MOTM

Hello all,
  I was just wondering when you would choose to use a spectrol 149 
series pot over the bournes pots. Thanks
dave

Several reasons:

a) the Spectrol are available in cermet (149 series). These are more temperature stable than
conductive plastic. Also, when I was first looking at pot choices, Bourns were custom ordered
(still are!) with a staggering 18 WEEKs lead time (shortened to 14 now).

b) The Spectrol pots I could order from Mouser in small quantities.

Paul S.

----- Original Message -----

From: "dave_oleksy" <faldska@...>
To: <motm@yahoogroups.com>
Sent: Tuesday, October 29, 2002 1:14 PM
Subject: [motm] Pots


> Hello all,
>   I was just wondering when you would choose to use a spectrol 149
> series pot over the bournes pots. Thanks
> dave
>
>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>

--- In motm@y..., "Paul Schreiber" <synth1@a...> wrote:
> Several reasons:
> 
> a) the Spectrol are available in cermet (149 series). These are
> more temperature stable than conductive plastic. Also, when I was
> first looking at pot choices, Bourns were custom ordered (still
> are!) with a staggering 18 WEEKs lead time (shortened to 14 now).


OK - to add something to this question: I assume the Spectrol pots 
are available in both cermet and conductive plastic?  If so, why not 
(for example) use only the Spectrol pots?

I am mostly curious due to the recent discussion on AH - the Bourns 
and Spectrol pots certainly feel different.  I think I prefer the feel 
of the Bourns pots (as someone said - they are very "silky", like the 
faders on an audio console.) The Spectrol 149 pots seem much more 
damped (more resistance) and the Spectrol 248? even more so.

Personally, I don't think I like the "damped" feel as much - but what 
is really odd is going between the Spectrol and Bourns is like a night 
and day difference.  Seems like it would be preferable to have a 
consistent feel?

Seth

Paul--

Are you saying in general, you would have used all
Bournes parts if they would have been feasible and
readily available????

--Shemp

> a) the Spectrol are available in cermet (149
> series). These are more temperature stable than
> conductive plastic. Also, when I was first looking
> at pot choices, Bourns were custom ordered
> (still are!) with a staggering 18 WEEKs lead time
> (shortened to 14 now).
> 
> b) The Spectrol pots I could order from Mouser in
> small quantities.


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I offer replacement pots (both Spectrol and Bourns) for $6.50ea. And, if you need a manual for a
purchased module(s),  send me an email.

Paul S.

To expand on Paul's answer:

You would use a cermet pot (149) in your coarse and fine tuning VCO 
controls (if you want it as stable as possible, that is).

Moe

----------------------------------
Several reasons:

a) the Spectrol are available in cermet (149 series). These are more
temperature stable than
conductive plastic. Also, when I was first looking at pot choices, 
Bourns were
custom ordered
(still are!) with a staggering 18 WEEKs lead time (shortened to 14 
now).

b) The Spectrol pots I could order from Mouser in small quantities.

Paul S.

----- Original Message -----

From: "dave_oleksy" <faldska@y...>
To: <motm@yahoogroups.com>
Sent: Tuesday, October 29, 2002 1:14 PM
Subject: [motm] Pots


> Hello all,
> I was just wondering when you would choose to use a spectrol 149
> series pot over the bournes pots. Thanks
> dave
>

--- In motm@y..., "Paul Schreiber" <synth1@a...> wrote:
> I offer replacement pots (both Spectrol and Bourns) for $6.50ea.
> And, if you need a manual for a purchased module, send me an
> email.  [...]

Some of you are probably confused by this response and are thinking, 
buy replacement pots? Huh? And as you might expect, there is a little 
more to this story!

Right after posting the "why not just use one brand" question, I 
called Paul expecting to ask a completely different question.  
However, "Spectrol vs Bourns" still seemed to be on his mind - so here 
is my summary of potentiometers 101:

There are essentially two base technologies: cermet and conductive 
plastic.  (This refers to the type of electrically resistive element 
used inside the potentiometer.)  Conductive plastic has the longest 
life so, all else being equal, it is the technology of choice!  
However, all else is almost never equal.  Cermet offers significantly 
lower electrical noise (Paul claims 10x) and, as such, it is preferred 
in a few critical applications such as tuning the frequency of an 
oscillator or filter.  (But you already knew this based on other posts 
to this thread.)


So, why choose one *brand* over the other?  Here are the details:

Spectrol offers conductive plastic elements (148 series) and cermet 
elements (149 series) in an otherwise equal form factor.  These 
Spectrol pots are only available with PC board "pins" - that is, 
intended to mount directly to a printed circuit board.  The standard 
Spectrol 148 and 149 series pots are linear taper.  Log taper is only 
available by special order and you must commit to quantity.

Bourns only offers conductive plastic elements.  Bourns pots are 
available with PC board "pins" AND with solder tabs for termination to 
wire.  Bourns pots are always "special order" (no distributor stock) 
but are available in both linear and log taper configurations.

The form factor (specifically, the distance from the centerline of the 
shaft to the base of the pot) is different between the Spectrol and 
Bourns pots and, as such, it is not possible to mix and match the two 
brands of pots on the same printed circuit.


So as it turns out, there does seem to be valid reasons why you might 
choose one brand over the other based on the requirements of a 
particular module.  (A specific example from Paul - EGs need large 
value log taper pots and it is expected that these pots will get a lot 
of use.  In this case, Bourns is the preferred solution as these are 
the long life conductive plastic and log taper is available as a 
standard configuration.  Sure enough, there are board mounted Bourns 
pots in the 800 EG!  In other modules where there is a mix of cermet 
and conductive plastic types mounted to the circuit board, the 
Spectrol types are used.)


Fine - but you are probably still wondering about the replacement pot 
comment?  Notice in my original question that I mention the Spectrol 
248 series - specifically, that I found the 248 series to be 
particularly stiff.  Wait a minute, what is the 248 series???  Well, 
it turns out that very early on (before Paul managed to convince 
Spectrol to build 148 series 100k log pots) some modules were built 
with this 248 series.  This Spectrol 248 series has a plastic busing 
around the shaft where all the other types have a metal busing - 
logically, this explains the difference in feel.  The 148 and 248 seem 
to be interchangeable otherwise.

Because the 148 series log pots are special order, I asked Paul if I 
could purchase a few of these from him should I decide that I really 
can't stand the feel of the 248 series.  He agreed, which I think is 
pretty damn nice of him!


Paul also agreed to provide me with a copy of the MOTM 300 assembly / 
calibration / operation manual - which was the real reason that I 
called him.  My MOTM setup doesn't have any VCOs yet and, as Cuari has 
put his MOTM system up for sale, I offered to buy a bunch of VCOs from 
him.  (He didn't have the module documentation - and I wanted to be 
sure I could get a copy just in case.)  So, now that I have some 
VCOs on the way I can really make some noise!  Oh wait, I still need 
to work on that patch cable deficiency... ;)


Seth

Kenton has discontinued the Pro-4 and is no longer
doing retrofits.  Are they winding down business
altogether?  What gives?

Below is a little article from Future Music.

--Shemp

 
 
 
September 12, 2002
Kenton discontinues retrofit kits, your last chance to
retrofit....

After 16 years of supplying MIDI retrofits for most of
the popular pre-MIDI analogue synthesisers, Kenton are
to discontinue the production of the retrofit kits
when the current stocks of circuit boards and 

components have been exhausted. For most models this
is expected to be at the end of this year, although
some models have gone already. If you have been
postponing getting your synth retrofitted, this is
your last chance as the retrofit kits will disappear
from the Kenton price list when the 2003 list is made.
Kenton's range of socket kits is unaffected by this
announcement. 

For more information please call freephone
08000-KENTON (08000-536866) or email
sales@....
 


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The BBC Radiophonic Workshop has just released
(November 26, 2002 in the US) a CD (also available on
vinyl) containing highlights of some of their more
experimental sounds.  It looks like it should be worth
checking out.

     http://www.amazon.com/exec/obidos/ASIN/B00006L9TM

In the UK:

    
http://www.amazon.co.uk/exec/obidos/ASIN/B00006L9TM


Some very good info on the BBC Radiophonic Workshop
can be found here:

http://www.glias.org.uk/glias/rws/pgs/a_toc.htm

Track Listing----
 1. La Grande Piece de la Foire de la Rue Delaware -
Malcolm Clarke
 2. Brio - John Baker
 3. Adagio - Dick Mills
 4. Geraldine - Roger Limb
 5. Bath Time - Malcolm Clarke
 6. Nenuphar - Glynis Jones/Malcolm Clarke
 7. Accentric - John Baker
 8. Major Bloodnok's Stomach - Dick Mills
 9. The Panel Beaters - Paddy Kingsland
10. Crazy Dazy - Dick Mills
11. Veils and Mirrors - Glynis Jones
12. Romanescan Rout - Malcolm Clarke
13. Schlum Rooli - Glynis Jones
14. Kitten's Lullaby - Roger Limb
15. Chino - John Baker
16. Waltz Antipathy - Richard Yeoman-Clark
17. The World of Science - Paddy Kingsland 


--Shemp (aka "The Panel Beater")

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