FETAudio FDA-2A Manual - B. Specifications:
FDA-2A Manual.doc
Rev. 1.0
Page 3
31-Aug-2012
B. Specifications:
1. DAC chip AD1955 and receiver chip WM8805 plus the discrete super sound IV
converter in pure class “A” operation.
2. On board full power supplier regulations for the DAC to work in standalone
hardware mode with 4 digital inputs (2 SPDIF – RCA x 2, 1 AES – XLR x 1, & 1
Optical – Toslink x 1) and one I2S (2x5 2.54mm pin header) input. Moreover one of
the RCA SPDIF input socket can be set to SPDIF out, but by doing so, number of RCA
SPDIF input will be one only.
3. Control buses for AD1955 and WM8805 chips are provided on board and thus it can
program into software mode and expand the functions of the DAC.
4. Accept up to 24bit/96k signal in NOS mode or 24bit/192k signal with ASRC Daughter
Board (Use same Daughter Board options of FDA-1B).
5. Output analogy level at about 1.5Vrms at 0dBFS digital input. Distortion is about
0.02% at 1kHz 0dbFS or below 0.04% from 20Hz-20kHz. Output impedance is about
150 ohm. Output mute is provided with relay shorting the signal to ground.
6. Power supply is AC 18V x 2 and 9V x 1 (same as FDA-1B transformer); min 40VA total.
7. The form factor of the PCB is similar to the FDA-1B with one discrete IV section and
one regulator removed. Since the PCB width is only 7.1 inches, it will fit into a half
full size case of about 9 inches width.
8. Board: 7.1 x 8 inches double sided 1.6mm gold plated FR4; 9 x M3 supporting holes;
max height part 35mm. Total fully assembled board height is 37mm.
9. The PCB layout is designed to accept both SMD and Through-Hole type components
for both capacitors and resistors. Note that although the resistors hole is just a TH
5mm pitch but 0805 SMD parts can be soldered on to it.
10. Future expansion to USB 2.0 (up to 24bit/192k) input using any USB to I2S module
solution is possible via the input daughter board using the I2S digital input at J5.
Component Choices
:
1. Best DAC chip AD1955 and best sound receiver WM8805 are used.
2. All logic parts are selected carefully to ensure digital input can work flawlessly up to
192k sample frequency.
3. Many Toshiba obsolete transistors are eliminated and better parts are selected from
various sources to ensure continue supply. Many Fairchild transistors are used for
the better specifications and easily available from Mouser or Digikey.
4. Vishay MRS25 and Xicon 50ppm 1% resistors are widely used.
5. Maintain the use of Elna Silmic II capacitors in the analogy discrete IV sections for its
best sonic performance.
6. Use more SMT capacitors (both E-cap and MLCC) in the digital section as they are
more stable with lower ESR. Example is Panasonic FK series. The 5600p and 1500p
IV low pass filter capacitors have changed to SMT COG type for more accurate and
stable performance.
7. ROHS compliance is the first choice for all components.
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