electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
CV & Gate Expander circuit voltage issue
Post new topic   Reply to topic Moderators: dnny, Uncle Krunkus, v-un-v
Page 1 of 1 [3 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
sixbyseven



Joined: Jan 28, 2016
Posts: 26
Location: hamilton, Ontario

PostPosted: Sat Sep 16, 2017 10:02 pm    Post subject: CV & Gate Expander circuit voltage issue Reply with quote  Mark this post and the followings unread

Hi There,

Has anyone built Ray's MFOS CV and Gate Expander circuit?

I am using an Arturia Keystep. and the voltage is fairly decent up and down 7 octaves, but the circuit seems to have an inconsistent drift

I am getting a voltage drift on the CV voltage outs.

Example (steps in octaves)

Voltage IN _> Voltage out from circuit
0.746 _> 0.746
1.746 _> 1.747
2.745 _> 2.735
3.741 _>3.607
4.740 _> 4.139
5.735_> 4.436


The drift after 5 octaves is almost 1.3 volts!

The circuit is here http://musicfromouterspace.com/analogsynth_new/CVNGTEXPANDER2015/pdf/cvngtexpand2015_schem.pdf

I am thinking it has to be either with the zener diodes (double checked the are both 1N5231B, oriented correctly and the resistors are all 10K 5%). The voltage on all 4 outputs (out 1 thru 4) is exactly the same. They all drift the exact same way. Ray mentions that there could be some offset voltage, but it should always be the same offset as the input voltage changes.

Should I try a different manufacturer for the 1N5231Bs?

_________________
Young enough to enjoy techno, old enough to remember a Z80 and tiny-C.
Back to top
View user's profile Send private message Visit poster's website
sixbyseven



Joined: Jan 28, 2016
Posts: 26
Location: hamilton, Ontario

PostPosted: Sun Sep 17, 2017 5:50 am    Post subject: Solved! Reply with quote  Mark this post and the followings unread

The 1N5231B Zener diodes have a reverse current leakage of 5 micro amps at 2 Volts. Ray mentioned that he did not use 5Volt zeners, but that he used 10 volt ones. The 1N5240B is the 10 volt version and does not starts the reverse leaking until 8 volts. This is why I got an exponential looking shift to the output voltage

I removed Z1 and Z2 from the board and retested and the voltage outputs are perfect, exact copies of the input. Anyones else building this take note:

Choose a Zenier where the reverse current leakage starts above the range you need, so if you want 7 octaves, use the 1N5240B instead of the 1N5231B.

_________________
Young enough to enjoy techno, old enough to remember a Z80 and tiny-C.
Back to top
View user's profile Send private message Visit poster's website
LukeLabs



Joined: Jan 11, 2020
Posts: 3
Location: Sydney, Australia

PostPosted: Sat Jan 11, 2020 10:51 pm    Post subject:   Reply with quote  Mark this post and the followings unread

I made two of these recently and can confirm replacing the Zeners with higher voltage versions drastically improves the performance.

I'm using 1N5240B's too and now have 10 octaves of usable CV output.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic Moderators: dnny, Uncle Krunkus, v-un-v
Page 1 of 1 [3 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use