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Another $2 tweak [message #31031] Mon, 21 March 2005 09:16 Go to next message
GarMan is currently offline  GarMan
Messages: 960
Registered: May 2009
Illuminati (2nd Degree)
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.

yes... [message #31032 is a reply to message #31031] Mon, 21 March 2005 13:27 Go to previous message
PakProtector is currently offline  PakProtector
Messages: 935
Registered: May 2009
Illuminati (2nd Degree)
I have used it before acquiring a good volume pot. A 100k resistor can also be used with the 50k pot. The variability of the input impedance is a very small issue IMO.
regards,
Douglas

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