SW1 bypasses the crossfeed network. I have reconfigured the original crossfeed schematic so that now the 100k resistor always bridges the bypass switch and thereby reduces any 'crackle' or 'click' or whatever you may call them. Don't omit these 100K resistors as they form a part of the crossfeed network and omitting them would bear undesirable results. Note that R6 and R9 are indicated as 4.53k, however the use of 4.7k resistors will be perfectly adequate in practice.
Click here to download the full size of the above Circuit.
I chose the NE5532 for this project. Since the source is a PDA's internal DAC, I didn't see the need to use premium opamps. Of course, if it makes you feel better, you can always use higher quality (expensive) opamps. Just make sure the opamp is capable of driving low impedances. LM6171, OPA2134, OPA2132, OPA134 and OPA4134 (dual) are some possible substitutes. It's likely that there are others. IC sockets are therefore a good idea if you have plans to upgrade the opamps.
The volume pot should be a linear type and would give, with the 15k resistor in parallel, the benefits outlined in ESP's A Better Volume Control.
The crossfeed is on a separate board in the prototype. I mounted it vertically on the main board using hot-melt glue. All the switches, jacks and volume control were also mounted on the enclosure using a hot-melt glue gun. I used generous amounts of hot-melt glue around the bases of all the capacitors as they are more susceptible to lead and track breaking due to vibrations.
My prototype uses two 9V alkaline batteries to give 9-0-9V supply. I get around 20 hours of operation at normal portable listening levels. The effect of the demise of a few pairs of alkaline batteries on my wallet has decided me to switch over to rechargeable batteries. A battery charger is now under construction.
This amp can also be powered by Project 05 using a 15-0-15V transformer. A 5VA transformer should have oomph enough for...
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: