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Re: Which is the BEST step attenuator

195.99.125.202

Hi there,

>>>The Elma switches come in gold plated and silver contacts. The silver ones are cheaper and may be better initially but after time will they degenerate faster and therefore sound worse than the gold ones?<<<

My problem with the Elma Switsches is that use some plating over Junk metal. The stuff I use has the entire contact and the solderpin as one solid piece of Silver.

>>>Which military switches and resistors do you use? Where can one get them?<<<

The Switches I use where made in the 1960's by GEC/Pleesy in the Northampton Plant in the UK. The Resistors are UK made precisition Metal Films which I do not know the Manufacturer of.

Neither Items are directly available to the public, but as far as the switches go, similar units can be found as Surplus in the US. It will take a little looking around but is well worth it. Cost for a 4-deck 30-Position for me was about $ 40....

>>>Have you tried a one step attenuator? ie. just one resistor for series and one for shunt calculated for your desired listening volume - no switches no wires as the resistor is soldered directly from input to output.<<<

As I use many sources and many different listening Levels, this is not really an option. But yes, it clears up things a little more over the Attnuator I use. Not very much though, I'd say this is a complement to the exceptional quality of the Switch I'm using.

>>>I find the shunt design gets you to or exceeds a ladder attenuator quality without the cost. Are you familiar with this design.<<<

We have tried that. Surprisngly (or actually not surprisingly) it does not give the same performance. My personal Take is that we hear the effects of the quite severe loading (low input Impedance) of the Shunt-Attenuator scheme on the preceeding stages.

Anyway, in one of the Euridice Preamp's (we build two of them recently) my Friend Jon used a Shunt Attenuator using a single 20k Vishay Series Resistors and suitable (mostly Holco) shunt Resistors. The other used a classic 100k Ladder Attenuator with Holco Resistors. All other Details of the Preamp's (Parts, Valves, output transformers and Powersupplies) where at this point identical between the two Preamp's.

The Sources where both an Audio-Synthesis DAX-2 DAC (intended to drive Audio-Synthesis own Shunt Attenuator (aka "Passion") and a Accoustic Precisition EIKOS DC-Player. Eithe runit is in the absolute Top-Class for Digital Equipment and has VERY beefy Output Stages.

Still, the Preamp with the Ladder Attenuator consitently sounded SUBSTANTIALLY better. Since then both Preamp's have been converted to Ladder Attenuation using Holco Resistors for most positiona and with Vishay's in the most often used positions.

>>>It's a fixed series resistor (use vishay since you only need 2) and variable shunt which uses a step attenuator to control the shunt resistance. So you always only have one resistor in the audio signal path.<<<

This is a very common misconception (or indeed from some manufacturers misrepresentation). The Switch and the shuntresistor allways remain in the Signal-Path (so are BTW Powersupplies and many other items usually claimed not be part of the Signal-path)....

Later Thorsten


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