Back of 12AX7 phonoFrequency response of 12AX7 PhonoDistortion measurement of 12AX7 phono
Price includes four tubes and capacitors upgrade.
Standard package is 12AX7 + 12AY7 to get 47dB gain.
You can replace 12AY7 with 12AU7, 12AY7, 12AX7 to get 40, 51 or 56dB gain. See below for more information.
Design Concept
Pure Class-A all vacuum tube design with zero negative feedback
Compatible with 12AX7 + 12AU7/ 12AY7/ 12AT7/ 12AX7 for different gains and different sounds.
Premium Quality Parts
Premium power transformer to ensure high performance, low noise and high reliability,
Kiwame resistors at important postions
Obbligato premium film gold capacitors to improve tranparency and clarity
Adjustable Gain
Why do we need adjustable gain? Phono cartridge manufactures produce their own specification with different cartridge’s output level and impedance.
How to make gain adjustable? Typical approaches usually sacrifice sound fidelity. (Note 1)
Therefore we use a different approach – adjusting gain level by changing tubes, therefore there’s no uncessary components that usually distort the sound.
Tubes
Gain level
Application
Sound
Availability
12AX7+12AU7
+40dB
May need another line preamplifier (with +10dB to +20dB gain)
12AU7: linear or well balance sound.
Popular NOS or old production are still easily accessible
12AX7 + 12AY7/6072A
+47dB
Suitable for most MM cartridges
12AY7: very warm and smooth
12AX7 + 12AT7
+51dB
Suitable for low output MM cartridges
fast dynamic sound with punchy bass
12AX7 + 12AX7
+56dB
Suitable for ultra-low output MM cartridges and some MC high output cartridges of +1mV.
12AX7/ECC83 Telefunken is still available though hard to find
Zero Negative Feedback topology
Simple one way feed through circuit arrangement to preserve simplicity in design. By not aiming to lower the distortion with negative feedback we instead design the tube circuit to work into pure class-A and let this linear spot bring out the best no manipulating sound.
The harmonic distortion is less than 0.1% at 4mV input and distortion figure will reduce nicely in linear proportion to the input signal level.
Layout
Internal construction of this phono is very simple, elegant and carefully laid out for symmetrical signal between left and right channel.
Dimension
19 x 26 x 10.5cm (W x D x H) *
Shipping Weight
4.0kg *
* All specification are subject to change without prior notice.
Specification
Frequency Response according to RIAA standard
+/- 0.5dB from 20Hz to 20KHz
Total Harmonic Distortion with 4mV input signal
less than 0.1%
S/N ratio (SINAD 20mV input, 400Hz & 30KHz filter on)
-82dB
Input Impedance
47K ohm
Output Impedance
600 ohm
Gain
+40dB to +56dB adjust by changing output tube (standard +47dB from 12AX7 + 12AY7)
Circuit arrangement
All vacuum tube 2 x 12AX7 (input), 2 x 12AY7 (output)
RIAA network
R/C zero negative feedback type
Bias Operation
Pure Class-A
Maximum input level
20mV from 20Hz to 20KHz
.
Note 1: Typical approaches usually sacrifice sound fidelity.
1) adjust negative feedback level. The higher dB in negative feedback, the lower the gain. This works like a dream, a nightmare dream. Not only it changes the gain, but it also change the output impedance, frequency response, harmonic distortion, phase shift etc, but because it only requires a few resistors (or trimmer pot) to implement, the cost saving is abundance, thus utilize in many phono stages nowadays.
2) attenuate the signal path of the circuit. This strategy is “Lazy Man” solution that works very much like first method but instead of intruding NFB circuit, it just like adding potentiometer to signal path. Dumping signal away from the next stage and add unwanted impedance into the signal path. Increasing signal impedance means increase noise, reduce bandwidth, reduce current drive.
Beautiful chassis and knob, supermally TVC, Japanese switches, silver RCA and silver hook up wire, shaft extensions are employed to shorten the signal paths.
Available in kit form or assembled.
Internal ViewBack Panel
SPECIFICATION
Input: Maximum 6 pairs RCA / XLR
Output: 2 pairs RCA/ XLR
One switch for additional 6dB gain
One switch for ground connection
One switch for XLR/RCA output
Shipping rate:
US/Canada/Europe/Australia/NZ/ Japan: $82
South East Asia : $40
Premium quality parts are used : supermalloy TVC, silver hook up wire, silver RCAs, solid aluminum chassis and beautiful chrome on brass knob. A compact remote control is included.
BASIC FUNCTION
Volume control: 0 to -46dB, 23-steps
Remote control and manual control
OPTIONAL FUNCTION
Select input device (can connect up to 6 devices by RCA or XLR cable Note 1) by hand or by remote control.
Connect to more than one amplifier by RCA or XLR cable
6dB gain
Break or connect output grounding
Connect to external ground wire
REMOTE CONTROL OPERATION
One button to increase volume
One button to decrease volume
One button to select input (need to press “enter” to confirm)
MANUAL OPERATION
Turn the knob to adjust volume.
Press the knob (don’t hold it) then turn it to select input, then press it again to confirm.
ASSEMBLY OPTION
Basic kit is a truly DIY kit. The front panel is silver in color with no hole and no cut out. Back panel is black with no hole.
Add $100 to have the front and the back panel drilled and installed with parts.
Add $200 to have a ready-to-use unit.
SHIPPING COST
Shipping weight is 5kg.
Note 1: The remote control board support maximum 6 pairs RCAs, or 5 pairs RCAs + 1 pair XLR, or 2 pairs XLRs (no RCA)
Many have asked us for a remote control for our Django TVC passive preamp. It’s great to adjust the volume from the sofa.
A few years ago we made a remote-controlled step motor for our 23-steps Seiden switch, it worked initially, but there were two major problems. Firstly, the switch stopped at the wrong position at times. Secondly, the step motor was quite noisy. Now our new relay-based remote control overcomes these two problems – and it’s reliable, durable and quiet.
How does it work? When an electric current passes through the coil inside the delay, a switch opens or closes the connection. It’s a mechanical switch like the Seiden switch. Audio signal only passes from one pin of the relay to the other pin. By using high quality audio grade relay, the signal path remains clean.
How much will it cost?
It costs more than other relay-resistors volume control because it uses a lot more delays. Below is my estimation:
Volume control, display, and remote control : about $219
Volume control, display, remote control and channel control : about $289
Operation:
Remote control : 2 buttons for volume control and 2 buttons for channel control
Front panel control : Press the knob to change channel or turn the knob to adjust volume.
Installation:
Drill one 15mm hole for a number display and one 5mm hole for IR receiver (optional: one 8mm hole for switch shaft for manual selection)
Availability:
The first prototype will be done in early December, 2014.
What do you think? Please share with us your thought.
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