To design a Tube Headphone Amplifier we need a triode with uncommon characteristics: enough voltage gain, low internal resistance and good anodic current. My first test was done with the E182CC (figure 1), but there is the limitation on the usable impedance of headphones in the range of 300 to 600 ohms for maximum performance. The output impedance of the amplifier is about 35 ohms, and I don't accept any damping factor less than 8. (About damping factor: for some, a damping factor of 4 or less is acceptable, but only because they have not heard a better tube headphone amplifier like this one.) The tubes that could be used are E182CC or 5687, but with the 5687, the gain is less. The E182CC is auto-biased to ground through the attenuator. It needs the 1K input resistor for stability, probably because there is no shield on middle of the tube.
Click here to download the full size of the above Circuit.
The LL1630 output transformer (also used in my Tube Headphone Amplifier with Digital Input) has a wide frequency response from 10Hz to 40kHz (+/-0.5dB), and a good inductance value to build a perfect headphone amplifier to drive headphones with impedance from 150 to 600 ohms. The LL1630 transformer here is used with parallel connection of the primaries. It must be gapped for a 10mA DC current, so that in parallel connection, it will run fine with the 20mA or less bias current of the output tube. When ordering this component from Lundahl, ask for LL1630/10mA.
About the power supply, I suggest this Reference Power Supply (figure 4) that gives the best result, but is not very cheap to implement. The 100 ohm resistors across the filament supply are center grounded for low noise. The rectification comes from a Hybrid Graetz Bridge (from a Fulvio Chiappetta article in the italian magazine "Construire HiFi") made with 1N5408 diodes and a RCA 5R4 rectifier tube. Although it has semiconductors, the sound depends on the rectifier tube, and the switching characterictic is that of the lower speed device - the tube. The hybrid tube bridge has the advantage that it can be driven from a single transformer secondary (the tube rectifier normally needs a dual secondary transformer).
The other components are not cheap, and here the highest quality parts must be used to get the maximum result. About passive components types, I don't leave...
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: