www.BobsDevices.com                    

MC Cartridge Step-Up Transformer (SUT) crafted with Altec Peerless 15095 or 15095a Transformers in a black powder-coated, hand-polished cast-aluminum enclosure.  

Price is $495.00

Click Here to purchase this item

Included is a ground/lift switch.  Includes premium construction with Premium Octal Sockets, C&K Brand Silver contact toggle switch, Silver plated OCC wire w/ Teflon insulation and Deluxe Gold Plated RCA jacks. 

These Vintage microphone/input transformers are wired to connect a moving coil cartridge (on a turntable) to a phono preamplifier, phono input of a receiver, or your system's preamp's phono input.

Unit has 1:10 (20 dB gain). 

What about Bob?:  I have personally built hundreds of step-ups and tested more than a dozen of the most popular input transformers and several step up pre-amps used to match moving coil MC Cartridges to phono stage preamps.  I take time to evaluate and incorporate suggestions and feedback I receive from my customers.  Each new design is personally scoped on a dual-trace Oscilloscope to ensure proper polarity, then sent a 0.5 mV signal @ 1 kHz to measure the ratio of the input and output voltage under conditions similar to how you would be using it. 

I listen to each and every unit to make sure it is sonically perfect.  My current reference cartridges include: a Denon 103R, an Accuphase AC-2, a Dynavector DV Ruby Karat, Supex SD-900 MKII, Shelter 901, Koetsu Rosewood Signature, and Koetsu Urishi Vermillion.  I use a VPI  Aries Extended turntable with superplatter and JMW 12.7 tonearm and listen through Strathearn Ribbon Speakers bi-amped with Infinity Watson subwoofers.  I custom make my interconnects from Cardas SRCA connectors and 89207 Belden Cable. If you have any special needs, I also custom build units for special situations, such as using XLR connectors for those with balanced inputs and outputs, or with multiple inputs for those with several turntables or tonearms. 

A Little about Matching:   Moving-coil cartridges have more energy than moving-magnet cartridges due the fact that their magnets are stationary, and can be stronger than those in the moving magnet cartridges. They typically have high current and low voltage, where a moving magnet cartridge has high voltage and low current.

To use a moving coil cartridge, you either have to amplify the voltage prior to reaching the phono preamp (by using a Head Amplifier); or to change the current into voltage that is high enough to be used by the phono preamp (by using a transformer). 

What is the difference between a Transformer and a Head-Amp:  The transformer is a passive device and therefore has certain advantages over a head amp or active device, which is most likely built with solid-state electronics (FETs, i.e. Field Effect Transistors).  Moving Coil Cartridges have low voltage but high current.   The transformer uses the extra current that is not needed and converts it to higher voltage to allow the cartridge to match the input of the phono preamp.  Whenever you introduce something into a circuit, there is an insertion loss.  Whether there is a greater insertion loss from a transformer or a head amplifier depends more on the quality of the components than on which type of step up device is used, but a well crafted SUT has fewer parts than a head amp.

Impedance vs. Output voltage:  With transformers used for matching the outputs of MC cartridges, you would want to match the output voltage, rather than the impedance, to get a better match.  (This is different from head amplifiers where you would want to match the impedance only.)  Many folks get caught in the trap of trying to match the cartridge impedance to a step up transformer.  If you do attempt to match the impedance, you will “choke out” the cartridge and it will sound flat. With step up transformers, you match voltage, not impedance, but you do need to make sure that there is sufficient head room with the reflected impedance so it does not “choke out” the cartridge.

A conventional RIAA phono preamp has a nominal reference level of 5mV at 1kHz.  All phono preamps are different, but typically output values below 2.5 mV or above 10 mV will either result in a poor S/N ratio or overload (clipping). The higher the ratio, the higher the gain (the louder it will sound).  Phono preamp manufacturers usually specify the input voltage as a minimum that is acceptable.  What usually is not specified is the maximum voltage that is acceptable before overloading.  The best sound is usually attained toward the high end of the range.

The MATH Part:  Take the output of your moving coil cartridge which is expressed in milli-Volts (mV) and multiply it by the step-up ratio of the transformer.  If this value falls between 2.5 mV and 10 mV, it will work.  (Remember that the 10mV is not the absolute.  It depends on the phono preamp you are using.)  The standard is 5mV (at 1 Khz), however most folks like to be in the range of around 7mV to match the volume coming from a CD player.  Now matching  is not always this simple, including the reflected impedance to consider, which is why you should take the time to ask what would be a good match for you.   

Please contact me if you are not sure, and I can help you look up your cartridge and phono preamp to ensure a good match.  I have many different transformers in stock and can custom build from a variety of transformers to your specifications.

About these Transformers:  These Altec Transformers were constructed with carefully designed and implemented windings without excessive leakage inductance or stray capacitance to insure excellent frequency response.  To reproduce these today, would result in a very expensive component, especially with today's strict environmental controls.   These are not the exact transformers you will get.  I have about 50 in stock so that I can match up pairs both in color and electrically.  The old Altec transformers vary widely and it is important to get a matched pair.  Even transformers from the same batch varied considerably.  I guarantee that the transformers work perfectly, and that the labels are what I consider to be in very good cosmetic condition (especially for 50-year old transformers).  There will be a few little nicks or scrapes on the labels and perhaps a tiny little ding on the case.  I guarantee this unit to not be DOA.  I take pride in each and every set and provide customer support to make sure that they work well in your system. 

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 the "GROUND" mode, both negative conductors are connected to the ground screw.  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.

www.bobsdevices.com contains information on how to best connect this unit to your system including information on grounding and a sketch showing a properly constructed interconnect cable. 

You can purchase this for $495.00.  Payment by paypal or by credit card.  

Click Here to purchase this item

Please email bob@ec.rr.com to order and to make sure this is a match for your system.  US shipping is $10 flat rate via Priority Mail.  International Shipping is $35 flat rate by Express Mail.