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Playing with impedance

When we first began playing with step-up-transformers (SUT) here at lencomotion audio, we wanted an easy way to vary the secondary loading. We had a variety of transformers, all of which sounded different with each cartridge, and to get an accurate idea of what each SUT was capable of, we had to be able to change the impedance for each cartridge. It needed to be something that allowed us to make changes without having to run to the solder station in the workshop. A quick rummage through our parts box led to the construction of the following pair of cables.

These were easy to make using standard male and female RCA phono plugs, a short length of high-quality cable, and a pair of standard DIL sockets mounted on project board and protected with heat shrink tubing. The DIL sockets are mounted in parallel with the signal cable, and allow resistors to be easily added to the circuit by plugging them in to the DIL socket.

The cables are now a permanent fixture in the listening room, allowing us to easily adjust impedance when playing with cartridges and step-up-transformers. Anyone currently using a SUT with a fixed impedance should have a go making a set of similar cables, and have a go varying the impedance of the system. If you find that adding a resistor improves the sound, then a similar value resistor can easily be more permanently soldered to the phono outputs. For those folks who are not interested in DIY-ing their own cables, contact us, and we would be happy to make up a set for you.

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Shure M7D: vintage cartridge meets vintage tonearm and turntable

The Shure M7D has been in our cartridge collection for just under a year. During that time it has been tried on  a number of turntables with different tonearms, but it has never spent enough time in any one set-up to truly settle in.

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The cartridge is fitted with a NOS N21D stylus. This is the version with the thin cantilever, designed to track at 1.5g-2.5g. Although this cartridge dates from the 70´s, so is not a contemporary of the Lenco P-77 tonearm, or the Thorens TD-124, both of which date from the early 60´s, it shares the same motor as the earlier Shure M3D from that period.

There were a few issues mounting the cartridge in the P-77 headshell due to the stylus being further back in the cartridge body than with most cartridges. To get the tonearm geometry correct, stand-offs were used to allow the cartridge to clear the lip at the front of the headshell. Although not ideal, the cartridge is well secured, and the mounting sled in the P-77 headshell allows the position to be easily adjusted when setting up the correct cartridge alignment.

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Unlike previous attempts with this cartridge, this set-up sounds surprisingly good. It is easy to see why the Shure M3D/M7D have such a large following. With a decent stylus assembly the cartridge provides a good sound stage and, while not the most detailed cartridge, has a nicely balanced presentation. It has a warm tone with very good mid-range resolution, good bass, but is slightly less convincing in the upper range. The highs are there, but lack the detail we are use to with other cartridges like the Grace F9 and Supex SD 900. Overall, listening with the M7D is really enjoyable. It plays well with a wide range of music making it a great all-round cartridge. It works extremely well with the P-77/Thorens TD-124 combination, and will be staying as part of the regular rotation of arms/cartridges for the Thorens.

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If the opportunity arises to get a Shure M7D, or the older M3D, with a decent stylus assembly, it is well worth try. In most set-ups these cartridges will perform admirably, providing a relaxed and enjoyable listening experience with most types of music.

 

 

 

 

 

 

 

 

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what to do with small, leftover, bits of silver wire?

The answer, use them to replace the leads on your favourite MC cartridge.

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The leads are held in place with heatshrink tubing, and the fit is very good once the tube has shrunk around the wire and pin.

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The results are were a pleasant surprise. Initial impressions are that there is a slight improvement in detail, with improved clarity in the highs. The obvious down side of this mod is that once in place, it is not possible to change the cartridge position in the headshell.