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In Reply to: What questions? posted by JeffH on May 25, 2012 at 06:49:25:
Ask them for a schematic. It's probably only two resistors but you need to know which. Or you can just measure them with a meter.
Your gear impedances look reasonable so there is a reasonable chance they will be fine, but you need to know. The concept of a fixed attenuator, i.e. -12dB only makes sense in the frame of a constant impedance system, usually 50, 75 or 600 ohms. Outside of that the actual performance does vary with your impedances.
If you have, or know someone who has a VOM, VTVM, DVM (you can buy a serviceable one of the latter at harbor freight for ~10$) Just measure three things...
1-The resistance through the device.
2-The resistance from the male end to ground.
3-The resistance from the female end to ground.
Whichever of the latter two is lower is the output. Assuming that it's the male end,2 then if R1+R2=R3 the internals are just an 'L' network, a "voltage divider" which is most likely.
I use open wire interconnects which are both exposed and broadband so I use matching networks at the ends. My outputs all seem to be about 100ohms and the cables are about 300 ohms. By the time all is said and done I end up with about 6dB of loss in the process which allows me to turn up the volume controls a way which is nice as it makes for smoother adjustment. SO, if you are really attenuating 12dB I'd expect you to definitely notice it in terms of where your volume knob ends up for listening.
With respect to where an attenuator should be applied, I'd try it on both ends of the cable using adapters as necessary to see if one sounds better. If you are just wanting the attenuation it doesn't matter, but if you are hoping to also ameliorate design deficiencies then where you place it can be important. At the source end it makes a nice resistive load for the driver which both increases it's phase margin and helps isolate it from the vaguries of the local electrical environment. At the amplifier end it provides some isolation for the input and reduces cable reflections.
Good luck with your endeavors! Although it seems rather unlikely, I believe that the dinking with interconnects that I did decades ago has probably been the largest single contributor to my long-term system satisfaction. While the magnitude of changes and energies involved seem like small potatoes, apparently they are important to the soul...
Rick
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Follow Ups
- RE: What questions? - rick_m 09:28:45 05/25/12 (0)
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