[sdiy] High-power Moog ladder VCF

[Bob Weigel]

On 12/9/2010 4:24 PM, Magnus Danielson wrote:
> On 12/09/2010 11:47 PM, lanterma at ece.gatech.edu wrote:
>> I asked Kevin if I could repost this, and he gave me the thumb-up...
>
> Feel the power of this VCF! The side-feature is that it is a 
> power-supply modulated filter :)
>
> Next thing I expect there to be followed by a tube equivalent...
>
> Cheers,
> Magnus
>
>> - Aaron
>>
>> On Dec 9, 2010, at 3:05 PM, Kevin Lightner wrote:
>>
>>> Btw, I made a crazy thing the other day:
>>>
>>> A discrete Moog ladder filter made from Minimoog schematics using 
>>> very large and mostly high-current components.
>>> 2N3055 TO-3 transistors only, big orangedrop caps, big resistors, etc.
>>> Just a crazy idea to see if I could make one that worked and for the 
>>> hell of it, could run on higher voltages and current.
>>> It worked the first time I powered it up. :)
>>>
>>> Technically I didn't make a VCF tho.
>>> I left off a couple trannys normally used for converting voltage to 
>>> current.
>>> Instead I added a 2w pot and control the current directly.
>>> I guess it's a CCF. ;-)
>>>
>>> This thing is about a foot long or more and maybe 6 inches wide.
>>> Silliest thing you've ever seen, but amazed because it works and 
>>> sounds great.
>>> I can run it as low as 4 volts and as high as what my PSU puts out, 
>>> 30 volts each rail.
>>> Gain structure changes considerably of course, but that's kinda the 
>>> fun of it all.
>>>
>>> So I guess I made the first Moog filter that can drive a speaker 
>>> directly without an amp? ;-)
>>>
>>> Here's a pic.... http://www.synthfool.com/bigfilter.jpg
>>>
>>> Kevin
>>
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I fully intend to build a synth with at least one fully tube signal path 
some day.  Long term dream of mine... about to work on an old Jennings 
unit though in the meantime :-)

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