Article about building Marshall 200W Leach Amplifier. For many years I looked for construction of HiFi amplifier wit a good parameters, enough power reserve and simple construction. I built a couple of amplifiers with integrated circuits MBA810, TDA2005, LM3886, but I was disappointed by their output quality and noise. I decide to built a classic construction with discrete components and bipolar transistors. Construction from Mr. Dudek was interesting, but I didn't like used components and complexity. All of my requirements satisfied construction of the Leach Amp. Circuit author publicates in a February 1976 in american journal. From these days circuit was not practically changed. Little changes are descripted on authors page.
Posted on Saturday, March 5, 2011 • Category: LED
The implementation of a RGB LED fader using 555 timer and 4029 digital IC is the objective of this project.
During the operation, the RGB LED is continuously cycled through the colors of the rainbow where the speed at which the colors change is adjustable. The switch between the different colors makes the effect very noticeable while a more relaxed effect happens when the colors fade into each other. These two options can be selected on this device.
The pulse generator based form a standard 555 timer is formed by IC1, C1, R4, R5, and VR1. The frequency of which, and hence the speed of the effect, as adjusted using the pre-set VR1. The pulses are fed into IC2 which is a 4029 binary counter whose outputs continuously count in a binary progression between 1 to 7. The transistors Q1, Q2, and Q3 are being driven by these outputs which in turn control each of the three colors of the RGB LED.
By passing through an RC network, the pulses are shaped before they reach their respective transistors. The fading effect between the colors or abrupt changing is produced by this shaping.
Posted on Friday, March 4, 2011 • Category: FM Transmitters
The goal of this project is for me personally to learn a little more about fm transmitters and fm bug making (may the HAM radio gods bless me in this pursuit). The ideal outcome of this project is a very small and full functional FM transmitter that we can stick into a plastic mint box.
In order to be able to build this, we'll have to learn a lot about amplifiers, LC oscillators, mixers, antennas and FM. This project assumes you're already comfortable build your own PCB boards. If you're not please take a look at the homemade pcb's tutorial before you continue. It will help you out a lot.
Posted on Friday, February 25, 2011 • Category: Amplifiers
Here's a Leach Amplifier based on 2SC5200 and 2SA1943 output power transistors that can provide up to 700W of power. The mechanical design is relatively simple, the transistors are placed on the two cooling profiles with a height of 66 mm, width 44mm, overall length 260mm. They are turned against each other Thus, from the cooling tunnel. Coolers are attaching the nylon backing which allows the assembly of transistors without washers, and thus better transfer of heat. DPS amplifier is at the top of the tunnel and the transistors are soldered from the bottom of PCB.
Posted on Friday, February 18, 2011 • Category: Amplifiers
The amplifier design includes not only the final stage of the source (rectifier, filter) and protection against DC voltage output amplifier and speaker connections delayed.
As already mentioned, the amplifier is designed as a single-module. This means that on one common board rectifier, filter capacitors, protection And definitely amplifier.
Regarding the components of the external solution, the solution based on the original Mr. Marshall Leach. The proposal is adapted for the proposal. in the amplifier are used for temperature sensing diodes are replaced with one sensing transistor mounted on the end of the main condenser and field Tranda. This transistor provides a thermal feedback and thus of a stable quiescent current amplifiers.
Privacy speakers are powered directly from the voltage amplifier. As for mechanical design, is probably the most complicated in the whole amplifier. Cooling is done by the Al blocks that are attached to the main cooling profile. ZH6465 profile is used. The terminal transistors to heat is released through Al strips with a thickness of 6 mm in the lateral beams and passing into the cooler. more pictures.
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