Pot rotation resistance: MOTM vs Hordijk vs Dotcom

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diophantine
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Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by diophantine »

Anyone who has used a Dotcom system and a Hordijk system knows that the pot turn resistance couldn't be more different. The Alpha pots in the Dotcom are of a standard feel, while whatever pots are used on the Hordijk spin with just a flick (very fun on the Rungler!).

How do the pots used on standard SynthTech MOTM modules fit in that spectrum? And is there a noticeable difference between the older Spectrol ones and the newer BI ones?

I've not used any MOTM, but have a number of PCBs & panels in that format (SynthTech, Blacet, Bridechamber, Synthcube, etc.) which I need to build. I want the pot rotation feel to be generally consistent between the MOTM modules I build. I'm hoping to use BI pots where I can, but where I can't are Alpha pots close enough in feel? or are the BI and/or Spectrol ones super spinney like those on the Hordijk system?
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by Dave Peck »

On the various MOTM modules that I have, there is a slight difference between pots that are mounted on the PCB and pots that are 'flying' (mounted on the panel, with wires to the PCB). Double-width modules will have one row of each type.

The non-PCB mounted pots have very low torque and spin freely, similar to pots used in Hordijk products.

The PCB mounted pots are just slightly stiffer, but not nearly as damped as pots used in Dotcom modules.

I don't have a personal preference, they are both fine with me.
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by diophantine »

Dave Peck wrote: Wed Jan 12, 2022 10:01 pm On the various MOTM modules that I have, there is a slight difference between pots that are mounted on the PCB and pots that are 'flying' (mounted on the panel, with wires to the PCB). Double-width modules will have one row of each type.

The non-PCB mounted pots have very low torque and spin freely, similar to pots used in Hordijk products.

The PCB mounted pots are just slightly stiffer, but not nearly as damped as pots used in Dotcom modules.

I don't have a personal preference, they are both fine with me.
Thanks! While I knew the original MOTM modules used a combination of Spectrol 149/148 and Bourns 95A1 for the board-mounted & flying-wire pots, respectively, I didn't expect them to really feel different, so that's good to know.

I did get some BI pots for a couple Time Machines that I need to build, but (without putting knobs on them yet) they felt a bit more stiff than I anticipated - thought they would feel more like the Hordijk. And I have a SynthCube panel PCB for the Klee, which is designed for Alpha 9mm pots, so it is mostly my OCD that is asking this question, I suppose!
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by JohnLRice »

It's been a long time since I owned that one Hordijk module I had but I have a lot of MOTM and it was joked from time to time that you could just breath on a knob and the value would change! :hihi: :eek: :rage:

Looking through my parts bins FWI, the blue Bourns pots with plastic used in a lot of MOTM modules have almost no turning torque-resistance and I really don't like them much, the BI with metal shaft have a light but nice resistance, the single and dual ganged Spectrol pot with metal shaft used in a select few places (MOTM-300 VCO I think?) have turning torque-resistance about half way between the blue Bourns and a Alpha pots, and the Vishay and Clarostat pots are getting into Alpha pot territory. It's all very subjective and will vary with pot age, ambient temperature, diameter of the knobs used, and the strength of the person turning the knobs (Mr. Burns or The Hulk? :hihi: )
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by Dave Peck »

Keep in mind that for many types of pots, the manufacturer can provide the same part in a variety of torques/dampings when the customer orders the part in quantity. So it is not always accurate to assume that 'Bourns pots feel xxx' and 'Alpha pots feel yyy' in general.
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by JohnLRice »

Dave Peck wrote: Thu Jan 13, 2022 12:17 am Keep in mind that for many types of pots, the manufacturer can provide the same part in a variety of torques/dampings when the customer orders the part in quantity. So it is not always accurate to assume that 'Bourns pots feel xxx' and 'Alpha pots feel yyy' in general.
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by cornutt »

Dave Peck wrote: Thu Jan 13, 2022 12:17 am Keep in mind that for many types of pots, the manufacturer can provide the same part in a variety of torques/dampings when the customer orders the part in quantity. So it is not always accurate to assume that 'Bourns pots feel xxx' and 'Alpha pots feel yyy' in general.
I did not know that, actually. I hope Paul Schreiber will come along and enlighten us a bit, since Bourns pots were used in a lot of MOTM modules. I have never noticed that they seemed particularly "loose", although I admit a preference for light touch, so maybe I just never noticed.

I have a couple of Modcan-A modules, and they seem to have pots with a very heavy feel, although that could be because of the small Davis knobs.
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by Dave Peck »

cornutt wrote: Thu Jan 13, 2022 6:42 pm
Dave Peck wrote: Thu Jan 13, 2022 12:17 am Keep in mind that for many types of pots, the manufacturer can provide the same part in a variety of torques/dampings when the customer orders the part in quantity. So it is not always accurate to assume that 'Bourns pots feel xxx' and 'Alpha pots feel yyy' in general.
I did not know that, actually.
Yup, I have worked on a few new product development projects that involved working with the pot or encoder manufacturer to select the version of the part with the 'right' feel for the application, get the final decision documented and set up the part number / BOM / P.O. schedule to make sure we always got that version with the approved 'feel'.

Tact switches have a similar issue - the same little pushbutton switch is often available in a variety of different tactile responses, ranging from very light to a hard 'click' that requires much more force.
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by diophantine »

Thanks Dave and John! This is all helpful.

I suppose I'll just build those two Time Machines with the BI pots and just play things by ear (or feel) from there.
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by synthetic »

I've worked on projects where everyone loved the feel of the encoder, but then we had to switch to something worse. Heartbreak.
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by BlinkyLights »

It's an underrated physical attribute of the whole shebang. Like a Ferrari vs a Yugo experience, in feel.

Some makers get it, or arrive there by accident, but man does it make a difference when it's dialed in just right.

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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by synthetic »

In the 90s I used to think, “if you put metal knobs on your mic pre you can charge $300 more.” Like when Focusrite and Avalon and stuff was coming out. Also people who sit down at a console and feel the faders go up and down. It’s important for sure.
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by diophantine »

Just to be clear, I'm not looking to have one feel vs another (I enjoy both my dotcom and my Hordijk!), just trying to keep things feeling generally consistent in this new system.
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by synthetic »

John, can you redo your chart showing Newtons of force for each pot?

;)
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

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mmmmmmpphhhh.. torque. *aaaahhh*
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by KSS »

diophantine wrote: Thu Jan 13, 2022 11:03 pm Just to be clear, I'm not looking to have one feel vs another (I enjoy both my dotcom and my Hordijk!), just trying to keep things feeling generally consistent in this new system.
Notwithstanding the reality Dave Peck brought up, I think you'll almost always find Alpha's 'heavier' to turn than BI's and other CP element pots. A quick way to get a general feel for which end of the spectrum rotary pots will fall under check their life. If it's in the tens of thousands it's likely carbon element and will generally have a higher resistance to turning than a conductive platic pot which will have a *significantly* longer life rating.

This means that if you're wanting to match up Alpha's and the others you will most likely be adding a 'friction pad' of some sort between the knob and panel on the CP pots. To bring them up to the heavier feel of the Alphas.

With faders of high quality you often have means to adjust the feel. Other sliders not so much. The friction pad methods can still work but it's tougher and the better approach is as Dave Peck outlined.
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by JohnLRice »

synthetic wrote: Fri Jan 14, 2022 3:19 pm John, can you redo your chart showing Newtons of force for each pot?
;)
ooohh, do you mean how many Fig Newtons I had to consume after turning each doodad to recover from the herculean effort? :burns:
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

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I'm gonna pretend that post was a fig-meant for my imgination.
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

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KSS wrote: Sat Jan 15, 2022 12:18 am I'm gonna pretend that post was a fig-meant for my imgination.
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

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much better!
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by Dave Peck »

KSS wrote: Sat Jan 15, 2022 12:18 am I'm gonna pretend that post was a fig-meant for my imgination.
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by modcan4ever »

Some of the Alpha-type pots eg open to the elements to some degree, will have a "grease" in them. The quantity and characteristics of the grease will affect the "feel". I would hazard a guess that the grease would also be affected by temperature and maybe humidity.
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

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modcan4ever wrote: Tue Jan 18, 2022 8:04 am Some of the Alpha-type pots eg open to the elements to some degree, will have a "grease" in them. The quantity and characteristics of the grease will affect the "feel". I would hazard a guess that the grease would also be affected by temperature and maybe humidity.
Agreed, especially on the temperature. I don't have air-conditioning for the hot summer months and I keep my house on the cool side during fall and winter (heat doesn't come on unless it gets under 58 F in the house) so the difference in feel of certain pots varies a lot with the seasons. :spin:
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

Post by josaka »

This has got to be one of the most "First World Problem" threads ever..
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Re: Pot rotation resistance: MOTM vs Hordijk vs Dotcom

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josaka wrote: Tue Jan 18, 2022 10:16 am This has got to be one of the most "First World Problem" threads ever..
Perhaps variations in rotational friction is just teary eyed commiseration. However, there is a lot to be said about potentiometer - and slider! - performance WRT construction and materials.
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