[
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2008, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]
71.32.21.57
I just built a passive attenuator using Radio Shack parts, based on Harry Haller's diyaudio thread of a few years back. I used two Rat Shack Alpha 10k audio taper mono pots (#271-1721), and two 1k ohm 1W 5% metal-oxide film resistors (#271-153).
Viewing the pots from the back with the three lugs pointing upward, I went from the left lug of one pot to the center pin of the positive "out" RCA, and the left lug of the other pot to the center pin of the negative "out" RCA. I then connected the center and right lugs of both pots together and linked them to the common grounds of the input and output pairs of RCA jacks. Lastly, I connected one 1k ohm resistor between the positive center pins of the input and output RCAs, and the other between the negative center pins of the input and output RCAs.
I'm using the attenuator with a Music Reference EM7 amp, driving Klipsch LaScala speakers. What I'm finding is that I have no volume until the two pots are at least a quarter open, and then there's a rapid rise to REALLY loud by the halfway point on the pots. So basically I have just a quarter turn of each pot that's usable for volume adjustment.
So...my questions are as follows:
1) Would different value resisters (say a 2.2k ohm or 3.3k ohm) give me more usable range on the volume pots...as in giving me volume right away, but tapering up more gradually?
2) Is it the ratio between the pot and resisters that determines the volume slope? For instance, would a 100k ohm pot and a 10k ohm resister (10:1) function identically to a 10k ohm pot and a 1k ohm resister (also 10:1)? Also, I recall reading somewhere that a 10:1 ratio like the setup I built is certainly okay, but going to a higher ratio (for instance, using a 50k ohm pot with a 1-4k ohm resister) can actually overdrive the driver section of the amp...is that correct? And would a 6:1 or 7:1 ratio actually be preferable to a 10:1 ratio? I think the input impedance on the EM7 amp is 150k ohms.
3) Radio Shack has limited resister offerings of the metal film variety, so I'm limited to carbon-type resistors if I want to try 2.2k or 3.3k ohm resistors. Do I need to be particular about the other resistor ratings in terms of 1/4 vs 1/2 vs 1 watt varieties, and 1% vs 5% tolerance? And I assume its a given that metal-oxide are always preferable to carbon film?
4) If I wanted to wire the attentutor just straight to the pots and not do the shunt-to-ground tweak, how would I do that? Using the layman's terms I use above (center pin positive to left/right pot lug, etc)?
Many thanks in advance! The Music Reference is a passive-friendly amp, and I'm really up for exploring the options.
A.
Follow Ups:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2008, Audio Asylum, all rights reserved ]