Pot 80k lin/log --> C5k

Ayra · Post by **Ayra** » 10 Apr 2025, 22:45

I put the Super Hard On inside a small 55x55x21 mm box and, not having the C5k, but also for reasons of limited available space, I would like to use one of the two very small pot of a Danelectro Rocky Road, one linear of 80kA and the other log of 80 kB. Which of the two is better to use to convert it to approximately C5k, the linear one or the audio one ? I tried a 5k resistor in parallel to 80 k linear pot between pin 1 and pin 3 but the excursion is not gradual and the gain increases only at the end, a little better with a 46k but it changes very little.

Any suggestions ?

Cub · Post by **Cub** » 11 Apr 2025, 07:48

Perhaps you could try and add another resistor between the wiper and the pin that connects to the source of the mosfet ? I'm not entirely certain about that or the value.
That little Dano pedal uses 9 mm pots, right ? Then the best solution would be to get a 5k 9mm antilog pot. Alpha makes these, you can probably find one at your usual pedal parts supplier store.

Ayra · Post by **Ayra** » 11 Apr 2025, 09:19

I know Alpha but it's a bit bulky, I was looking for a smaller one and discovered that in the drawer I have the two Danelectro pots that are much less than 9mm and would be perfect
https://ibb.co/RGJSmYr4

Vitallka · Post by **Vitallka** » 11 Apr 2025, 20:30

You can get an antilogarithmic relationship if you connect legs 1 and 2 of an 80K linear potentiometer with a 5.6K or 5.1K resistor. Connect the transistor source to the second leg of the resulting potentiometer, and connect the first leg of the potentiometer to ground.
Although, I would change the booster circuit so that no DC current flows through this potentiometer and causes noise. To do this, the potentiometer can be replaced with a 4.7K constant resistor, and a capacitor leg, say 47-100 μF, can be connected to the transistor source, and the other leg of the capacitor connected to ground through the potentiometer

Ayra · Post by **Ayra** » 11 Apr 2025, 23:08

Vitallka wrote: ↑11 Apr 2025, 20:30 You can get an antilogarithmic relationship if you connect legs 1 and 2 of an 80K linear potentiometer with a 5.6K or 5.1K resistor. Connect the transistor source to the second leg of the resulting potentiometer, and connect the first leg of the potentiometer to ground.

...and leg 3 of the pot ? With leg 3 floating the volume is almost at maximum and does not change if I rotate the pot.

Ayra · Post by **Ayra** » 12 Apr 2025, 12:57

mike25 wrote: ↑12 Apr 2025, 07:00 Use the 80kB log pot wired in reverse — that gets you closest to the feel of a C5k.

Thanks but i had already tried it and same result, in the end it's like a switch.

Vitallka · Post by **Vitallka** » 12 Apr 2025, 17:59

You can attach a 1.5K-2.2K resistor to the linear potentiometer between the third and first legs. This will reduce the adjustment range, but this way the booster will respond more sensitively to turning the potentiometer knob.

Ayra · Post by **Ayra** » 12 Apr 2025, 21:34

Vitallka wrote: ↑12 Apr 2025, 17:59 You can attach a 1.5K-2.2K resistor to the linear potentiometer between the third and first legs. This will reduce the adjustment range, but this way the booster will respond more sensitively to turning the potentiometer knob.

Thank you for your interest but unfortunately not works, the sweep always focused at the end, from 3 o'clock to 4 o'clock and with both linear and log.

Vitallka · Post by **Vitallka** » 13 Apr 2025, 04:09

If you had enough space in the box, then, as an alternative, you could assemble a booster according to this scheme and a potentiometer with a logarithmic dependence would fit there very well.

Ayra · Post by **Ayra** » 13 Apr 2025, 10:45

Thanks but the box is very small, i know the Super Duper but if i don't have space for a pot let's not talk about it for two

Vitallka · Post by **Vitallka** » 13 Apr 2025, 12:17

And try another idea: in a logarithmic potentiometer, connect the first and third legs with a 4.7k resistor. Connect the third leg to ground, and connect the second leg to the source of the transistor.

Ayra · Post by **Ayra** » 13 Apr 2025, 17:19

So, at minimum, at 7:30, there is a little bit of signal, then it almost disappears and then returns to 3 o'clock and increases rapidly to maximum at 4:30. With the R between 1 and 3, I shorted legs 1 and 2, and so the pot starts at minimum but does not disappear and remains constant until 3 o'clock, and then increases rapidly to maximum.

Ayra · Post by **Ayra** » 15 Apr 2025, 16:46

The result at minimum is below unity and I thought I could be satisfied but the transition to unity is not at all easy and it is easy to find yourself with a volume that increases too suddenly.

Goldschitter · Post by **Goldschitter** » 16 Apr 2025, 04:02

Why not just use Soulsonic's "Crackle Not Ok" circuit instead? Wire the source to ground and use 150K or even 220K resistors as the gate dividers. Sure the input impedance will be low but slap a JFET buffer on the front and you can make it as high as you want, 5meg like the SHO or higher even. The genius of Soulsonic's design is it doesn't make a shitload of noise when you adjust the gain, and the pots you're apparently stuck using will work way better than what you're currently trying to get them to do.

Ayra · Post by **Ayra** » 16 Apr 2025, 11:47

I tried but I had some problems due to some bad welding I think, then I didn't have time and then I put it aside.

Pratically, I am limited by the size of the pedalboard and consequently by the size of the box that must contain the PCB which in turn cannot be larger than the dimensions I mentioned at the beginning and therefore the potentiometer must necessarily be of the miniature type.