[sdiy] AS3340/CEM3340 revG

Tony Allgood oakleysound at gmail.com
Mon Apr 10 09:51:42 CEST 2023


 > They sometimes have an unacceptable drift, which is not present when 
I substitute an original 3340. Has anyone else experienced this?

Yes. I tried to use them in an Oberheim OB-Sx and they didn't work well 
at all. The ones fitted to voices 1 and 2 were stable, but the ones 
fitted to voices 3, 4, 5 and 6 were unstable and couldn't be used.

In the OB-Sx case I surmised that the problem was related to the power 
supply connections as the higher number boards were further along the 
motherboard. However, no amount of additional local capacitive 
decoupling fixed the problem. Nor did increasing the size of the 0V bus 
have an affect.

Replacing them with CEM3340 rev G fixed the problem completely.

However, I was using the original AS3340. This has now been replaced 
with the improved AS3340A. This supposedly fixes the issues found in the 
first version. The biggest of which was the pitch change when pulse 
width was altered. I have yet to try these but I am keen to do so.

Thonk, here in the UK, sells the CEM3340 rev G.

Cabin Global, in the US, (and others) sell the AS3340A.

Tony

www.oakleysound.com


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