Brand: Bob's Devices


Bob's Devices CineMag Sky 30 MC Step Up Transformer (1:15/1:30 RCA)

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Available as switchable or non-switchable.

Boost your MC cartridge with the natural sounding MC Phono Step-Up Transformer from Bob's Devices!

Bob's Devices MC Step Up Transformers are Hand-Made upon order and are ready to ship in approximately 1-2 weeks!

Will this work with my MC Cartridge? We can answer that! Simply let us know what Cartridge and Phono Preamp you have and we'll do the rest! Email or call us today at: or 800-782-3472.

The hand crafted CineMag Sky 30 MC Step-up Transformer (SUT) is built with new CineMag SKY (Blue Version) Transformers and gold plated hardware in a hand polished black powder coated cast-aluminum enclosure. All lettering is laser etched and included is a switchable premium construction, C&K Brand Silver contact toggle switches from high to low gain, deluxe gold plated RCA jacks and ground/lift.

Recommended Step-Up Ratio Based on Internal Impedance and Output Voltage of Cartridge

Voltage (mV) 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7
Internal Impedance (Ω)
5 40 40 40 30 30 20 20 20 15 15 15 10 15 10 10 10
10 40 40 30 20 20 20 20 15 15 15 15 10 10 10 10
15 40 40 30 30 20 20 20 20 15 15 15 15 10 10 10 10
20 40 30 30 20 20 20 20 15 15 15 15 15 10 10 10 10
25 30 30 20 20 20 15 15 15 15 10 10 10 10
30 30 30 20 20 20 15 15 15 15 15 10 10 10 10 10
35 30 30 20 20 15 20 15 15 15 15 15 10 10 10 10 10
40 30 30 20 20 15 20 15 15 15 15 10 15 10 10 10 10 10
45 30 20 20 15 15 15 15 15 10 15 10 10 10 10 10

This chart (based on using MM inputs with 47k Ohms impedance setting on phono stage) is not accurate for Denon Cartridges.

Note: Where 2 numbers appear, either can be used.

Why would you buy a step-up transformer instead of just sticking with a high-gain phono preamp? Because, with exceptions, transformers offer better sound--providing more drama, more color, and, especially, greater touch and impact.
-Art Dudley,, Febuary 2017

The CineMag Sky SUT features newly designed ultra high quality laminations, lower inductance and superior sound! The transformers for the CineMag Sky SUT were specially designed and tested with several low-output moving coil cartridges. These are very difficult transformers to construct and require a precision manufacturing process that can only be done by David Geren at CineMag. Unlike the 1131, the SKY has custom designed laminations and the inductance of the SKY is even lower. In addition, the bandwidth is extended a little further.

These specially designed transformers are wired to connect a moving coil cartridge (on a turntable) to a phono preamplifier, phono input of a receiver, or your preamp's phono input. The SKY 30 is switchable for 1:15 (24dB) or 1:30 (30dB).

The grander point, of course, is this: If you own an Ortofon SPU or similar low-output MC cartridge and you're looking for a giant-slayer of a step-up transformer, this may be the product you've been waiting for. The Bob's Devices Sky 40 won't make serious phonophiles forget all about the Hommage T1--or the Audio Note AN-S8, or the Western Electric 618B, or any of the other transformers that might lay claim to the title The Best--but it will give hobbyists of less-than-extravagant means a chance to wring even more enjoyment from their favorite records.
-Art Dudley,, Febuary 2017
In listening to the Cinemag Sky 30, I was distinctly aware that this device is not an emotional instrument. It is, rather, a transparent, analytical, and musical device that reveals a tremendous amount of information in the details of a recording. The Cinemag Sky 30 is extraordinarily good at opening up a soundstage and placing instruments within that space with a clear sense of the air around them. Imaging, detail retrieval, intimacy, resolution are all qualities the Cinemag Sky 30 has in spades. With multiple versions (Sky 20 and 30), it offers versatility for use with many different cartridges and phono stages....I would highly recommend Bob's Devices Cinemag Sky 30 if you have the budget to accommodate it within your overall financial allocation.
-Eben Field,, November 2015

Construction Techniques

All connections are Resistance soldered using the American Beauty system which avoids heat damage to the delicate insulation on the hair-like wires of the transformers. Test equipment is very low current to avoid saturating the transformer cores. You can count on a premier product that is state-of-the-art.

This unit includes a grounding post that can be used to connect your turntable ground and your preamplifier ground. It also includes a ground "lift" switch. In all modes, the transformer cases and faraday shield internal to the transformers are connected to the ground screw. In the "ground" mode, the phono system minus sides (negative sides) are connected to the grounding lug. This configuration works well for those systems where the turntable ground is connected to the negative leads coming from the phono cartridge or where the negative inputs to the preamp are internally connected to ground. In the "lift" mode, none of the conductors in the RCA jacks are connected to the case, ground, or shield and there is no electrical connection between channels. This design allows you much flexibility to mitigate for ground loops regardless of the configuration of your other equipment.


  • Switchable for 1:15 (24dB) or 1:30 (30dB)
  • In/Out RCA Connections

Special Note: The CineMag Sky 30 SUT is available for special order at a fixed ratio (1:15 or 1:30), without a switch at the same price. Optional XLR connectors are available on a larger custom chassis without laser etching for an additional $350. Please contact us at or 800-782-3472. Please allow 1-2 weeks for order fulfillment.

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