Introducing ASRA RD-7500 OTL/OCL DAC. This is Allnic’s fifth digital to analog converter to date. The OTL/OCL technology was first used in Allnic’s original headphone amplifier – the HPA-5000. From this evolved an entire line-stage preamplifier product line, headphone amplifiers, a Signature phono preamplifier, and the last three digital to analog converters. Similar to the line-stage preamplifier line, each OTL/OCL DAC model offers subjective strengths that make it unique, adding benefit to music systems when strategically applied.
While the digital specifications of the ASRA DAC mirror the ‘Signature’ D-15,000, there are some significant differences. ASRA has only one SABRE chip; the D-15,000 has two. The D-15,000 features I2S connectivity, while the ASRA features universal Bluetooth capabilities. While each of these DACs features independent digital and analog power transformers, only the D-15,000 'Signature' has complete digital galvanic isolation. The power transformers for each model have the same material and construction but are spec'd optimally for each circuit. Furthermore, the OTL/OCL circuit topography is unique to each. The D-15,000 uses four tubes per channel, while ASRA has only one tube per channel – the 5687, with equivalent options: E182CC, 7044, 6900, 7119. This makes tube rolling, even for the rarest unicorn, affordable.
ASRA RD-7500 Digital Analog Converter
- Non-Feedback (Zero Negative Feedback)
While Negative Feedback (NFB) is an engineering “correction tool” used to adjust measured figures, Non-Feedback is an “artistic frontal assault” that maximizes the inherent purity of the components.
Category
Negative Feedback (NFB)
Non-Feedback (Allnic)
Design Philosophy
Compares output to input to correct errors Amplifies the input signal exactly as it is Distortion (THD)
Lowers distortion figures artificially Resolved through the component’s own linearity Response Speed
Micro-delays occur due to loop latency Instantaneous response without delay (Transient) Phase Characteristics
Possible phase distortion in high frequencies Extremely stable phase across all bandwidths Output Impedance
Forcibly lowered through feedback Determined solely by the component’s low internal resistance Sonic Character
Precise but can be somewhat flat Vividness, vast openness, and natural harmonics Design Difficulty
Relatively easy due to corrective circuitry Extremely difficult; the circuit itself must be perfect The Essential Difference: If feedback is a method of “fixing a mistake after it happens,” Allnic’s Non-Feedback is a method of “ensuring no mistake happens from the very beginning.” This design is made possible by the 5687 vacuum tube's overwhelming linearity
OTL/OCL (Output Transformer-Less / Output Capacitor-Less)
Through its OTL/OCL design, the RD-7500 completely removes the physical signal barriers of output transformers and coupling capacitors. This realizes true broadband transmission—from DC to ultra-high frequencies far exceeding the audible range—without phase distortion or information loss.
Removal of Transformer (L): By fundamentally blocking leakage inductance and distributed capacitance that degrade high-frequency resolution, it secures a crystal-clear high end.
Removal of Capacitor (C): By breaking down the reactance (XC) barrier that blocks low frequencies, it eliminates low-end phase shift. The result is an extremely elastic and fast bass response.
Single-Stage 5687 Vacuum Tube Amplification
In a DAC, signal purity is more important than excessive amplification. For this reason, the RD-7500 insists on a Single-Stage 5687 amplification circuit.
Realization of the Shortest Path: Unlike IC/TR circuits or multi-stage amplification circuits that pass through dozens of components, the RD-7500 prevents signal contamination at the source through a single stage of amplification.
The Power of Direct Drive: The 5687 tube features very low internal resistance and high transconductance. This allows it to secure sufficient gain and low output impedance simultaneously with just one stage, driving the connected amplifier with powerful authority.
The World’s Most Precise DAC Chip (ESS ES9039PRO)
Precise analog transmission begins with perfect digital reconstruction. The RD-7500 is equipped with the ES9039PRO, the flagship chip from ESS Technology, widely regarded as the finest DAC chip in existence.
- HyperStream IV Architecture: Utilizing 4th-generation technology, it undergoes a conversion process far more sophisticated than previous generations.
- Ultra-High Resolution Data Processing: Based on a 32-bit, 8-channel architecture, it achieves overwhelming Dynamic Range (DNR) and extreme Total Harmonic Distortion (THD+N). It perfectly restores even the micro-details hidden within digital sources.
By combining the world’s best chip, the ES9039PRO, with Allnic’s proprietary Single-Stage, Non-Feedback, and OTL/OCL technologies into a single circuit, the pinnacle of digital precision and analog purity is achieved!
Category
Item
Details
Digital Inputs
Input Terminals
One (1) USB, One (1) Optical, One (1) AES/EBU, One (1) Coaxial Bluetooth
Bluetooth 5.1 (aptX, aptX-LL, aptX-HD, aptX Adaptive) Digital Performance
DAC Chip
One (1) ES9039PRO (32-bit HyperStream IV Architecture) Sample Rates
PCM: 44.1kHz – 384kHz / DSD: DSD64 – DSD512 DoP / S/PDIF
DoP: up to DoP512 / S/PDIF: up to 192kHz Output Performance
DNR: +132dB / THD+N: −122dB / Output: Balanced 2Vrms Supported OS
USB Input
Windows (7, 8, 10/11), Mac (OSX 10.6+), Linux (UAC2 compliant) Analog Specifications
Circuit Type
Full OTL/OCL (Output Transformer-Less / Output Capacitor-Less) Vacuum Tubes
5687 x 2 Gain / Impedance
Gain: +5dB / Output Impedance: 500Ω S/N Ratio
-110dB Physical & Control
Front Panel
Buttons & LEDs (USB, Optical, AES/EBU, COAX, BT, Ext. Clock) Dimensions (W×D×H)
35.5cm x 44.5cm x 14.0cm (14 x 17.5 x 5.5 inches)