Design Concept
The only phono pre-amplifier with pure Class-A all vacuum tube design with zero negative feedback circuit that allows user to customize gain and experience variety of tonal characteristic simply by just changing the vacuum tube (tube rolling). Famous 12AU7, 12AY7, 12AT7 and 12AX7 are all compatible and will produce different gain/character which greatly enhance flexibility and enrich musical experience in any analog turn table system.
Adjustable Gain
Nowadays we enter resurrected era of analog playback, turn table, system because it offers unsurpassed musical expression although the difficulty in operation/set up, the cost of maintenance and the cost of associated equipment are higher than digital media. But it comes with its own price. Unlike current digital media industry where standard output level of source component has been realized by equipment manufacturers, the phono cartridge manufactures produce their own specification with so many different cartridge's output level and impedance that confusing and complicating the matter of selection to match cartridge and phono stage to the end user. Some clever phono stage designs offer solution by adding adjustable gain to their phono pre-amplifier, but not realize that typical gain adjusting circuit work against the fidelity that user strive for. Popular methods to adjust gain in circuit are
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.
The new Minute Phono Stage offers variation in circuit gain to cope variety of cartridge different signal output level by using the purest gain control of all, that is the gain of different type of tube. Each tube design can result in different signal gain by the pitch of control grid wire, the dimension & distance & shape of internal construction etc, and this is the true intrinsic property of each type of tube. By using the gain of tube there is no need to add extra component (attenuator) or NFB to control the overall gain of the circuit maintaining the simplicity and allow user to hear the inner details of each tube that usually lost by other design. |
