This revision reduced the signal level and
treble response in the preamp for a smoother
sound in both cathode and fixed bias modes.
The power supply was also revised for lower
B+ voltages to the EL84 plates. `This amp was built on the chassis of an
Electar Tube 30 amp, which is advertised
as a 20 watt Class A amp.
Click here to download the full size of the above Circuit.
This variation uses a crossline 150k/1200pF
RC network after the PI coupling caps to
reduce the AC voltage on the EL84 grids
and to cut some of the highs. This variation uses zeners across the
EL84 grid stoppers to limit the AC voltage
on the grids. The optional 100pF caps
across the 100k * resistors add an LPF
effect triggered by the signal level. This is the final version of the Blues Express
amp. The zener limiting circuit was removed
and a modified cross-line MV was installed
in its place. The bias/grid load resistors were
returned to their original value of 220k.
The 2nd stage supply was rewired to B+5
instead of B+4 and the 0.22uF/630v poly cap
from B+5 to ground was drawn in. A center-off DPDT switch was used
to toggle the grid load of the 3rd stage from 56k
to 82k in the two "blues" modes, while dropping
to 45k to cut the gain a bit in the "Fat" mode. The switchable conjunctive filter was used to smooth
out the response of the amp, making the 250pF caps
across the 2nd and 3rd plate resistors unnecessary.
With the .022uF and .033uF caps in series the net
capacitance is .0132uF.
The Smooth switch is a local feedback loop between
the plate and grid of the 2nd stage. The traditional
value of 22M allows for a compressed sound while
the alternate value of 44M has a more subtle effect.
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
characters left: