Bob's Devices SKY 10-S Step-Up Transformer

Switchable 1:5 / 1:10 MC step-up with longer core and revised winding. With RCA and/or XLR inputs and outputs. Hand-built in the USA

Bob’s Devices SUTs are built one at a time with point-to-point wiring and no circuit boards, then individually tested. The SKY 10-S is the “S” revision of the original SKY 10—same compact footprint and switchable gain, but with a longer core and a subtle winding change that yields a heavier, more authoritative presentation in highly resolving systems.

The ratios remain 1:5 (LOW) and 1:10 (HIGH), preserving the model’s versatility across a wide range of low-output moving-coil cartridges. The design runs passively, adding no active-stage noise, and targets wide bandwidth and dynamic headroom.

Connectivity is flexible: a front-panel ground post with a Ground/Lift toggle helps you tame ground loops, and you can order the SKY 10-S with different connector configurations (RCA, XLR, or mixed) to suit your system layout.

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

Series/Revision: SKY 10-S (longer core, revised winding over SKY 10)

Operating Principle: Passive MC step-up transformer (no active gain stage)

Electrical

Step-Up Ratios (Low, High): 1:5, 1:10

Connectivity

Inputs/Outputs: Configurable—RCA and XLR options available 

Grounding: Ground post with Ground/Lift switch

Construction

Build: Hand-made, point-to-point wiring; no PCBs

Manufacture: Hand-crafted in the USA