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
  EdisonRex Edison's Electronic Review
Please visit the chat
 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
matched transistor sub for VCA/VCO
Post new topic   Reply to topic Moderators: Scott Stites
Page 1 of 1 [15 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
jbaken



Joined: Feb 07, 2012
Posts: 7
Location: brooklyn

PostPosted: Tue Feb 07, 2012 12:33 pm    Post subject: matched transistor sub for VCA/VCO Reply with quote  Mark this post and the followings unread

Hey, so I'm trying to sub-out the LM394 for the VCA/VCO and was wondering if it would be possible to use a JFET LSK389 instead of something like the SSM2210 which is expensive and harder to find.. thoughts?
Back to top
View user's profile Send private message
prgdeltablues



Joined: Sep 25, 2006
Posts: 162
Location: UK
Audio files: 10

PostPosted: Wed Feb 08, 2012 4:36 am    Post subject: Reply with quote  Mark this post and the followings unread

I don't think you can use a jfet to replace the LM394/SSM2210 - the schematic is the usual two npn exponential converter. But you easily use two matched discrete transistors. There's a thread where Ian Fritz gives a very simply method of hand matching (http://electro-music.com/forum/viewtopic.php?highlight=transistor+ian&t=18365)

Peter
Back to top
View user's profile Send private message
jbaken



Joined: Feb 07, 2012
Posts: 7
Location: brooklyn

PostPosted: Thu Feb 09, 2012 1:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

im aware of the manual matching but was saving that for last resort.. are the ssm2210s from china on ebay bogus? any luck with those ?
Back to top
View user's profile Send private message
Mongo1



Joined: Aug 11, 2011
Posts: 411
Location: Raleigh NC

PostPosted: Thu Feb 09, 2012 3:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
are the ssm2210s from china on ebay bogus? any luck with those ?


Well, I think the key word there is 'luck'.

The dual transistor problem is one we all face. You either have to match those trannies yourself or just bite the bullet and pay for something you can trust. I don't think there's a magic solution available.

One thing to think about. Frequency tracking is the single most important quality when determining if a VCO is useful or not. Your ear can easily detect tracking and drift problems. The matched trannies are the single most important part of that function. So - if you're going to spend too much money on anything, the trannies are the place to do it.

Gary
Back to top
View user's profile Send private message Send e-mail
mph



Joined: Aug 25, 2007
Posts: 66
Location: France

PostPosted: Fri Feb 10, 2012 2:47 am    Post subject: Reply with quote  Mark this post and the followings unread

There are some subs currently in production, but they are quite expensive.
I've used some MAT12 (free samples Wink ) in the Yusynth VCO's and they worked perfect. I don't remember other references but I know they exist even if the MAT12 is the easiest to get.
Back to top
View user's profile Send private message
jbaken



Joined: Feb 07, 2012
Posts: 7
Location: brooklyn

PostPosted: Tue Mar 06, 2012 1:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

so i ended up caving and buying some ssm2210s from bridechamber. those should work nicely. My new question regards one of the transistors on the CGS VCO - the 2N4856. is this thing necessary if I don't plan on using the Sync function? based on some assistance looking at the schematic it appeared that this was all that it was doing, however i could way off. has anyone built this thing without the 2N4856?
Back to top
View user's profile Send private message
Mongo1



Joined: Aug 11, 2011
Posts: 411
Location: Raleigh NC

PostPosted: Tue Mar 06, 2012 1:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
has anyone built this thing without the 2N4856?


If they have, they haven't been able to use their VCO.

That transistor is the one that shorts out the cap, thus starting the oscillation cycle again. The board won't work without it. You may be able to find a substitute, but you need SOMETHING there.

The sync signal just comes in and prematurely triggers a new cycle to start.

Gary
Back to top
View user's profile Send private message Send e-mail
jbaken



Joined: Feb 07, 2012
Posts: 7
Location: brooklyn

PostPosted: Tue Mar 06, 2012 1:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks for the quick reply! i guess i should bite the bullet and stop trying to cut corners.
Back to top
View user's profile Send private message
Mongo1



Joined: Aug 11, 2011
Posts: 411
Location: Raleigh NC

PostPosted: Tue Mar 06, 2012 1:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
thanks for the quick reply! i guess i should bite the bullet and stop trying to cut corners.


I used to do exactly the same thing. Then I went about it a different way. I found that there are some things you can save large amounts of money on if you plan to build a bunch of equipment.

Take resistors for instance. I found a chinese place on Ebay that will sell you 1000s of them for almost nothing. You get 40 or 50 each of a wide range of values. Some of them you'll never use, but it still makes financial sense.

For values you use all the time (1M, 100K etc) I go to mouser and buy 200 of them for $4. The quantity discounts are absolutely insane. I also buy most transistors and diodes in large quantity.

IC sockets from China - they work fine and are very low cost.

Switches? NO - you get what you pay for there.

Caps- for typical ceramic discs I go to Chinese companies again. Big bags of them for almost nothing.

There are a lot of things out there like that - it just takes a while to find them.

Gary
Back to top
View user's profile Send private message Send e-mail
lysander



Joined: Apr 10, 2012
Posts: 2
Location: London, UK

PostPosted: Tue Apr 10, 2012 10:03 am    Post subject: Reply with quote  Mark this post and the followings unread

I've bought these last week:
http://www.ebay.co.uk/itm/170786362078

they haven't arrived yet so I can't comment on whether they do work... fingers crossed !

EDIT: realising this is looking a bit spammy. But long time lurker here, and I'm also on Muff with the same username.
Back to top
View user's profile Send private message
Mongo1



Joined: Aug 11, 2011
Posts: 411
Location: Raleigh NC

PostPosted: Tue Apr 10, 2012 10:21 am    Post subject: Reply with quote  Mark this post and the followings unread

Not spammy at all. Please let us know if that pans out. It's a good price for that chip if they work...

Thanks
Gary
Back to top
View user's profile Send private message Send e-mail
jbaken



Joined: Feb 07, 2012
Posts: 7
Location: brooklyn

PostPosted: Tue Apr 10, 2012 10:31 am    Post subject: Reply with quote  Mark this post and the followings unread

So, I've built and tested this module along with several other modules (DUSG, Active Real Ringmod, VCAX2)
The only thing is while calibrating the VCO, i moved the fine and course knobs around a bunch to get in tune- my question is, can i move the knobs back to center position and simply turn the zero *trim to the right spot without losing my span? i would hate to tune this thing again.. it was a nightmare so im hesitant to just go for it.

edited in case others get confused by the question

Last edited by jbaken on Tue Apr 10, 2012 11:20 am; edited 1 time in total
Back to top
View user's profile Send private message
Mongo1



Joined: Aug 11, 2011
Posts: 411
Location: Raleigh NC

PostPosted: Tue Apr 10, 2012 11:17 am    Post subject: Reply with quote  Mark this post and the followings unread

If you're talking about the 'Trim Zero' adjustment, I think you should be able to move that around. Just don't mess with the 'span'.

Gary
Back to top
View user's profile Send private message Send e-mail
jbaken



Joined: Feb 07, 2012
Posts: 7
Location: brooklyn

PostPosted: Tue Apr 10, 2012 11:21 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks! ill give it a shot then.
Back to top
View user's profile Send private message
lysander



Joined: Apr 10, 2012
Posts: 2
Location: London, UK

PostPosted: Wed Apr 11, 2012 2:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

So reporting on the MAT02EH above which I have received today :

- Pretty terrible packaging. All the pins are quite bent and one of the units had two pins broken on arrival. Fixable with some ugly soldering job but annoying.

- I tested a couple with my DMM - number one Hfe of the pair tested around 540 for each side ( not sure how accurate the measurement is ), number two tested around 495 for each side which is just a touch below the spec ( does it matter ? ) if I'm reading the sheet correctly - but again it's probably within the error tolerance of my DMM.

So as far as I can tell from my noob's point of view they seem genuine and it's a pretty good deal. Maybe I should have kept it to myself Wink
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 [15 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 » Ken Stone designs - CGS
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
mps board

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