The Cavalli-Kan Kumisa III stereo headphone amplifier
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  • Jan 2007: CK²III circuit boards are available.

Overview

The Cavalli-Kan Kumisa III ("CK²III" or "CKKIII") is a high-end DIY stereo amplifier for dynamic headphones. It was designed with an emphasis on maintaining simplicity in the signal path, and utilizes an all-discrete, fully-complementary topology featuring a JFET input stage, current-mirror VAS (voltage gain stage), Sziklai complementary feedback pair (CFP) output stage, and no global negative feedback. See the Schematic diagram section for details.

CK²III is also ideal as a pre-amplifier line stage. Just add multiple inputs and a selector switch. Its low output impedance and high output current capability allows it to drive a power amplifier over long interconnect cables without signal degradation.

Designed to be a compact AC-powered desktop unit, the CK²III provides high performance with relatively minimal complexity for an all-discrete design. In conjunction with an off-the-shelf enclosure solution, the CK²III is simple and inexpensive to build. See the Tech highlights section for details.

Based on the Kumisa III by Benny Jørgensen, CK²III adds several significant enhancements by Alex Cavalli. Alex and AMB teamed up and performed SPICE simulations and fine-tuning, as well as printed circuit board layout. The project was conducted with community participation, in an open-source manner on the headwize forum, and the result is an exceptional amplifier you see here. See the History & acknowledgements section for more details.

CK²III is designed to be easy to build, but is not recommended as a first-time project for the beginner.

WARNING: Building the CK²III will require that you work with AC line voltage, which is a lethal shock hazard. If you don't know what you're doing, please ask someone who is experienced to help you.

To obtain the blank printed circuit board and some related parts, visit the AMB audio shop. Other parts are available from online vendors. See the Parts list section.

Please be sure to read every section of this site carefully before attempting to build the CK²III amplifier. If you don't thoroughly understand everything, please consider having someone more experienced to build the amplifier for you, or build a simpler project.

The scope of the CK²III project

The CK²III project is primarily centered around the main headphone amplifier board, which incorporates a regulated dual-rail DC power supply onboard. To build a working amplifier, you will also need a power transformer of the appropriate rating, as well as select and/or build an enclosure chassis to house the amplifier board. The transformer can be located in the same enclosure as the amplifier board, or in a separate case for maximum isolation from magnetic field interference. The CK²III circuit board was designed to slide into a Hammond 1455Q160x (external transformer) or Hammond 1455Q220x (internal transformer), but it could also be used in other enclosures. For further information see the Parts list sections. Also, read the AMB DIY audio forum to see what others are doing to build their CK²III amplifiers.

Click to enlarge images:
An assembled CK²III circuit board A CK²III board with the upgraded σ78 and σ79 ultra low noise voltage regulators
(see parts list for details)

What skills and tools are needed

You should know how to read a schematic diagram and correlate it to the circuit board layout, identify electronic parts and their pin-outs, have decent soldering skill, and be proficient with a multimeter. You need at least a basic set of tools for electronics work, such as a good soldering iron and accessories, screw drivers, needle nose plier, diagonal wire cutter, etc. For the chassis case, you will also need to be familiar with using the tools that are necessary, such as an electric drill, bits, center punch and others.

Why not offer a full kit

AMB is not prepared to stock all the needed parts and offer them as a full kit. This amplifier also provides a number of customizable options that makes it unwieldy for such a kit. Lastly, this amplifier is Alex Cavalli and AMB's contribution to the DIY community rather than a for-profit product, AMB cannot assume the commercial support role that might be implicit with a full kit.

Why not offer completed amplifiers

This is intended to be a project for DIYers, and AMB is not set up to manufacture completed amplifiers.

Professional builders

Inquire with the following list of professional builders if they would build you a completed CK²III amplifier, in case you cannot build one yourself.

Where to get help

Be sure you read all the information at this site. If you cannot find an answer to a question, or encounter a problem you cannot solve, the best place to get support is the AMB DIY audio forum. Search the forums for an answer before asking a question. Your question may have already been asked and answered.

AMB's own CK²III (click image to enlarge)
See more photos in the CK²III gallery





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