[sdiy] Newbie question: Diode ladders

[Scott Gravenhorst]

Tim Ressel <madhun2001 at yahoo.com> wrote:
>Scott,
>
>When you say "signal applied to the control element"
>do you mean the audio path and not the control
>voltage? 

Sorry, yes, the audio...

>There is the case of filters's gain
>increasing as Q increases, requiring the input to be
>reduced to avoid clipping at peak resonance. An
>example would be the Paia design where the 'Q' pot was
>dual-gang: one part ran 'Q' up while the other
>attenuated the input. Those clever Paians.
>
>In the case of 3080's, its just cause they have oddles
>of gain.

I've heard it said here that OTAs will distort given too much
input, and I've seen MOSFETs used as VCRs do this too, I was
wondering what devices tolerate what levels of input.  The
FatMan's VCF is a typical LM13600 SVF and it has a 100:1
attenuator feeding the audio input of the OTA, signal level
before the attenuator is expected to be around 8 volts P-P, so it
applies about 80 mV.  H11F1 devices distort after 100mV or so,
I'm wondering is this pretty typical for other filter designs?  I
had wanted to play with an SVF design using H11F1 as a VCR and
abandoned it because of this attenuation need, but if this is
fairly typical, maybe I shouldn't sweat the small sh!t and just
do it...


>
>
>--- Scott Gravenhorst <music.maker at gte.net> wrote:
>
>> Sticking my face back in here - seems like the
>> nonsense is over, hopefully
>> it will stay that way.
>> 
>> Question about VCFs in general:  I have taken notice
>> that many, maybe most
>> VCF designs require a rather low signal level
>> applied to whatever control
>> elements are used for tuning.  Diodes, BJTs, FETs,
>> OTAs, MOSFETs, all seem
>> to need attenutation (what about vactrols?) to avoid
>> distortion.  Is the
>> acceptable signal level applied at this point
>> similar or the same for each
>> of these techniques?  
>> 
>> Can someone give basic approximate figures for what
>> levels are acceptable
>> for each kind?
>> 
>>
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>> 
>> -- Scott Gravenhorst | LegoManiac / Lego Trains /
>> RIS 1.5
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>> 
>> 
>
>
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---------------------------------------------------------
- Where merit is not rewarded, excellence fades.
- Hydrogen is pointless without solar.
- What good are laws that only lawyers understand?
- The media's credibility should always be questioned.
- The only good terrorist is a dead terrorist.
- Governments do nothing well, save collect taxes.

-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
-- Linux Rex         | RedWebMail by RedStarWare
-- FatMan: home1.gte.net/res0658s/fatman/
-- NonFatMan: home1.gte.net/res0658s/electronics/
-- Autodidactic Master of Arcane and Hidden Knowledge.