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Newby attenuator question

post #1 of 3
5/8/09 at 11:05am
Thread Starter 
Hello all,
I have been trying to become familiar with the "in's and out's" of attenuators before I finalize my choice for my amp build. When looking into stepped attenuators vs. say Alps Blue pots I am not sure what the benefit is supposed to be? Does a pot alter sound quality simply by its design or is it the "wear and tear" that is to be expected over time that makes a stepped system a better choice? If a high quality variable resistor does not taint the sound in its initial "like new" state would it not be better to use a row of variable resistors with input coming from a "make before break" rotary switch and setup so all of the resistance steps are equal? I realize that this configuration would have several other issues such as cost, installation method, and a few other problems but putting those aside is this reasonable thinking or just a dumb idea a newb can't get out of his mind.
Thank you for your time.
rotokid
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post #2 of 3
5/8/09 at 11:24am
You basically described a "Ladder" attenuator, which is generally the desired way of doing switched attenuators, so that at any switch position, there are only two resistors in the circuit. It is superior to a standard attenuator, since you are much less likely to have channel imbalance (variations between resistance of the two channels of the pot, at any given position, usually the worst at the lowest settings), as long as you are using very high tolerance resistors in the ladder. One of the issues I have with stepped attenuators, is the limited number of positions(usually 24) that you get with a traditional switch. Unless you got with something like a Twisted Pear Joshua tree, which has something like 128 discrete steps, there is always a chance that you want the volume to be between one step or another..
Another issue that comes up with the switched attenuators is the quality of the switch itself and how well it stands up to use over time. Thats why the DACT attenuators are so expensive: very, very good switches.

There are some other relay based attenuator devices out there that DIY'ers are working on that look interesting too.. something I might consider if I ever get around to building one of the "super" amps..
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post #3 of 3
5/8/09 at 7:04pm
Thread Starter 
Thank you for your response. You are correct I did mean ladder type. You also touched on one of the reasons I was looking toward setting up a ladder type attanuator with variable resistors. I would be able to tune the resistors with a closer tolerance in my normal listening range. I have to admit though I think I may be approaching the "If it aint broke" point in my thought process.
Thanks again
rotokid
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