This is the Flat moving magnet Phono Preamp project
published in the
Pro Audio Design Forum. The Flat Phono Preamp is designed for the
LP archivist, mastering facility, record manufacturing or any
professional application requiring high quality, low-noise, no-nonsense Flat playback for moving magnet or moving iron cartridges.
A Flat, Non-Equalized Fully-Balanced Preamplifier Board for RAW Recording
The Flat Phono Preamp board is a fully balanced instrumentation amp designed
specifically for direct coupling to moving magnet phono cartridges or moving
coil carts using external transformers. The flat, non-equalized preamp is ideal for RAW archival transfers where RIAA or custom EQ is applied in DSP. When paired with the RIAA EQ Monitor Switcher a fully-analog path with RIAA EQ is possible. The fully-differential input connections
are jumper-selectable for either balanced (floating) tonearm wiring using
shielded twisted pair cables or unbalanced grounded RCA coaxial
interconnect. Highest hum rejection is realized when the input connections are
fully-balanced. Using either input configuration common
mode rejection is realized on-board using a pair of high-accuracy THAT1240 line
receivers in a "double-balanced" cross-coupled output.
Jumpers on the Flat Phono
Preamp select either 47K or 100KΩ resistive termination with capacitive
terminations of 0 to 200 pF in 50 pF steps. Two sets of jumper-selectable gain
adjustments are available for setup with different sensitivity carts or disc
reference levels. Both jumper settings range from +14 to +40 dB. (Balanced outputs
are 6 dB higher in level and range from +20 to +46 dB).
The Flat Phono Preamp is fully DC-coupled from cartridge to output owing to its
low bias current balanced input and DC common mode rejection.
A unique advantage of the Flat Preamp is its ability to be remotely located at
the turntable and powered by bipolar DC. This permits cartridge leads to the
preamp to remain short allowing long low-impedance output signal lines to feed the RIAA
EQ/Monitor Switcher or Workstation A/D converter. The split preamp configuration
is ideal for cutting lathes, archive facilities and residential settings where
separation from the lathe or turntable and the workstation or transfer console
is needed.
The Flat Phono preamp may be populated with a wide variety of dual op amps
including the bipolar NE5532, NJM2114, NJM2068 and FET input OPA2134. (Assembled
PC boards are shipped with NJM2068DD inputs due to their slightly lower noise.
Other ICs available upon request.)
Flat Moving Magnet Phono Preamp With Balanced Input and Balanced Output, Assembled and Tested
- Brand: KA Electronics/Rockmore-Labs
- Product Code: PTS-FMMP-PC-AT
- Availability: Pre-Order
-
$199.95