I'm pretty obsessed with phasers (among other things!) I've looked at a few vintage FET phaser schematics recently that have made me want to try a few experiments and see what happens, namely:
Maestro: http://analogguru.an.ohost.de/193/schematics/Maestro_MPS-2.gif
Univox: http://analogguru.an.ohost.de/193/schematics/Univox_MicroFazer.gif
Bad Stone: http://www.freeinfosociety.com/electronics/schemview.php?id=380
What I find interesting about these phasers is the drain/source resistor value (or lack of any in the Maestro). As I understand it, this resistor's job is to reduce distortion, the higher it's value the deeper the deeper the phasing but the more distortion. The MXR P90 uses 22k, while the P45 is slighly more elaborate again, and slightly higher quality than the P90.
Also take a look at this: http://www5b.biglobe.ne.jp/~houshu/synth/PhaseFet0205.GIF
So how does the Maestro get away with no drain/source resistor? I'm guessing by using FETs with a higher vgs than one would find suitable for use in a P45/P90 (I've built varients of both). I have loads of FETs, and my starting point is a matched sets with vgs of -2.5v, which were too high for my previous P90 build.
Here's my schematic, now phasing on the breadboard:
(http://i210.photobucket.com/albums/bb292/frequencycentral/SonicDeathRay6.gif)
As you can see, it's pretty stripped down, but owes something to the P45 as well as the Maestro. I'm using 2n5485 FET's, the opamps are two TL084's. It sounds really nice, initially I got a touch of distortion as the LFO reaches the bottom of it's cycle, but I was able to limit the sweep by choosing a cap value of 0.01uF between the gates and sources. As there are six stages, there are a few choices for regen - I tried them all and found that the best ones were 4 and 5 stages apart, so there's a mode switch for this. 3 stages apart also sounded good, so I may end up using a three way switch. The different regen modes each give a very different feel, much more so than switching the phaser itself between 4 and 6 stages. The 2n5485 I'm using are matched at -2.5 Vgs, I also tried another set matched at -2.3 Vgs which also sounded good. I even tried half a dozen unmatched 2n5485 with equally good results. The cap values in the phase stages are markedly highly than one would expect, I initially tried smaller values but the notches were too high. I also tried Univibe values, but the 0.47uF just sounded best.
So there you have it, a stripped phaser which breaks a few rules - I should have called it Phase Insurrection. I don't know how it will work with different FET types, or FETs with lower Vgs than I used, but using the values specified it works just fine. Soundclips when I finally get my mic back!
Interesting, you could try a static phase shift stage or 2 in the regeneration path to see what other rules you might break!!
The P45 has the RC network between drain and gate which reduces distortion. Mike Irwin told me that it does not prevent distortion, though. It merely moves the threshold for distortion upwards. His take on it was that although the threshold was moved upwards, when distortion DID occur, it was of an ugly variety, and ultimately he preferred the more gradually onset of distortion than the all-or-none arrangement, so opted for omitting the RC network. At the same time, I note that Mike's predilection is for synths, which have a higher amplitude signal level than guitars (usually line-level or higher). So, his decision model may be a bit different than most people here.
As for the drain-source resistance, keep in mind that the needed resistance is going to be a function of the cap value, where you want the notches to be, and what the drain-source resistance is when the JFET is biased "in the zone". The function of the drain-source resistor is just to set a minimum notch frequency. So, for the MPS-2, if those FETs had a d-s resistance of 150k when biased just right, the lowest possible notch would be at 106hz. Note that although the P90 uses 22k d-s resistors in parallel with the JFET, they also use .05uf caps. If the JFET d-s resistance is high enough that the combined parallel resistance is 22k, then the lowest notch location is at 145hz. Since the d-s resistance is probably going to be in megohms, rather than infinity, we can safely assume that the lowest notch frequency is likely somewhere around 180-200hz.
When the LFO output voltage is most positive, you're almost certainly forward-biasing the JFETs. I would either shift the audio portion's bias more positive, or the LFO's bias more negative (or both!), to try and reduce distortion while increasing the range of the sweep.
I like the low parts count; seems like you could do a lot more stages and still keep the size reasonable. I like it. Too bad I still haven't gotten around to building your other phaser yet.
awesome ! .... phasers rule ! .... ( i'm still working on the Causality 4 builds .... )
Quote from: earthtonesaudio on June 04, 2010, 12:04:36 PM
When the LFO output voltage is most positive, you're almost certainly forward-biasing the JFETs. I would either shift the audio portion's bias more positive, or the LFO's bias more negative (or both!), to try and reduce distortion while increasing the range of the sweep.
I'll give that another try, playing with the audio bias does increase the range but also adds distortion at the bottom of the LFO sweep. I've no distortion now, I've had to reduce the range of the sweep a little to get that.
doc drop tells me he's going to breadboard it this weekend, maybe
panterafanatic will too? I'll be interested in a second opinion with a different set of FETs, on the other side of the world.
After another play with this thing, it's clear to me that there are four possible taps for the regen, each one markedly different and useable, so I'm going to include a 4 way switch, with 4 LED's to indicate which mode is on. The only four way switches I have are quite large rotary, so it's going to have to be in a bigger enclosure than a 1590B - maybe an excuse for a bigger circuit with a couple more swept stages and two static stages in the regen path?
Quote from: frequencycentral on June 04, 2010, 03:23:45 PM
...maybe an excuse for a bigger circuit with a couple more swept stages and two static stages in the regen path?
Now you're thinking buddy!
Small Bear sells a really compact 1p6T rotary switch. It has a screwy layout for the connections to the pins. I have used it for switching caps and it works great. I made a small pcb to mount it and make it easier to add the caps. It can easily stand upright in a BB box.
You could cut down the board and connect your leads where I have the numbers for the caps. Note that positions 5 and 6 are flipped due to the weird arrangement of contacts on the switch.
(http://i48.tinypic.com/4lm1qd.jpg)
(http://i47.tinypic.com/300uqlc.jpg)
Quote from: frequencycentral on June 04, 2010, 11:37:45 AM
What I find interesting about these phasers is the drain/source resistor value (or lack of any in the Maestro). As I understand it, this resistor's job is to reduce distortion, the higher it's value the deeper the deeper the phasing but the more distortion. The MXR P90 uses 22k, while the P45 is slighly more elaborate again, and slightly higher quality than the P90.
ok, so you understand that there is a trade-off of "some" sort ...
the trade-off is transfer linearity to resistance range (slope of transfer around zero-crossings)
Quote
So how does the Maestro get away with no drain/source resistor? I'm guessing by using FETs with a higher vgs than one would find suitable for use in a ...
that's where you loose it ... you need to read the Vischay "jFET-VCR" paper I've mentioned numerous times in this silly forum
read it 100 times or more, so it starts to sink in ...
I know you guys are allergic to math, but that's where it's ... at
I hate to say it but your post is once again saying that something fundamental is being overlooked, n'est-ce pas ?
---
so then, there's the delusional concept of "matching" that has been introduced by a chap who obvisouly can't swim his way out of a glass of circuit analysis (the flying mulcher guy) - but I've already said anough about this already ... my educated guess is this is greatly part of the reason why you guys are still to this day whacking your head on the wall of this cage ...
read the paper yourself instead of seeking advice from others who obviously haven't read it,
or have but can't "really" figure it out ...
remember, it's impossible work for those who lack the proper conceptual tools
app notes are written for design engineers - ie., people who are potentially trained to read between the lines ...
people who, more importantly, know why the math does what it does - as opposed to someone memorizing and regurgitating "trick" equations ... I have shamed several senior design engineers in my work who do just that to appear knowledgeable
unfortunately, it's very common in analogue design circles ...
I see it here all the time
Only my 123rd post.
Let me guess. You have a lot of friends on this forum.
Read this 100 times or more so it starts to sink in.......
"I will not be a pompous a**hole".
Please shame me with a short sweet summation of what we are all missing. I'm, to this day, still under the impression that FETs would need to be matched for this purpose do to their loose tolerances. Which all comes from what I've read here.
Quote from: soggybag on June 04, 2010, 07:11:11 PM
Please shame me with a short sweet summation of what we are all missing. I'm, to this day, still under the impression that FETs would need to be matched for this purpose do to their loose tolerances. Which all comes from what I've read here.
Let's not go there. Life is far too short to take so seriously what should just be fun. Please let's not spoil the fun of this thread with a flame war.
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
Anyway, back to our scheduled programme. :icon_eek:
I'm sure I recall Mark Hammer posting a link to a phaser with fixed stages in the regen path, but I can't for the life of me remember which phaser it was. Mark?
Tomorrow I'm going to add a third TL084 to the circuit - 2 extra swept stages, and 2 fixed stages in the regen path. As I'm getting 4 choices of regen flavour currently, two extra stages should add another two regen options to play with. I can't quite imagine what two fixed stages in the regen path will sound like, but I'm gonna find out for sure - maybe I could use a DPDT toggle to select or bypass these two stages for further sonic possibilities. I just have to get some more 10k resistors...........fkg phasers, so many 10k resistors............!
To be honest I'm trying to ruffle any feathers. I'd really like to hear a short explanation about getting around the idea of having to use matching FETs for things like Phase 45. Which is what I thought Eb+7 was getting at.
Quote from: MikeH on June 04, 2010, 03:44:19 PM
Quote from: frequencycentral on June 04, 2010, 03:23:45 PM
...maybe an excuse for a bigger circuit with a couple more swept stages and two static stages in the regen path?
Now you're thinking buddy!
bi-phase :icon_twisted: we're all thinking it. you know you want to!
Quote from: soggybag on June 05, 2010, 12:18:39 AM
To be honest I'm trying to ruffle any feathers. I'd really like to hear a short explanation about getting around the idea of having to use matching FETs for things like Phase 45. Which is what I thought Eb+7 was getting at.
Just don't bother, it really doesn't make that much difference ::)
Quote from: frequencycentral on June 04, 2010, 11:37:45 AM
.... The 2n5485's I'm using are matched at -2.5 Vgs, I also tried another set matched at -2.3 Vgs which also sounded good. I even tried half a dozen unmatched 2n5485 with equally good results .....
how would i go about matching the 2n5485's ? ... can i do this without a scope ?
Quote from: frequencycentral on June 04, 2010, 07:16:22 PM
I'm sure I recall Mark Hammer posting a link to a phaser with fixed stages in the regen path, but I can't for the life of me remember which phaser it was. Mark?
Well, your memory took you 95% of the way there. :icon_biggrin: Here's the other 5%. It's this one (many thanks to Rob Strand). Note that there is a fixed stage in the feedback path to mimic what would, more or less, be true if it was a 6-stage phaser and the feedback was going from the 6th to 2nd stage. Since each phase-shift stage (fixed or variable) is inverting, the feedback needs to pass through an odd number of stages to present an inverted signal to mix back in. Because the fixed stage accomplishes that inversion, that permits the feedback to be directed to the first stage, instead of the 2nd as most of us are accustomed to seeing.
The AM97C11 is long gone (At least as far as anyone knows. If you spy some, please report back.), and only has 4 FETs on board, which more or less explains why Ross adopted the approach they did.
I said "more or less be true" above, because there is more phase shift introduced in the feedback path than there is in the direct path. I've never tried this out. so I have no opinion on what it sounds like, but it may be interesting, and a little different at the lower end of the sweep. You will note that R23/C10 form a
lowpass filter going to the non-inverting pin, instead of the highpass filter we see throughout the rest of the swept stages here (C2/C4/C6/C8 each form highpass filters with their respective drain-source resistances). As such, it adds more phase shift the lower the frequency. In this instance that added phase shift commences a bit above 300hz. This might be an interesting add-on to insert into a P90, though my instinct would be to use a dual op-amp on a daughter board, with one cap to ground of maybe .015uf, and the other as .05uf, just to spread out that extra phase shift a little farther across the spectrum. In one of my Ropez phasers, I used the little patch-point pads that Francisco graciously provides to insert a pair of fixed stages, making 6 in total, and quite like the result. My added stages are of the lead (CR) rather than lag (RC) type, so the additional phase shift is added as you sweep upward.
(http://www.home-wrecker.com/ross_phaser_orange2.png)
Hmmm, I'm wondering how worthwhile it would actually be to.....
Quote.....add a third TL084 to the circuit - 2 extra swept stages, and 2 fixed stages in the regen path.
.....given that this sounds pretty rich already. And that as Mark states, the Ross used fixed stages in the regen path to accomodate rich 'six stage style' regen in what is otherwise a four stage phaser. Performing those mods would make the circuit half as big again - for maybe just a little more whoosh, law of diminishing returns. I guess I have to try it to find out, but I imagine I'll end up sticking with what I have already (with the addition of more switch regen options) unless the mods are really groundbreaking.
I'm finding the different regen taps really interesting. Conventional wisdom is that 3 stages apart is the minimum, and that it must be an odd number of stages.
puretube turned me on to the fact that it doesn't
have to be an odd number in the Causality 4 thread.............
Quote from: puretube on November 27, 2009, 05:41:00 PM
Quote from: frequencycentral on November 27, 2009, 05:33:42 PM
But it has to be an odd number of stages right?
Who says: "ODD" anymore, when such a circuit is shifting its phase-relations from at least zero° to almost or even over 360°
for almost any frequency ??? :icon_mrgreen:
....and he's correct of course. What surprises me is that even 2 stages apart sounds really good. The four regen modes really do make it sound like four different phasers, some low and bass heavy, others stratospheric.
Quote from: stringsthings on June 05, 2010, 05:11:13 AM
Quote from: frequencycentral on June 04, 2010, 11:37:45 AM
.... The 2n5485's I'm using are matched at -2.5 Vgs, I also tried another set matched at -2.3 Vgs which also sounded good. I even tried half a dozen unmatched 2n5485 with equally good results .....
how would i go about matching the 2n5485's ? ... can i do this without a scope ?
The GEOFEX FET matching fixture, just a very small circuit and a DMM, build one onto your breadboard, or even make a hardwired perf/vero/PCB fixture:
http://www.geofex.com/Article_Folders/fetmatch/fetmatch.gif
Quote from: frequencycentral on June 05, 2010, 07:50:28 PM
The GEOFEX FET matching fixture, just a very small circuit and a DMM, build one onto your breadboard, or even make a hardwired perf/vero/PCB fixture:
http://www.geofex.com/Article_Folders/fetmatch/fetmatch.gif
thank you ! ... that's a good read on GEO ...
......ah, screw this puny 6 stage malarkey, after seeing Strategy's Tau Pipe phaser I'm gonna make this bitch with 16 stages and 12 regen taps.........!
Heck Yeah !!! ;D
Quote from: soggybag on June 05, 2010, 12:18:39 AM
To be honest I'm trying to ruffle any feathers. I'd really like to hear a short explanation about getting around the idea of having to use matching FETs for things like Phase 45. Which is what I thought Eb+7 was getting at.
Here's the appnote JC was talking about, or I presume it's this one anyway.
http://www.alldatasheet.net/datasheet-pdf/pdf/161774/VISHAY/AN105.html (http://www.alldatasheet.net/datasheet-pdf/pdf/161774/VISHAY/AN105.html)
I've only read it once, so it hasn't all sunk in yet :) I get the bit about the resistors reducing distortion. but I don't
yet see how the information relates to the need or otherwise to match FETs.
I for FETs, the only thing I've got is apparently 2N5457s, are these close enough to the 2N5485s? (Edit: I'll just test it out now and find out.)
I also do not know how to match the FETs.. Do I check for leakage or hFE?
Quote from: panterafanatic on June 06, 2010, 08:10:14 AM
I for FETs, the only thing I've got is apparently 2N5457s, are these close enough to the 2N5485s? (Edit: I'll just test it out now and find out.)
I also do not know how to match the FETs.. Do I check for leakage or hFE?
I did try some 2n5457, which produced clicking/thunking. They were not matched, or even measured. When I get time I'll measure and match them and try them.
For FET matching see the link to the GEOFEX matching fixture on page 1.
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
I'm now thinking of making this a modular design, with the LFO and input stage on one board using a NE5532, together with the speed and regen pots. Then I'll design a layout for a 4 stage board using a TL084 and four FETs, with pads to add as many additional 4 stage board as desired. How cool is that?
Quote from: slacker on June 06, 2010, 07:42:59 AM
Quote from: soggybag on June 05, 2010, 12:18:39 AM
To be honest I'm trying to ruffle any feathers. I'd really like to hear a short explanation about getting around the idea of having to use matching FETs for things like Phase 45. Which is what I thought Eb+7 was getting at.
Here's the appnote JC was talking about, or I presume it's this one anyway.
http://www.alldatasheet.net/datasheet-pdf/pdf/161774/VISHAY/AN105.html (http://www.alldatasheet.net/datasheet-pdf/pdf/161774/VISHAY/AN105.html)
I've only read it once, so it hasn't all sunk in yet :) I get the bit about the resistors reducing distortion. but I don't yet see how the information relates to the need or otherwise to match FETs.
Shame on you for only bothering to read it once. Don't come back until you've read it the other 99 times. :icon_lol: I'm so clever I might only have to read it 50 times........
I'd of thought by now you'd just have this stuff jacked straight into your cyborg brain box.
Quote from: frequencycentral on June 06, 2010, 08:40:12 AM
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
I'm now thinking of making this a modular design, with the LFO and input stage on one board using a NE5532, together with the speed and regen pots. Then I'll design a layout for a 4 stage board using a TL084 and four FETs, with pads to add as many additional 4 stage board as desired. How cool is that?
sounds very cool ....
but wouldn't the regen pot go on the same board as the FETs and the TL084?
attaboy frequencycentral! 8)
Quote from: frequencycentral on June 06, 2010, 05:18:37 AM
......ah, screw this puny 6 stage malarkey, after seeing Strategy's Tau Pipe phaser I'm gonna make this bitch with 16 stages and 12 regen taps.........!
Just to report in on my breadboard progress...
I have it up and phasing, but it is a very uneven phase. I think I must not have a stage going or something? If I turn up the Mix knob it gives me a tremelo since there is no sound during part of the cycle.
I used 2N5485's, but I made no attempt to match them. That might be part of the problem.
Anyway, I'll report back if I make any progress. Maybe I just need 16 stages! :icon_idea: :icon_razz:
Quote from: earthtonesaudio on June 04, 2010, 12:04:36 PM
When the LFO output voltage is most positive, you're almost certainly forward-biasing the JFETs. I would either shift the audio portion's bias more positive, or the LFO's bias more negative (or both!), to try and reduce distortion while increasing the range of the sweep.
Thanks Alex, that really worked well. the LFO bias voltage divider is now 220k/150k (the 150k to ground), much wider sweep - very, very nice. The LFO was previously 'topping out a little', this has totally cured it.
Quote from: doc_drop on June 06, 2010, 03:47:26 PM
Just to report in on my breadboard progress...
I have it up and phasing, but it is a very uneven phase. I think I must not have a stage going or something? If I turn up the Mix knob it gives me a tremelo since there is no sound during part of the cycle.
I used 2N5485's, but I made no attempt to match them. That might be part of the problem.
Anyway, I'll report back if I make any progress. Maybe I just need 16 stages! :icon_idea: :icon_razz:
PM'd!
Quote from: frequencycentral on June 05, 2010, 07:50:28 PM
What surprises me is that even 2 stages apart sounds really good. The four regen modes really do make it sound like four different phasers, some low and bass heavy, others stratospheric.
My mistake. I'm using 3, 4, 5 and 6.
2 doesn't work. I got confused. ???
Quote from: slacker on June 06, 2010, 07:42:59 AM
Quote from: soggybag on June 05, 2010, 12:18:39 AM
To be honest I'm trying to ruffle any feathers. I'd really like to hear a short explanation about getting around the idea of having to use matching FETs for things like Phase 45. Which is what I thought Eb+7 was getting at.
Here's the appnote JC was talking about, or I presume it's this one anyway.
http://www.alldatasheet.net/datasheet-pdf/pdf/161774/VISHAY/AN105.html (http://www.alldatasheet.net/datasheet-pdf/pdf/161774/VISHAY/AN105.html)
I've only read it once, so it hasn't all sunk in yet :) I get the bit about the resistors reducing distortion. but I don't yet see how the information relates to the need or otherwise to match FETs.
that's the one ... ok, let's spill the beans with Ann Margret thrown in for good meaure
aside from distortion issues there are two things to worry about here
they are, the input control range and the output value range
the paper is very clear about defining the input control range,
it is done in terms of the important device parameter Vp ... all the graphs are normalized to that value
the paper assumes "you" know what that value is for your device(s)
it's the starting point of a good design methodology
for example,
fall outside of that range and you hit the asymptotic resistance wall and you'll get "thunk" in the response if there isn't
a limiting resistor in parallel with the jFET channel ... stay within it too much to be safe and not much will happen
also,
have those ranges lay unequal and your devices will not track each other in right proportion - ie., not all your channel
resistances will be moving by same amount cause curve is asymptotic ... in other words you're wasting your time trying to
get something out of your (multi-stage) hardware when some of the stages are just not doing anything ...
why go through the trouble ?
if you're manufacturing units for mass production and yu just want something that "works" that's one thing, but if you're
aiming to DIY a killer phasor me thinks you'd want to use this kind of fuel in your recipe ... otherwise, like Einstein said, you
keep banging your head on the wall and slowly turn insane
---
engineers who are familiar with jFET matching know it's a two dimensional affair as I've pointed out many times ... BJT
devices on the other hand involve estimating Is for matching ... to characterize jFET's one needs to know Idss and Vp
characteristics ... even though there is somewhat of a trend between the two values there also is a random gaussian
distribution offseting the trend ... otherwise, matching jFETs would simply involve resting for one value (may as well make
that Idss cause it's the easiest to measure accurately) ... Vp is not despite what some people think - it's an asymptotically
derived value ...
so, to come back to the above problem one must ask the following question:
does the Keen test say anything about Vp ?
the answer: absolutely not at all ...
otherwise everybody and his favorite pet monkey in industry/academia would already know about it and make use of it
a simple drawing suffices to explain why this is a bogus idea
---
so, enough with that false-matching nonsense ...
let's look at the design of a phasor from a generalized perspective
the same thing applies to opto-cupler based designs btw
you have a resistance range you'd like to control ...
you assume that you have a way of doing the characterization/matching correctly
there are two approaches you can take ...
(i)
one is to take your bag of devices and figure out how to accurately estimate Vp for all of them
(I use an interpolation technique applied to a square-root transformed data set - pretty obvious why)
the result is close to being linear but not quite because jFETs are not perfectly quadratic in transfer
(a moot point really)
after grouping the devices that have close Vp values do an Idss test between them and pair the ones that come out closest
again now, you've got you best shot at having devices that have matching (Vp, Idss) value pairs for a given test voltage
then, from that info, you can tailor a control circuit that will suite the four or six devices you've singled out for this purpose
set the mean value somewhere within the 0v-to-Vp range and make sure the control voltage at the grid stays within that
range then your next and final step is to set the sweep of the voltage so that it lands as close to each end of that range to get
maximal resistance variation from your devices ... if they are properly matched your devices will behave in a similar way within
that range as VCR cells
(ii)
the other approach is to try and fit devices to a given pedal circuit (because it's known to work) - which really, is but a fixed
control circuit ... what you guys are doing is trying to make your device lot fit to the output of that control circuit
take a wild guess which approach has a better chance of landing a more intense sounding phasor circuit ??!
---
this is the same set of constraints I face in my opto-coupler based phasors but in my case I've made it so my control
circuit has an offset and scaling control built in so I can tailor the response to my cells ... so it's very similar except you guys
are forced to deal with a control circuits that generally do not offer those features, plus opto-couplers don't have that
asymptotic resistance wall as jFETs do ...
if it were me and I wanted to get good strong phasing out of jFET's I would first of all select a jFET type that gives me a
comfortable (wide enough but no too wide) control range to begin with - it obviously has to fit within the voltage supply
range for one ... then I would worry about figuring out a better control circuit than what appears in many production line
circuits ... these are often short-cut circuits that won't help you much in this kind of endeavor ...
a simple triangle wave LFO with a variable bias ref and output intensity control should give you the offset and scaling
control you need ... this is all you'll ever really need to know about designing the best jFET phasor possible ...
---
now, the real challenge is figuring out how to estimate Vp more accurately because it can't be measured directly
such an idea as having 3% error at 10nA is complete bologna btw ...
you guys owe me a beer
I owe you a couple for the Traynor mods!
Quote from: Eb7+9 on June 08, 2010, 02:29:33 AM
that's the one ... ok, let's spill the beans with Ann Margret thrown in for good meaure
aside from distortion issues there are two things to worry about here
they are, the input control range and the output value range
the paper is very clear about defining the input control range,
it is done in terms of the important device parameter Vp ... all the graphs are normalized to that value
the paper assumes "you" know what that value is for your device(s)
it's the starting point of a good design methodology
for example,
fall outside of that range and you hit the asymptotic resistance wall and you'll get "thunk" in the response if there isn't
a limiting resistor in parallel with the jFET channel ... stay within it too much to be safe and not much will happen
also,
have those ranges lay unequal and your devices will not track each other in right proportion - ie., not all your channel
resistances will be moving by same amount cause curve is asymptotic ... in other words you're wasting your time trying to
get something out of your (multi-stage) hardware when some of the stages are just not doing anything ...
why go through the trouble ?
if you're manufacturing units for mass production and yu just want something that "works" that's one thing, but if you're
aiming to DIY a killer phasor me thinks you'd want to use this kind of fuel in your recipe ... otherwise, like Einstein said, you
keep banging your head on the wall and slowly turn insane
---
engineers who are familiar with jFET matching know it's a two dimensional affair as I've pointed out many times ... BJT
devices on the other hand involve estimating Is for matching ... to characterize jFET's one needs to know Idss and Vp
characteristics ... even though there is somewhat of a trend between the two values there also is a random gaussian
distribution offseting the trend ... otherwise, matching jFETs would simply involve resting for one value (may as well make
that Idss cause it's the easiest to measure accurately) ... Vp is not despite what some people think - it's an asymptotically
derived value ...
so, to come back to the above problem one must ask the following question:
does the Keen test say anything about Vp ?
the answer: absolutely not at all ...
otherwise everybody and his favorite pet monkey in industry/academia would already know about it and make use of it
a simple drawing suffices to explain why this is a bogus idea
---
so, enough with that false-matching nonsense ...
let's look at the design of a phasor from a generalized perspective
the same thing applies to opto-cupler based designs btw
you have a resistance range you'd like to control ...
you assume that you have a way of doing the characterization/matching correctly
there are two approaches you can take ...
(i)
one is to take your bag of devices and figure out how to accurately estimate Vp for all of them
(I use an interpolation technique applied to a square-root transformed data set - pretty obvious why)
the result is close to being linear but not quite because jFETs are not perfectly quadratic in transfer
(a moot point really)
after grouping the devices that have close Vp values do an Idss test between them and pair the ones that come out closest
again now, you've got you best shot at having devices that have matching (Vp, Idss) value pairs for a given test voltage
then, from that info, you can tailor a control circuit that will suite the four or six devices you've singled out for this purpose
set the mean value somewhere within the 0v-to-Vp range and make sure the control voltage at the grid stays within that
range then your next and final step is to set the sweep of the voltage so that it lands as close to each end of that range to get
maximal resistance variation from your devices ... if they are properly matched your devices will behave in a similar way within
that range as VCR cells
(ii)
the other approach is to try and fit devices to a given pedal circuit (because it's known to work) - which really, is but a fixed
control circuit ... what you guys are doing is trying to make your device lot fit to the output of that control circuit
take a wild guess which approach has a better chance of landing a more intense sounding phasor circuit ??!
---
this is the same set of constraints I face in my opto-coupler based phasors but in my case I've made it so my control
circuit has an offset and scaling control built in so I can tailor the response to my cells ... so it's very similar except you guys
are forced to deal with a control circuits that generally do not offer those features, plus opto-couplers don't have that
asymptotic resistance wall as jFETs do ...
if it were me and I wanted to get good strong phasing out of jFET's I would first of all select a jFET type that gives me a
comfortable (wide enough but no too wide) control range to begin with - it obviously has to fit within the voltage supply
range for one ... then I would worry about figuring out a better control circuit than what appears in many production line
circuits ... these are often short-cut circuits that won't help you much in this kind of endeavor ...
a simple triangle wave LFO with a variable bias ref and output intensity control should give you the offset and scaling
control you need ... this is all you'll ever really need to know about designing the best jFET phasor possible ...
---
now, the real challenge is figuring out how to estimate Vp more accurately because it can't be measured directly
such an idea as having 3% error at 10nA is complete bologna btw ...
you guys owe me a beer
did you get up on the wrong side of the bed today?
I've got this about halfbreadboarded atm, but I'm wondering, what would it sound like (tonally) if you paralleled a stage or two? Would it sound the same or mess with the phasing more. My breadboard is the very small one from Futurlec and I don't think I could fit another IC, hell, I don't know how I'm fitting the FETs on it yet.
After much deliberation of where to take this next, I've decided on a 14 stage implementation. This is based on using four TL084, one for the input stage, one for the LFO and 14 phase stages. This will fit comfortably on a 30x28 piece of perf. I've been having a lot fun with different regen taps, which I'm finding a lot more interesting than switching the number of phase stages. I've also aquired a very small 1P6T rotary switch (thanks!), so have come up with a novel way of gettting a possible 12 different regen types out of one 1P6T switch and one SPDT. By using the SPDT as a 'parity' switch I can select between either odd or even stages, then the 1P6T rotary can select between any of the six odd or six even stages. I've tweaked a few values in the LFO to control the sweep and get the best out of it, and I've completed drawing up the perf layout. Just a few more tests to run..........
I realised this schematic is hard to read, so here's a direct link too: http://dl.dropbox.com/u/967492/Sonic%20Death%20Ray%2014.GIF
(http://i210.photobucket.com/albums/bb292/frequencycentral/SonicDeathRay14.gif)
Swwwwoooooooosssshhhh :)
Quote from: slacker on July 03, 2010, 07:44:17 AM
Swwwwoooooooosssshhhh :)
Oh :'( I was hoping for Swwwwwwwwwoooooooooooooooooooosssssssssssssssssshhhhhhhhhhhhhhh!
Here's the unverified artwork for the 14 stage derivative, quite a few jumpers in the interest of keeping it compact. Not a bad size for a 14 stage phaser! I developed this layout from a 6 stage layout I did, I'll post up the 6 stage too if anyone's interested.
(http://i210.photobucket.com/albums/bb292/frequencycentral/SDR14PCB.gif)
(http://i210.photobucket.com/albums/bb292/frequencycentral/SDR14PnP.gif)
O.K. Capt. Perf-ulous,
I'm interested in this again... :icon_razz:
If we can't have a sound clip, can you verbally compare the sound to any other "Causalities" we may have heard :icon_question: :icon_twisted:
Quote from: doc_drop on July 03, 2010, 12:14:27 PM
If we can't have a sound clip, can you verbally compare the sound to any other "Causalities" we may have heard :icon_question: :icon_twisted:
Quote from: Capt. Perf-ulous on July 03, 2010, 10:29:45 AM
Swwwwwwwwwoooooooooooooooooooosssssssssssssssssshhhhhhhhhhhhhhh!
this looks great, will definitely make this my next phase shifter!
- strategyh
Quote from: Strategy on July 03, 2010, 01:18:27 PM
this looks great, will definitely make this my next phase shifter!
- strategyh
Thanks! A few caveats:
- Wait until it's verified
- The FETs are everything
- I've built this around a specific set of FETs
- The FETs are everything
- It may well not work without a specific set of FETs
- The FETs are everything
- As the 14 stage calls for 14 matched FETs of a specfic range you may need to buy 100's
- The FETs are everything
- A classic case of 'the unrepeatable circuit' ?
I will add this to the "challenge" pile! :icon_twisted:
O.K. well as long as it is
QuoteSwwwwwwwwwoooooooooooooooooooosssssssssssssssssshhhhhhhhhhhhhhh!
and not just Swwwooooshh. :icon_rolleyes:
I guess the FETs don't make a difference either!
I do wonder if there aren't "magic" combos of unmatched FETs and just dumb luck in getting a nice/unique sounding phaser. Hmmm, socket them all?.... Maybe get a SSSSHHHHHHwoooooooooshhhieSHHHWooooooooooooosh going...
OH NOOOO now I have to build another phaser :D
..... interesting, Mr. Spock .... :icon_mrgreen:
Here's the prototype on the breadboard. 4 x TL084 and 14 x 2N5485 with a Vgs of 2.3 to 2.5. The toggle switch bottom left is the parity switch, and feeds the regen path back into either the first or the second phase stage, for odd or even numbered stages in the regen path. On the breadboard I'm just using jumpers to select which stage I'm feeding back from, but on the finished unit it will be a 6 way rotary. The even regen stages all have a very different sound to the odd stages. Using the 10, 11 and 12 stage regen paths are almost verging on flanging.
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0012.jpg)
Bloody hell Rick! That looks like an absolute monster, I'd be very very very interested to hear it.
Wow! This looks very radical! When can we hear a soundclip?
By request, here's the layout for the 6 stage version. By using the Mode and Parity switches in combination, any of 3, 4, 5 or 6 stages or regen can be selected. I decided on two toggle instead of a rotary as they'll take up less room, but if you do want to use a rotary there is provision for that too by using the additional (unused) grey pads. I can't be bothered to explain how right now, but a full explanation will be forthcoming if anyone actually builds this and decides to use a rotary.
Just a couple of things missing from this layout:
- no polarity protection diode (no room!)
- a (1K) resistor is needed to limit the maximum speed of the LFO (no room!), hook it up between the LFO either of the LFO pads and the LFO pot
Please bear in mind that this is a phaser designed to work with a particular measured set of FETs as opposed to a phaser designed to be biased to suit whatever FETs you use.
(http://i210.photobucket.com/albums/bb292/frequencycentral/SDR6PCB.gif)
(http://i210.photobucket.com/albums/bb292/frequencycentral/SDR6PnP.gif)
Hey! Wow! Just found something really cool - toggling the Parity switch really fast while playing sounds awesome. I think I'm going to have to add this as an automated feature, controlled by a second LFO. Hmmm just need to work out how to implement it........
Oooo, that's a lot of nice coloured wires there. Reminds me of a tube amp, for some reason. :icon_mrgreen:
Ok, this is how I've implemented parity modulation:
(http://i210.photobucket.com/albums/bb292/frequencycentral/SonicDeathRayParityModulation.gif)
I've made a second LFO, driving two home-made vactrols. The LEDs are so configured so that they flash alternately as the LFO goes through it's cycle. So at the top of the LFO sweep the regen path is returning through an odd number of stages, and at the bottom of the sweep regen is returning through an even number of stages. I cannot begin to describe the sound this is making. I guess it's hard to imagine what a 14 stage phaser sounds like, let alone the difference between odd and even regen paths, let alone what modulating between odd and even regen paths sounds like. It kind of imprints another modulation over what's already there. Used clean, with slow phase and fast parity modulation it's like a vibe on top of the phase. Used distorted it's a talking-robot-synth-guitar-armageddeon-machine. You'll just have to wait for the soundclips. Does anyone have any idea what I'm talking about?
This is a very intriguing thread, great work. I like the look of that 6 stage version. Although the idea of matching FETs sounds like a problem, not to mention the FETs you are using are not the standard stuff floating around my parts box.
I think I speak for everyone when I say "soundclips and Youtube vids are a must for this circuit". No pressure, though. :icon_smile:
Here's an idea for a future modification: expression pedal jacks so it's possible to change the sound while playing.
Yeah man take it easy, we're not eager to see "HD videos with separately recorded audio mic'ed from the amp" at all.. ... I mean you've just had two tiring days of recording videos behind you now, right? we understand.
Quote from: ~arph on July 28, 2010, 07:55:37 AM
Yeah man take it easy, we're not eager to see "HD videos with separately recorded audio mic'ed from the amp" at all.. ... I mean you've just had two tiring days of recording videos behind you now, right? we understand.
:o I have no mic at the moment, but I'll record some clips DI'ed tomorrow. You won't be dissappointed........
Here's some clips, recorded direct to soundcard, so a little sterile. Tele Custom > BMP > Phaser > Soundcard
Stepping through the stages (http://dl.dropbox.com/u/967492/Stepping%20through%20the%20stages.mp3)
Parity modulation (http://dl.dropbox.com/u/967492/Parity%20modulating%20through%20the%20stages.mp3)
I'll do some clean clips a little later.........
Cool!
Good deep phasing, the parity modulation sounds interesting, you do seem to loose a lot of depth in the phasing.
Thanks for posting!
Yeah the parity modulation is interesting, though a little too 'square' at the moment. I've got to play with the LFO to get the LEDs to fade on and off instead of switching on and off. I may try some different LFOs, maybe a PSO. I think you lose some depth with the parity modulation as the two regen paths are out of phase and cancel to some degree.
So, I was told this thing goes, "Swwwwwwwwwoooooooooooooooooooosssssssssssssssssshhhhhhhhhhhhhhh! "
But, it sounds more like "WooooooowWoooooooooooooowWoooooow" to me. What's up with that? :icon_twisted:
Rick, I know the ROG Tri-Vibe has a sweet sine wave shaped LFO. Maybe you should look at that one?
I am definitely going to build one of these. It is too sexy not to!
That sounds great, I like the flangerish ringing in the first clip, almost like it's on the verge of self oscillating.
wow, that sounds cool and far out.
I had another idea about how to implement parity modulation. What if we add a single phase stage in the regen path, not fixed, but modulated by a single FET driven by it's own LFO? That way the regen signal would get flipped over between in phase and out of phase thus creating parity modulation?
Quote from: frequencycentral on July 31, 2010, 08:46:52 AM
I had another idea about how to implement parity modulation. What if we add a single phase stage in the regen path, not fixed, but modulated by a single FET driven by it's own LFO? That way the regen signal would get flipped over between in phase and out of phase thus creating parity modulation?
Implementing that as a phase shift stage would be interesting; because the "polarity" would be frequency dependent. An alternative idea, somewhere between this and the LED/LDR method posted eariler, would be to modulate a JFET instead of the switch in a polarity reverser (http://www.geofex.com/article_folders/polarity_reverser/polarity_reverser.htm) type circuit.
Parity modulation LFO redesigned, perf'ed and tested, home-made vactrols rolled. And the main PCB arrived today from my PCB man (http://www.guitarpcb.com/).....
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0001-21.jpg)
......and some perf-porn for Slade:
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0002-18.jpg)
Here's the new parity mod circuit and layout. A little more graduated than the previous version. Incidentally, this circuit can also be used to replace pretty much any pot configured as a voltage divider, though you might want to limit the dark resistance of the LDRs by using resistors in parallel. Imagine - LFO control of BM tonestack, or of mixing between two signals, or..........
(http://i210.photobucket.com/albums/bb292/frequencycentral/SonicDeathRayParityModulation-1.png)
(http://i210.photobucket.com/albums/bb292/frequencycentral/ParityPCB.gif)
(http://i210.photobucket.com/albums/bb292/frequencycentral/ParityPnP.gif)
PCB layout verified! Just hooked it up! This thing sounds awesome - even quieter than on breadboard. I can't wait to get it boxed up now......
(http://i210.photobucket.com/albums/bb292/frequencycentral/100_0004.jpg)
The more observant amongst you will have noticed that the FETs are having sex. This is the secret of good phasing IMO.
Fet-sex, ha?! You vouyerist cyborg!
Not just sex.
It looks like a full blown orgy ;D
Are you sure El H didnt do that layout ? :icon_twisted: :icon_wink:
This is how I am proposing to implement the (quite complex) regen options:
(http://i210.photobucket.com/albums/bb292/frequencycentral/SDRRegenWiring.gif)
The two regen inputs are on the left, one stage apart. The DPDT selects either parity modulation (from the parity modulation board) or fixed odd/even parity (selected by the SPDT). Then the regen pot and limiting resistor. Finally the 6 regen taps (each two stages apart) selected by the 1P6T rotary switch.
Hey, why don't you make the switch to select manual parity or parity modulation into a 3pdt stomp?
Would be nice to have that option while you're playing ;)
Quote from: Slade on August 13, 2010, 01:29:35 PM
Hey, why don't you make the switch to select manual parity or parity modulation into a 3pdt stomp?
Would be nice to have that option while you're playing ;)
Wow what a good idea, how could I not have thought of that? ::)
Because it's a young'n idea.
Is it possible to get a ultra long sweep like one can get out of a Whetstone Phaser? http://www.youtube.com/watch?v=zLKvcuQSyHY
Quote from: tuckster on October 05, 2010, 01:04:42 AM
Is it possible to get a ultra long sweep like one can get out of a Whetstone Phaser? http://www.youtube.com/watch?v=zLKvcuQSyHY
I think I'm going to tinker around with my causality4 instead of building a new phaser. But is it technically possible to get such a long sweep with both "Rick Phasers" (without substituting the whole PCB)?
Box drilled, graphic applied, panel populated. Now for the off-board wiring nightmare to come.....
(http://dl.dropbox.com/u/967492/Sonic.jpg)
Awesome looking pedal :icon_cool:
Love those nippleds...
Hmmmm,, nice phasers on stunning.. :)
Just replying so I can get this in my "unread posts" filter :) I love Rick's work.
I see you got rid of the aluminum edge trim but it does look like it would fit right into the 23rd century Star Trek world. I like that black panel look, very modern and futuristic at the same time. 10 points extra for styling! Good job Rick :)
^^^
The MAN himself! A big thanks to Steve Mavronis for etching the IDmark graphic for me - great job! Yeah, I had to trim the silver border, it would have fitted the (Eddystone) enclosures I usually use, which have square corners, but for this build I bought a black powdercoated 1590BB from Banzai (great price BTW) and it had rounded corners, so I had to lose the border to get the fit.
For this build I was going for a 1970's analogue synth type feel - hence the mix of red and green LEDs white boxes around the controls.
Jesus, Rick!
That is Sweeet!
The wiring is a little messy, as I *assumed* it might need debugging, so I left them purposefully long. But it worked first time anyway. Actually, most of the wiring is hidden below the motherboard anyway, there's a second board hiding under there too. This was not a fun build. It has taken me 6 hours straight to wire it all up.
Major big ups to:
Steve Mavronis for etching the IDmark graphic for me.
Barry Bardell @ guitarpcb.com for making the PCB for me.
(http://dl.dropbox.com/u/967492/SDR%20Pics/SDR1.jpg)
(http://dl.dropbox.com/u/967492/SDR%20Pics/SDR2.jpg)
(http://dl.dropbox.com/u/967492/SDR%20Pics/SDR3.jpg)
(http://dl.dropbox.com/u/967492/SDR%20Pics/SDR4.jpg)
If you could layout the switches on to the board it may simplify this quite a bit. Go on Rick, I dare you :icon_rolleyes:
Haha!
^^^
I'll never build another at any price anyway. I only built this so you guys would know I have the best phaser in town. :D
:icon_eek:
Quote from: frequencycentral on October 26, 2010, 11:19:22 AM
^^^
I'll never build another at any price anyway.
Maybe as a gift then? :icon_lol:
HAHAHAHAHA! You Mexicans have a great sense of humour!
Yeah, and be careful, I'm learning some irish jokes, you english bot :icon_mad:
Hey Slade,
Add numpty and island monkey to your vocabulary.
6 hours... :icon_eek:...well worth it though!..very cool pedal...
love the id label (nice one steve)..
come on then, lets see the lights flashing too!...video demo?...
rob the island monkey!..wtf is a bot?..
Soundclip!!
http://dl.dropbox.com/u/967492/Sonic%20Death%20Ray.mp3 (http://dl.dropbox.com/u/967492/Sonic%20Death%20Ray.mp3)
Crap guitarist >>> Tele Custom (bridge HB) >>> Big Muff (sometimes) >>> SONIC DEATH RAY >>> VJ Clone >>> Shure SM58 >>> Event Gina 24 >>> Wavelab.
Just trying to show all of it's features. The clean bits are just the phaser, with parity mod on it kind of sounds like a fast vibrato with a slow phase at the same time.
nice..dave brock would be proud to have that!...whoooooooshhhhhhhhhawkwwwwwwind.............. :icon_cool:
Quote from: deadastronaut on October 28, 2010, 10:12:55 AM
nice..dave brock would be proud to have that!...whoooooooshhhhhhhhhawkwwwwwwind.............. :icon_cool:
hahaha Dave Brock is probably the reason why I love phasers. ;D
ha ha..yeah!...should have done silver machine with that!.... ;)
or psychedelic warlords....
nice pedal man!.
Quote from: frequencycentral on October 28, 2010, 10:14:23 AM
Quote from: deadastronaut on October 28, 2010, 10:12:55 AM
nice..dave brock would be proud to have that!...whoooooooshhhhhhhhhawkwwwwwwind.............. :icon_cool:
hahaha Dave Brock is probably the reason why I love phasers. ;D
Please would you post here the total layout of your incredible pedal an the PCB of thiss monster i want to make one it´s alucinate!!!!!!! and incredible to me!!! and one question it will be funcional to chanche the FET´s with the 1N5457 or 5458 one´s???? thanks for your attention I´m from PERÚ !!!!
Quote from: frequencycentral on October 28, 2010, 10:14:23 AM
Quote from: deadastronaut on October 28, 2010, 10:12:55 AM
nice..dave brock would be proud to have that!...whoooooooshhhhhhhhhawkwwwwwwind.............. :icon_cool:
hahaha Dave Brock is probably the reason why I love phasers. ;D
Please blog here the entire layout the conections and a PCB for direct etching!!!! wooooooooooowwwwww!!!! I want that fantastic pedal man!!!!!!!!!!!!!!
Just read the thread, it's all here.
Just heard this clip . Are you quite sure you didn't squeeze an old analog synth into the box ?
Awesome is not a strong enough word !
Quote from: frequencycentral on August 05, 2010, 10:20:53 AM
Parity modulation LFO redesigned, perf'ed and tested, home-made vactrols rolled. And the main PCB arrived today from my PCB man (http://www.guitarpcb.com/).....
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0001-21.jpg)
......and some perf-porn for Slade:
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0002-18.jpg)
There is no reference to your PCB or LAYOUT please post here the PCB and the layout!!!!!!!!!
Thank a lot!!!!!! it´s the real pedal I see!!!!
Quote from: frequencycentral on August 05, 2010, 10:20:53 AM
Parity modulation LFO redesigned, perf'ed and tested, home-made vactrols rolled. And the main PCB arrived today from my PCB man (http://www.guitarpcb.com/).....
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0001-21.jpg)
......and some perf-porn for Slade:
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0002-18.jpg)
I don´t see any PCB !!!! please post here yor PCB and layout!!!! thanks!!!!!! It´s a real unique pedal!!!!!
Save your !!!!!!!!!!!!!!!!!!!!!!!!!!! and search the thread!!!!!!! page 3 :icon_evil: You know how to use a internet forum?!?!?
thanks tuckster you save my live!!!! cause I'm getting crazy!!!!!! I was redirecting directly for this page!!!!! thanks a lot!!!!
http://catb.org/esr/faqs/smart-questions.html
http://en.wikipedia.org/wiki/Netiquette
Is it so hard two click the Button? You posted so many times.. If you had just clicked through the pages you woudn't have had to wait (I hope that was written the right way.. I hate english ;D)
Quote from: GodSaveMetal on November 02, 2010, 07:30:39 PM
......and one question it will be funcional to chanche the FET´s with the 1N5457 or 5458 one´s???? thanks for your attention I´m from PERÚ !!!!
I don't know. I did try some of those FETs without much luck early on during development, but their Vgs was way off with respect to the 2N5485's I used. The FETs, and their (matched) Vgs are
everything in this circuit. To get it working with different FETs/Vgs you may have to tinker with the LFO's feedback resistors and voltage divider. Good luck with your build, if you dare. I looking forward to the debug thread with anticipation. This is not your average phaser build. :icon_biggrin:
woow!! frecuency, i´m amazed about this phaser machine! coungratulations!
A little question. How could i match the fet´s?
And, where did you buy the plastic cover for the pot´s?
thanks
Quote from: Dr.maligno on November 17, 2010, 08:22:37 AM
woow!! frecuency, i´m amazed about this phaser machine! coungratulations!
A little question. How could i match the fet´s?
Thanks!
GEOFEX FET matcher: http://www.geofex.com/Article_Folders/fetmatch/fetmatch.gif
Quote from: Dr.maligno on November 17, 2010, 08:22:37 AM
And, where did you buy the plastic cover for the pot´s?
What the clear plastic covers on the backs of the pots? They come as standard on Tayda's Alpha pots: http://www.taydaelectronics.com/servlet/the-Potentiometers--fdsh--Variable-Resistors-cln-Rotary-Potentiometer/Categories
how I connect the LED monitor of the PARITY and PHASE speed? you made a footswitch for the auto/manual modulation!!!! what a great idea please how I made the conenections of all the LEDs monitors?
Quote from: GodSaveMetal on November 22, 2010, 08:14:04 AM
how I connect the LED monitor of the PARITY and PHASE speed? you made a footswitch for the auto/manual modulation!!!! what a great idea please how I made the conenections of all the LEDs monitors?
I basically used this wiring diagram: http://www.diystompboxes.com/smfforum/index.php?topic=84968.msg723519#msg723519 But I used a DPDT instead of an SPDT, and a 3PDT stompswicth instead of a DPDT, and used the extra poles to connect the status LEDs. The two LFO rate LEDs are tapped off the outputs of the LFO opamps.
Draw the conection of the The two LFO rate LEDs that are tapped off the outputs of the LFO opamps!!!! please!!!!
^^^
I highly recommend you to not make this pedal until you have more building skills, at least for making your own layouts. I mean it, it's a really hard circuit, and more if you don't have enough knowledgement. I'd suggest that you buy one from Rick, but I think h won't be building it for a time.
Quote from: Slade on November 22, 2010, 05:40:26 PM
^^^
I highly recommend you to not make this pedal until you have more building skills, at least for making your own layouts. I mean it, it's a really hard circuit, and more if you don't have enough knowledgement. I'd suggest that you buy one from Rick, but I think h won't be building it for a time.
+1
With the greatest of respect to
GodSaveMetal, if you are asking for a wiring diagram for how to wire an LED to the output of an opamp, you will have a very very hard time successfully building this pedal. I have built dozens of pedals and amps, but this one tough for me. Populating the PCBs was easy, but it took me a whole day to do the off-board wiring. I'm not holding anything back, everything you need to know to build this pedal is already here in the thread, but I'm assuming a certain level of knowledge is already there on the part of the prospective builder. I certainly don't have the time or inclination to write a step-by-step tutorial. I really hope this doesn't come across as condescending, but I think your attempt to build this pedal would cause you (and therefore me) a great deal of heartache, and is very likely to result in a non-functional pedal.
My intention is only didactical because I´m teacher of science and want to teach to my students how far can they will go with guitar effects; but thanks a lot for your help
Quote from: frequencycentral on August 12, 2010, 10:08:43 AM
PCB layout verified! Just hooked it up! This thing sounds awesome - even quieter than on breadboard. I can't wait to get it boxed up now......
(http://i210.photobucket.com/albums/bb292/frequencycentral/100_0004.jpg)
Bumping this cause I just saw it on your site. Is there any reason for the horrible layout? It's zay bigger than it has to be, even for putting LFO and audio on one board. No wonder you weren't eager to do another. :icon_lol:
Quote from: Valoosj on April 09, 2011, 10:25:54 PM
Is there any reason for the horrible layout? It's zay bigger than it has to be, even for putting LFO and audio on one board. No wonder you weren't eager to do another. :icon_lol:
Oh! I thought I'd done pretty good! :'(
The main board, which is an entire 14 stage phaser including the LFO is 28 x 30. Compare this to Tonepad's Phase 90 which is 20 x 21 for only 4 stages. Which means the SDR is exactly twice as big as the P90, but adds 10 more stages. The practicality is that each phase stage needs to see vref and LFO, as well as each opamp package needing to see ground and +ve, and the audio path blah blah blah.
The second parity modulation board was an afterthought, after I'd had the main board etched. It houses the second LFO and optos. I've now redesigned this board to be pot mounted, which cuts down a lot of off-board; it now also mounts the bulk of the LEDs as well as a lot of the switch routing stuff.
The main challenge of the prototype was basically the small enclosure size. I've opted for a bigger enclosure for the production run - that, coupled with the new parity board, makes for an easier build than the prototype ever was.
BTW, some of the production run are going into Prymaxe in NJ, which I'm pretty stoked about!
......so, if anyone's designed a smaller, better laid out 14 stage phaser with parity modulation and multiple regen taps....... :icon_biggrin:
I'am in no way capable of designing such a marvellous pedal. What I could do to offer you some help with, is with any layouts for future projects.
You know I like keeping things (certain things only :icon_mrgreen:) small ;)
can you get the sound of all "other" phasers (mxr, boss, etc) on this pedal?
i wanted to make this but it would seem that some of the images necessary to create this has been deleted by photobucket.e.g..the layouts and all.
it would be nice if frequency central could reload those images...thanks..
A buddy came over with a Maxon Rotary Phaser on the weekend, and let me pop the hood. It can provide up to 10 stages of phase shift, but only 6 are swept, and the remaining 4 are fixed, identical to the MXR Phase 100.
@mark hammer
do you have a copy of those image files for sonic death ray?
some images in this thread has been removed by photobucket.
I would imagine the best person to ask is Rick Holt himself.
Quote from: mr_deadmaxxx on January 11, 2012, 10:27:36 PM
i wanted to make this but it would seem that some of the images necessary to create this has been deleted by photobucket.e.g..the layouts and all.
it would be nice if frequency central could reload those images...thanks..
I've recently had a bad experience with a forum member supplying a clone of one of my designs to one of my distributors. Which led me to the decision to limit the amount of information I share on some of my designs which put food on my table and a roof over my head. This affects only a very small proportion of my published work on DIYSB, but SDR is one (Gemini is another). Sad situation to have to be in.......... :(
I understand your point.
Guess I'll go with Casuality 4. No Fets to match.
Can I incorporate SDR's Parity mod board http://www.diystompboxes.com/smfforum/index.php?topic=84968.60 (http://www.diystompboxes.com/smfforum/index.php?topic=84968.60) to the Casuality 4?
Quote from: frequencycentral on January 12, 2012, 06:52:09 PM
Quote from: mr_deadmaxxx on January 11, 2012, 10:27:36 PM
i wanted to make this but it would seem that some of the images necessary to create this has been deleted by photobucket.e.g..the layouts and all.
it would be nice if frequency central could reload those images...thanks..
I've recently had a bad experience with a forum member supplying a clone of one of my designs to one of my distributors. Which led me to the decision to limit the amount of information I share on some of my designs which put food on my table and a roof over my head. This affects only a very small proportion of my published work on DIYSB, but SDR is one (Gemini is another). Sad situation to have to be in.......... :(
Really sorry to hear that, this sort of dishonesty on whomever's behalf really backfires on both the person themselves aswell as the whole community as people inevitably can't disclose their designs for fear of plagiarism/ undercutting. Your approach to feedback stages is really cool, I may even implement parity modulation at some point, but growing from the knowledge of the builders around me would be, to me, clearly profitable in the long run than simply sniffing around for designs to steal until the community grows wary and stops sharing.
Whoever does this should change their username to Scorpion And The Frog!
Quote from: frequencycentral on January 12, 2012, 06:52:09 PM
I've recently had a bad experience with a forum member supplying a clone of one of my designs to one of my distributors. Which led me to the decision to limit the amount of information I share on some of my designs which put food on my table and a roof over my head. This affects only a very small proportion of my published work on DIYSB, but SDR is one (Gemini is another). Sad situation to have to be in.......... :(
That is indeed a sad situation. Guys like you are contributing
so much (I have at least five FC projects at various stages in my pipeline - thank you :)), and some selfish tw@t just spoils the whole show. I hope we still get to see more of your cracking designs in the future Rick, though you're absolutely right to want to protect your livelihood. I would.
Rick/anyone: I wonder if the schematic may be had privately, by email? I almost certainly wont be building it, and have no intention of sharing--just interested in seeing it, maybe learning something. If, not, hey, 'scool, protect your own IP as you see fit and you don't owe me anything, but seeing as the participants of this thread do have it, I fugured no harm in asking. Feel free to reply by PM, if preferred.
Ben