The Phono Stage
The Altmann Phono Stage combines exceptional sound quality and unique features.
The Altmann phono stage is a 2-stage, passive-RIAA, virtual-ground design.
It has a powerful output section (similar to that of the Attraction DAC).
There are a total of 12 Op-amps at work.
To accomodate a variety of different pickup cartridges, the gain of each stereo channel of the two gain stages is individually adjustable by a total of 4 red jumpers, which are located in the middle of the circuit-board as shown above.
This allows the use of loud MM pickups (i.e. Pickering NP/AC, Ortofon GT, etc), normal loudness MM cartridges (i.e. Grado, Audio Technica) or silent / MC cartridges (Denon DL-103, Benz Micro, Koetsu, Zyx and so on).
A recommended cartrdige is the Audio-Technica AT-91.
The input of the Altmann Phono Stage is shunted to ground via 47kOhm, however each input channel also featurs a connection post close to the input RCA plug for mounting any kind loading components, just as you desire or as your cartrdge manufacturer recommends.
The circuit design has been optimized for shortest signal path and lowest possible noise level.
The practical outcome of this setup is a level of sound quality that is unrivalled.
In order to make the phono stage more versatile, especially when it comes to high-quality, high-sample-rate recording of vinyl with the Altmann Creation ADC, a second set of jumpers has been implemented (shown black on circuit board), which allow for individual adjustment of the hi-frequency- and lower mid-frequency-band (departure from the standard RIAA curve).
In other words: the functions of the filter-correction jumpers are laid out, to make vinyl records work, which do not sound well with standard RIAA correction.
See below a closeup of the phono-stage circuit-board with red jumpers (gain setting) and black jumpers (RIAA filter adjustment).
Like the BYOB amplifier, the complete electronic assembly of the Altmann Phono Stage is vibrationally optimized, as the pcb is flat-press-mounted on a specially treated spruce-board. This construction is time-consuming during manufacture, but improves sound quality, as all components are mechanically coupled to a musical sound board.
Analog input and outputs are high-quality RCA connectors, that are directly singal- and ground-soldered to the pcb.
The Altmann Phono Stage is designed to be powered by a single 12V car- or motorcylce battery, as battery power is pure, and a prerequisite for low-noise phono amplification. Power consumption is 200mA.
The unit is reverse polarity protected. Battery status is monitored by a blue power-LED.
You may load the Phono Stage User Manual here.