The TEA 1:10 MC step-up, based on two Tribute Audio MC transformers:

This project is very simple, because it is foundamentally based on the very interesting Tribute Audio 1:10 MC transformers, which are very good components if compared with their prices (about 250 Euro).

Pieter Treurniet (Zuidhorn, Nederland) is the guy who builds these MC transformers using different transformation ratioes, at customer request. In the picture aside you can see how these “sweets” comes from postage dispatch: be carefull that your sons will not eat them! About the connections there are few words to say: each transfomer has only a two couples of pins: the Primary (cartidge input) and Secondary (output for the phono preamplifier). Only... for my taste the “+” and “-” pins are too close each others.

These MC transformers have a very special core, which is done with cobalt amorph material, as visible on the second picture. Internal wiring are copper.

To build the step-up you just need to connect the input/output pins to a couple of RCA plugs and... that is it! Well, before to start look at the “parts” picture.

What I have used is:

From the pictures you can see how I mdeled the copper foil to form a sort of Faraday shild, which will be connected to the ground point (star grounding technique).

In the following pictures you can see how I made it. The copper foil is adapted to fit inside the metal case. The RCA plugs are fixed to the backside panel. The MC transformers are fixed to the base using only blue-tak and, finally, the silver wire is used for the electrical connections. Note all the grounding wires connected in a single point.

The final result is probably not so nice as using a wooden box, but in this way the transformers are very well shielded. In fact, there is no particularly high background noise using this 1:10 step-up.

What about the sound? Well, the first impression is of very high details and frequency broad extension, but I need to use it more time, and to try different cartridges, before to say how good it is.

For now, I can say that it surely is much better than a similar cost product, like the Ortofon MC20.

Tino © April 2007

Upgrading the Tribute Audio MC transformers with a Zobel output network:

After my recent test of the fabulous My Sonic Stage 303 step-up I discovered the load variable with frequency concept, so I decided to try it in my home made Tribute step-up. As explained there, the basic idea is to load the transformer output with a series of a capacitor and a resistor, which will be put in parallel with the phono input resistance (usually 47 kOhm). When the frequency is low, the cap acts like an open circuit, and the load is given only by the phono input resistor. For high frequencies the cap is a short circuit and the load is given by the parallel of the phono input resistor and the damping resistor in the series. The transition usually occurs in the mid-high frequency rang, so that the top audio frequencies will be damped more than the low frequencies. A part from the My Sonic exaple, I have found that Jensen always suggest the use of this Zobel network for their MC step-ups and also Sowter has such an example.

The varying load: on the left scale the effective resistance present on the transformer output, while on the right scale it is reported on the transformer input side (neglecting the transformer resistance), as will be seen by the cartridge.

The varying output for a cartridge with 40 Ohm of internal resistance (Benz LP, Denon 103,...): there is about a 1dB of attenuation above 5kHz, due to the damping resistance. With a 5 Ohm cartridge the attenuation is much lower.

After some reasoning, I decided to try the following values: 470pF for the cap and 22 kOhm for the damping resistor, and above you can see the simulated response that I'm expecting. The loading resistance seen by the cartridge will vary from 470 Ohm (47 kOhm/102) at low frequency to less than 200 Ohm [(47k//22k)/102] above 20 kHz. For the cap I choose what I was told are the best small-value cap ever made: the silver-mica Soshin SE99, while as damping resistor I chose a carbon Riken 0.5W. Since I was working on the Tribute step-up, I decided to replace also its cheap RCA golden sockets with some vintage rhodium Kimber female connectors.

The very hard to find Soshin SE99 silver mica caps

The Soshin fixed with Blue Tak and soldered to the Riken resistor.

The two Zobel networks on the step-up outputs.

A piece of Stillpoint ERS cloth was put on each side, to prevent EMI/RFI interference.

The last touch of art was to put two small pieces of Stillpoint ERS cloth on both the lateral side, where the copper shield was not close.

When I first tried it, I used my old Koetsu Red for testing and was really impressed by the results. It was much better than with the old version of my Tribute step-up, in particular in the low frequency energy response. I don't know if all the improvement was due to the Zobel network or if also the Kimber rhodium and ERS were important upgrades, but the result overcome my expectations. I have found it so good that I have used for a long while the Koetsu and just recently I have mounted the Benz LP. From a very first impression the result are good but not so impressive as with the Koetsu, so it seems that the Zobel damping is more effective on low resistance cartridges. Maybe I will probably add more comments on the LP sound, so... stay tuned!

Tino © March 2009