3S4 Direct Heated Tube Preamp

2P2 (3S4) Direct Heated Pentode (Triode Strapped) Tube Preamp - U$190 / RM780

Direct heated tubes sound is pure and warm, with very high resolution due to the minimalist tube design where the heater is the cathode itself. The low frequency is taut and solid, mids are warm and smooth, highs are airy and very extended.

 

Components selection

• Fully point-to-point wiring, convenient for modifications and tuning
• Brand new 5Z4P – 1pc, and 2P2-J – 2pc.
• Chassis is made of solid teak wood. The wood grain is clear and rich. All chassis are one and only – classis and nostalgic.
• Non-magnetic top plate – 2mm ALU, bottom plate – 1.5mm ALU
• Circuit are fully hand-wired, with silver plated tube sockets and gold plated copper RCA
• 5Z4P tube rectified, with CLC filer of 33UF Nippon Chemicon + 150UF Philips high speed low ESR capacitors, 10H choke. Tube rectification has better tone and body, with lower power supply ripple (more finesse, lower hum)
• Twin 240Vac 65mA high voltage supply. 2P2 uses LM317 regulator IC to provide 2.8V DC filament supply to have zero hum on output
• Italian AV 1.8UF MKT high quality film coupling capacitor
• 35W EI power supply with high grade SiFe core – runs cool, does not rattle
• High quality 10H choke is used for lower noise floor
• Taiwan Alpha 09 – B100K volume pot is used (as good as Alps Japan)
• Dimension: 33cm D x 20cm W x 16cm H (including pots and RCA)
• Weight: ~3KG (4KG including packaging)

Note: This is a low cost entry product and may have slight cosmetics imperfections. Picky perfectionist – please look elsewhere.

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.

Stepped Attenuator

Ultra high quality stepped attenuator and tone generator - perfect for tube or solid state preamps!

Have you ever wondered why vintage amplifiers or vintage audio gears have the tone that you cannot find in modern audio equipment? There are many factors, like transformers, wires, tubes, capacitors, and RESISTORS!

Vintage audio gears mostly use carbon composite or carbon film resistors and that's one of the main reason they sound warm, mellow with golden yellowy tone. The down sides with carbon composite or carbon film resistors is their stability (value change over temperature) and tolerance (+10% is normal). Using these AB carbon resistors at the volume is the best place - why? They never get hot at this position and this reduces the value drift over time.

What we have bellow is a very unique stepped attenuator you cannot find in other places - it is a high quality stepped attenuator made with MATCHED carbon composite / carbon film resistors! Having a carbon volume pot (stepped attenuator) at the front gives you the TONE you cannot find with other type of volume pots! 

This is a MUST HAVE! Now some pictures before we go to the details.

Note: We can do a fully built passive preamp if you wish. Email us for various available options. 

24 steps stereo series type stepped attenuator (Price: U$159/pc)

* Military grade silver plated copper switch
* NOS Allen Bradley 0.5W carbon film resistors
* Impedance: 50K Ohm (54.3K to be exact)
* Impedance value may drift slightly over time due to environment humidity and temperature 
* Series type instead of ladder type to maximize AB carbon comp resistors tonality
* Attenuation -60dB ~0 (~2dB step)
* Matching ~1% (AB carbon resistors have very low tolerance, to get to 1% is almost an impossible tasks!) 

Dimensions
* 6.6cm (diameter) 5.2cm (length) 
* Mounting hole 10mm 
* Pole length 1.4cm, pole diameter 6mm, pole thread 10mm
* Position lock screw 22mm

Note: this is a military grade ultra durable switch with high rotary tension and requires bigger knob for switching (a high quality bakelite 4cm knob is included) 

Other grades (higher and lower) and types of stepped attenuators are available too, please write to us for more details (L-type ladder, 23-46 steps, Dale resistors, Holco resistors, Elma switch, and etc):

Audiophile M7 Preamp

RM8000 per unit.

M7 Preamp Link


Fully built with audiophile components, double C core power transformer, stepped attenuator, Japan KOA resistors, Mundorf capacitors and various other audiophile parts.