|HOME|
|DIY FAQ|
|GEO FAQ|
|Debugging Page|
|Links|
|Schematics|
|Wiki| |Layouts
Gallery| |STORE|

|AMPAGE|
|GEOFEX| |AMZ|

Welcome, Guest. Please login
or register.
Did
you miss your activation
email?
April 10, 2014, 11:13:40 AM

944595
Posts in 101474 Topics by 31614 Members

Latest Member: swisher

DIYstompboxes.com
|  DIY
Stompboxes  |  Building
your own stompbox  |  How
to improve almost any phaser

0 Members and 1 Guest are
viewing this topic.

«
previous next
»

Pages: [1] 2
3

Author

Topic: How to improve almost any phaser  (Read 13563
times)

Mark
Hammer

Posts:
21466

How
to improve almost any phaser

« on: November 06,
2009, 08:12:29 AM »

I tried a quick and easy
experiment with a Ropez/Ross phaser last night and
was pleased with the outcome.  The boards
that Francisco Pena laid out and sells for that
phaser make it easy to implement, but it can be
applied to practically any phaser you can think
of.

When it comes to phasing, the result is
a product of the sum total of all
phase-shift applied.  So, 4 stages of phase
shift provide up to a maximum of 90-degrees of
phase shift per stage at any given frequency,
which totals a maximum of 360 degrees of phase
shift.  Essentially, you get one notch
produced per 180 degrees of total phase shift, so
360 gets you two swept notches.

Since the
sum total phase shift is what matters, not all the
stages have to sweep.  certainly most of them
need to, or else you wouldn't hear any swirl, but
they don't ALL need to.  A great many
commercial phasers make use of this principle, and
include some fixed stages on top of the swept
stages.  Probably the most commonly
encountered example is the venerable MXR Phase
100, which uses 6 LDR-based swept phase-shift
stages, but adds 4 more fixed stages on top of
that for a total of 10 stages, producing up to 5
notches ("up to" because not all notches are
audible or within the passband at all points in
the sweep).  Boss also uses the addition of
some fixed stages to spruce up some of their
phasers.

So, last night I decided to throw
in 2 stages of fixed allpass/phase-shift to this
Ropez, via a small daughter board that could be
easily assembled in a postage-stamp, sized piece
of perfboard, and hot-glued to the side of the
chassis.  I used what has become almost
standard fare for such things: a 4558, 10k
feedback resistors in each stage, 10k to the
inverting input, .01uf to the noninverting input,
and 10k to Vb.  That's a total of one 8-pin
DIP, 6 resistors, and 2 capacitors.  You've
seen this a million times.

The Ropez (at
least the last iteration of it) has a number of
pads aimed at integrating another quartet of swept
allpass stages to make an über-phaser with 8 swept
stages.  On the diagram, two of these pads
are labelled X and Y and are for inserting the
additional 4 stages that Francisco made a
daughterboard layout for.  Cut the path
between these two pads, run X to the input of one
of the fixed stages, run the output of the second
back to Y, connect your V+, gnd, and Vb, and away
you go.  You now have 6 stages, 4 swept, and
2 fixed.  The same logic can be applied to a
Small Stone,  Phase 90, or whatever.
The regeneration works exactly as
before.

How does it sound?  A little
richer, and to my ears a little more pleasing at
the top of the sweep.  Not surprising since
the added phase-shift really only starts to kick
in above 1500hz or thereabouts.  I tried it
out with the piezo bridge pickup on my Parker this
morning, and it sounds great for that.  I
like the vibrato produced when the dry is
cancelled a little better too.  On this
particular phaser, I have a switch for going from
phaser to phasefilter (two stages are converted
from allpass to lowpass), and am pleased to report
that the mod does not interfere with the pleasing
sound of a phasefilter.

While it might be a
little tricky doing this to a P90 installed in a
1590B chassis, it may well be possible to build it
onto a small, low-profile board it you are handy
with surface-mount op-amps and 1/8w
resistors.  It's one of those things that you
can build on a small daughter-board and try out on
whatever phaser you have handy.  If you like
it, keep it, and if you don't, it's no big deal to
put things back the way they were.

But on
the whole, definitely worth trying.

Logged

aziltz

Posts: 1157

grad
student

Re:
How to improve almost any phaser

« Reply #1 on:
November 06, 2009, 09:18:07 AM »

I don't want to detract from
such a detailed and focused thread, but I looked
around quickly for "phasefilter" as it seems
really interesting.

Is it possible that
this is how the EHX Worm gets all its
multi-effects?  At first glance, it looks
like a multi-stage phase shifter, but by
redirecting the feedback and a few outputs (?) you
can get Tremolo, "Wah" and Vibrato all from the
same LFO and "shifting network".

Are there
any concrete or schematic examples of how to wire
phasefilter from an existing phaser?

Thanks
for all the info Mark.  I'll surely try this
and your new suggestions for additional fixed
allpass/phase shift stages in the
future.

Logged

Mark
Hammer

Posts:
21466

Re:
How to improve almost any phaser

« Reply #2 on:
November 06, 2009, 10:32:06 AM »

Ton Barmentloo is a generous and
well-respected member of this forum.  I make
a point of not inquiring about any of his designs
in too much detail because I know that IP is his
livelihood.  The Worm is one of his.
That being said, the Worm is optical, and the
phase-filter option is something that essentially
relies on using OTAs (3080, 13600, 3094, etc) for
the allpass stages.

You can learn more by
looking up the SSM2040 datasheet ( http://www.synthdiy.com/show/?id=85
) and by looking at the design of the AMS-100
phase-shifter projects in DEVICE ( http://hammer.ampage.org/files/Device1-6.PDF
).

The original phase-filter idea, from
John Blacet, assumed the user would be combining
clean plus processed signal.  In playing
around with it, I found that some excellent and
truly distinctive sounds could be obtained by
using only the wet signal.  As a
result, if I'm going to implement aphase-filter
setting/function, I always include a vibrato
(dry-cancel) switch as well.

Logged

puretube

Posts: 7153

but, err, I`m not
really here...

Re:
How to improve almost any phaser

« Reply #3 on:
November 06, 2009, 03:15:01 PM »

The "WORM" is just a
3-stager...

Logged

www.puretube.com

puretube

Posts: 7153

but, err, I`m not
really here...

Re:
How to improve almost any phaser

« Reply #4 on:
November 06, 2009, 05:39:44 PM »

Mark: your understanding my
positions is well appreciated!

Philtering,
Worming, Wahbrating, and Vibwahting can be done
with all those more or less known
circuitries/technologies/topologies...

the
"Worm" bore out of the fact, that the textbook
"...pass-transformations" and the Fourier and
Hilbert thesis`
didn`t tell me all I wanted to
know...

for me, the all-pass was
missing in there...

Now when you look
at the simplest allpass building block: the
phasesplitter with an R and a C
between
the inverting and the non-inverting output of a
triode or BJT,
1.: you`ll see that from one of
the outputs
the R-C series-hookup
looks
like a Lo-Pass,
while from the opposite phased
output,
it looks like a
Hi-Pass...

Combining (adding/summing)
these, we get an All-Pass, as is well
known...

now: Serially combining Hi- And
Lo-pass gives a Bandpass...

Subtracting a
Hi-pass from the dry turns into a
Lopass,
Subtracting a Lo-pass from the dry
turns into a Hipass;

... sorry- I got
distracted while typing ...

now: if one
combines the lowpass or highpass during the right
phase-relationship
with the original ( = dry )
signal or with the 1st All-pass (@ the proper
amplitude.relationship)...

[will be
continued, one day...]

Logged

www.puretube.com

aziltz

Posts: 1157

grad
student

Re:
How to improve almost any phaser

« Reply #5 on:
November 06, 2009, 06:19:10 PM »

i didn't mean to sidetrack the
thread, but at the same time, thanks for those
comments!

Logged

petemoore

Posts:
18696

As Yet
Unrated

Re:
How to improve almost any phaser

« Reply #6 on:
November 07, 2009, 09:39:49 AM »

On my Tonepad Small
Stone PCB, it looks like an insertion point for
the extra stages could be made by cutting the
trace between R33 and R41 ?
The two
added stages would consist of what is between Q6
emitter and Q10 emitter?

Logged

Convention creates
following, following creates
convention.

Mark
Hammer

Posts:
21466

Re:
How to improve almost any phaser

« Reply #7 on:
November 07, 2009, 04:32:20 PM »

Yep.  From the looks of it,
that's a viable insertion point.  And what
you're going to insert there is essentially a
replica of what you see built around IC6 in the
RPH-10 diagram shown here.  The diagram shows
5k6 resistors to Vb.  I used 10k, but you can
use whatever you want, keeping in mind that the
corner frequency where they start contributing 90
degrees of shift is given by the ever-popular F =
1 / (2 * pi * C * R).

Logged

Mark
Hammer

Posts:
21466

Re:
How to improve almost any phaser

« Reply #8 on:
November 09, 2009, 01:45:12 PM »

Playing around with the pedal
last night, I became convinced that I need to
figure out how to envelope-control it.  The
sound of a gradual upward swell with two notches
and lowpass, and some resonance, using only the
wet signal, is lush, lush, lush.  Like a
dreamy synth pad when applied to chords.
Tack a bit of chorus and decent reverb on top, and
you have no need for guitar synths.

The
trick is not just getting envelope control,
though.  One needs to keep in mind that the
sort of sound produced when the on-board LFO is
set for slower speeds is NOT equivalent to a
straightforward amplitude envelope.  The LFO
sweep moves upward exponentially, so there would
need to be some sort of envelope follower that
would:
a) provide sufficient lag and control
over attack/rise time,
b) translate that attack
into an exponential sweep,
c) convert that
exponential sweep into suitable current to feed
the OTAs.

But believe me, the resulting
sound is worth it. I gotta make some clips of
this.

Logged

space_ryerson

Posts: 450

Tim M.

Re:
How to improve almost any phaser

« Reply #9 on:
November 09, 2009, 04:42:24 PM »

You've definitely got my
attention! I wonder if I could fit this (with the
envelope) in a Phase 90 where the battery would
reside?

Logged

Mark
Hammer

Posts:
21466

Re:
How to improve almost any phaser

« Reply #10 on:
November 09, 2009, 06:15:40 PM »

With an envelope follower, it
would need your battery slot to be able to fit in
a 1590B, although without an envelope follower,
the pair of additional stages actually take up
fairly little room, and would even allow you to
keep the battery in.  The dual op-amp itself
is the biggest part.  1/8W resistors take
hardly any space, and you can certainly use small
monolithic ceramic caps for the phase shift stages
without any space or audio quality
concerns.

Note, however, that the rising
sweep I'm talking about is not attainable on a
P90.  It needs an OTA-based phaser like the
Ross or Small Stone, or the DOD FX20.

Logged

petemoore

Posts:
18696

As Yet
Unrated

Re:
How to improve almost any phaser

« Reply #11 on:
November 09, 2009, 07:08:02 PM »

What is the partial schem
from ?
It's stages differ from the SS
stages, no Q followers [ ], but it has a feedback path
that...goes a different way than the
SS's.

Logged

Convention creates
following, following creates
convention.

Mark
Hammer

Posts:
21466

Re:
How to improve almost any phaser

« Reply #12 on:
November 10, 2009, 09:02:49 AM »

Well, I made a 2-stage
daughter-board last night, as small as I could,
using 1/8W 10k resistors and small ceramic .01uf
caps.  The op-amp was a normal 8-pin DIP
dual.  Total footprint when done was 5 perf
holes by 10 (plus the board area between the holes
along the perimeter and where the next row of
holes would be).  The small caps and
resistors assured that the IC (unsocketed) was
effectively the "tallest" component on the
board.  So, this is pretty darn small, and
the sort of thing one could easily fit somewhere
in a 1590B, between a pot and the side of the
chassis.  In some respects, the wires
connecting it to the main board occupy more space
than the daughter-board
itself.

pete,
The partial schem is the
Boss RPH-10, which uses a pair of IR3109 chips for
allpass stages, in addition to the op-amp stages
shown.  It is basically the Boss PH-2 phaser
pedal, plus some extra bells and whistles.
The IR3109 is four OTAs in a package, similar to
the old SSM2040, but made specially for
Roland/Boss.  It allows for a fairly compact
phaser when you want to have a lot of
stages.  Consider that it would replace four
CA3094s or a pair of LM13600 chips.

Logged

space_ryerson

Posts: 450

Tim M.

Re:
How to improve almost any phaser

« Reply #13 on:
November 10, 2009, 10:35:34 AM »

Quote
from: Mark Hammer on November 09, 2009, 06:15:40
PM

With an envelope follower, it
would need your battery slot to be able to fit in
a 1590B, although without an envelope follower,
the pair of additional stages actually take up
fairly little room, and would even allow you to
keep the battery in.  The dual op-amp itself
is the biggest part.  1/8W resistors take
hardly any space, and you can certainly use small
monolithic ceramic caps for the phase shift stages
without any space or audio quality
concerns.

Note, however, that the rising
sweep I'm talking about is not attainable on a
P90.  It needs an OTA-based phaser like the
Ross or Small Stone, or the DOD
FX20.

Thanks Mark. 5x10 perf is
tiny!

If I really feel the need for a
rising sweep, I'll take a look to see if my other
phaser is OTA based. It's an old Tokai, which I
haven't really analyzed circuit of.

Logged

petemoore

Posts:
18696

As Yet
Unrated

Re:
How to improve almost any phaser

« Reply #14 on:
November 11, 2009, 02:27:28 PM »

I have the parts,
hot iron, everything laid out...but just couldn't
seem to try it without understanding better, or
having a schematic for it.
The RPH-10
opamps [around IC6] are wired quite differently
than the arrangement in the Small
Stone.
Looking at the Tonepad
Schematic, Cut the connection between R33
and R41.
Describing the RPH-10's IC6
..Insert circuit:
10k/.01uf [10k
to an OA Neg input, also the 10k feedback
resistor], .01uf to "10k-Vbiased" +oa input.

Output through 10k to a duplicate
wired circuit [the other side of Dual OA] 6k8
output from the second opamp back to the board
splice point.
Also V+ and Gnd. to
Dual opamp.
The reason I ask is
because the circuit I wish I could draw up [layout
creator giving fits for sometime trying], looks
quite unrelated to the phase stages shown in the
Small Stone, at the same time, I like that they
look simpler.

« Last
Edit: November 11, 2009, 02:32:13 PM by
petemoore »

Logged

Convention creates
following, following creates
convention.

StephenGiles

Posts:
5371

Re:
How to improve almost any phaser

« Reply #15 on:
November 11, 2009, 03:55:57 PM »

Quote
from: Mark Hammer on November 09, 2009, 06:15:40
PM

With an envelope follower, it
would need your battery slot to be able to fit in
a 1590B, although without an envelope follower,
the pair of additional stages actually take up
fairly little room, and would even allow you to
keep the battery in.  The dual op-amp itself
is the biggest part.  1/8W resistors take
hardly any space, and you can certainly use small
monolithic ceramic caps for the phase shift stages
without any space or audio quality
concerns.

Note, however, that the rising
sweep I'm talking about is not attainable on a
P90.  It needs an OTA-based phaser like the
Ross or Small Stone, or the DOD
FX20.

This is my adaptive peak
following envelope generator

Could be useful in this
application.

« Last
Edit: November 11, 2009, 04:10:10 PM by
StephenGiles »

Logged

If you don't go when you do
want to go, then when you do go you'll find that
you've
gone.

frequencycentral

Posts: 4881

Kicking the sh!t of
of your speakers since 2008

Re:
How to improve almost any phaser

« Reply #16 on:
November 11, 2009, 04:12:03 PM »

Watching this thread like a
hawk!

So Mark, how would you contrast the
addition of two static stages versus the addition
of two modulated stages?

Logged

http://www.frequencycentral.co.uk/

Mark
Hammer

Posts:
21466

Re:
How to improve almost any phaser

« Reply #17 on:
November 11, 2009, 04:50:43 PM »

It's a slightly different
sound.  Remember that when all stages are
modulated, the point where they add up to enough
phase shift to produce notches keeps moving.
The fixed stages I described add their maximum
phase-shift above 1590hz (with amounts lower than
90 degrees below that point), but not before
it.  So in a way, the effect becomes a little
stronger or more evident during the uppermost
parts of the sweep.  It's not huge, I have to
say, given that it is after all only 2
stages.  But it's almost like the unit
evolves from 2 to 3 notches as you move past the
halfway point in the upward sweep.  All those
companies that added fixed stages on top of the
swept ones knew what they were doing.

Logged

frequencycentral

Posts: 4881

Kicking the sh!t of
of your speakers since 2008

Phasers
gone wild

« Reply #18 on:
November 14, 2009, 09:08:08 AM »

I just received my Ropez PCB and
the 4 extra stages board. Well I might as well
wedge a few more (static) stages in there too! I
was thinking of two quad opamps on a daughter
board, both configured as 4 static stages, so with
4 static stages either side of the Ropez extra
stages board.

Logged

http://www.frequencycentral.co.uk/

StephenGiles

Posts:
5371

Re:
How to improve almost any phaser

« Reply #19 on:
November 15, 2009, 04:17:53 AM »

Quote
from: frequencycentral on November 14, 2009,
09:08:08 AM

I just received my Ropez PCB
and the 4 extra stages board. Well I might as well
wedge a few more (static) stages in there too! I
was thinking of two quad opamps on a daughter
board, both configured as 4 static stages, so with
4 static stages either side of the Ropez extra
stages board.

Mmmm could be easier to
just build an Eventide Instant Phaser!

Logged

If you don't go when you do
want to go, then when you do go you'll find that
you've
gone.

Pages: [1] 2
3

«
previous next
»

Jump to: Please select a destination: ----------------------------- DIY
Stompboxes ----------------------------- => Building your own
stompbox ===>
Pictures => Digital
& DSP =>
Store ----------------------------- Projects
-----------------------------
=> Beginner Project
=> IC-based Overdrive
=> Diode-Compression Op Amp

Powered by SMF 1.1.19 | SMF
© 2013, Simple Machines
Page
created in 0.083 seconds with 16 queries.