M7 Tube Preamp

KSL-M7 Modified Tube Preamp U$290

This is a modified high quality preamp based on KSL-7 design, being capable of using 12AT7, 12AY7 and 12AU7 tubes in a same preamp. 

Modifications

• I – Tube rectifier uses a bigger tube 5Z4P instead of 6X4
• II – Remove solid-state based voltage regulator and DC filament supply, in exchange, uses two 15H choke and AC filament supply for better musicality and sound
• III – Point to point wiring, with better control of noise/hum. Only can hear very slight hum when ears are close to the speaker with volume turned to maximum, with power amp of gain 20, and 90dB/w/m speakers. 

Materials

• I – Solid teak wood as chassis, 200mm W x 60mm H x 300mm D (measurements do not include knobs, feet or RCA)
• II – Made in Taiwan high quality RCA sockets (side – input, middle – output). 15A power supply switch, 10A rated IEC input.
• III – Alps 16 Made in Japan A100K volume pot
• IV – 4 Philips 100UF power supply capacitor (warm and sweet sounding). Coupling capacitor – TE (Hong Kong) copper pin 0.22UF film capacitor.
• V – Silver plated ceramic tube sockets.
• VI – Metalized film resistor (signal), and metal oxide resistor (power)
• VII – 24AWG OFC copper signal wires
• VIII – 15H 100mA EI57 x 30mm stack, fully shrouded choke, with Japan Z11 SiFE 65W power supply transformers using fully copper wires – cool running, do not rattle, and stable for long term operation

Set includes signal and rectifier tubes (Shuguang 5Z4P, matched pair of Sylvania 12AT7 triple mica). Can replace with 12AT7, 12AY7, 12AU7, ECC81, ECC82 and 6072 tubes.