Block diagram of the PAMP-PSU board
The Sefirot architecture includes the following boards, all available in this webstore:
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Super Balanced Input (SUPER-BNCD-INPT)
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Baxandall Volume Control (BAX-VOL-CTRL)
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Headphone Amplifier Stage (HEADPHONE-OPAMPLFR)
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Bandwidth Definition & Subbass Low-Pass Filter (BWLP-FLTR-MONO)
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Summing Amplifier Module ( SUMMING-AMP-L+R)
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LLLL-INDICATOR Log-Law LED Level System (LLLL-INDICATOR)
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Power Supply Module (PAMP-PSU)
The choice of the transformer for this power supply unit, depends on the mains input of your country, either 115Vrms/60Hz or 230Vrms/50Hz. Regardless, the transformer’s capacity should be between 25VA and 36VA. The transformer’s output is expected to be around 36Vrms with a mid-tap, creating two branches with centered references at 18Vrms each. Subsequently, the transformer’s secondary is linked to a diode bridge rectifier, and following this stage, it connects to a group of reservoir capacitors.
In addition to the LM317 and LM337 regulators, this board can accommodate an L7815 regulator to facilitate the single-supply operation of a DAC board.
The mutual shutdown system takes charge of deactivating the regulator that remains operational after the other one ceases functioning due to an unforeseen fault. This safeguards all Op Amps in the signal path. In the final stage, you’ll find the output capacitors, and the VCC and VEE rails deliver power from this point to the boards that constitute the Sefirot preamplifier.
The following are the main features of the PAMP-PSU board:
- Programable supply output voltage (±15 to ±17 V are recommended for Op-amp operation). Output current up to 1 A assuming a proper heatsink for the regulators.
- The footprint can accommodate a bridge rectifier with multiple snubber capacitors to prevent the generation of HF noise.
- Allows the installation of multiple HF filtering capacitors in the main supply rails to prevent any noise reaching the output.
- The system features a mutual shutdown mechanism that protects operational amplifiers on connected boards from damage caused by asymmetric supply rail failures. It ensures these op-amps only operate under safe voltage conditions.
- High-quality double-sided plated-through-hole PCB (Lead-free HASL) with solder mask on both sides and full screen print.
- PCB size: length=92mm, width=75 mm. It incorporates four M3 fixing holes.
- PSRR LM317: >70 dB @ 1 kHz
- PSRR LM337: >78 dB @ 1 kHz
- Ripple noise: better than -104 dB for LM317 and -110 dB for the LM337.
A couple of interconnection diagrams to build a preamplifier using different boards designed by Olas Audio are displayed below.
Interconnection between different Olas Audio boards to build a preamplifier with two separate Low pass/Bandwidth Definition filters
Interconnection between different Olas Audio boards to build a preamplifier with one Summing Amplifier and a Low pass/Bandwidth Definition filter
The published price is for the PCB only. A bill of materials and assembly instructions will be provided upon purchase.
