Saturday, January 28, 2012

High Gain Stereo Tube Preamplifier

High Gain Stereo Tube Preamplifier

This is the circuit diagram of stereo tube preamplifier, give you high gain with high performance output. This circuit should work fine with a 6J5, 12SX7, 6CG7, or 12AU7 as the lower tube, and a 6BX7, 12B4, or triode-connected 6BQ5 as the upper tube. Any of the miniature TV dual triodes such as 6DE7 or 6EW7 can serve as both top and bottom triodes since they contain a medium-mu and a low-mu section. (This wouldn't be my choice, since the octals seem to sound better, but you may choose the tubes you like.)

Tube Preamplifier Parts List:

R1,R5 = 100 1/4W carbon
R2,R6 = 100 1W metal film
R3 = 1M 1/4W metal film
R4 = 10k 25W wirewound
R7 = 10k 1/2W metal film
VR1,VR2 = Part of Alps quad volume/balance control
C1 = 2uF 400V polypropylene
C2 = 10uF 400V polypropylene
V1 = 12SN7GT (GE) or 6SN7GT (see text)
V2 = 6BL7GT (GE)

This circuit require special power supply circuit. The power supply is regulated, has slow warmup inherent in its operation. The power supply for this tube preamplifier is in simply designed. The tube 6AS7G for looks; it's much bigger and lights up more impressively than a 6080. The only problem was with the voltage standard since gas tubes are capable of impressive noisemaking.

power supply for High Gain Stereo Tube Preamplifier

Power Supply Parts List:

R1 = 10 1/2W metal film
R2,R3 = 20k 10W wirewound
R4 = 10k 1/4W metal film
R5 = 18k 1/2W metal film
R6 = 56k 2W metal film
R7 = 27k 2W metal film
C1 = 10uF 400V polyprop
C2 = 220uF 400V electrolytic
C3 = 0.1uF 400V Mylar
C4 = 2uF 400V polyprop
T1 = power transformer, 250-0-250V 50mA, Thordarson 24R09 or similar
T2 = filament transformer, 24V CT 2A, Mouser 41LK020 or similar
L1 choke, 20H 50mA, two Triad C-3X in series (see text)

Other components needed: (8) ceramic octal sockets, (5) 7-position ceramic terminal strips, (6) chassis-mount RCA sockets, aluminum chassis 15" 4" 3", AC power cord with strain relief, knobs for pot, DPDT miniature switch, Teflon-insulated wire, 1/4" copper tubular braid, stereo 1/4" panel-mount phone socket, assorted hardware.

Read more about High Gain Stereo Tube Preamplifier, visit this page

About Audio Amplifier
An audio amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 - 20 000 Hz, the human range of hearing) to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain.

The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification, equalization, tone control, mixing/effects, or audio sources like record players, CD players, and cassette players. Most audio amplifiers require these low-level inputs to adhere to line levels.

While the input signal to an audio amplifier may measure only a few hundred microwatts, its output may be tens, hundreds, or thousands of watts. More explanation about power audio amplifier can be found at

This is a video tutorial about how to a very simple audio amplifier based on the LM386 amplifier chip. It can be built for less than $20 (or might be less than $8 in some countries) and used to amplify any low level audio signal including a guitar, bass or mp3 player.

Watch the video:

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