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Handling the Module

Swell uses a sub-miniature vacuum tube (valve) at its core. This device was manufactured decades ago for Soviet military and aerospace applications—designed for field radios, MiG fighter avionics, and early orbital satellites. Built to meet stringent specifications for extreme environments, these valves are exceptionally robust internally. However, they are still fragile glass devices with vacuum-sealed envelopes that require careful handling.

Special Care and Handling

  • Power Supply Quality: The module includes internal voltage regulation to protect the valve filament. However, poorly regulated Eurorack supplies with excessive ripple, noise, or voltage spikes can affect normal operation or damage the module. Ensure your case power supply provides clean, stable ±12V rails.

  • Do Not Touch the Valve: The valve uses flying wire leads rather than rigid pins. The glass-to-metal seals where these leads exit the envelope are sensitive to mechanical stress. Do not press down on the valve with your fingers or flex the leads. Repeated stress can fracture the hermetic seal, causing vacuum loss and failure. The leads act as springs to suspend the valve above the PCB—avoid poking or handling unnecessarily.

  • Mechanical Shock: Dropping or sharply impacting the module will likely damage the valve. Handle with care during installation and transport.

  • Minimize Electrical Interference: Poorly designed digital modules can introduce high-frequency switching noise and current sag on the power rails. Because the valve's grid is highly sensitive, RF and audio-frequency interference will be amplified by the filter circuit. Place Swell away from noisy modules and avoid dense digital module clusters on the same power bus.

  • Microphonics: These valves exhibit low microphonic noise under normal conditions. However, tapping the module or subjecting it to constant vibration (e.g., loud subwoofer feedback, unstable mounting) will produce audible ringing. Avoid sustained mechanical stress.

Normal Operation

During normal operation, an orange glow is visible beneath the valve. This is part of the module's design and indicates proper filament biasing.

It's normal to hear a "bell-like" decay ringing triggered when the module switches are activated, jacks are plugged/unplugged or any other mechanical movement affecting the Eurorack case. This is normal behaviour of valves in general due to their microphonic feedback noise explained above.

Fault Indication: If the orange glow disappears while the module is powered and the rest of your system is functioning normally, this indicates a serious fault. Power down immediately and contact Bartola support.

If Swell Sounds Noisy

At high gain settings — Boost ON, Gain switch High, and Drive turned up — Swell's amplification is extreme. Any noise present on the power rails or induced into the signal path will be amplified and become audible. This is expected behaviour at these settings, not a fault.

The valve's grid is exceptionally sensitive. A Eurorack case running a heavy load of digital modules, a budget switching PSU, or a shared power bus carrying significant current draw from adjacent modules will all contribute noise that the valve stage will amplify.

First: confirm it is system noise, not a module fault

Turn the Gain and Drive knobs fully CCW (zero). If the noise disappears or reduces significantly, Swell is amplifying noise already present in the system — the module is working correctly. If noise persists at zero gain, contact Bartola Instruments support.

Steps to reduce audible noise:

  1. Check your PSU load — add up the current draw of all installed modules. Most Eurorack supplies become significantly noisier above 70–80% of rated capacity. If you are close to the limit, move modules to a second case or upgrade the supply.
  2. Identify noisy neighbours — digital modules and switching power supplies in close proximity inject switching noise onto shared power buses. Common culprits: microcontroller-based oscillators, effects processors, sequencers, and modules with OLED displays. Swell's valve grid will pick this up. Note which modules share your power bus.
  3. Relocate Swell — move it to a different power bus within the case, or physically away from dense digital module clusters. Even a few HP of separation can make a measurable difference.
  4. Use a power filter — a bus board with additional LC filtering between the PSU and Swell's connector will attenuate rail noise before it reaches the module.
  5. Upgrade your PSU — a quality linear or well-regulated switching supply produces significantly lower rail noise than budget converter units. If the PSU fan or a switching converter is audible through the system, it will also be audible through Swell at high gain.