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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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The Lenco P77 tonearm

The Lenco P77 is a rare beast, and one of the most unique vintage tonearm you are likely to come across. We have had one in our system here for the last 4 years, and it gets regular use on the Thorens TD-124. As a high mass arm it is ideally suited to low compliance cartridges, and is a great match for the Denon DL-103.

As most folks will never have seen one of these arms up close, we thought we would put together a short video showing the major features of the arm, and it main component parts. The video is posted below, and is hosted on our new lencomotion audio YouTube channel which you can find here

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Mat matters

One of the problems most vintage turntables face, and the Lenco is no exception, are platters which ring badly. The rubber platter mat found on most turntables controls this ringing to some extent, but there are better solutions now available. A common solution used on the heavy platter Lencos are silicone O-rings placed around the platter lip. Unfortunately, this is not an option on a Lenco using the standard top plate, or for those who do not like the appearance of the silicone rings. In these situations using a mat to damp the platter is the easiest, and often, the best solution.

While the traditional rubber mat may work to damp platter ringing, it is considered by some to over-damp the system. This can rob the music of energy and dynamics. Thankfully there are platter mats available in a variety of different materials such as glass, acrylic, carbon fibre, and even leather, to name just a few. Most of these work well at reducing ringing , some better than others, and all impart there own sonic signature on the music.

Acrylic mats are among the most cost effective. There are many different makes available, and all those which we have tested work well, and provide a very neutral presentation. More exotic materials such as glass, carbon fibre, copper, and bronze also work well, but are more expensive. In some cases, substantially more expensive.

Another option is laminated, or multi-material mats. These have multiple layers of the same, or different materials. These layers, and the interfaces between, are more effective at reducing vibrations than a single layer of material. The interfaces between layers reflect and refract vibrations, acting as a filter, attenuating, redirecting, and/or converting this energy. The more interfaces, the greater the effect. How effective these mats are will depend on the materials used, the construction and, in the end, the listeners own preferences. As mentioned earlier, each mat will have its own sonic signature, and each user their own preference for a specific sound. Experimentation is the key to finding your ideal mat.

We mentioned earlier in this post that acrylic mats are an economical option. as such, they offer a good starting point for experimenting with different materials and mat designs. Here, at lencomotion audio, we think we have found a great mat that combines both acrylic and high density EVA foam in a laminate mat. The 1877 PHONO EH-Strobo turntable mat provides excellent platter damping, and a neutral presentation.

The mat can be used either acrylic, or foam side up, and has 50 and 60Hz strobe marking on the acrylic side. The strobe markings are large, and easy to read, allowing you to accurately set the speed of your turntable. This is now our favoured mat for all our Lenco turntables.

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Phono plugs and an ´El Coto´ upgrade

One of the biggest problems when building affordable audio interconnects is finding good quality RCA phono plugs for terminating the cables. There are a number of good economy plugs available, such as the Neutrik REAN, and Amphinol However, look above this level, and the offerings rise quickly in price, and the law of diminishing returns kicks in.

We have been searching for a good quality, mid-level, phono plug to upgrade our El Coto silver interconnect. The Neutrik plugs, while good, really were the weak point with this offering. Silver provides excellent conductivity, and to make the best use of this, the phono plugs also needs to provide a good index of conductivity. Solid silver would be the best, but prohibitively expensive. A close second, and much more affordable, is tellurium copper with a conductivity index (IACS) of 98/99%. Compare this to brass, or bronze with an index of 56%, and you can see the significant improvement over the Neutrik, and Amphenol plugs.

We now have two different phono plugs using tellurium copper. Our top of the range plug, the RC90S, is silver plated with an anodised aluminium body, and can be found on our El Coto MKII interconnects. The more economical RC85S has gold plated contacts, and features a POM/anodised aluminium body. This plug now features on our upgraded EL Coto interconnects.

The RC90S phono plug found on our El Coto MkII interconnect


El Coto interconnect with new RC85S phono plugs

As well as offering these RCA phono plugs on our top of the range cables, we are now offering these for sale our shop. The plugs are supplied in pairs, and supplied with a quantity of high silver content solder, so you can ensure the highest quality connection between terminals and cables.















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Spark suppression for your Lenco power switch

For a number of years we have been offering replacement spark suppression capacitors for Lenco turntables. These capacitors are effective at reducing arcing on the power switch, which can substantially shorten its life. In addition, this arcing can also create a loud ´pop´ from your speakers. While this X2 capacitor works, it is more of a cost effective solution, rather than the best solution.

A better solution to switch arcing is a RC suppression, or snubber, network. This employs a resistor and capacitor in series, and is more effective at dealing with inductive arcing which occurs during switch activation. The energy stored in the inductor, the motor in the case of the Lenco, will subject the switch contacts to a high voltage as the motors magnetic field collapses. This voltage will arc across the open contacts, much like a cars spark plug, until the gap is too large. The suppression network acts to absorb this energy and safely drain it from the circuit.

Over the past couple of months we have been testing a few different suppression networks, and we have finally found one which we think offers the best solution for a Lenco turntable. These suppression networks are readily available, but all the ones we found were designed for PCB mounting, and therefore had very short legs. This can be problematic for mounting to switches in solid plinths where access is through a long hole. To make mounting as easy, and suitable for the greatest variety of scenarios, we searched for a snubber with long leads instead of the standard PCB wire legs. We finally managed to source an RC suppression network with 5cm long insulated cable legs which employs a 120ohm resistor in series with a 0.1uF capacitor. This combination works extremely well with the Lenco motor for silent, arc-free shutdown.

The down side of this solution is the cost. RC suppression networks are more expensive than standard X2 capacitors, but as these will last many years before needing replacement, the cost over the life of the turntable is small. These RC snubber networks are now available to order our store.