[sdiy] SEM filter questions

[Magnus Danielson]

On 04/22/2012 02:37 PM, Doug Terrebonne wrote:
>
>
> --- On Sun, 4/22/12, Tom Wiltshire<tom at electricdruid.net>  wrote:
>
>> The OB-X is about the point at which it changes over. It
>> retains the CA3080 SEM filter, but the oscillators and
>> envelopes are already CEM chips.
>
> No that's not correct. The only CEMs in the OB-X are the CEM3310 EGs. The oscs are 3046 based. I have all the OBs right here. :)

That is how I recall it too. The CEM3310 EGs makes perfect sense, as the 
SEM EGs wasn't neither full ADSR nor CV controllable, which is needed 
for a polysynth. Some time ago I even compared the schematics. 
Similarities where striking except for the apparent differences. Lost 
the details but recall the general approach.

The OB-Xa was more of a clean-up and then the OB-8 boasts about how many 
less trimmers you need to turn, yeat the filters still needs trimming 
and the trimming notes isn't very helpful. A bit of SW there would have 
helped. The OB-8 oscillator trimming is nice, as you only trim one 
trimmer to get it within range, and from then on the SW does the rest.

Cheers,
Magnus