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25 Watt MosFet Audio Amplifier - High Quality simple unit. No need for a Preamplifier (added 9/04)

25 Watt Music Amplifier - schematic only, no description  (electronic schematic added 08/08)

500w 4X150A/7034 Tube 26-30MHz VHF output amplifier - ….(design added 08/08)

A DC-Coupled Tube Amplifier With Futterman Output Stage for Dynamic Headphones - The Futterman output stage in this tube amp offers the choice of DC- and AC-coupled outputs. The class AB design can output up to 24mW into a 30-Ohm load or nearly 500mW into a 600-Ohm load.  Designed by Rudy van Stratum  (circuit design added 04/05/06)

A Fender-Tone Tube Headphone Amplifier - This tube amplifier with sonic controls has a paralleled White cathode follower output stage for driving low impedance headphones. The sonic controls consist of a Fender tone stack (bass, mid and treble), and ambience and blend controls. Includes simulation files for use with OrCAD Lite software.  Designed by Alex Cavalli  (circuit design added 04/05/06)

A Low-Voltage Class-A Tube Headphone Amplifier - This OTL design features a high-voltage power supply that is less than half of the one used in the author's first amp and most other tube amps, but without compromising performance.  Designed by Helmut Ahammer  (circuit design added 04/05/06)

A Single-Ended OTL Amplifier for Dynamic Headphones - A simple OTL design that uses just two tubes (dual triodes) for stereo. It has a common cathode input stage direct-coupled to a cathode follower output stage.  Designed by Aren van Waarde  (circuit design added 04/05/06)

A SRPP-Input Tube Amplifier For Headphones And Loudspeakers - This transformer-coupled design uses a series regulated push-pull input stage and a parallel-triode cathode bias output stage. The audio output transformer is hand-wound from a kit. The amp will drive both headphones and speakers.  Designed by Tony Frazer  (circuit design added 04/05/06)

A Tube Headphone Amplifier/Preamp with Relay-Based Input and Power Switching - A tube headphone amplifier inspired by the "Top-Level" and "No-Compromise" amps of Andrea Ciuffoli, except that the output stage uses a triode-connected pentode. Because this amp also serves as a preamp, the author has put in a sophisticated relay-based switching system (both input source selection and power supply). The power supplies also feature slow-on ....Designed by Helmut Ahammer  (circuit design added 04/05/06)

A Vacuum Tube Microphone Preamp / Direct Box Project - From January 1997 EQ Column, includes phantom power supply... (circuit design added 10/06)

A Zero-Feedback SRPP-Input Headphone Amplifier - Features a series regulated push-pull input stage and transformer-coupled output stage with an output impedance of about 2.5 ohms. It has zero global feedback for open, natural sound without any harshness.  Designed by Simon Busbridge  (circuit design added 04/05/06)

All-Triode Direct-Drive Tube Amps for Electrostatic and Electret Headphones  - Two electrostatic headphone driver designs: the second is DC-coupled and uses high voltage Apex op-amps as DC regulators. They will drive Stax and Sennheiser electrostatic phones, and the author includes directions for adapting the designs to other models. These are "the best electrostatic headphone amplifiers currently available, anywhere in the world." Will also drive electret headphones. Recommended ....Designed by Kevin Gilmore  (circuit design added 04/05/06)

Altec 1566A:Vacuum Tube Preamp & Direct Box Project - There are all sorts of tube circuits, some of which actually deliver The Sound people associate with Vacuum Tubes.  Did you know, for example, that asymmetrical distortion generates even-order harmonics while symmetrical distortion produces odd-order harmonics?  Neither vacuum tubes nor transistors are exclusively responsible for either type of distortion, ....(added 4/02)

Baby of Camel: All-directly-Heated Pushpull Amp Spy Photos - Project a Camel is a take-no-prisoners DHT PP based on Lynn Olson Aurora topology. Unfortunately, I'm stuck waiting for Lundahl transformers (three months... that famous Nordic attention to detail... one turn a day...).Well, before Camel is born, there was his baby

Battery heaters in a tube amplifier - This simple circuit controls 6.3V SLA heater batteries (two batteries are shown, but it is stackable to practically unlimited number of batteries). Batteries are floating in 'on' state, paralleled in 'off' (external charger) state. If any battery voltage falls below threshold for more than 1 second, the circuit latches up in 'off' state, disconnects the batteriesr...(electronic design added 07/07/07)

Brute Force In A Line Stage (100% Tube!) - An OTL mu follower design. "One, often forgotten, purpose of the preamp is to drive headphones. I listen with a pair of AKG K240s, which is a relatively easy load to drive. This all-tube line stage and driver can power them, without resorting to output transformers."  Designed by Eric Barbour  (circuit design added 08/08/08)

Capacitive Sensor - Special design for shop-windows animation.  Useful for many types of touch controls.   (electronic circuit added 06/07/08)

Dark activated switch - started this project with the idea to build a simple single-ended tube amplifier. I didn't have any experience with the construction of tube amps so I was looking for a beginner's project. Such a project should be simple (for easy debugging) and it should …(electroninc design added 04/05/06)

Designing A Pocket Equalizer for Headphone Listening (Solid State and Tubes) - Design principles and circuits for building opamp-based headphone amplifiers. This article reviews selection criteria, feedback configurations, capacitor coupling, RF shielding, output stage topology, short circuit protection, equalization, acoustic simulation, headphone distribution amplifiers and power supply options. Also ....Designed by HeadWize  (circuit design added 04/05/06)

Direct Coupled 15 Watt Amp - ….(design added 08/08)

Dynakit Mark E 40 Watt Power Amplifier - (circuit / schematic added 09/08)

Get more Power with a Boosted triode #1 - 04/03/03 EDN-Design Ideas:  Even though 6L6 beam-power tubes have been around for 66 years, they are still quite popular for use in electric-guitar amplifiers, and its cousin, the 6CA7 (EL34)power pentode, is a favorite among audiophiles. The developers of these tubes designed them for pentode-mode operation, and they deliver maximum audio power in this mode.....(design idea added 02/05)

Get more Power with a Boosted triode #2 - 06/12/03 EDN-Design Ideas:  This Design Idea is a reprint of an earlier one that contained errors in graphics (Reference 1). Even though 6L6 beam-power tubes have been around for 66 years, they are still quite popular for use in electric-guitar amplifiers, and its cousin, the 6CA7 (EL34)power pentode, is a favorite among audiophiles.....(design idea added 02/05)