Posted by GarMan [ 216.13.136.38 ] on March 21, 2005 at 10:16:28:
I did a tweak on my Grounded Grid preamp this weekend that not only cost just $2, but gave a noticable improvement. The tweak is nothing new and even has a name for it, but I'm too lazy to look up the name.
Until I get my act together to order a good pot, I've been using the $1 versions from a local surplus store. I reconnected the pot this weekend so that the input signal bypasses the cheap pot altogether.
Material required: 2 high quality 50K resistors, 1 50K pot
Connection:
Input to one end of 50K resistor
Other end of 50K resistor to wiper of pot (centre)
Input of gain stage to wiper
Ground prong 3 of pot
Leave prong 1 of pot disconnected
This as the effect of varying the input voltage without the signal going through the pot at all.
Downsides are minor:
Input impedence varies between 50K at no volume to 100K to full volume
Full volume is -6dB attenuated (vs. 0dB)
Improvement is most noticable when you're using cheap crappy pots. This may not be as good as using a high quality stepped attenuator, but it's a hell of a lot cheaper.
Gar.
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