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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: Re: Which is the BEST step attenuator posted by DG on August 5, 1999 at 06:47:07:
Hi again,>>>A better comparison would have been to have both ladder and shunt attenuators having the same input impedances.<<<
That unfortunatly is (as you should know) impossible.
A Ladder Attenuator has a Variable Output Impedance which is maximally 1/4 of the nominal Impedance (So a 100k Attenuator will have a worst-case Z-Out of 25kOhm).
A Shunt attenuator on the other hand has a variable Input Impedance and a Variable Output Impedance which can be at the maximum equal to that of the Series Resistor.
>>>Otherwise you wouldn't know if you are listening to impedance related distortion or other distortions of the signal path like solder junctions.<<<
Well, the Impedance Levels where fairly similar. Due to less solder joints and so on, the Shunt Attenuator should have sounded better, but alas did not. To change the Shunt Attenuator to have 100k Series Resistance would have induced a massive and undue HF Rolloff.
>>>The true test is when a certain attenuation level is selected, both the series and shunt resistance of the ladder and shunt designs have the same values, then any difference in sound quality would be due to everything else except impedance matching.<<<
You don't get my point, do you. My point is that in practice, in the real world, in that place where use Equipment, that there the Ladder-Attenuator sounds superior.
If the Shunt Attenuator sounds better in your test at one specific Level Setting but the Ladder Type sounds bettear at all others, it is in practice superior. And do please allow me to note that the tests where level-matched and blind, as well as having included experienced listeners with long experience with both the System used (Eletrostatic Speakers, with Dynamic woofers below 100Hz and floor mounted 15" Subwoofers, 4-Way active using Croft modified Quad 2, Croft OTL and Rotel Monoblocks for the Subbass).
>>>That's exactly what I did in a few scenarios using exactly the same series and shunt resistor values. The results in order of quality:
The point I was trying to make was referring to (2) where you can get the same (sometimes better) sound from a shunt design compared to a ladder attenuator but at a lower cost since you use half the amount of resistors and usually have less solder junctions that the signal has to pass through<<<
That alas is unfortunatly not true. As noted. Due the fact that any Shunt Design MUST present a much lower (much harder to drive) Load to the preceeding Device, it will usually cause a much higher level distortion form the preceeding devices. So while the Shuntattenuator ALONE, might be identical or even better than the Ladder Attenuator.
But used in a conventional HiFi-System, a Ladder-Attenuator having the same worst case output Impedance will present a much higher Input Impedance and as a result the OVERALL performance of the system will be better.
Remember, Audio Design is Holistic, not Atomistic.
Later Thorsten
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Follow Ups
- Re: Which is the BEST step attenuator - Thorsten 10:44:16 08/05/99 (0)
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