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.

EL84 Single Ended Amplifier

6N1 + 6P14 (EL84) Solid Wood Chassis Tube Amplifier U$290

Parameters and specifications

6N1 – 1pc, 6P14 – 1 pair

6P14  = EL84

6N1 = 6922 equivalent 

• Output power: 3.5W / 8 Ohm
• Frequency response: 30Hz – 40kHz +/- 1dB
• Input sensitivity: 800mV
• Noise: <= 5mV
• Operating voltage: 230Vac / 200mA + 6.3VCT / 3A
• Power consumption: 70W
• Input impedance: 10K Ohm
• Output impedance: 4 / 8 Ohm (Z11 – EI57 * 30mm stack OPT)

Notes:
I. Load (speaker) must be connected when the amplifier is switched on. Switching on without load will cause the output transformers and/or tubes to be burned and damaged. This is not covered in the warranty. 

II. Please specify 4 Ohm o4 8 Ohm when ordering.

III. Diode bridge rectification with 6Z4 parallel at output as buffer / slow turn-on, to gain higher output current, protection and tube rectification tonality.

IV. 6P14 is commonly used as output tube in radio receivers. The tone is colorful, full body and nostalgic, especially suitable for vocals.

V. The speaker binding post are gold plated copper, with very thick plating, not those that will easily oxidize or scraped off after several use. Power supply switch is high quality 8A 250Vac rated.

VI. This is a real tube amplifier, and uses output transformers at coupling between tube and speakers. This is not the cheapo fake tube amplifier with fake “tube lamps” as decoration.

Tips

I. A true tube amplifier requires 3 transformers at least – 1 power transformer and 2 output transformers. Such arrangement on our amplifier minimizes the interference between them to the lowest level, ensuring higher SNR. Our amplifiers uses 75W power transformers, and do not hum or do not generate high heat. Output transformers are made of high quality 0.35mm Z11 SiFe from Japan (Z11 has higher permeability and therefore generates higher primary impedance = better bass than those H14, H18 grade SiFe cores).

II. The amplifier is hand made with point to point wiring for every components made. No PCB!

III. The chassis is made of solid ash wood. The solid wood is dried properly before being made into chassis. It is sanded and painted multiple times before being used. The grain is rich and deep, simple and nice. Top plate is 3mm ALU, bottom plate is 1mm ALU.

IV. Size is 25cm W x 30cm D x 13cm H). It weights 5KG. It has ample internal space for further upgrades – change to better oil capacitors or audiophile power supply / coupling capacitors.

V. The power supply uses Philips 150UF, Nippon Chemicon 47UF and 22UFx2 high voltage electrolytic capacitors. High wattage cement resistors + 5H choke are used together with the capacitors to form a CLCRC filter network, to achieve high suppression of power supply ripple. Noise floor is ~2-5mV.

VI. Coupling and bypass capacitors are made in German, WIMA MKP film + antique oil capacitors – high definition and warm. Rubycon from Japan (330UF 35V) are used as cathode bypass capacitor for 6P14. Volume pot is from ALPS Japan, 100K.

VII. The output transformer (5K:4/8) and power transformers are custom made. Quality is stable and reliable. 4 Ohm or 8 Ohm output needs to be mentioned when ordering. Default will be 8 Ohm.

VIII. Output power is 3.8W x 2. It sounded as loud as if it is a 20W x2 solid state amplifier.

IX. This amplifier is suitable for higher efficiency speakers or small bookshelf speakers. Single full range driver will be perfect. The amplifier works in full class A operation, with low distortion, sweet, warm and mellow sound.

X. We ensure safe packaging for the amplifier. The tubes are separately packed.

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.