[sdiy] Phase shifters & Compandor chip availability

[Tim Ressel]

Mike, 

Thanks for the info. A few questions. The soft
limiting you mention is in relation to the GE diodes
on the resonance feedback path, yes? I was wondering
what those were for. 

You say the Quadra compandor is superior. What are
those pots I see in the schematic?? They look custom.
Some sort of VC attenuator? Are they available? Also I
am wondering if the extra expense of using MAT04s in
the ladder would be worth it. Lower noise and all
that.

--tr


--- eq927 at freenet.carleton.ca wrote:
> Hi Tim,
> I've also built a couple of modified Quadra phasers
> similar to JH's 
> design. JH has (had?) a good write-up on the very
> questions you ask on 
> his website. The compander serves two purposes  -
> one is noise reduction 
> - the other is to balance the clipping level of the
> diode soft limiter 
> with the input audio signal in order to provide a
> pleasant (not 
> speaker-blowing) mellow self-oscillation at high
> regen settings. Aside 
> from the ladder design and compander, the phaser is
> a bit unusual in 
> that the main output is in inverse mode (eg. n
> notches, n+1 peaks), 
> giving a hollow band-limited sound at high regen.
> The first unit I built 
>  worked first try, with randomly selected CA3046.
> The second unit 
> distorted, and this was traced to a CA3046 where the
> Vbe of one of the 
> transistors was markedly different from the rest.
> The compander design 
> used in the Quadra is superior to the NE570/NE571
> (both in performance 
> and parts availability).
> Regards, Mike


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