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 
Live streaming at radio.electro-music.com

  host / artist show at your time
  Rob Adventures in Sound
Please visit the chat
 Forum index » DIY Hardware and Software » YuSynth
Simple VCA Amplitude?????
Post new topic   Reply to topic Moderators: Scott Stites
Page 1 of 1 [6 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
mrmrshoes



Joined: Feb 19, 2011
Posts: 73
Location: Newcastle Upon Tyne
Audio files: 4

PostPosted: Sat May 31, 2014 7:19 am    Post subject: Simple VCA Amplitude????? Reply with quote  Mark this post and the followings unread

I've just built the Simple VCA and it seems to be working, I think, But I haven't done any serious configuring yet apart from trimming A2 to mute input signal when the gain control is in a CCW position. When this is configured the amplitude on the output of the VCA is about ¼ of the input amplitude. Is this normal? I haven't matched the transistor pair yet just used two from the same batch for basic tests.

I know you can change the gain of the VCA with R10 & R11. I'm thinking I’ve got a working board and just need to configure these. Has anyone experienced the same behaviour?

I've check all component values on the board as well as for other problems like Shorts/Opens/Cold Joints and everything looks good.

The VCA is set-up for AC operation.

Any input would ready help me out.

Cheers

mrmrshoes
Back to top
View user's profile Send private message
Benjamin AM



Joined: Nov 04, 2010
Posts: 72
Location: Boise

PostPosted: Thu Jun 05, 2014 7:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Curious what the control input voltage is.
Back to top
View user's profile Send private message
mrmrshoes



Joined: Feb 19, 2011
Posts: 73
Location: Newcastle Upon Tyne
Audio files: 4

PostPosted: Sun Jun 08, 2014 9:04 am    Post subject: Reply with quote  Mark this post and the followings unread

I have figured out my problem man. I spent a couple of days checking over the board, replacing parts and looking for Shorts and opens. All the wiring looked good as-well, so I was pretty stumped.

When I was testing the VCA I had all the pots and nanner sockets attached to my panel. When I eventually remove the gain pot from the panel I realized that I had the wrong value pot (10K) instead of 100k. This explains the lack of amplitude when trimming A2 trim pot.

I feel pretty stupid. Well you can't win them all. Embarassed
Back to top
View user's profile Send private message
Benjamin AM



Joined: Nov 04, 2010
Posts: 72
Location: Boise

PostPosted: Sun Jun 08, 2014 11:15 am    Post subject: Reply with quote  Mark this post and the followings unread

You shouldn't be to embarrassed, it happens to everyone.
Back to top
View user's profile Send private message
gdavis



Joined: Feb 27, 2013
Posts: 161
Location: San Diego

PostPosted: Sun Jun 08, 2014 8:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

If it makes you feel any better, I just realized my LFO wasn't working because I put the TL074's in backwards Embarassed
_________________
My synth build blog: http://gndsynth.blogspot.com/
Back to top
View user's profile Send private message
AlanP



Joined: Mar 11, 2014
Posts: 26
Location: New Zealand

PostPosted: Mon Jun 09, 2014 1:47 am    Post subject: Reply with quote  Mark this post and the followings unread

Hah, when I was trying to dial in my Minimoog VCF, I couldn't work out why adjusting T1 did nothing to the voltage on Q1... until I noticed the resistor attached to it was 100K, not 1k8.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic Moderators: Scott Stites
Page 1 of 1 [6 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 » YuSynth
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