SergeModular

Hi all,

I am a bit confused about the difference between the PHA and the 2PHA. Could someone explain the basic differences? It appears that the 2PHA actually has LESS outputs than the PHA (where is the 1080 degree out?) Sorry if this is a stupid question! Thanks in advance for any info.

Gregg.

http://www.hermetech.net/

Hello Gregg (and all others interested.)

In a nutshell the "Basic" phase shifter circuit can take an input
signal and phase shift it between 0 and 180 degrees. In order to get
more phase shift you have to chain several circuits in series. That
is...2 circuits in series will give 0 to 360 degrees three circuits
will give 0 to 540 degrees and so on.

Just to clarify....in series means the output of one phase shifter
is the input to the next an so on.

Now.... in the basic Serge PHA phaser the maximum phase shift is
1080 degrees which means a total of 6 stages (6 times 180 degrees) in
series.

In the Dual Phaser 2PHA one phaser has a maximum of 360 degrees (2
stages) and the other has 720 degrees (4 times 180 degrees).

LOW AND BEHOLD !!! both units use a total of 6 stages.

AS with most of Serge's modules, he likes to use the same circuits
over and again in different configurations to maximize his "returns".
For example...the Dual Transient Generator uses exactly the same
circuit board as the Dual Universal Slope Generator. I would hazzard
to guess that the Quadrature Oscillator is merely a Variable Q VCF
set to permanently self oscillate. Etc. Etc.

Hope this explanation helps out.

Truth is....Neither Phaser module is much to write home about. To get
it usable you have to use an external mixer in order to introduce
feedback giving that all important "Resonance" that "Thick" phasing
requires. The 2 stage (360 Degrees) output on the 2PHA is all but
unusable in making the traditional "Phase Shifter" sound.

The best use for the 2PHA is to run the same signal into both
inputs and run the two outputs in stereo. Then use different
modulation on both and you'll get a fairly descent "Stero Thickener"

That's all for now........Cheers....Dean


--- In SergeModular@yahoogroups.com, darkflame 23 <darkflame23@p...>
wrote:

The earlier phasers didn't have built in feedback, my 6 year old STS
model has it. No external mixer needed. You have to patch MIX out back
into IN 2 input with a short cord. This setup allows other stuff (like
filters, etc) to be inserted into the feedback loop.

And the sound is very good imo, and useful.

The Quadrature Oscillator is NOT "a Variable Q VCF set to permanently
self oscillate." It has its own unique PCB.

The Phaser does indeed use the "slow" vactrols as in the old Buchla
Quad LP Gate and the Wiard Borg Filter.

-Nick Liebrecht

> IIRC it's based on vactrols. Anyone know if that was Serge's or Rex'
> idea?

Serge. Vactrols were used right back in the early Serge phasers
(mid 70s). Serge did patent another phaser design but AFAIK it
never got used in any modules



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Thanks Nick,
I stand corrected ( though If you would be kind enough to
share a little MORE info that what it's NOT I'm sure many, like
myself would appreciate it.) Looking at the description in the
catalog I see the two outputs have voltage controlled gain. This
would imply the need for 4 VCA's (2 for the actual oscillator circuit
and one each for the two output gain controls)
Having said that a more informed guess would be that the Quadrature
Oscillator uses the Quad VCA PCB with a piggyback control board.

BUT !!! as before I stand to be corrected. :)

Cheers....Dean.

Hi all,

Thanks for all the info on the Serge phasers. I have the first Telomere CD, so will take another listen!

I guess what I really wanted to know though, was what is the difference in functionality between the Phaser and the Dual Phaser, and is it worth shelling out the dosh for the Dual version?

Gregg.

http://www.hermetech.net/

Hi all,

Thanks for all the info on the Serge phasers. I have the first Telomere CD, so will take another listen!

and what a fine CD it is.

could someone please explain how to introduce feedback into a dual phaser? i'm not getting good results here. thx,

blake

-- 

M. Blake Wilson is OdysseySounds
Email: mbw@...
Web: http://members.cox.net/mbw/construction.htm
Music: http://artists.mp3s.com/artists/242/matthew_b_wilson.html
Serge: http://groups.yahoo.com/group/SergeModular/

--- In SergeModular@yahoogroups.com, Blake Wilson <mbw@c...> wrote:

Hi!

I'm not really sure about the VCA content of the quadrature
oscillator [QUO] because I haven't had to fix any. I know it has a
real VCO in it and it must have the two VCAs on the outputs. The
[QUO] has its own dedicated PCB, which is not stacked. It is the
same type of oscillator needed in a frequency shifter. In fact, it
is one of the three boards used in the frequency shifter.

It uses the traditional matched transistors and tempco in the expo
converter rather than the "oven" used in the [NTO] and [PCO]. The
[NTO] is a stacked module. It contains the basic oscillator board as
used in the [PCO] and another board containing the waveshaper and
other features unique to the [NTO].

There is a really cool triangle quadrature oscillator design in
Juregen Haible's frequency shifter project.

check it out:
http://www.oldcrows.net/~jhaible/tonline_stuff/hj_fs.html

I hope this helps everyone's curiosity. It's about all I know about
the [QUO]. I hope I haven't revealed any trade secrets!

-Nick Librecht