[sdiy] SEM filter questions

[Magnus Danielson]

On 04/22/2012 07:37 PM, Tom Wiltshire wrote:
>
> On 22 Apr 2012, at 13:37, 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.
>
> Sorry, my mistake. I've checked and you're quite right.
>
>> I have all the OBs right here. :)
>
> Lucky you!
>
> It's very interesting to see the evolution of the Oberheim designs from the SEM through the nearly-SEM OBX to the nearly-CEM OB-Xa and OB-8, all the way to the two-chip CEM voice (3374/3372) of the Xpander. It's a fascinating story, told in synth service manuals!

Indeed.

It's also interesting to see how calibration evolved, and reading the 
ECOs to see how the instruments evolved as they learned.

Things changed, evolved. Even the MiniMoog "Model D" has numerous 
improvement steps. The "Model D" craze is a bit strange in this context. 
Again, the service manuals tell more of the story than many of the 
articles written.

For instance, it is quite common for the tempco-resistor to sit waaay 
off what they are supposed to compensated. Not the piggy-back mounting 
we are used to now. We are standing on the shoulders of giants, and the 
giants where struggeling!

Cheers,
Magnus