env decay range?

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gzifcak
 
Posts: 150
Joined: Wed Oct 26, 2005 3:46 pm

env decay range?

Post by gzifcak »

hi,
has anyone successfully changed the range of the decay envelope? i'm not talking about the depth, but the minimum and maximum decay. i tried changing the value of r138, which sure enough gave me zappy tight decays (wicked sounding!), but it also turns the accent envelope into a little click! i'm looking for a modification to the accent to compensate. looks like the next thing to try is the accent decay mod, but just find a static resistor value (instead of a pot) that works with the decay mod installed. it sounds like it's affecting the attack too, though. any ideas?
thanks,
greg

gzifcak
 
Posts: 150
Joined: Wed Oct 26, 2005 3:46 pm

Post by gzifcak »

aha! according to the devilfish notes at http://www.firstpr.com.au/rwi/dfish/release.html the minimum decay time = 200 ms, which is also the fixed time of the accent sweep envelope. this leads me to believe that they do indeed rely on the same resistor. anyone know how to isolate the accent's timing from the decay's? any ideas are welcome.

devilfish notes:

The TB-303's Main Envelope Generator (MEG) had a time variable between 200 ms and 2 seconds – as controlled by the Decay pot. On accented notes, the decay time was fixed to 200 ms. In the Devil Fish, there are two new pots for MEG decay – Normal Decay and Accent Decay. Both have a range between 30 ms and 3 seconds. The MEG drives the filter via the Env Mod pot. On accented notes the MEG also drives the filter frequency via the Accent pot which drives the Accent Sweep Circuit. The output of the Accent Sweep Circuit adds to the VCA volume, in addition to the current produced by the Main Envelope Generator described above. The Accent Sweep circuit, together with the Resonance Pot turned to the right, gives the distinctive acidee "wow" upwards filter sweep at the start of accented notes. Now that the time of the MEG can be manually controlled for accented notes, the "wow" or "wapp" time can be made shorter or longer.

thanks,
greg

gzifcak
 
Posts: 150
Joined: Wed Oct 26, 2005 3:46 pm

Post by gzifcak »

well,
the x0xd0x point to c13 as the one that determines the sweep speed, so maybe i'll try enlarging that while decreasing r138 for shorter min decay. otherwise, i'll cut the trace between ic12 pin 3, and reconnect it through an additional resistor that's the original value of r138. that seems like maybe the right choice.
thoughts?
greg

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