electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
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
MFOS State Variable VCF Noise / Output Level Issue [solved]
Post new topic   Reply to topic Moderators: dnny, Uncle Krunkus, v-un-v
Page 1 of 1 [4 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
roglok



Joined: Aug 28, 2010
Posts: 159
Location: uptown

PostPosted: Fri Jan 20, 2012 4:32 pm    Post subject: MFOS State Variable VCF Noise / Output Level Issue [solved] Reply with quote  Mark this post and the followings unread

I need your help guys. I just powered up my MFOS 12dB VCF - everything works, but there are two issues:

1. The output level is very low

2. The circuit injects a considerable amount of white noise somewhere before the actual filter (i.e. the LPF can remove it completely)

I bet those issues are related, but I'm a noob and don't know where to start bugtracking. I've checked the board for any cold solder joints and swapped some of the op-amps to no avail.

Any ideas?
Thanks!

Last edited by roglok on Wed Feb 01, 2012 1:32 am; edited 1 time in total
Back to top
View user's profile Send private message
roglok



Joined: Aug 28, 2010
Posts: 159
Location: uptown

PostPosted: Sat Jan 21, 2012 1:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Please, somebody help me. I've managed to build the Steiner Synthacon VCF and other circuits on stripboard without any problems - now I'm working on my first professional PCB for the modular and it's driving me nuts!

The debugging so far involved switching to a +/-15v PSU, swapping all ICs and checking resistor values, but I can't get rid of the bloody noise. It's not static or ground loop hum, but a rather musical type of noise. I can make a recording if that helps... Could it be related to a bad cap? I've used film capacitors for the 0.1µF bypass caps and WIMA FKP for the integrators.

I'm grateful for any suggestions.
Back to top
View user's profile Send private message
haxster



Joined: Feb 01, 2006
Posts: 244
Location: MONTEREY PARK, CA 91754
G2 patch files: 2

PostPosted: Tue Jan 31, 2012 10:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

The Noise Level whistle is normal. Mine has that too. I have built several and all have that noise in one form or another.

As for the Signals being too low. You want to change the Input resistors from 1M to something like 100k-470K. 1M makes it sound too low.
Back to top
View user's profile Send private message
roglok



Joined: Aug 28, 2010
Posts: 159
Location: uptown

PostPosted: Wed Feb 01, 2012 1:31 am    Post subject:   Reply with quote  Mark this post and the followings unread

Thanks for the clarification, haxster!

I figured the "low volume" was due to my input signal not being hot enough. Since the resonance level does not change with gain, the signal level was low in comparison to the oscillating filter. With a signal around +/-5V, the levels are just fine.

I wonder why Ray, given the excellent explanation on his projects, has not mentioned the noise issue at all. If it's a feature, I can live with it. Just thought something's wrong there...
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 [4 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
e-m mkii

Please support our site. If you click through and buy from
our affiliate partners, we earn a small commission.


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