[sdiy] Group buys: Alpha-style, dual pots, and Joysticks (WAS: RE: Dual-gang reverse-log pot group buy ?)

[Tom Wiltshire]

Be careful not to confuse Alpha Taiwan Electronics Ltd with Alpha  
Products Inc, CA. Both companies produce similar pots, and I was told  
by Alpha Products that both companies have their manufacturing  
facilities in China.

http://www.taiwanalpha.com/en/product.htm
http://www.alpha-products.com/Products/VU-Pots/vu-pots.html

They both produce "Alpha" pots. The Alpha Taiwan ones have a  
lowercase courier "a" in a circle on them. The Alpha Inc ones have a  
greek letter alpha, I think.
Some people also get confused with Alps pots, since "Alp" could be  
taken as short for Alpha.

http://www.alpsusa.com/

I hope this helps. I know I had it all tangled up for a long while.

Regards,
Tom




On 18 Nov 2008, at 14:47, flightofharmony wrote:

> Comments inline
>
> -> -----Original Message-----
> -> From: David G. Dixon [mailto:dixon at interchange.ubc.ca]
> -> Sent: Monday, November 17, 2008 10:43 PM
> -> To: 'flightofharmony'; 'Andre Majorel'
> -> Cc: synth-diy at dropmix.xs4all.nl
> -> Subject: RE: [sdiy] Group buys: Alpha-style, dual pots, and  
> Joysticks
> (WAS: RE:
> -> Dual-gang reverse-log pot group buy ?)
> ->
> -> flightofharmony asked:
> ->
> -> >> I don't know - what markings do they have on the case? <<
> ->
> -> They have no markings on the metal canister (which is a gold  
> color), and
> -> "B100K" in white letters on the top front of the plastic pc- 
> board part of
> -> the pot.  (I only have B100K versions of this particular pot.)   
> I have a
> -> feeling that they are the same pots that Futurlek sells (they look
> exactly
> -> the same based on the pictures of the latter I've seen on the web).
>
> A good rule of thumb: Always avoid unmarked components, with marked  
> ones at
> least you know who to avoid should they be garbage.
> Futurlec sells Alphas though. In my quest for pots I found  14  
> different
> manufacturers that make pots identical to Alpha - does anybody know  
> who
> developed this design first?
>
> Anyway, the Song-Huei pots  have a stylized "SH" stamped in the  
> back cover,
> and GH have a - wait for it - "GH" stamped in the back cover.
>
> -> The problem with them is that they do not appear to admit  
> desoldering and
> -> reuse, and I'm not really even sure that they work terribly well  
> the
> first
> -> time.  It would seem that the resistive strip becomes  
> disconnected from
> the
> -> riveted metal pins after soldering.  Perhaps some of the plastic  
> from the
> -> pc-board part of the pot is getting between the two and breaking  
> the
> contact
> -> (some of the plastic seems to "boil" if the soldering iron is  
> held on the
> -> lug long enough to flow the solder joint -- these are all pc- 
> mount pots,
> by
> -> the way, including the Alphas).  If I pull on the wires, I can  
> sometimes
> -> reestablish the connection.  For example, if this pot is a  
> frequency knob
> on
> -> a VCO, then pulling on the wires causes the frequency to go  
> sharply up or
> -> down as the contact is reestablished and rebroken.  Sometimes, just
> jiggling
> -> the wires causes the same effect.
> ->
> -> At least 33% of these pots failed to work after rewiring a panel.
> However,
> -> none of the Alpha pots I used (all the non-B100K pots on the  
> panel, as it
> -> happens) failed to work upon reuse.  I'm sold on Alpha pots, and  
> every
> -> synth-diy'er I know swears by them, so they seem like a very  
> safe buy.  I
> -> would say that it's definitely worth an extra dime or two per  
> pot to get
> -> reliable performance and avoid having to redo panels!
>
> I remember when you posted about those issues.
>
> To be honest, I have always disliked Alphas. The construction is  
> erratic,
> stamping tolerances are sloppy, even the rotational torque is widely
> inconsistent (from tight to almost freewheeling). In one bag,  
> direct from
> the Thailand factory, some had gold covers, others silver; some  
> stamped with
> the little "a" in a circle, some with the word "alpha", some with  
> the value
> stamped as well (but only the B100k, none of the others), and some  
> that were
> not press-stamped, just ink-stamped; two different shaft lengths  
> when I only
> ordered one; nuts and washers of different materials and stamping  
> processes;
> some with mangled mounting pins - a couple had the pin-mount  
> portion of the
> PCB broken completely off; loose rivets on the PC pins, and  
> different styles
> of said rivets.
>
> Hell, even the font and ink used to print the resistance value on  
> the front
> PCB vary greatly. The same for shaft wobble.
>
> I ordered some of the 0.25" round shafts from Mouser once. They  
> came with
> much nicer quality nuts & washers than any others I had seen on  
> other shaft
> styles, so yet another incongruity. The washers were still sloppy  
> and, when
> I tightened the nuts, the threads stripped out of the nut before  
> they were
> anywhere close to being tight enough to prevent movement of the  
> frame. The
> 0.25" shaft uses the same bushing as the 6mm shafts,  but the shaft  
> is ~6.35
> mm. Allow for manufacturing variances and you have around  
> 0.2mm-0.3mm height
> of thread (made of low shear strength pot metal) to fix the pot.
>
> Alpha has factories in Thailand, Taiwan, Hong Kong, and Guangdong &  
> Shanghai
> in China, maybe others as well. You never know what you will get.
>
> Both the Song Huei and the G&H pots have some tiny features that  
> show a bit
> more attention to usage issues that the Alphas I have seen did not:  
> The PC
> mounting pins have anti-rotation bumps around the rivet point (the
> electrical connection can be greatly compromised if you force the  
> pin to
> rotate around the rivet); the aforementioned I.D. tolerance on the  
> panel
> washer; and, from what I've seen, consistency!
>
> Your Alpha mileage may vary : )
>
> I just like to make sure to keep everything in perspective. By the  
> way, did
> anyone here check out the GH booth at NAMM 2008 in LA and have an  
> opinion to
> share?
>
> ~flight
> flight at flightofharmony.com
> http://www.flightofharmony.com
>
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