[sdiy] Moog ladder theory questions

[cheater cheater]

Dave, Naoki,
thanks a load! Very useful!
This means that the difference (between the beta=+infinity model and
the beta=200 original) in output from each stage could be around -50
dB which is very little.. but still audible! Especially if this effect
is dependant on frequency (which I am not sure is true but think it
could be).
Thanks Andy for helping me with those calculations.

Cheers
Damian

On Fri, Jan 16, 2009 at 4:23 AM, Naoki Iwakami <naoki.iwakami at gmail.com> wrote:
> Sorry I might misread your question.
> My transistors are 2SC1815 and beta is around 200.
> It's a general purpose AF transistor I usually use, I mean you don't
> need  any "special" transistor for ladder VCF.
>
> -- Gan
>
> On Thu, Jan 15, 2009 at 6:49 PM, cheater cheater <cheater00 at gmail.com> wrote:
>> Guys!
>> this has completely derailed :)
>> I just want to know what transistors you use in your circuit boards,
>> and what beta they have.
>> :)
>>
>> Cheers
>> D.
>>
>> On Thu, Jan 15, 2009 at 6:12 AM, Naoki Iwakami <naoki.iwakami at gmail.com> wrote:
>>> Hi cheater cheater,
>>>
>>> It's quite detail but I believe beta difference between left to right
>>> in the ladder create slight unbalance in the ladder output.  I think
>>> that's why the minimoog service manual mentions about matching
>>> transistor.
>>> (http://www.fantasyjackpalance.com/fjp/sound/synth/synthdata/16-minimoog/002/905-matching-transistor.gif)
>>>
>>> But in my experience this issue is not so critical.  When  I used
>>> 2SC1815, very generic transistor easily available in Japan, I tried
>>> the Moog matching method but most of the transistors are within the
>>> recommended range already.  Also I've not heard of any transistor
>>> ladder VCF problems among my friends due to lack of transistor
>>> matching.
>>>
>>> Thank you,
>>> -- Gan
>>> http://gaje.jp/
>>>
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>