[sdiy] AS3340/CEM3340 revG

jslee john at sleefamily.org
Thu Apr 13 00:52:55 CEST 2023

Hi Tony,

AS3340A sounds like great news. I’d paused building a set of Thomas Henry’s “VCO Maximus” because nobody seemed to have really solved the pulse width issue. Sounds like it’s time to get back on it!



On Mon, 10 Apr 2023, at 17:51, Tony Allgood via Synth-diy wrote:
>> 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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