[sdiy] Harry Bissell's guitar synth envelope follower

[Michael E Caloroso]

Harry remarried and had a child.  His priorities changed rather abruptly.

MC

On 11/25/15, BrightBoy <jdec at mindspring.com> wrote:
> Here's a burning question I've had lately....
>
> What happened to Harry?
>
> He used to be quite active on this list and Analogue Heaven
> and then suddenly disappeared.
>
> Has he moved his participation to a different forum(s)?
>
> Jeff
>
> -----Original Message-----
>
>>From: Tom Wiltshire <tom at electricdruid.net>
>>Sent: Nov 25, 2015 5:57 PM
>>To: synthdiy diy <synth-diy at dropmix.xs4all.nl>
>>Subject: [sdiy] Harry Bissell's guitar synth envelope follower
>>
>>Hi All,
>>
>>I've been studying Harry Bissell's clever envelope follower, as described
>> in full here, if you haven't seen it:
>>
>>	http://m.eet.com/media/1141271/18042-122602di.pdf
>>
>>I've got a question about the output filtering. The relevant section is
>> here:
>>
>>	http://electricdruid.net/images/HarryBisselEnvFollow.png
>>
>>I understand the round-robin resetting of the three peak detectors. That
>> bit is ok. Please give me a hand getting my head around the next bit;
>>
>>The three diodes provide the highest of the peak detector outputs (minus
>> the diode drop, presumably) to the filter network.
>>The filter network consists of D28+R208, R205, C67, and R321 (note that
>> this is 10K here, but 1K in the article).
>>
>>Now, what I don't get is what the time constants of the filter are. Would
>> it be the following? -
>>
>>1) R205 + C67 provide the attack constant, except…
>>2) When D28 conducts (e.g. large rapid attacks) R208 will dominate the
>> attack constant ( R208 and R205 in parallel)
>>3) R321 + C67 provide the decay constant.
>>
>>Have I got this right?
>>
>>Thanks!
>>Tom
>>
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