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
ARP 3620 Keyboard S&H - IMF3958 Dual FET Substitution?
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
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
AndyR1960



Joined: Feb 16, 2007
Posts: 284
Location: Manchester UK
Audio files: 5

PostPosted: Fri Sep 13, 2013 3:03 am    Post subject: ARP 3620 Keyboard S&H - IMF3958 Dual FET Substitution? Reply with quote  Mark this post and the followings unread

I'm having a tiny problem with the S&H section of the ARP3620 Keyboard clone I'm building - although it's working (more or less) I'm currently testing the board using two unmatched 2N5459 FETs in place of the elusive IMF3958 (or the expensive 2N3958)

I started thinking if the Dual FET business was really necessary - why not just take it out along with the LM1458 op-amp and replace the whole shebang with an LM442 or similar?

Do you think it would work? I can't see any reason why not... I just don't want to start tearing into my beautifully crafted PCB Wink

I've attached the original circuit along with what I THINK may work.

Any comments would be gratefully accepted.


Original S&H.jpg
 Description:
Original ARP 3620 Circuit
 Filesize:  80.29 KB
 Viewed:  52 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

Original S&H.jpg



Modified S&H.jpg
 Description:
Modified circuit
 Filesize:  67.96 KB
 Viewed:  51 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

Modified S&H.jpg


Back to top
View user's profile Send private message
THeff



Joined: Sep 01, 2006
Posts: 218
Location: Florida
Audio files: 30

PostPosted: Fri Sep 13, 2013 9:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Andy,

This is petty much what Yves is doing on his Dual Gated Slew module.

http://www.yusynth.net/Modular/index_en.html

-Tim
Back to top
View user's profile Send private message
AndyR1960



Joined: Feb 16, 2007
Posts: 284
Location: Manchester UK
Audio files: 5

PostPosted: Fri Sep 13, 2013 9:16 am    Post subject: Reply with quote  Mark this post and the followings unread

THeff wrote:
Hi Andy,

This is petty much what Yves is doing on his Dual Gated Slew module.

http://www.yusynth.net/Modular/index_en.html

-Tim


Thanks for the pointer Tim, looks like I'm heading in the right direction... I'll give it a try - can't do any harm Smile
Back to top
View user's profile Send private message
steffensen



Joined: Jul 11, 2012
Posts: 95
Location: Sweden

PostPosted: Sun Aug 17, 2014 2:47 am    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960,
Did this work out? Smile
Back to top
View user's profile Send private message
AndyR1960



Joined: Feb 16, 2007
Posts: 284
Location: Manchester UK
Audio files: 5

PostPosted: Tue Aug 19, 2014 2:28 am    Post subject: Reply with quote  Mark this post and the followings unread

steffensen wrote:
AndyR1960,
Did this work out? Smile


I never got round to trying it Wink

I discovered that the original problem I had (voltage droop on the second voice output) was due to a missing cap and not the FETs Embarassed

The two 2N5459's work fine. I also tried it without matching them (but they were from the same batch), and it still works with no problems, so I wouldn't get too hung up about sourcing IMF3958/2N3958.
Back to top
View user's profile Send private message
steffensen



Joined: Jul 11, 2012
Posts: 95
Location: Sweden

PostPosted: Tue Aug 19, 2014 6:54 am    Post subject: Reply with quote  Mark this post and the followings unread

Cool, thanks for the info.
I too had great results by using 2x 2N5459's instead of the expensive 2N3958 on my 4027-1 clones.
Not all pairs work out ideally though, but those from the same tape always seem to do however!
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
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
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