ASM-1 parts question

[Tony Clark]

> Gene Stopp recommends using only metal film precision resistors on the
> ASM-1 board, which makes perfect sense to me, but my question is this:  Are
> 1/8 W components acceptable?  It seems to me that because of their smaller
> size, they will be easier to fit on the board, but I don't want to make a
> mistake in accumulating parts, or CERTAINLY not in "stuffing" the circuit
> board.

   In most all circumstances, yes.  What you have to be careful of is 
making sure that the power rating is not exceeded.  A good way to do this 
is to use the formula (V^2/R = W).
   Using this formula, W = .125W (1/8W)
   We also can assume that the max voltage we can place across a given 
resistor is Vcc-(-Vcc).  Assume 30V for this.
   Then rewrite your formula (V^2/W = Rmin) or 30V^2/.125W = Rmin.
   Your smallest sized 1/8W resistor should then be 7.2Kohms.  Of course 
this is a very cautious approach.  Typically the maximum voltage across 
any given resistor will most likely be only 15V, so that would then give 
you a Rmin of 1.8Kohms.
   Consequently, 900ohms is the smallest 1/4W resistor that should be 
used at 15V!  However, although there are some values smaller than this 
(i.e. 220ohms or even 22ohms!) the voltages across them normally can't 
reach 15V.  But I'd definately not use 1/8W resistors in their place!  
Definately not anything less than 1Kohms.

> Also, how have builders' experiences been re log vs. linear pots for the
> various panel controls?  Any feedback would be appreciated....  I'm itching
> to get started, but want to make the most researched and qualified design
> decisions I possibly can before committing to the project.

   There was a whole thread on this not long ago.  I haven't used enough 
log pots to be able to answer this well.

> I realize that these questions may be pretty stupid; many of the posts to
> this mailing list go WAY over my head.  I'm a professional musician, not an
> engineer, although I do have some electronic project building experience. 
> Sorry if I'm below the level of some of you geniuses out there, please
> indulge me!  

   That's what this list is for!  To share the knowledge!

   Tony

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I can't drive (my Moog) 55!
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Tony Clark -- clark at andrews.edu 
http://aupe.phys.andrews.edu/~clark
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