[sdiy] Overdriving 4069UB

[Scott Gravenhorst]

This is what I imagined you did - now I've got to try it, I'll be using both
synth sounds and/or guitar.  

When you say "warm", would that be warm like vacuum tube sonic warmth?

Best if I just try it...  Many thanks.

Seb Francis <seb at burnit.co.uk> wrote:
>Funny you should ask, I've just this minute uploaded a gif of the 
>schematic ...
>http://burnit.co.uk/sdiy/stuff/mosfet_distortion.gif
>
>It really is a lovely sounding distortion, and it's useful to be able to 
>set the number of stages to get anything from 'subtle' to 'insane'.
>
>I've been testing it with 3 things: Oakley 3031 with some filter 
>resonance, Waldorf Pulse with a fat saw wave patch and no resonance, and 
>a 909 bass drum clone.  This seemed like a good cross section of sources 
>(these are the kind of things I like to distort anyway).
>
>The circuit differs from others I've seen with the 4049/4069 as it has 
>no high frequency roll off (I tried it, but I preferred to let all 
>frequencies through then EQ later, or indeed before, if it was wanted).  
>For guitar distortion you might want to add some caps across some or all 
>of the 4069 stages to roll off the high frequencies.
>
>Remember to tie any unused inputs of the 4069 to ground (or make a 2nd 
>channel - that's what I'm doing).
>
>Seb
>
>P.S. The current circuit takes the risk of exceeding the 4069 input 
>voltage specification if the input is hot and the drive level is set 
>high - it gives a nice hard clip sound when you drive it real hard like 
>this.  Having just read Harry's email, I might change this a bit to save 
>damaging the IC.
>
>
>Scott Gravenhorst wrote:
>
>>Very interesting, do you have a schematic up that you can share?
>>
>>What sort of signal(s) did you test with?
>>
>>Seb Francis <seb at burnit.co.uk> wrote:
>>  
>>
>>>Well, I've been getting some really nice results with using between 1 
>>>and 3 stages of a 4069UB for distortion.  The MOSFET clipping has a 
>>>really warm sound to it.  (Incidently the 4049 really wasn't so good - 
>>>the clipping was way too asymmetrical.)  Anyway, more on this later .. 
>>>I'll publish the final circuit in due course.
>>>
>>>What I'm concerned about in my circuit design is whether it is safe to 
>>>drive the 4069 beyond its absolute maximum input voltage.  The quoted 
>>>absolute maximum range is -0.5V to VDD+0.5V (VDD=15 in my circuit).
>>>
>>>The input current is limited by a 10K resistor (with a DC blocking cap 
>>>in series before it), so although the opamp driving it can kick out up 
>>>to 28V ptp, the voltage at the 4069 input gets clipped to approx 17V 
>>>ptp.  This is a bit beyond the quoted absolute maximum, but I guess as 
>>>long as the current through the internal protection diodes is limited by 
>>>the 10K resistor then this is ok??  Is this a safe assumption?
>>>
>>>Seb
>>>
>>>
>>>    
>>>
>>
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>>
>>-- 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.
>>
>>
>>
>>  
>>
>

---------------------------------------------------------
- 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.