ADC SS-115X (1986)

Name: ADC SS-115X
Brand: ADC

Flick the power switch and amber LEDs come up across ten sliders. The power supply hums, and the chassis feels like it could survive a minor earthquake.

Overview

The ADC SS-115X is a late-'80s Japanese 10-band stereo graphic EQ, built when "prosumer" gear still meant pro-level circuits in a home-friendly case. It is big and heavy, and after 30 minutes of use it gives off a faint smell of warmed capacitors. It does not try to disappear in the chain. The front panel has sliders with dimpled caps, each backlit by a soft amber LED. Around them are tape monitor switching, level meters, and a power switch that clicks like a camera shutter. In 1986, audiophiles were finally getting gear that let them shape sound closely at home, and this unit made a living room feel like a control room. The sliders give ±15 dB, so "surgical" only goes so far.

Inside it is an analog discrete design built around JRC4559D op-amps. They are known for clean gain and low noise, though not quite as silky as the NE5532s that were gaining favor at the time. The SS-115X wasn't chasing audiophile purity. You could crank the 63 Hz band to shake drywall, or notch out 2 kHz if your vinyl pressings were shrill. The range runs from 31.5 Hz to 16 kHz, which covers nearly the full audible spectrum and made it one of the more comprehensive EQs in its class. Output level is shown on dual bar-graph meters driven by AN6877 ICs, one per channel. It's not a spectrum analyzer like the SS-315, but it's close enough to feel professional.

This wasn't ADC's flagship. It sat between entry-level tone controls and high-end parametric rigs, just above the basic SS-100 series and below the SS-315, which added real-time frequency analysis and more refined metering. The SS-115X lacked the bells and whistles of its bigger sibling, but it delivered precise, wide-range equalization in a build that still turns heads. It shared its DNA with the SS-115, differing mostly in minor circuit revisions and possibly output stage stability. Documentation is sparse enough that the distinction remains hazy among collectors. Both models came from a window when Japanese manufacturers were still using thick steel chassis, high-quality potentiometers, and overbuilt power supplies, before cost-cutting crept in toward the end of the decade.

Specifications

Manufacturer	ADC Professional Group
Production Years	1986
Original Price	Not documented
Equalization Bands	10 per channel
Frequency Points	31.5 Hz, 63 Hz, 125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz, 8 kHz, 16 kHz
Adjustment Range	±15 dB per band
Gain Accuracy	±1 dB
Maximum Input Level	4 V RMS or higher
Maximum Output Level	4 V RMS or higher
Input Impedance	Not documented
Output Impedance	Not documented
THD	Not documented
S/N Ratio	Not documented
Inputs	Stereo line in, stereo tape in (x2)
Outputs	Stereo line out, stereo tape out (x2)
Tape Monitoring	Switchable dubbing between tape decks
Level Meters	LED bar graph (AN6877 IC, per channel)
Power Supply	Internal linear transformer-based supply
Power Consumption	Not documented
Weight	Approx. 8–10 kg (estimated from build)
Dimensions	430 mm (W) × 145 mm (H) × 320 mm (D)
Construction	Steel chassis, aluminum front panel
Op-Amps	JRC4559D (discrete design)

Key Features

Ten-Band Precision with Real Analog Feel

The SS-115X has ten fixed frequency bands, each with ±15 dB of cut and boost. That gives it more authority than most of its contemporaries. By 1986 standards, that was serious firepower. Most budget EQs were still stuck at ±10 dB, and even some higher-end models didn't reach down to 31.5 Hz or up to 16 kHz. This one does. The sliders have a slightly damped action, stepped enough to stay put and smooth enough to glide under a fingertip. They're not motorized and they're not backlit with rainbow LEDs. Each slider controls a dedicated filter stage, and because it's all analog and discrete, there's no latency, no quantization, and no digital artifacts.

Integrated Tape Monitoring and Dubbing

In an era when dual cassette decks were still part of high-fidelity systems, the SS-115X included full tape loop functionality with two sets of tape in/out jacks and a switchable monitor path. You could route your source through the EQ, listen to the processed signal, and record to either tape deck, or both, with a single flick. The dubbing function allowed direct Deck A to Deck B transfer without engaging the main EQ circuit, so the original signal path stayed untouched.

LED Bar Graph Meters and Illuminated Interface

The SS-115X lacks the real-time spectrum analysis of the SS-315, but it has dual LED bar graph meters driven by AN6877 ICs. They show output level per channel, which is useful for catching clipping or balancing left/right response. The meters aren't peak-hold, but they respond quickly enough to show dynamic shifts. The slider bank is backlit by a warm amber glow. The ADC logo on the front panel was originally illuminated by a small incandescent bulb, though few survive today, as the filament bulbs were prone to burnout and are not easily replaced. In a dimmed listening room, the lighting makes adjustments easy.

Historical Context

The mid-1980s were a turning point for home audio. CDs had launched in 1982 and by 1986 were gaining traction, but analog gear was still king in most living rooms. The ADC SS-115X arrived when graphic equalizers were no longer just for live sound or car audio. They were becoming status symbols in high-end home systems. Japanese manufacturers like Sony, Denon, and Kenwood were pushing hard, but niche players like ADC Professional Group carved out space by offering pro-grade features at accessible prices. ADC wasn't as big as Yamaha or Technics, but their "Sound Shaper" line had a reputation for solid engineering and no-nonsense functionality.

The SS-115X competed in a crowded field. On one end were basic tone controls built into receivers. On the other were expensive parametric EQs used in studios. The SS-115X sat in the middle, affordable enough for serious hobbyists and capable enough for semi-pro setups. It wasn't designed to win frequency response shootouts, but to give listeners control. In 1986, people were discovering that not all records sounded good on all systems, and room acoustics were finally being taken seriously. The SS-115X gave them a tool to fight bass nulls, tame harsh highs, and make their gear sound more "theater-like." Visual feedback mattered too, with the meters and glowing sliders, because audio was becoming as much about experience as fidelity.

Collectibility & Value

Today the ADC SS-115X is a sleeper in the vintage audio market. It doesn't have the cult status of a Rane or the pedigree of a Drawmer, but it's a solid performer for the price. Working units in good condition typically sell between $60 and $120, with mint examples, especially those with original boxes, manuals, and unblemished sliders, fetching closer to $150. Non-working units are often listed for under $50, but that's where the risk begins.

The most common failure points are the electrolytic capacitors in the power supply, which tend to leak or dry out after decades. When they go, they can leave corrosive residue on the PCB, requiring careful cleaning and replacement. The original mains cable is another weak spot. Many units came with thin, two-core wires that show signs of cracking or poor grounding. Upgrading to a three-core cable with proper earth connection is strongly advised, for both safety and performance. The slider potentiometers are generally sturdy, but years of dust and oxidation can lead to crackling or channel dropouts. Electrical contact cleaner can help, but some owners report that heavy contamination requires disassembly and even washing under running water. Experienced restorers have documented it as a drastic but effective method.

Before buying, check that all sliders move smoothly and produce no noise when adjusted. Test both tape loops and the main output path. Verify that the meters respond to signal and that the power switch engages cleanly. Don't expect the illuminated ADC logo to work. Most bulbs are long dead, and replacements are not standard. If the unit powers on but hums excessively, especially when low bands are boosted, it's likely a sign of failing capacitors or ground issues.

Restoration isn't trivial, but it's manageable for intermediate DIYers. A full recap of the power supply and signal path can cost $30 - $50 in parts, plus time. Once refreshed, the SS-115X holds up well and delivers a clean, neutral tone. It won't transform a bad system, but in a well-tuned chain it's a capable tool for vinyl equalization, room correction, or creative mix shaping.