Sky Moving Coil Step-Up Transformer for VPI Turntables

This fully integrated Step-up Transformer/VPI Interface Box is designed o improve the performance of VPI turntables when used with a low-output Moving Coil Phono Cartridge. This unit is a direct replacement for the standard VPI Interface Box. The VPI Interface Box combines a top-of-the-line Bob's Devices Step Up Transformer (SUT) with a VPI Interface Box.

This unit eliminates a full set of interconnects plus their connectors from the phono playback circuit. The path between the moving coil cartridge and the phono preamplifier is as critical as it is sensitive, thanks to the very low voltage and current being transmitted. Further, this path is also subject to RF and other interference, so EFI/RFI shielded cables are mandatory between the SKY and your phono stage inputs. By streamlining this path you will hear a large improvement, as Bob says "the fewer stones in the road the smoother the ride."

NOTE: This item is considered a special order item, is built to order and cannot be returned. If you have questions about this unit, please contact us prior to purchase. Each unit takes approximately 7-10 business days to build and ship and is covered uneder Bob's Lifetime Warranty against Manufacturer's Defect.

Compatible with all VPI JMW tonearms configured with the push-lock 4-Pin LEMO connection, including the Fatboy and 3D Printed.

Each unit comes with detailed instructions on how to swap out the stock VPI box for the Bob's Devices VPI-SUT.

     NOTE: To assure compatibility, please enter MC Phono Cartridge and MM Phono Stage in the text box above!

All Sky models include  a ground post which is used to connect the turntable ground and your preamplifier ground.

A nice touch is that Bob's Devices also includs a ground "lift" switch, here's how it works:

In all modes, the transformer cases and faraday internal shielding to the transformers are connected to the ground screw.

In the "Ground" mode, the negatives of the phono system are connected to the ground 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 for much greater flexibility when seeking to mitigate ground loops, regardless of the configuration of the other equipment.

The S-Series is a step-up (pun intended) from their predecessors.  These models are heavier and meatier. They feature the same ratios as before and are designed for highly resolving analog systems. Bob 's Devices spent a great deal of time developing the S-series, trying many combinations while trying to improve on the standard set by their previous series.

They found that by increasing the length of the core, they were able to change the winding scheme just a bit, which results in a much more  open, more dynamic and more fluid presentation. You will definitely "Hear the Magic."

Ultra High quality laminations, lower inductance and superior sound. These transformers were especially designed and tested with several low-output moving coil cartridges. The transformers used are very difficult to construct and require a precision manufacturing process. The construction techniques used are the same as in other Bob's Devices series, except that the inductance of the SKY-S series is much lower. In addition, the bandwidth is extended further into both extremes.

SKY 20-S : Features switchable ratios of 1:10 in LOW (+20 dB) and 1:20 in HIGH (+26 dB)
SKY 30-S: Features switchable ratios of 1:15 in LOW (+24 dB) and 1:30 in HIGH (+30 dB)
SKY 40-S Switchable: Features switchable ratios of 1:20 in LOW (+26 dB) and 1:40 in HIGH (+32 dB)
     NOTE: To assure compatibility, please enter MC Phono Cartridge and MM Phono Stage in the text box above!

A Sky Step-Up Transformer increases the output of your MC cartridge to a level high enough to work with an MM phono stage!

In order for the SUT to work correctly, you'll need to know two things:
     A) The amount of gain your MM phono preamp has and...
     B) The output voltage of your MC phono cartridge

Most modern MM phono stages have 40dB of gain.  However, some MM phono stages have far less gain and we've even heard of some having a bit more. The gain specification is published for every MM phono stage made, so before going further, do your research and ensure you know how much gain you're working with. Once you have that figure, use the handy reference guide below to figure out approximately how much total gain you'll need to optimally drive your MC phono cartridge.

Once armed with that info, simply select the Sky SUT from the Variants list on the previous tab to select the version with the optimum amount of gain for your ideal output level.

Example: Your MC cartridge has 0.3mV output. Looking at the gain chart below, it appears you'll want about 60dB of gain for optimal playback. If your phono stage has 40dB of gain, select the Sky 20-S, which delivers +20dB of gain, for an ideal 60dB of gain. The Sky 20-S also gives you the option of switching in an extra 6dB of gain, should your next MC cartridge have lower output.

NOTE: If you don't see your cartridge's precise voltage shown below, don't worry! These broad voltage segments are provided merely as guidelines. When in doubt, err on the side of slightly higher gain.

If your cartridge has:
0.5mV output (or higher), you'll want a total of ~55dB of output
0.4mV output, you'll want a total of ~58dB of output
0.35mV output, you'll want a total of ~59dB of output
0.3mV output, you'll want a total of ~60dB of output
0.25mV output, you'll want a total of ~62dB of output
0.2mV output, you'll want a total of ~64dB of output
0.15mV output, you'll want a total of ~67dB of output
0.1mV output, you'll want a total of ~70dB of output

     NOTE: To assure compatibility, we ask that you please enter your MC Phono Cartridge and MM Phono Stage in the text box above when ordering. This way we can verify the Sky SUT you're purchasing is compatible with your analog rig!