Bob's Devices SKY 40-S Step-Up Transformer

Switchable 1:20 / 1:40 MC step-up with heavier core and refined winding. Handcrafted in the USA

Bob's Devices SUTs are hand-made, one at a time, using point-to-point wiring and are individually tested. No circuit boards are used. The SKY 40-S runs passively, adds no noise, and is designed for highly resolving analog systems.

The SKY 40-S is an upgrade from the SKY 40. It is heavier and uses a meatier core material, resulting in a slightly taller transformer than the original. Says Bob's Devices, "It was hard to upgrade the SKY 40. We tried many combinations and found that by increasing the weight and length of the core, we could also change the winding scheme to reduce capacitance. You will 'Hear the Magic.'"

The SKY 40-S has the same ratios as the original: 1:20 in low and 1:40 in high. If your system is particularly revealing, you will notice improved dynamics, bandwidth, and clarity, along with the same black powder-coated cast-aluminum enclosure with laser-etched lettering.

SUT with MM Phono Vs. MC Phono

Most moving-coil phono preamps add an extra gain stage to boost the tiny MC signal up to moving-magnet level, but that almost always raises noise and compromises sound. That's a lot of gain needed on a very delicate signal.

A Bob’s Devices step-up transformer (SUT) avoids those trade-offs: it’s passive, silent, and purpose-built to match your specific MC cartridge to any MM phono input.

Instead of dealing with switches, jumpers, and noise level inside an all-in-one preamp, you get the cleanest signal path, better cartridge matching, and a lower noise floor.

If you want your MC cartridge to deliver everything it’s capable of—clarity, dynamics, and a quieter background—you’ll get it with a dedicated Bob’s Devices SUT.

Specifications

Transformers

Lamination/Core: Heavier core material optimized for low-level performance

Electrical

Step-Up Ratios (Low, High): 1:20, 1:40

Connectivity

Inputs/Outputs: Choose from RCA and XLR

Grounding: Ground post with Ground/Lift toggle

Switching Hardware: Premium silver-contact toggles for Gain and Ground

Construction

Enclosure: Hand-polished black powder-coated cast-aluminum; laser-etched labeling

Wiring: Point-to-point; no PCBs

Manufacture: Hand-built in the USA