At RBSK studio, we’ve recently adopted a new method for connecting analog audio sources—especially vinyl turntables—to our broadcast system. The core idea is simple: digitize the analog signal right after preamplification and transmit it optically to the mixer computer. The result? A completely galvanically isolated (electrically decoupled) signal path that’s immune to hum and interference—even with ultra-sensitive vinyl signals.
Here’s a breakdown of how the system works, what advantages it brings, and a few thoughts on the broader landscape of integrating analog gear into modern digital workflows.
Step-by-step: From Turntable to Broadcast
- Turntable & RIAA Preamp:
The fragile, low-level signal produced by a turntable’s cartridge is first amplified using a separate RIAA preamp. This stage equalizes the frequency response according to the RIAA standard—boosting lows and attenuating highs—and brings the signal to line level. This is the only analog amplification in the chain. - Analog-to-Digital Conversion (ADC):
The line-level signal from the preamp is then fed into an external ADC. In our setup, the audio is digitized with a high sample rate (96 kHz) and encoded as 24-bit ADPCM. This ensures accurate capture of the analog waveform with minimal distortion or noise. - SPDIF Over Toslink (Optical):
The resulting digital audio stream is transmitted via an SPDIF (Toslink) optical cable to the studio mixer. This form of transmission uses light—literally—so there is no electrical connection between the source and the receiver. That’s the key to achieving full galvanic isolation. - Optical Receiver / USB Audio Interface:
On the mixer side, the optical signal is received by a Toslink-enabled USB interface, which shows up on the studio computer as a standard stereo audio device. From this point on, the vinyl audio is handled like any other digital input in the system. - Digital Signal Processing (DSP):
Inside the mixer software, the vinyl audio is routed, EQ’d, compressed, and prepared for AM transmission. All of this is done in the digital domain—no further conversions—until the final output stage to the transmitter (TX), where it’s finally converted back to analog for modulation.
Why Optical? Because Ground Loops Are the Enemy
The biggest win with this method is the elimination of hum, buzz, and unpredictable interference. With no direct electrical path between the turntable setup and the mixer, there’s no opportunity for ground loops to form. That means no “ground hum,” no low-frequency rumble, and no chasing ghosts in the signal chain.
Vinyl cartridge outputs are extremely sensitive to interference. Even minor ground differentials or poor cabling can induce audible 50 Hz hum, which the RIAA EQ curve only amplifies. Using an optical cable breaks that loop completely and keeps the signal path pristine.
And because digital audio is inherently resilient—either it arrives, or it doesn’t—there’s no gradual degradation or introduced noise from electromagnetic interference. The signal that enters the Toslink cable is exactly what shows up at the DAW or broadcast processor.
Fully Digital Signal Path – The Benefits Multiply
Once digitized, the vinyl signal stays digital throughout the entire processing chain. This offers multiple advantages:
- Preserved Quality: A well-designed ADC captures the full dynamic range and warmth of vinyl. Some modern phono preamps with integrated ADCs boast signal-to-noise ratios over 120 dB and total harmonic distortion as low as -117 dB. In practical terms, the digitized signal is indistinguishable from its analog source.
- Flexible Processing: Digital EQ, filtering, de-clicking, and dynamic shaping can be done with surgical precision, without adding noise or distortion. Effects are layered in software, not hardware, so every tweak is reversible and clean.
- Repeatability & Reliability: Digital chains are stable. No oxidized jacks, no funky cable capacitance, no analog drift. What works today will work tomorrow—exactly the same.
- Cleaner Broadcast Chain: Because the signal remains digital all the way to the transmitter input, there’s no need for multiple AD/DA conversions. Final analog output happens only once: right before modulation.
Other Digital Vinyl Approaches – and Why We Didn’t Use Them
Some turntables today include built-in USB or SPDIF outputs. While convenient, many of these suffer from low-quality ADCs that compromise fidelity. According to independent tests, many consumer-level USB decks offer bit-depths below 20 bits in real-world performance, limiting dynamic range.
Our choice to separate the RIAA stage, ADC, and Toslink output allows full control over each link in the chain—optimizing for professional audio quality at every step.
But… What About the Purists?
We hear you. Some audiophiles insist that vinyl should remain fully analog. While that’s a valid philosophy, it’s also worth acknowledging that a clean digital chain can outperform an analog one—at least in terms of noise, hum, and signal integrity.
With high-end ADCs and proper isolation, you preserve the warmth of vinyl without introducing extra noise. No more mystery buzzes, cable-related signal dropouts, or unwanted coloration from aging preamps. What you get is the true sound of the record—faithfully preserved and ready for the airwaves.
Conclusion: Vinyl, Digitally Done Right
RBSK’s new signal path gives us the best of both worlds: the tactile charm and sonic character of vinyl, paired with the reliability, silence, and flexibility of digital audio.
From stylus to software to studio mixer—sound now travels as light. That’s not just poetic. That’s progress.
🎙️✨