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 Forum index » DIY Hardware and Software
ARP 3620 Keyboard S&H - IMF3958 Dual FET Substitution?
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AndyR1960



Joined: Feb 16, 2007
Posts: 279
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
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Original ARP 3620 Circuit
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Original S&H.jpg



Modified S&H.jpg
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Modified circuit
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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
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AndyR1960



Joined: Feb 16, 2007
Posts: 279
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
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