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Line Stage Kit
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Balanced Triode Parallel Feed Line Stage Kit
Now available - the newest version of the Line Stage kit. Fully balanced from input to output, the line stage will accommodate both balanced and unbalanced inputs and outputs, due to the use of Lundahl input transformer phase splitter and Lundahl output transformer. Schematic
This kit is suitable for anyone needing an excellent line stage. Developed in conjunction with Raleigh Audio, it features moderate gain, low output impedance, wide bandwidth, and extraordinary sound quality. The circuit is, on the one hand, classic, while on the other hand, state-of-the-art. It uses a transformer output in a cathode-connected parallel feed configuration that was used by Western Electric over 60 years ago. However, is uses a depletion mode MOSFET constant current source (CCS) that is more effective than anything available to Western Electric engineers. The transformers employed are the new LL1674, another superb amorphous core unit from Lundahl. The amplifying device is the awesome Russian 6N1P dual triode. The 6N1P filaments are current regulated for low noise.
The kit uses all top quality parts, among them: Kimber Kaps, Mills wirewound resistors, Kiwame carbon film resistors, and Caddock metal film resistors. See picture below.
Gain: 5dB
Output impedance: 330 ohms
Frequency response: 6Hz to 60KHz , +0dB, -3dB
The kit is simple enough for anyone with soldering experience and the knowledge to safely handle the high voltages (~200vDC) present at several points on the energized circuit board. All of the parts necessary to complete the printed circuit board assembly are included, as shown in the photograph. Of course, the constructor must provide an enclosure, jacks, switches, volume potentiometer (the DACT switched resistor control works well here, www.nutshellhifi.com), and other minor parts. The boards were designed to be narrow enough to retrofit into a number of existing preamp chassis as an "upgrade". The dimensions of the PC board are 8.5 inches by 1.7 inches. About 3.0 inches are required to clear the top of the 6N1P. The circuitry requires 180-220vDC @ 32mA and 11-12vDC @ 1.2A for two channels.
An innovative current source-based power supply kit is also available. It goes beyond what can be achieved sonically by a conventional power supply, with increased resolution and lower noise. See description below.
Balanced Triode Parallel Feed Line Stage Kit (two channels) $635
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Current Source Power Supply Kit
An innovative power supply kit designed explicitly to power the Balanced Parallel Feed Triode Line Stage kit is now available. This kit draws from the classic tube power supply designs while incorporating modern technology not available to the designers of yesteryear. The result is a marriage of the smoothness of a tube rectifier with the precision of a MOSFET current source that gives an incredibly clean and transparent sonic presentation. Take a look at the schematic here. Only film capacitors are used in the high-voltage section, eliminating the sonic footprint of electrolytic capacitors. This supply is so clean and transparent that you could hear the grunge contributed by generic resistors if they had been used. Careful listening evaluation resulted in the use of Caddock, Mills and Kiwame resistors critically chosen to achieve sonic excellence. As well as the high-voltage section, the supply also provides a low-voltage section to power the tube filament regulators in the Line Stage. As frosting on the cake, an input mains power line noise filter is included. All of the electronic components are mounted on a 2.5" by 7.7" PC board. To support this power supply, you need to separately provide an input power connector with fuse, a power-on switch, and a power transformer. The transformer should provide something in the range of 240VAC - 250VAC at 70mA, and something in the range of 12VAC - 13VAC at 2.7A. The Lundahl LL1683 is suggested.
Current Source Line Stage Power Supply $145
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Mood Indigo Line Stage Kit
Here is the complete kit version of the Balanced Triode Line Stage Kit and Current Source Power Supply Kit. All of the parts necessary to construct a professional line stage preamp are included in the kit. The instructions are extensive and e-mail help is available in the event of questions. For more details see www.raleighaudio.com.The price of this kit is $1799.
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