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Subject: Re: ac vs dc question

From: "grotechef" <grotechef@...>
Date: 2003-07-27

hi jb,
and: wow! thanks!! this has been very clear! thanks for writing this!

i did find something 'strange' in the 2600 book, while searching for
the text you mentioned in your reply.

on page 39 (ring modulator) of the arp 2600 book there's a drawing of
ac-coupled ∗low frequency∗ square and saw waves (these are dc
normally, right?).

these do not look like i would have expected.

it seems like the squarewave has been shifted partly upward and
partly downward, and the saw has been in an accident :)

is this because they are low frequency waveforms?

> The MOTM 110 is AC coupled -- it will not pass a DC signal. the
majority of
> uses for a VCA in a modular synth are to control an audio signal.
The MOTM 110
> is perfectly suitable for this type of use. However, there are
times you will
> want to gate a control voltage which may have a DC component
(offset), and the
> 110 won't work for this application though the MOTM 190 will IIRC.

so, i can't use the 110 to vc an enveloppe (which is a 100% dc
voltage)(eg into audio in of vca). (the eg cannot be morphed into an
ac waveform, right?)

but using a pulse lfo instead of an enveloppe would work because the
pulse gets ac-coupled by removing some dc-component/offset, makin it
an ac-waveform?

(is this correct?)

> Get the Allen Strange book, "Electronic Music"

i will. i found this on the web:

"My text, Electronic Music, has been reissued by McGraw-Hill Primus
Editions. It may be difficult to get in Europe so if anyone wants a
copy
please contact me direct at <astrange@...>

I can send you copies at my cost + shipping/etc which should be well
under $40.00 US each

Cheers-

Allen Strange "

greetings,
chef!