono Jack sockets

SW1____________1 pole 3 ways rotary switch (Optional, see Notes)
SW2____________SPST Mains switch

F1_____________1.6A Fuse with socket

T1_____________220V Primary, 48V Center-tapped Secondary 20 to 30VA Mains transformer

PL1____________Male Mains plug

SPKR___________One or more speakers wired in series or in parallel
Total resulting impedance: 8 or 4 Ohm
Minimum power handling: 20W

25 Watt MosFet Audio Amplifier

[b:acbecb2875]High Quality simple unit
No need for a preamplifier[/b:acbecb2875]

[b:acbecb2875]Notes:[/b:acbecb2875]
* Can be directly connected to CD players, tuners and tape recorders. Simply add a 10K Log potentiometer (dual gang for stereo) and a switch to cope with the various sources you need.
* Q6 & Q7 must have a small U-shaped heatsink.
* Q8 & Q9 must be mounted on heatsink.
* Adjust R11 to set quiescent current at 100mA (best measured with an Avo-meter connected in series to Q8 Drain) with no input signal.
* A correct grounding is very important to eliminate hum and ground loops. Connect to the same point the ground sides of R1, R4, R9, C3 to C8. Connect C11 to output ground. Then connect separately the input and output grounds to power supply ground.

[b:acbecb2875]Technical data:[/b:acbecb2875]
* Output power: well in excess of 25 Watt RMS @ 8 Ohm (1KHz sine wave)
* Sensitivity: 200mV input for 25W output
* Frequency response: 30Hz to 20KHz -1dB
* Total harmonic distortion @ 1KHz: 0.1W 0.014% 1W 0.006% 10W 0.006% 20W 0.007% 25W 0.01%
* Total harmonic distortion @10KHz: 0.1W 0.024% 1W 0.016% 10W 0.02% 20W 0.045% 25W 0.07%
* Unconditionally stable on capacitive loads

For the power supply see: PS25.gif

Source: [url]http://www.redcircuits.com/Page2.htm[/url]

Copyright Flavio Dellepiane

A kit is available, mail to: info@redcircuits.com with subject [i:acbecb2875]25 Watt MosFet Audio Amplifier Kit[/i:acbecb2875]Parts:2 x 47K 1/4W Resistors (R1,R4)
1 x 4K7 1/4W Resistor (R2)
1 x 1K5 1/4W Resistor (R3)
1 x 390R 1/4W Resistor (R5)
1 x 470R 1/4W Resistor (R6)
1 x 33K 1/4W Resistor (R7)
1 x 150K 1/4W Resistor (R8)
1 x 15K 1/4W Resistor (R9)
1 x 27R 1/4W Resistor (R10)
1 x 500R 1/2W Trimmer Cermet (R11)
3 x 10R 1/4W Resistors (R12,R13,R16)
2 x 220R 1/4W Resistors (R14,R15)
1 x 8R2 2W Resistor (R17)
1 x R22 4W Resistor (wirewound) (R18)

1 x 470nF 63V Polyester Capacitor (C1)
1 x 330pF 63V Polystyrene Capacitor (C2)
2 x 470µF 63V Electrolytic Capacitors (C3, C5)
4 x 100nF 63V Polyester Capacitors (C4,C6,C8,C11)
1 x 100µF 25V Electrolytic Capacitor (C7)
1 x 10pF 63V Polystyrene Capacitor (C9)
1 x 1µF 63V Polyester Capacitor (C10)

5 x BC560C 45V 100mA Low noise High gain PNP Transistors (Q1-Q5)
1 x BD140 80V 1.5A PNP Transistor (Q6)
1 x BD139 80V 1.5A NPN Transistor (Q7)
1 x IRF530 100V 14A N-Channel Hexfet Transistor (Q8)
1 x IRF9530 100V 12A P-Channel Hexfet Transistor (Q9)

Power supply:

1 x 3K3 1/2W Resistor (R1)
1 x 10nF 1000V Polyester Capacitor (C1)
2 x 4700µF 50V Electrolytic Capacitors (C2, C3)
2 x 100nF 63V Polyester Capacitors (C4, C5)
1 x 200V 8A Diode bridge (D1)
1 x 5mm. Red LED (D2)
2 x 3.15A Fuses with sockets (F1, F2)
1 x 220V Primary, 25 + 25V Secondary 120VA Mains transformer (T1)
1 x Male Mains plug (PL1)
1 x SPST Mains switch (SW1)

10W Audio Amplifier with Bass-boost

This design is based on the 18 Watt Audio Amplifier, and was developed mainly to satisfy the requests of correspondents unable to locate the TLE2141C chip. It uses the widespread NE5532 Dual IC but, obviously, its power output will be comprised in the 9.5 – 11.5W range, as the supply rails cannot exceed ±18V.
As amplifiers of this kind are frequently used to drive small loudspeaker cabinets, the bass frequency range is rather sacrificed. Therefore a bass-boost control was inserted in the feedback loop of the amplifier, in order to overcome this problem without quality losses. The bass lift curve can reach a maximum of +16.4dB @ 50Hz. In any case, even when the bass control is rotated fully counterclockwise, the amplifier frequency response shows a gentle raising curve: +0.8dB @ 400Hz, +4.7dB @ 100Hz and +6dB @ 50Hz (referred to 1KHz).

[b:ae84083036]Notes:[/b:ae84083036]

* Can be directly connected to CD players, tuners and tape recorders.
* Schematic shows left channel only, but C3, C4, IC1 and the power supply are common to both channels.
* Numbers in parentheses show IC1 right channel pin connections.
* A log type for P2 will ensure a more linear regulation of bass-boost.
* Do not exceed 18 + 18V supply.
* Q3 and Q4 must be mounted on heatsink.
* D1 must be in thermal contact with Q1.
* Quiescent current (best measured with an Avo-meter in series with Q3 Emitter) is not critical.
* Set the volume control to the minimum and R3 to its minimum resistance.
* Power-on the circuit and adjust R3 to read a current drawing of about 20 to 25mA.
* Wait about 15 minutes, watch if the current is varying and readjust if necessary.
* A correct grounding is very important to eliminate hum and ground loops. Connect to the same point the ground sides of J1, P1, C2, C3 &C4. Connect C9 to the output ground.
* Then connect separately the input and output grounds to the power supply ground.

[b:ae84083036]Technical data:[/b:ae84083036]

Output power: 10 Watt RMS @ 8 Ohm (1KHz sinewave)

Sensitivity: 115 to 180mV input for 10W output (depending on P2 control position)

Frequency response: See Comments above

Total harmonic distortion @ 1KHz: 0.1W 0.009% 1W 0.004% 10W 0.005%
Total harmonic distortion @ 100Hz: 0.1W 0.009% 1W 0.007% 10W 0.012%
Total harmonic distortion @10KHz: 0.1W 0.056% 1W 0.01% 10W 0.018%

Total harmonic distortion @ 100Hz and full boost: 1W 0.015% 10W 0.03%

Max. bass-boost referred to 1KHz: 400Hz = +5dB; 200Hz = +7.3dB; 100Hz = +12dB; 50Hz = +16.4dB; 30Hz = +13.3dB

Unconditionally stable on capacitive loads

Source: [url]http://www.redcircuits.com/Page61.htm[/url]

Copyright Flavio DellepianeParts:1 x 22K Log.Potentiometer (Dual-gang for stereo) (P1)
1 x 100K Log.Potentiometer (Dual-gang for stereo) (P2)
1 x 820R 1/4W Resistor (R1)
3 x 4K7 1/4W Resistors (R2, R4, R8)
1 x 500R 1/2W Trimmer Cermet (R3)
1 x 82K 1/4W Resistor (R5)
2 x 47K 1/4W Resistors (R6,R7)
1 x 10R 1/2W Resistor (R9)
1 x R22 4W Resistor (wirewound) (R10)
2 x 470nF 63V Polyester Capacitor (C1,C8)
2 x 100µF 25V Electrolytic Capacitors (C2,C5)
2 x 470µF 25V Electrolytic Capacitors (C3,C4)
1 x 47pF 63V Ceramic or Polystyrene Capacitor (C6)
1 x 10nF 63V Polyester Capacitor (C7)
1 x 100nF 63V Polyester Capacitor (C9)
1 x 1N4148 75V 150mA Diode (D1)
1 x NE5532 Low noise Dual Op-amp (IC1)
1 x BC547B 45V 100mA NPN Transistor (Q1)
1 x BC557B 45V 100mA PNP Transistor (Q2)
1 x TIP42A 60V 6A PNP Transistor (Q3)
1 x TIP41A 60V 6A NPN Transistor (Q4)
1 x RCA audio input socket (J1)

Power supply parts:
1 x 1K5 1/4W Resistor (R11)
2 x 4700µF 25V Electrolytic Capacitors (C10, C11)
1 x 100V 4A Diode bridge (D2)
1 x 5mm. Red LED (D3)
1 x 220V Primary, 12 + 12V Secondary 24-30VA Mains transformer (T1)
1 x Male Mains plug (PL1)
1 x SPST Mains switch (SW1)