[sdiy] Digital control

[Bill Berzinskas]

If anyone comes across the mbase schematics, or has any info on it, please 
let me know.   i heard one in action recently, and it was phenomenal.. 
although at about $450 US..   i think i'll try to clone it or something 
similar..   i'm thinking its prob a mod'd 909 clone by the sound of it..

----- Original Message ----- 
From: "mark verbos" <mverbos at earthlink.net>
To: "Johannes Öberg" <johannes.oberg at gmail.com>; "synth diy" 
<synth-diy at dropmix.xs4all.nl>
Sent: Monday, February 28, 2005 3:17 PM
Subject: Re: [sdiy] Digital control


>I didn't see the Mbase01 scematic, I just looked at the PCB and saw those 
>chips.  Obviously, using a DtoA converter that is shared for everythign is 
>the cheapest way to go.
>
> Mark
>
>
>
> Johannes Öberg wrote:
>
>>Thanks for your help guys!
>>
>>Are the Mbase01 schematics available somewhere, or does anybody know
>>how they implemented the DCR's? How did the Polysix or other early
>>patchmemory synths do it?
>>
>>The digital resistor chips are to expensive for me unfortunately. If I
>>would try to build a digitally controlled analog synth (of course,
>>this is more like dreaming than considering) I would need alot of
>>digitially controlled "pots". What's the _cheapest_ way of doing this
>>with an acceptable reproducability and resolution (say at least 6
>>bits) ? IIRC the old polysynths used to use a single D/A going into
>>these crazy mega-sample'n'hold chips, going into VCR's. Are these
>>SnH's still an alternative? Can't it be done in a simpler way, if one
>>accepts poorer stability or something?
>>
>>The other alternative seems to be multiplying DAC's, but this can't be
>>a cost-effective way of doing it, can it? Or did I misunderstand? I'm
>>believing you mean that I should use one DAC per pot. It sure seems
>>compellingly simple enough though.
>>
>>Shouldn't it be possible to use a totally el-cheapo method, something
>>like a single transistor as the VCR and either a giant sample'n'hold
>>thing or perhaps even the old one-bit-D/A from the microcontroller? Or
>>am I totally naive? Any linearity problems could be compensated for in
>>software, methinks. As most of the 'digitally controlled resistors'
>>would replace pots for non-timecritical stuff (like Attack rates) slow
>>settling time (or what it's called) due to slow samplerate for the D/A
>>wouldn't be a problem.
>>
>>/Johannes
>>
>>
>