The input stage is comprised of a both halves of a 6SL7 octal dual hi-mu triode in a differential amp configuration with a 1ma constant current cathode load. I'm using field-effect (constant-current) diodes for simplicity. the diff amp approach was chosen for good power supply rejection, ease of balancing, good gain, and ease of application of *feedback*, if desired (hey, i like to keep an open mind...). It also takes care of phase-splitting right up front.
Note: I've returned the constant current diode cathode to -9V instead of ground in order to avoid the non-linearities about the pinch-off region (Vpo ~= 1.5V).
Click here to download the full size of the above Circuit.
The driver stage is comprised of a both halves of a 6SN7 octal dual medium-mu triode, also in a differential amp configuration, with a 4.7ma constant current cathode load. Because the normal bias gives me about 8.5V on the common cathodes I can return this constant-current diode directly to ground (Vpo ~= 3V).
Output stage
Push-Pull 2A3's using cathode bias. I'm currently using a quad of 750 ohm, 5W resistors bypassed by a 100uf/100V *electrolytic*. Output Transformers are stolen from a Grundig console EL84 amp. Impedance ratio is 6K:4ohm, but I'm using 8ohm speaker for 12K plate to plate load. This is about 3-4X the recommended load per RCA. Power is down considerably from what is could be. (For example, 8.5W with 4k load vs. 5.6W with 12k load.) I decided to go with this transformer for now figuring that the distortion would be minimized. Don't Know if I've passed the point of diminishing returns but there is only one set of secondary leads so I can't experiment too easily.
An other *interesting* feature of this transformer ratio is that if I simply pull out one tube from each channel I am left with a Single-ended amp with a 3k load. This is right out of the book...3k load for Eb=250V. Cool....
Of course there is the matter of 60mA unbalanced DC. We'll just have to see how it works out. So far I've only briefly tried this *Single-ended* mode. Not sure if it's the naturally higher distortion, the OPT's...
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: