Good designs of Expo Converters? Was: [sdiy] Multiplexed Expo Converter?

[Jerry Gray-Eskue]

Here are some write ups on expo converters:

http://www.mik-music.org/ExponentialConverter&bl=y#A_common_exponential_conv
erter

http://home.comcast.net/~ijfritz/sy_cir7.htm

http://home.comcast.net/~ijfritz/sy_cir9.htm

PAiA has a little different take on temperature compensation:

http://paia.com/ProdArticles/9700faq.htm

A good place to see various implementations are VCO schematics.

- Jerry

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of cheater cheater
Sent: Saturday, August 01, 2009 11:38 AM
To: synth-diy
Subject: Good designs of Expo Converters? Was: [sdiy] Multiplexed Expo
Converter?


Scott,
thanks for your answer. I didn't know expo FM was inharmonic, I'll
need to check that stuff out, it sounds really neat actually -
inharmonicity is one thing you can use to make sounds much more
interesting. On another note, PM is sort of like FM but not - it's
very fun - check it out if you ever get a chance. Patch something
across an accumulator cap or something (it would be more involved than
that to get real Phase Modulation but might give you some form of
foretaste)

Guys, what are some good designs of Expo Converters?

Cheers
Damian

On Fri, Jul 31, 2009 at 8:08 PM, Scott Nordlund<gsn10 at hotmail.com> wrote:
>
>> 1. FM
>> I thought 'linear' audio rate FM was supposed to be much better. What
>> can you guys tell me about expo vs linear fm? I have seen some VCOs
>> with 'linear fm in', I guess that just bypasses the EC?
>>
>> Or is 'linear' audio rate FM better for the specific reason that
>> removing the EC makes the system simpler and hence easier to make very
>> good?
>
> Exponential FM is inharmonic, so it's generally less musically useful.
>
>> 2. PM
>> Correct me if I'm wrong, but I think PM again doesn't need an EC, does
>> it? Even if it's DC modulation...
>
> Analog phase modulation is used sometimes for radio signals, but I don't
if or how it could be implemented for musical purposes (I can't think of any
examples, phase shifters aside).
>
>> 3. AM/RM
>> I don't think AM needs EC.. at all... correct me if I'm wrong, please.
>
> You could run the two input signals through exponential converters, sum
them, then run that through a logarithm...
>
>
>
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