So I tried this with my homemade amp a short while ago after getting some new 100k POTs that are linear type B ones since my original became quite scratchy and was cutting out from being a used part.
Put a 47k resistor from the middle POT pin to ground of it in my circuit and it performs surprisingly well.
Is it log? Hell if I know, but it does ride the volume up much more slowly until it reaches a point where ears and linear pots don't match and it ramps it up properly to my ears.
I made sure to first do a line load test and put a 47k resistor across the line inputs to my amp with volume at max and input set low and dumped the 47k across it and it didn't decrease volume level so there seems to be no issue with pull-down or impedance issues.
Curious how many of you have done this to convert linear volume potentiometers to pseudo log types and your experience.
For those lost to what I am talking about here is some essential reading in my opinion..
http://geofex.com/Article_Folders/potsecrets/potscret.htm
Put a 47k resistor from the middle POT pin to ground of it in my circuit and it performs surprisingly well.
Is it log? Hell if I know, but it does ride the volume up much more slowly until it reaches a point where ears and linear pots don't match and it ramps it up properly to my ears.
I made sure to first do a line load test and put a 47k resistor across the line inputs to my amp with volume at max and input set low and dumped the 47k across it and it didn't decrease volume level so there seems to be no issue with pull-down or impedance issues.
Curious how many of you have done this to convert linear volume potentiometers to pseudo log types and your experience.
For those lost to what I am talking about here is some essential reading in my opinion..
http://geofex.com/Article_Folders/potsecrets/potscret.htm
Last edited:
47k is to large of a resistor on a 100k pot if you want to emulate an audio taper, it should be more like 10k to 20k. More info here: Potentiometers (Beginners' Guide to Pots)
Mike
Mike
Well in this case I kind of like the effect between the low and high value.
Regular linear POT has too large of a non-log effect.
Resistance values below 35-47k seem to have too high of a jump from smooth to loudness.
I figure it is kind of between extremes. Maybe it is the loading on the input to the volume control or something else along the path, but it just sounds right with half the value of R across the POT volume control.
Below 35k or so I start to notice some volume loss on full dial volume also, so it may be a trade off.
I tried 15k and 22k and they made little difference. The detrimental point seemed to be below 15k and above 47k when it came to making it sound smoother to the ear when playing with the volume dial. I figure there is a bit of play there considering the wide variance in resistance on the POT.
Last edited:
Hi, +1 in general advice, around 15% bypass is best, rgds, sreten.
Last edited:
Most Sources can drive 10k and the cable.
That gives one a lot of leeway in choosing a vol pot.
Take a 100k vol pot feeding a 47k Rin amplifier.
When turned up to max volume the Source sees 100k||47k||cable capacitance or about 32k||500pF
Adding on a 15k log faking resistor changes the loading to 100k||47k||15k||cable capacitance or about 10k||500pF
Any competent Source should easily drive that loading.
If not then buy a new Source with adequate cable driving capability.
The cable probably draws more current than the 10k equivalent.
The 10k only draws 0.3mApk on typical CDP @ 0dBfs.
That gives one a lot of leeway in choosing a vol pot.
Take a 100k vol pot feeding a 47k Rin amplifier.
When turned up to max volume the Source sees 100k||47k||cable capacitance or about 32k||500pF
Adding on a 15k log faking resistor changes the loading to 100k||47k||15k||cable capacitance or about 10k||500pF
Any competent Source should easily drive that loading.
If not then buy a new Source with adequate cable driving capability.
The cable probably draws more current than the 10k equivalent.
The 10k only draws 0.3mApk on typical CDP @ 0dBfs.
Last edited:
I know this is an old thread but I wanted to let you know that I tried a 100k resistor with a 500k pot and the taper seems to work fine. I am using it for guitar tone control.
It is a better aproximation of a log scale than a normal log pot, which usually consists of two 'speeds' only
Most “log” pots have two sections in series. A high ohm and a lower ohm. Makes a log faking pot.
This is cheaper than cutting the element to make real log taper.
This is cheaper than cutting the element to make real log taper.
Thank you for this information. I went with the 1/5 value resistor and got good results with my linear pot.
While this thread is back up, let me note that this "trick" is good for a control range of perhaps 30 dB only. Probably good enough for something like a 20 dB input level trim, but good log pots will cover 50-60 dB or more.
Not a good solution: the extra resistor pulls current through the wiper, which create contact rectification/distortion.
I see your point, but I found it to work very well. First encoutered the idea here
Potentiometers (Beginners' Guide to Pots)
Look under "changing the law". Bar the non substantial error, otherwise it's great.
For a limited time because of wear due to current in the wiper.
I highly recommend the Baxandall's pseudo-log active volume control where the cursor ils loaded by a very impedance.
