Description
Price includes 2 x Russian 12AX7 and 2 x Russian 12AY7. 12AY7 can be changed to 12AU7 or 12AX7 to have different sound tastes and different gain level. (See below for more information.) Design Concept Pure Class-A all vacuum tube design with zero negative feedback
- Premium low noise, stable power transformer
- Kiwame carbon resistors at important positions
- Obbligato gold capacitors
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 unnecessary 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
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.
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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.
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