the Moon Base Xplorer

beepetc. · Joined: Mar 07, 2018 Posts: 6 Location: Denmark

Okay, it works now!
I've changed the 1n4148's to LED's, which seemed to make the major difference (as well as giving visual feedback to the individual stages (uuuh, blinkenlights!)) . I've also changed the output capacitor from 10uF to 1uF, as well as changing the value of the resistor connecting 9V to reset on the 555 timer, from 100K to 47K.
I'm not always sure what I'm doing, but I feel like it's going in the right direction!

THANKS! Very Happy

PHOBoS · Posted: Fri Aug 03, 2018 1:33 pm Post subject:

Great

Haven't tried it with LEDs myself but I guess because of the higher forward voltage the maximum voltage
to which the caps gets charged will be lower, not sure why that works for you but hey if it works Laughing

beepetc. · Joined: Mar 07, 2018 Posts: 6 Location: Denmark

Is the transistor after the two pots working as a buffer? My friend removed it, and connected to EG out directly to the base of the VCA transistor, which works for him. We're getting different results with the same components. Confused

It's super strange. When I have the 100k resistor from reset to VCC, the EG is sustained infinitely. When I remove it, it works like a charm.

This is my version of the schematic.
Posted Image, might have been reduced in size. Click Image to view fullscreen.

This is his (prettier) version.
Posted Image, might have been reduced in size. Click Image to view fullscreen.

All unused input pins have been tied to ground, for good measure.

Edit. The VCA sounds clearer with the buffer transistor and has a longer release time. Without it, the signal gets dirtier, as well as a more nasal character.

Just Say Noise! · Joined: Nov 14, 2011 Posts: 17 Location: Portland, Oregon

PHOBoS · Posted: Wed Dec 01, 2021 1:54 pm Post subject:

It's a zener diode which unlike a regular diode is made to break down at a specific voltage (not break it as in destroy it).
In this case it's a 10V zenerdiode which means that when the voltage over it gets to 10V it starts to break down and conduct
in the opposite direction aswell. This will limit the maximum voltage over the capacitor in AR mode. Without it the voltage
would keep rising to pretty much the supply voltage which is higher then it gets in AD mode.

Just Say Noise! · Joined: Nov 14, 2011 Posts: 17 Location: Portland, Oregon

Thanks for explaining that PHOBoS! I was getting confused at all the different specifications for diodes when trying to source it. So its the "Nominal Zener Voltage" or "Vz" that you are referencing. looks like a 1N4740A, according to datasheet, has a VZ of 10v, so that should work. Great little envelope generator. Thanks for sharing it!

PHOBoS · Posted: Thu Dec 02, 2021 12:10 pm Post subject:

Besides breakdown voltage the power rating can be of some importance. Not because too much current can destroy it,
though that is of course also important, but for it to properly do its zener thing there has to be a minimum amount of current
flowing through it. I believe this minimum current increases with a higher power rating. I usually use 0.5W zeners or
whatever is available but I think for this application the 1N4740A (1W) would probably work fine aswell.