[sdiy] CV offset question.

[Magnus Danielson]

From: harrybissell <harrybissell at prodigy.net>
Subject: Re: [sdiy] CV offset question.
Date: Sun, 20 Nov 2005 12:30:09 -0500
Message-ID: <4380B29F.F05BDC14 at prodigy.net>

> Jeez, Paul  (re: $4 opamp)
> 
> <mr rogers mode on>
> 
> "can you say P-A-i-A, kids ???"   :^P
> 
> Paul's suggestion of using the positive and negative regulators is a good
> on, it will prevent changes in the overall supply from affecting the offset.
> In the PAiA case, there are probably 1,001 other points that need to have
> similar treatment.  The simple "resistor divider" suggested by Paul Perry
> might be a more expedient solution.
> 
> Engineering is usually about trading cost/complexity for performance. Sad
> to say, I usually side with Mr. Schreiber in the "damn the cost I want it to work
> perfectly" camp.  PAiA might be called the "anthesis" of that philosophy.
> For that reason, some PAiA users report good success and others are less satisfied.
> I have never heard a post to the effect of "My MOTM is erratic in operation". You
> pay for the difference.

I certainly agree, you get what you pay for. On the other hand, a typical synth
circuit and a typical synth mechanics (pots, caps, chassi, connectors, etc.)
the later part is easilly half the price anyway, so why not spend just a little
more on the first part and get something good instead. I think some cost-savers
is a little too concentrated on the wrong stuff. Paul's MOTM stuff is certainly
not compromising on either parts, but I am sure Paul isn't doing the most
expensive stuff that he could do, just putting the balance more towards overall
performance than overall price-pressure. I would by a PAIA-kit just for the
fun and simpleness for the money. Have the MIDI-2-CV kit, and it is certainly
alot of functionality at a cheap price, but don't claim it to be accurate and
extensive like a good MIDI-2-CV converter. You do get several usefull
functions, which are all on the simple side but usefull never the less.
But then again, I don't expect preciseness from it. Mechanics is another thing
which one has to sort out for oneself. Paia is more playfullness for the masses
and MOTM more usefullness for the professionals. As long as you know what you
are buying, there is nothing wrong with either off these, as long as you get
your moneys worth. If I would find myself paying MOTM-prices for Paia-quality
and functionality, then I would be unhappy.

Engineering is eventually about finding the balance between price and
performance, and at which point this balance is, depends on the intended market
and their expectations. For instance, Panasonic and Technics is two brands with
basically the same designers at Mitsubishi, same designers making different
balances between price and performance. You buy the brand which fits your
expected balance between those, so you decide which balance you want and need.

In the end, there is no single right answer to any of these questions, I value
the hints about cheap and dirty solutions as much as those giving me precission
for a price. Which one I choose depends on what I need to do at design-time for
a particular design. I even like to toy around with "forbiden" solutions, which
are dirty like hell, just for the fun of breaking the rules, but that doesn't
make me value other solutions less if they give me the precission.

Cheers,
Magnus - senior system architect as daytime occupation