I finally got around to upgrading my VCI to rotary faders instead of sliders. I’m a house DJ and have played on rotary volume mixers for the past 12 years. My mixers have all been vestax… PMC-17 with rotary, PMC-26, PMC-25 with rotary, and now VCI-100R.
The mod is simple. Purchase 10K audio (log) potentiometer, I used alps. You only need a mono pot as the VCI has no real stereo sound going through it. I pulled my knobs from the PMC-26 and milled the black cover plate on a cnc mill.
Hey finetuning vci looks awesome…i was thinking of doing the same mod myself on a vci 300 any chance you can give me the link to buy these pots cant find them anywhere ???
Are you sure about the Log pots? The VCI doesn’t do anything with audio loudness, it just converts the voltage across it into a value to send as MIDI. I would have thought the sliders were linear 10K.
Basically all the controls (Dials, faders, buttons) on the VCI are analog then they are decoded to digital for the USB output. Why didn’t they use digital encoders since the VCI has no audio passing through it??? I suspect they designed it this way because the analog parts are cheaper and Vestax probably has a ton of the parts form the analog mixers. Plus the analog parts keep the same feel as the other mixers in their line.
So they use a mono pot, but the wiring is unconventional. typically you attach two wires to a pot. The VCI uses three, thus using both sides of the log pot. Wire 1&2 is for standard log curve and wire 2&3 is for reverse log curve. They are superimposing two log curves to create a linear response and then doing the analog to digital conversion. I think this has more accuracy than linear pots. Correct me if I’m wrong.
The end result is smooth transition of volume from zero degrees to 300 degrees rotation.
Nicely done! I want to get into modding but sort of afraid to do anything serious. Namely I want to convert some existing knobs to never-ending knobs like the jogs.
nice mod mate…would love to see a full description of how you made the mod…how about using alps pots like used in the old school urei rotary mixer? is that possible??? great job btw…
Nice mod! .. i prefer faders, but it looks sweet as
Rather than create a new thread, thought i’d ask here:
Can anyone shed light on what i’d need to do to change the small black rotaries on the VCI-100 to be the same type as the others? - The main ones i’m wanting to change are the 2 in the middle of the EQ section
The hard way is to replace the small potentiometers on the circuit board with new ones that are the same as the other larger ones on the board. I’m not sure where to get the exact replacement rotary parts Vestax uses. The old pots would have to be de-soldered from the circuit board and then replaced with new ones. Part clearance may be an issue.
The other way would be to make an adapter that can attach onto the small black rotary and then attach to the new bigger knob. This may be less stable, although its worth a try…
I may try the easy version myself since I have access to lathes and mills. I’ll post the response when I finish them.
[QUOTE]So they use a mono pot, but the wiring is unconventional. typically you attach two wires to a pot. The VCI uses three, thus using both sides of the log pot. Wire 1&2 is for standard log curve and wire 2&3 is for reverse log curve. They are superimposing two log curves to create a linear response and then doing the analog to digital conversion. I think this has more accuracy than linear pots. Correct me if I’m wrong.
[/QUOTE]
This is the wrong way of looking at it, in an analogue audio circuit decreasing the volume of a signal is acheived by limiting the current. So thats why most of the time the configuration in an analogue mixer will only use 2 of the three pins found on every potentiometer, it is acting as a variable resistor.
When making a midi controller the information you want from the pot is its current rotational position, this can be found by measuring the potential (voltage) from the wiper (center pin) to on of the other pins.
To measure a potential you have to have a reference voltage, so the end pins will be connected to the a/d reference power supply, and to ground.
I would say linear pots would be best in this application, I believe tracktor processes the midi for the level control to mimic the logarithmic response of many analogue mixers, so by using the log pots you will increase this effect even futher, this may be what you like however.
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