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 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
Pots quality
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whomper



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PostPosted: Tue Jul 29, 2008 11:36 pm    Post subject: Pots quality Reply with quote  Mark this post and the followings unread

I have built several CGS modules and have used pots of brand Alpha as they are very cheap compared to costly alternatives.

My main concern here is the effect on module and sound quality of cheaper mechanics.

Is there any difference in accuracy and more importantly for me, sound quality, of using brands such as Spectrol or Bounrs over what I have been using? Is the investment worth the difference?

I would be greatly interested to hear your views.

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CJ Miller



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PostPosted: Wed Jul 30, 2008 3:38 am    Post subject: Reply with quote  Mark this post and the followings unread

Cermet or conductive plastic is going to be more accurate than carbon. Keep in mind though that there is a lot of vintage and modern equipment out there which has used carbon pots, and caused no complaints. Hardly anybody actually wears out pots, but they more often get dirty and/or corroded. I am not very keen on wirewound pots, due to issues with accuracy and feel. Even if your Alphas aren't sealed, if they are at least covered, kept out of damp, and played every so often they will probably cause you no problems. Alphas offer a tactile resistance when turning which I find pleasant.

I would much prefer getting better pots myself, but as I'm sure you've noticed, the other big difference is price. My modular is in its infancy so there are still other parts to get. When I had more money months ago, I was thinking of buying a quantity of good pots, but decided on buying a sack of a few hundred Alps carbon pots for like $30. This way my modular gets built sooner, and if I really need better pots I'll buy them in a few years.

For things like VCOs, pitch controls, modulators, etc I suspect that accurate pots do make a difference, but don't know how much. I don't have a musical background, and would hardly know "in-tune" if I heard it. If you have a strong sensibility for musical pitch it might be worth the extra expense.
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andrewF



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PostPosted: Wed Jul 30, 2008 7:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Just another opinion - if you are really concerned about sound quality and noise, build or buy the best power supply you can get and think carefully about panel wiring.
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whomper



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PostPosted: Wed Jul 30, 2008 8:14 am    Post subject: Reply with quote  Mark this post and the followings unread

Can you elaborate a little about panel wiring? what are the best practices involved?
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andrewF



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PostPosted: Wed Jul 30, 2008 5:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

Maybe the best way is NO panel wiring - all board mounted components.
but that is not always possible, try using twisted pairs - one wire to ground the other is active, this is a cheap but effective option, you can easily buy multi-core cat-6 cable (maybe it is cat-7 now?), strip the outer sheath and find 4 or 5 twisted pairs inside.
Or use shielded core wire, more expensive etc.

Of course keep the wiring as short as possible.

I don't bother with shielded core, I use cat-6 or recycle wire from dead PCs.
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211



Joined: Jul 18, 2006
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PostPosted: Thu Jul 31, 2008 2:44 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi all,

Is there a mechanic quality difference between Alpha's 16mm and 24mm pot ? My 16mm tend to die too fast.

24mm are stronger ? or have more reliable carbon tracks ?
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CJ Miller



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PostPosted: Thu Jul 31, 2008 4:04 am    Post subject: Reply with quote  Mark this post and the followings unread

211 wrote:
Hi all,

Is there a mechanic quality difference between Alpha's 16mm and 24mm pot ? My 16mm tend to die too fast.

24mm are stronger ? or have more reliable carbon tracks ?


Yes, in my experience the 24mm are much stronger. Thanks for reminding me, I had forgotten about the 16mm ones. Those were flimsy. Some all-plastic Piher pots are garbage also. The 24mm ones I bought from Radio Shack years ago have no problems, but I haven't sampled them lately.
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211



Joined: Jul 18, 2006
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Location: Marseille - France

PostPosted: Thu Jul 31, 2008 5:51 am    Post subject: Reply with quote  Mark this post and the followings unread

You're right CJ Miller, those Black plastic Piher PC16 are eye candy, but really bad.

Sadly, Alpha 16mm are usefull because 2 of them can fit on 1U width Motm/dotcom panels with 2 small knobs.

But now I'll go for 24mm ones for critical knobs.

Thanks for your advices !
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Rykhaard



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PostPosted: Thu Jul 31, 2008 8:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Thank you greatly for mention of the quality on a couple of the plastic and 16mm pots! I've debated in the past, getting some 16mm's. Shocked Sad I wont, now.

Last night at work I was checking out the latest announcements on the new Bourns updates. I was quite impressed by the pricing. A rock solid 10 turn pot, good for 2,000,000 full rotations for $14 Canadian. (Fairly much the same currently in U.S. and Aus.)

Outside of fine tune, I'm trying to think if there're any other places that I could really use. I'd like to get a couple. Smile
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neandrewthal



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PostPosted: Thu Jul 31, 2008 10:50 am    Post subject: Reply with quote  Mark this post and the followings unread

CJ Miller wrote:
211 wrote:
Hi all,

Is there a mechanic quality difference between Alpha's 16mm and 24mm pot ? My 16mm tend to die too fast.

24mm are stronger ? or have more reliable carbon tracks ?


Yes, in my experience the 24mm are much stronger. Thanks for reminding me, I had forgotten about the 16mm ones. Those were flimsy. Some all-plastic Piher pots are garbage also. The 24mm ones I bought from Radio Shack years ago have no problems, but I haven't sampled them lately.


Oh crap. I just switched to 16mm so I could pack them tighter, and they feel way better! I really can't stand the feeling of the 24mm anymore now that I have the smooth 16mm. On top of that I just switched to smaller knobs. The 16mm pots still feel a little tight with small knobs. The 24mm feel tight even with big knobs. I don't even want to know what a small knob on a 24mm feels like.

Anyway, where are you guys getting your alpha pots. Does anyone know if the ones from small bear are better than the cheaper ones from futurlec?

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CJ Miller



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PostPosted: Fri Aug 01, 2008 5:20 am    Post subject: Reply with quote  Mark this post and the followings unread

neandrewthal wrote:
Oh crap. I just switched to 16mm so I could pack them tighter, and they feel way better!


Well, they may or may not be the same ones I used. They make a variety of pots , I've liked some but not others.

If you want to save space I really recommend 1/8" pots! It is quite easy to score high quality pots surplus without spending much money. A high-quality 1/8" pot will probably last longer than a low-quality 1/4" one. If I was making a real gigging synth which was going to get dragged and thrown around I'd go for something more rugged, but in a home or studio environment these pots can last. I have even bought some knobs which were actually about 0.3" wide, which is the smallest I have ever seen!

Because they are so small, I usually try to save my good 1/8" pots for modding equipment, since it is so much easier to squeeze them in.
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neandrewthal



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PostPosted: Fri Aug 01, 2008 10:08 am    Post subject: Reply with quote  Mark this post and the followings unread

CJ Miller wrote:

If you want to save space I really recommend 1/8" pots! It is quite easy to score high quality pots surplus without spending much money.


Interesting. What brands would you recommend and where do you get them?

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CJ Miller



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PostPosted: Tue Aug 05, 2008 2:48 am    Post subject: Reply with quote  Mark this post and the followings unread

neandrewthal wrote:
Interesting. What brands would you recommend and where do you get them?


New, they'd cost a lot, just like good 1/4" pots. But they appear as surplus inventory more often. Brands from usual suspects: Bourns, Spectrol, Clarostat, Allen Bradley, etc. Got them from ebay auctions, places like All Electronics and Electronics Goldmine. I don't see much out there now, but they do turn up. It hasn't been unusual for me to find high-end 1/8" pots for between $1-$2 each. One time I bought 150 Clarostat 100k pots, really nice ones, for $35 - which would have ordinarily bought me two or three of them.
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fonik



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PostPosted: Tue Aug 05, 2008 4:45 am    Post subject: Reply with quote  Mark this post and the followings unread

andrewF wrote:
...you can easily buy multi-core cat-6 cable (maybe it is cat-7 now?), strip the outer sheath and find 4 or 5 twisted pairs inside.

thank you andrew for mentioning that.
i got about 30 feet CAT-7 cable left from wiring my house and it didn't occur to me to use it for wiring my modules!!!

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Funky40



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PostPosted: Fri Aug 08, 2008 6:01 am    Post subject: Reply with quote  Mark this post and the followings unread

211 wrote:
Hi all,

Is there a mechanic quality difference between Alpha's 16mm and 24mm pot ? My 16mm tend to die too fast.

24mm are stronger ? or have more reliable carbon tracks ?


I asked the very same question in a (the) german Synth DIY community.
there was not really an answer from the electronic specailist(s)

Now i have used so around 200x 16mm Alphas, and i have over 100x 16mm Alphas allways in use in my System.
I'm a extreme knob twiddler when patching. i use my Synth as others do with their Virus C.

I've never had one failure. I DIY since 2 Years.
the 16mm alphas are much smoother to turn then the 24mm Alphas.
With small Knobbs even the 16mm alphas could be smootherfor knob twiddling, but it's ok.
the 24mm Alphas would fit into my Knobspacings too, but they are to strong to turn.

Assuming that i have to replace 1-3 pots per Year would be ok for me.
No reason to get into panic.
I would be more if i'd used the 248series spectrols. about those i know a bad story.
Lots of failures ......there was aSynth built with those ( i had one too, and i had failures too . might be that it was just one bad batch.....)
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