[sdiy] Aries modular schematics detail

[Grant Richter]

I finally got around to putting up that web page.

Aries AR-329 Phase/Flanger schematic

Some Electronics Workbench analysis of the phase shift ladder from Jurgen's
phaser with phase and magnitude plots. Perhaps transistors are not emitter
followers?

A diode only variation of the phase shift ladder (has anyone seen it
before?)

http://www.musicsynthesizer.com/Diode%20Phaser/Diode%20Phaser.html

> From: houshu at dsp.cl.nec.co.jp
> Reply-To: houshu at luke.dsp.cl.nec.co.jp
> Date: Mon, 21 May 2001 10:35:56 +0900
> To: jhaible at t-online.de (jh.)
> Cc: grichter at asapnet.net, synth-diy at node12b53.a2000.nl
> Subject: Re: [sdiy] Aries modular schematics detail
> 
> Hello JH and List,
> 
> I was wrong.  JH is right.  Transistor ladder in Quadra phaser is an
> almost perfect all pass filter.
> 
> I checked my note and analyzed again in the weekend.
> 
> First of all, my memory was wrong. What I analyzed was not phaser, but
> low pass filter using Quadra style transistor ladder.
> 
> Anyway, my analysis results are:
> 
> * LPF based on EMS style diode ladder (EDL) has different transfer
> function (frequency response) from LPF based on Moog style
> transistor ladder (MTL). (Very famous as Grant mentioned.)
> * Quadra style transistor ladder (QTL) can be an all pass filter
> (APF).
> * EDL can not be an all pass filter (APF).
> * MTL can not be an APF.  At least very difficult.
> * (QTL based LPF, which I imagined from Quadra, does not have the
> same transfer function as MTL based LPF nor EDL based LPF.)
> 
> I had a very interesting weekend.  Thank you so much.
> 
>> Date:    Fri, 18 May 2001 11:32:54 JST
>> From:    jhaible at t-online.de (jh.)
>> 
>>>> I don't think the use of transistors is essential to the design, such as
>> the
>>>> difference between the Moog transistor ladder and the EMS diode ladder.
>>> 
>>> I agree with you here.  I analyzed the transistor ladder phase shift
>>> network using a simple transistor model (voltage controlled current
>>> source), and found that it is equivalent to a diode ladder.
>> 
>> I think I did the same analysis some years ago, but came to different
>> results.
>> But that's all I remember - I must look it up again.
>> 
>> 
>>> Actually, I suspect that the transistor/diode ladder networks (not
>>> Moog complementary transistor ladder for high pass filter) can not be
>>> exact phase shifter (all pass filter), because each stage is not
>>> isolated.
>> 
>> If memory serves, *that* was the difference between using diodes and emitter
>> followers. Single stage would be the same, but transistors prevent loading
>> effects. But as I said, memory is very cloudy here, I must look again.
>> 
>> Transistor ladder is still no perfect all pass filter, though. That's why
>> this
>> phaser sounds much better with resonance than without I guess.
>> 
>> JH.
> - -- ---- ----------- --- --- - ----- -- --- --- - - ------ - - - --
> Osamu HOSHUYAMA                    NEC Corporation  Kawasaki JAPAN
> --------------------------------------------------------------------
> 
> 
>