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Moving Coil Phono Step-Up Kit The problem of getting enough gain to use a moving coil phono cartridge with a preamplifier designed for moving magnet cartridge use without lots of noise is easily solved using a Lundahl MC step-up transformer. These transformers are used by several high-end audio manufacturers for this same purpose. The Basic Kit was profiled and praised by Art Dudley in Stereophile magazine in 2007. There are two levels of the Moving Coil Phono Step-Up Kit available, the Basic and Premium kits. These kits both provide two channels of transformer-based MC Step-Up for stereo reproduction.
Basic MC Phono Step-Up Kit The Basic Kit now employs the new Lundahl LL9226 for improved sound. This transformer is a rethinking of the already very good LL9206, incorporating what was learned in the development of the LL1931. It offers across-the-board better perfomance than its predecessor. The Basic unit can be set up for 14, 20 or 26 dB of gain when equipped with LL9226 transformers. Alternatively, the Basic kit can also be supplied with LL1678 transformers for 18, 24, or 30dB of gain, if you have a particularly low output MC cartridge or low gain phono preamplifier. The gain configuration is achieved by soldering jumpers on the PC board supplied with the kit. Sockets for resistors on the secondary side of each transformer are provided on the PC board so that the user can optimize resistive loading for the best sound. Premium MC Phono Step-Up Kit The Premium Kit is supplied with the new LL1931 MC step-up transformers. These were developed by Lundahl in conjunction with K&K Audio as a higher performance alternative to the LL9206 and LL1678. They use the same amorphous cobalt core material, but are substantially larger. The coils are wound with Cardas "6 nines" high purity copper wire. The design was optimized for low to medium output MC cartridges and the sonic performance with these cartridges is exceptional. The LL1931 provides 18dB and 24 dB step-up capability that is switch selectable, A higher step-up ratio version of the LL1931, the LL1941, is also available for very low output cartridges or for use with low gain phono preamps, yielding 24dB and 30dB step-up. There is also grounding flexibility designed into the kit to allow the best performance with different types of tonearm cabling. Sockets for resistors on the secondary side of each transformer are provided on the PC board so that the user can optimize resistive loading for the best sound. The kit includes connectors, transformers, PC board, wire, hardware, and enclosure. The enclosure is a black powder coated diecast aluminum case that provides exceptional RF shielding. The wire used in the kit is the excellent AG23 silver wire made by DH Labs. The RCA connectors are rhodium plated Cardas units. The enclosure is physically small (5.5" x 2.75" x 1.75", 14cm x 7cm x 4.5cm), so it can be located conveniently. The K&K Audio MC Phono Step-Up Kits are not really "newbie" kits, but can be constructed successfully by anyone with good mechanical skills and some soldering experience. Included with the kit is a step-by-step instruction manual. K&K Audio stands behind you as you build with telephone/e-mail support. However, if you feel that this kit is beyond your skills/inclination, we offer it assembled to your specifications, as well. Basic Moving Coil Step-Up Kit: $325
Upgrade Kits for Older K&K Phono Preamp Kits Because the topology of the K&K Audio Phono Kits has not changed over the years that they have been in production, as we have learned more about the circuit and tested improvements successfully, we have been able to offer them as upgrade kits to bring your K&K Audio phono preamp up to (or nearly, as physical constraints dictate) the level of the current product. Your original SE kit or early Maxxed-Out Kit can be improved to the basic level of the kit described below by applying the upgrade kit below. If you assembled your phono preamp, this is a straightforward project to complete with detailed instructions with pictures for all previous kits. If you bought your phono preamp assembled, then we will complete the modifications for you, test it to verify performance, and audition it to ensure sonic success. If you have a SE Phono Preamp Kit that already has the Cardas capacitor upgrade and the input stage upgrade or a Maxxed-Out Kit with PC board Revision levels 1,2, or 3, you can select from the options below. If you are unsure or need the earlier upgrades, please call to discuss. K&K Audio Phono Preamp Upgrade Kit: $65
Maxxed-Out Phono Preamplifier Kit The basic design of the Maxxed-Out Phono Preamplifier has been the mainstay of K&K Audio phono preamp kits since 2003. Over this time we have relentlessly worked to substantially improve the sonic performance of this topology through the use of improved component parts and additions to the basic topology that have removed performance limitations. All of these improvements have been embodied in the latest versions of the Maxxed-Out Phono Preamplifier Kits presented below. If you check the forums for comments on the previous designs you will find posts comparing these units in a favorable light to much more expensive commercial products. While we won't make a claim that you can't get a better phono preamplifier for $20K or $30K, we do believe that you will have a great deal of difficulty finding either a better kit product, period, or finding a better "big name" commercial product for less than a few times the price of the Maxxed-Out Kits. The family of K&K Audio Phono Preamp Kits accommodates most users' LP playing needs. The kits are equipped to handle moving magnet or moving iron cartridges and, for moving coil cartridges, an input transformer can be added to step-up the lower cartridge output voltage. The circuit was developed to combine the best qualities of tubes and semiconductors and achieve a better result than could be had with either technology alone. The first stage for a moving magnet cartridge consists of a medium transconductance JFET / triode (6N23P/6DJ8/6922/7308) cascode amplifier loaded by a cascode constant current source. This stage is capable of very high gain (about 50dB) with very low noise. An all tube cascode could have been used, but without the simplicity and noise performance of the hybrid approach. The hybrid cascode drives a precision passive RIAA network. This feeds a cascode constant current source loaded triode that is transformer coupled to the outside world using the parallel feed configuration. The lack of DC in the output transformer primary allows the use of a superb cobalt amorphous core Lundahl transformer in the Premium Kit, or, for economy's sake in the Standard Kit, a very high quality high nickel core Lundahl transformer. Because the output is transformer coupled, both balanced (XLR) and unbalanced (RCA) connections are supported, achieving the same excellent sound. The power supply is a robust, low noise choke-loaded design. There are several options for customization of the Maxxed-Out Phono Preamp Kit. These options fall into two classes, parts quality options, and functional options, like the optional volume control. The entry-level Standard Maxxed-Out Kit uses high quality parts such as ElectroCube, Cardas, Panasonic, and Elna SilMic II capacitors, PRP and Takman resistors, and Cardas and Neutrik connectors to achieve the best sound in its price class. The Premium Maxxed-Out Kits use Mundorf, Cardas, Panasonic, and Silmic II caps, Teflon/collet style tube sockets, Audio Note and Shinko tantalum resistors, and Cardas and Neutrik connectors for the best sound, period! The circuit topologies (and the PC boards) are the same, so it is possible to upgrade the Standard kit to the fully optioned Premium kit, as your resources allow. The K&K Audio Maxxed-Out Phono Preamp Kits are not "newbie" kits, but can be constructed successfully by anyone with good mechanical skills and some soldering experience. You must have a soldering set-up, reliable voltmeter, and appropriate hand tools, and be able to tell the difference between a resistor, a diode, and a capacitor, as well as follow detailed instructions. Included with the kit are a 20+ page instruction manual and a CD-ROM with pictures of various assembled components and techniques. K&K Audio stands behind you as you build with telephone/e-mail support, and, if necessary, will finish/troubleshoot a complete kit for a modest time-based fee. To give you further choices, you have the option of purchasing either Main Board Kits to which you must add power supply magnetics, switches, connectors, and an enclosure, etc.; or Complete Kits, which include all of the parts necessary for a complete phono preamplifier, except the solder, tools, and the time to assemble it. It is also possible to have your kit professionally assembled for an additional charge. Furthermore, you can add function options to your kit to enhance its usefulness in your music system. A stereo volume control and two selectable inputs are available as options (see below). The Standard Kit is available with a matte black powder-coated front panel and the Premium Kit is available with a semi-gloss black powder coated front panel or a metallic silver powder coated front panel and anodized knob(s) to match. The finished dimensions of either kit are 18" (46cm) wide, 13" (33cm) deep, and 4" (10cm) high. The Standard Kit weighs about 21 lbs. (9.5kg) and the Premium Kit weighs about 23 lbs. (10.5kg). The measureable performance specifications for the two levels are:
See the K&K Audio Maxxed-Out Phono Preamp Kit schematic here. Standard Kits The Standard Kits are intended as "entry-level" products that compete favorably with well-respected products selling in the retail high-end audio market for $2000-$4000. Furthermore, a Standard Kit is upgradeable to the sonic equivalent of the Premium Maxxed-Out Kit if you should choose to do so later, so your purchase is not a "dead-ended" investment. There are two standard phono preamp kit offerings: Standard Maxxed-Out Main Board Kit and Standard Maxxed-Out Complete Kit. Standard Main Board Kits The Main Board Kit includes the PC board and parts with which to populate it. If you combine a completed Main Board Kit with your chassis, power transformer, power supply choke, input and output jacks, AC input/fuse and a power switch, you will have an excellent MM phono preamplifier. All instructions necessary to assemble the main board are provided including a CD-R with pictures to illustrate parts orientation, etc. The board is shown at right as it will look when you have assembled it. Standard Maxxed-Out Main Board Kit: $599 Standard Complete Kit The Complete Kit contains every part for building a high-end MM phono preamplifier. The Standard Maxxed-Out Complete Kit includes:
The appearance is similar to that of the Premium Maxxed-Out Kit below excluding the push buttons and LEDs on the front panel. Standard Complete Kit: $1349 Assembled and Tested Standard Complete Kit: $1649 Options for Standard Complete Kits
Premium Kits Main Board Kit All of the main board parts are included (you must supply power supply magnetics, switches, connectors, MC input components, and an enclosure to make a complete preamp), as well as detailed assembly instructions and a CD-R full of assembly pictures, to build a 43/49dB gain moving magnet phono preamplifier circuit. If you combine a completed Main Board Kit with your chassis, power transformer, power supply choke, input and output jacks, AC input/fuse and a power switch, you will have a first-rate MM phono preamplifier comparable to retail units selling for several thousand dollars. Premium Maxxed-Out Main Board Kit: $949
Premium Complete Kit
Premium Maxxed-Out Complete Kit: $2449 Assembled and Tested Premium Maxxed-Out Complete Kit: $2849 Options There are several options for the Maxxed-Out Complete Kit that can be easily installed at the time of building the unit. Volume Control Option The output impedance of the K&K Audio Maxxed-Out Preamplifier (with main board gain set to "Low") is low enough to drive a volume control directly, thereby facilitating phono-only systems without the need for a line stage preamp. The Volume Control is a shunt device that puts two fixed, low value resistors in the signal path, preserving the balanced/unbalanced output versatility. The variable shunt element is custom constructed from a 23 position Seiden switch and discrete surface mount audio-grade metal film resistors. Only one resistor is present as a shunt element at each volume control setting in each channel. In addition, there is a volume control bypass switch for each channel on the volume control itself so that you can remove the volume control resistors from the signal path in the phono preamplifier to facilitate its use with a line stage again at any time. The power amplifier being driven should have at least a 50Kohm input impedance. Volume Control Option: add $250 Two Input Option For those of you with two turntables or two tonearms/cartridges on one turntable, the Premium Maxxed-Out Phono Preamp can be outfitted with two inputs (one MM and one MC input; or two separate MC inputs) that are switchable from the front panel. In either case, each input (MM or MC) has its own 8 position resistive loading switch. If you choose the MM + MC two input option, you will also have an 8 position capacitive loading switch for the MM input. The loading values are supplied as follows:
On a special order basis (more time and, possibly, more cost) other values can be supplied. The MC transformer can be chosen from these: LL1681, LL1931, LL1933, LL1941, LL1943, LL1931Ag, LL1933Ag, or LL1941Ag. Only one MC input transformer can be accommodated per channel, so only one MC step-up setting is available for both MC inputs in the case of a 2 x MC input unit. See the pictures below for the front and back panel configurations. Two Input Option with copper wire MC transformers: add $300
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