DIYstompboxes.com

DIY Stompboxes => Building your own stompbox => Topic started by: Freppo on October 05, 2014, 10:05:38 AM

Title: PWM phaser in the works
Post by: Freppo on October 05, 2014, 10:05:38 AM
Hi there folks

Here is a phaser project that i'm working on.  :)
It uses a CD4066 CMOS switch insted as variable resistors and a CD40106 for both the PWM and LFO duties (for now).


The distortion is from my camera and the hiss in the beginning is from the fans in my oscilloscope.
Around 1:08 I turn up the feedback (regen)

The schematic is just a first draft of what I have on the breadboard now. Things like Vref and power connections are not shown.
(http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/3885407_orig.png)
Full size: http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parasit-phaser.pdf (http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parasit-phaser.pdf)

I really like how I managed to utilize the CD40106 and keep the parts down, but I think I'll have to ditch the CD40106 LFO.  :-\
The tringle wave from the CD40106 is kinda distorted and weak. A better LFO will allow the PWM sweep to go deeper and have a better sweep.
Now the pulse wave frequency is very high (about 95khz) to work with the low output LFO.. which also means high current consumption.

I will also add some noise reducing (emphasis/de-emphasis) and maybe a fixed phase shift stage in the feedback path, ala Ross Phaser.

Anyway, just though I'd share. Perhaps someone will find this interesting :)

cheers
/ Freppo
Title: Re: PWM phaser in the works
Post by: mth5044 on October 05, 2014, 10:39:03 AM
Awesome idea! I look forward to your updates.
Title: Re: PWM phaser in the works
Post by: armdnrdy on October 05, 2014, 11:50:43 AM
Good job..it's nice to see someone working on something a bit outside of the norm.

I don't know if you've seen the ADA Final Phase schematic. The Final Phase uses CD4016s in the same fashion as the 4066....to switch in/out resistance in the phase stages.
Title: Re: PWM phaser in the works
Post by: jatalahd on October 05, 2014, 01:43:53 PM
Sounds good and the idea is definitely interesting. Thanks for sharing!
Title: Re: PWM phaser in the works
Post by: Freppo on October 05, 2014, 03:47:28 PM
Good job..it's nice to see someone working on something a bit outside of the norm.

I don't know if you've seen the ADA Final Phase schematic. The Final Phase uses CD4016s in the same fashion as the 4066....to switch in/out resistance in the phase stages.

Thanks. I'll check out that ADA Phaser, sounds interesting!
I started this because I wanted to build a phaser that doesn't need matched JFETS or LDRs.
The CD4066 solution is nothing new, but it works really well.

I'm on the fence if I should keep it as simple as possible..
...or go all out and add another bunch of stages or make it a bi-phaser and run it on +/- 12 volts and put it in a rack..
The extra headroom would sure be welcome.. hmm.. ideas ideas. :)

/ Freppo
Title: Re: PWM phaser in the works
Post by: anotherjim on October 05, 2014, 04:09:50 PM
Interesting.

Of that LFO, I'm sure you know the amplitude will be fixed by the threshold of the gate used. If you have an inverter spare, maybe you can overcome those thresholds by making a Schmitt trigger out of 2 of them in series, with a feedback resistor from the second output back to first input and a resistor in series with the input. The amplitude should depend on the ratio between feedback & input resistor. Input resistance has to be lower than the feedback. I know this works with ordinary CMOS gates, but I've never tried with ones that already contain Schmitt triggers.

The shape of the LFO may be worth a tweak. I've noticed the waveform on the charging capacitor in those circuits can vary according to the magnitude of the RC values. Have you tried a smaller capacitor and higher resistance? The wave always looks better to me with less charge/discharge current in the timing cap.



Title: Re: PWM phaser in the works
Post by: stringsthings on October 05, 2014, 05:07:22 PM
sounds good so far to me!  :)   looking forward to putting this one together.  ( currently working on the Raygun Youth Chaos Fuzz )
Title: Re: PWM phaser in the works
Post by: Freppo on October 05, 2014, 05:33:11 PM
If you have an inverter spare, maybe you can overcome those thresholds by making a Schmitt trigger out of 2 of them in series
Great idea! But I can't quite wrap me head around how to do it. Do you have any example I can have a look at?
CMOS logic is still pretty new to me and i'm being ill and should be lying in bed today so my head is kinda mushy :icon_rolleyes: :icon_sad:
Have you tried a smaller capacitor and higher resistance?
Yes, I've played around with all kinds of combinations and smaller caps makes the sweep more uneven at slow rates

I've been playing around with another LFO today, a wien-brige sinewave LFO. It has a much stronger output and nicer sweep.
But it add more complexity to the circuit and needs a dual-pot.. and I would rather keep it simple.

I think a charge pump could be a good solution to beef up the CD4106 LFO, and the headroom would not hurt for the s/n ratio.
But then again, added complexity.. Maybe I'll have to realize that there is no easy way to make a great phaser  :icon_lol:
Title: Re: PWM phaser in the works
Post by: Freppo on October 05, 2014, 05:34:24 PM
sounds good so far to me!  :)   looking forward to putting this one together.  ( currently working on the Raygun Youth Chaos Fuzz )

Awesome!  :icon_redface:  :icon_smile:
This one might not be very DIY friendly though. It will certainly be too large for vero
But I will share a PCB layout when it's completed
Title: Re: PWM phaser in the works
Post by: amptramp on October 05, 2014, 10:00:15 PM
It looks like your design may converge on the Paul Nelson phaser of 2009.  It has a high-frequency astable made from one TL064 and another for the LFO.  I copied the schematic once but I don't have the link to where I got it.
Title: Re: PWM phaser in the works
Post by: anotherjim on October 06, 2014, 04:11:01 AM
(http://i1374.photobucket.com/albums/ag414/ashdalestudio/CMOSLFOdetail_zpsbe7d680e.png) (http://s1374.photobucket.com/user/ashdalestudio/media/CMOSLFOdetail_zpsbe7d680e.png.html)

a and b make a non-inverting gate. R1 is the feedback and R2 the input. This completes a Schmitt trigger. c is the integrator here making a conventional tri/sqr oscillator. This is with 4069/4049UB inverters. Schmitt should work using any CMOS logic so long as the feedback is positive (non-inverting).

So, I'm wondering if it will make an equivalent "single schmitt inverter" as you have with the 40106 by building the Schmitt with 2 inverters with resistors and feed the timing cap from the output of the first inverter (because to oscillate, it must be inverting).


Title: Re: PWM phaser in the works
Post by: kingswayguitar on October 06, 2014, 05:50:03 AM
the audio sounds pretty good to me freppo
cool seeing the scope at the same instant
cheers
Title: Re: PWM phaser in the works
Post by: Freppo on October 06, 2014, 05:55:53 AM
It looks like your design may converge on the Paul Nelson phaser of 2009.  It has a high-frequency astable made from one TL064 and another for the LFO.  I copied the schematic once but I don't have the link to where I got it.

I got the idea to use a CD4066 swith as a variable resistor from an article by Rod Elliott, but I've seen the Nelson phaser. At first I tried to use a astable oscillator followed by a comparator pwm. It worked ok, but had a limited pulse width because the triangle wave got a bit distorted at high frequencies. Probably because I did something wrong. The CD40106 is far simpler and the pulse wave is perfect so it seems like a easier solution.

The easiest way would be to use a PIC chip for the PWM/LFO (as R.G. Keen has done with a similar phaser), but I know nothing about programming so..

gate. R1 is the feedback and R2 the input. This completes a Schmitt trigger. c is the integrator here making a conventional tri/sqr oscillator.
Thanks! I'll give it a try :)
Title: Re: PWM phaser in the works
Post by: deadastronaut on October 06, 2014, 06:18:58 AM
sounds great freppo, 8)





Title: Re: PWM phaser in the works
Post by: Kipper4 on October 06, 2014, 06:39:10 AM
Sounds excellant. Thanks for sharing. ;D
Title: Re: PWM phaser in the works
Post by: Digital Larry on October 06, 2014, 11:21:00 AM
Brilliant!   :) ;)
Title: Re: PWM phaser in the works
Post by: Freppo on October 06, 2014, 01:35:44 PM
Thanks all for the positive comments :)

I'm aiming at doing a stompbox friendly version and a more extreme version (for the studio)
The only problem is that i'm running out of space on my breadboard  :icon_smile:

/ Freppo
Title: Re: PWM phaser in the works
Post by: Mark Hammer on October 06, 2014, 01:47:17 PM
Nice.

1) Why are there two 100nf caps I the feedback loop?  Isn't one sufficient?

2) If you've going to use 3 chips, may as well make the third chip a quad, rather than dual, op-amp.  I know the 4066 only has 4 switches on it, but you can use the additional pair of op-amps for two fixed stages, as Rick Holt did for the Causality phaser.

3) The 40106 has 6 inverter stages, but you've only used 4.  That's not wrong, but there is the option of adding a second LFO to sum with the first one, and introducing some aperiodicity, or simply having two different rate presets to select between.
Title: Re: PWM phaser in the works
Post by: Freppo on October 06, 2014, 02:51:13 PM
Nice ideas Mark!
Why are there two 100nf caps I the feedback loop?  Isn't one sufficient?
Yes, I've actually been alittle confused about the purpose of the second cap myself. I took the feedback (more or less) out of another phaser that had two caps like that.
But as you say, one should be sufficient so I will remove the second one. :)
2) If you've going to use 3 chips, may as well make the third chip a quad, rather than dual, op-amp.  I know the 4066 only has 4 switches on it, but you can use the additional pair of op-amps for two fixed stages, as Rick Holt did for the Causality phaser.
I was going to make the third chip a quad anyway, but for other (less interesting) uses - one to buffer Vref (seem to reduce most of the LFO ticking bleeding into the signal)
and maybe that last op amp to buffer or beef up the LFO. Seems like it could be a good idea? But for the studio version I'll go all out and definitly add a couple of more passive stages aswell. :)

3. Great idea! I'll play around with a second LFO.
Thanks for the suggestions!  :)
Title: Re: PWM phaser in the works
Post by: nelson on October 08, 2014, 11:30:08 AM
I haven't visited the forum in years and the first thread I click on mentions me.

It's a sign, I must start building stompboxes again. :)

Good luck with the phaser. I haven't done any stompbox stuff in years, so sorry I don't have much to add.
Title: Re: PWM phaser in the works
Post by: armdnrdy on October 08, 2014, 11:55:33 AM
Welcome back Nelson!
Now get to work!  :icon_wink:
Title: Re: PWM phaser in the works
Post by: Mark Hammer on October 08, 2014, 12:28:45 PM
Nice ideas Mark!
Why are there two 100nf caps I the feedback loop?  Isn't one sufficient?
Yes, I've actually been alittle confused about the purpose of the second cap myself. I took the feedback (more or less) out of another phaser that had two caps like that.
But as you say, one should be sufficient so I will remove the second one. :)
2) If you've going to use 3 chips, may as well make the third chip a quad, rather than dual, op-amp.  I know the 4066 only has 4 switches on it, but you can use the additional pair of op-amps for two fixed stages, as Rick Holt did for the Causality phaser.
I was going to make the third chip a quad anyway, but for other (less interesting) uses - one to buffer Vref (seem to reduce most of the LFO ticking bleeding into the signal)
and maybe that last op amp to buffer or beef up the LFO. Seems like it could be a good idea? But for the studio version I'll go all out and definitly add a couple of more passive stages aswell. :)

3. Great idea! I'll play around with a second LFO.
Thanks for the suggestions!  :)
The op-amp/JFET Ross Phaser uses an interesting approach wherein the feedback signal from the 4th stage passes through a fixed 5th stage back to stage 1 (instead of stage 2).  Essentially, it mimics the feedback path of a 6-stager, without having to resort to 6 stages.
Title: Re: PWM phaser in the works
Post by: ~arph on October 09, 2014, 05:44:04 AM
Why not go all the way and add another quad and another 4066 and go eight stages.  ;D
Title: Re: PWM phaser in the works
Post by: Freppo on October 09, 2014, 11:40:05 AM

It's a sign, I must start building stompboxes again. :)
Good luck with the phaser.
Thanks Nelson! Didn't expect you to visit the thread.
Yes, why not start building again?  It's a sign, for sure. ;)

The op-amp/JFET Ross Phaser uses an interesting approach wherein the feedback signal from the 4th stage passes through a fixed 5th stage back to stage 1 (instead of stage 2).  Essentially, it mimics the feedback path of a 6-stager, without having to resort to 6 stages.
Yes, that a very cool trick and something I maybe wanted to add (as I wrote in my inital post).
Now I had one 1/4 of a quad opamp left, so it was perfect for that application. :)

Why not go all the way and add another quad and another 4066 and go eight stages.  ;D
Yes, actually why not.  :icon_biggrin: But I want to try to keep it a stompbox-friendly size for now.
Maybe in the rack-mounted "studio version" :)
Title: Re: PWM phaser in the works
Post by: Mark Hammer on October 09, 2014, 11:44:46 AM
The op-amp/JFET Ross Phaser uses an interesting approach wherein the feedback signal from the 4th stage passes through a fixed 5th stage back to stage 1 (instead of stage 2).  Essentially, it mimics the feedback path of a 6-stager, without having to resort to 6 stages.
Yes, that a very cool trick and something I maybe wanted to add (as I wrote in my inital post).
Now I had one 1/4 of a quad opamp left, so it was perfect for that application. :)
:icon_redface: :icon_redface:  Too distracted by the schematic to pay attention to the content of the post!  :icon_rolleyes:
Title: Re: PWM phaser in the works
Post by: Freppo on October 09, 2014, 11:48:12 AM
This is my progress and I dare say that it's just about finished.  :)
Maybe just a couple of tweaks here and there, but overall i'm very satisfied with the results.

I added a switchable second LFO that can make a odd wave-shape modulation together with first LFO.
And I added a switch to change the sweep (and tone of the phasing) though another inverter.

(http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/307307_orig.png)
Full size: http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parasit-phaser_final.pdf (http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parasit-phaser_final.pdf)

Demo-video coming soonish, maybe sometime next week.
Now I have to study for a important test..  :icon_sad:

/ Freppo
Title: Re: PWM phaser in the works
Post by: Freppo on October 09, 2014, 01:02:50 PM
The op-amp/JFET Ross Phaser uses an interesting approach wherein the feedback signal from the 4th stage passes through a fixed 5th stage back to stage 1 (instead of stage 2).  Essentially, it mimics the feedback path of a 6-stager, without having to resort to 6 stages.
Yes, that a very cool trick and something I maybe wanted to add (as I wrote in my inital post).
Now I had one 1/4 of a quad opamp left, so it was perfect for that application. :)
:icon_redface: :icon_redface:  Too distracted by the schematic to pay attention to the content of the post!  :icon_rolleyes:

 ;D Np Mark. I may actually have read about the ross phaser feedback in one of your old posts..  :icon_rolleyes:
Keep sharing the knowledge and inspiration!
Title: Re: PWM phaser in the works
Post by: Mark Hammer on October 09, 2014, 01:53:24 PM
Incidentally, the 4n7 cap in the feedback loop of the feedback stage is a great idea.  I've noticed that higher feedback settings can often be accompanied by more cumulative hiss.  Some phasers will attempt to address it by using a treble-limiting cap in the feedback loop of the final phase-shift stage.  In some respects, it tackles the same problem the same way.  On the other hand, if you aren't using much feedback/regeneration you still forfeit top end.  While inserting treble-cut in the feedback path itself allows for full-bandwidth phasing when little or no feedback is applied.
Title: Re: PWM phaser in the works
Post by: Kipper4 on October 09, 2014, 08:13:05 PM
Putting this on my to do list thanks Freppo.
Good luck with the test.
Title: Re: PWM phaser in the works
Post by: deadastronaut on October 10, 2014, 04:21:59 AM
any phaser than removes the need for matching 4 fets is cool in my book... 8) 8) 8)

nice work freppo.. 8)

look forward to the vid demo..

Title: Re: PWM phaser in the works
Post by: bloxstompboxes on October 10, 2014, 10:08:23 AM
Putting this on my to do list thanks Freppo.
Good luck with the test.

Same here!
Title: Re: PWM phaser in the works
Post by: anotherjim on October 10, 2014, 11:21:16 AM
So, if you were to use (cough!) a PIC, AVR or one of the smaller Arduino's, you would use a PWM port without a filter straight to the CMOS switch inputs (given any necessary voltage level shift)?
In Arduino, I think this just means cyclically changing the variable in an Analog Write command. Maybe an easy way to get into some coding again. Hmmmm....
Title: Re: PWM phaser in the works
Post by: Freppo on October 10, 2014, 12:03:48 PM
So, if you were to use (cough!) a PIC, AVR or one of the smaller Arduino's, you would use a PWM port without a filter straight to the CMOS switch inputs (given any necessary voltage level shift)?
In Arduino, I think this just means cyclically changing the variable in an Analog Write command. Maybe an easy way to get into some coding again. Hmmmm....
Yes! That would probably work just fine. :)
Title: Re: PWM phaser in the works
Post by: ~arph on October 10, 2014, 12:42:18 PM
Yes, but make sure to set the pwm mode to fast, or you'll hear it. And I think you either power and switch the 4066 from the same 5v supply or use four bits to do the level shifting. As I am not sure if the 4066 supply must be higher than the signal level swing
Title: Re: PWM phaser in the works
Post by: GodSaveMetal on October 10, 2014, 06:55:40 PM
any phaser than removes the need for matching 4 fets is cool in my book... 8) 8) 8)

nice work freppo.. 8)

look forward to the vid demo..



Me too!!! and looking for your PCB yeahhhhh!!!!!!!!!!!!!!!!!!
Title: Re: PWM phaser in the works
Post by: Freppo on October 11, 2014, 06:09:52 AM
A little update..

I've built it up on PCB today that I designed during the small hours.
(I should be stuying but I'll do that later  :icon_rolleyes: )

It works, but I have a clicking sound now that goes tick tack, tick tack..  :(
At faster rates it sounds like a frantic clatter, like a some kind of monster bug running on concrete
I don't have this problem on the breadboard.

Does anyone have an idea what could be the cause or how to solve it?

Here is the PCB for reference. http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parasitephaserpcb.pdf (http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parasitephaserpcb.pdf)
I don't recommend anyone building it until this issue is solved. Demo video will have to wait aswell. Frustrating!

/ Freppo
Title: Re: PWM phaser in the works
Post by: Kipper4 on October 11, 2014, 06:16:40 AM
What happens if you disconnect the lfo? No Ticking?
Title: Re: PWM phaser in the works
Post by: anotherjim on October 11, 2014, 11:00:50 AM
Oooh, nasty when that happens.

Your layout looks sensible - LFO's all in one corner and wiring to pots & switches close by. Have you boxed it?

Try feeding the 40106 +ve supply pin 16 via a resistor before the filter caps. Say 270ohm?
If the pots have metal bodies, try fitting a ground wire to them - those can radiate quite badly if not screened.
Twist the wires to the LFO controls. Screened wire on ALL audio.

Last Vibrato I made had horrible ticking before boxing it (but didn't on the proto board). The foot-switch body was picking up off the LFO speed & depth pots - then injecting via stray capacitance to the switch contacts and into the high impedance (1M) input! Was fine once boxed.
Title: Re: PWM phaser in the works
Post by: Freppo on October 11, 2014, 11:05:39 AM
What happens if you disconnect the lfo? No Ticking?

Yes

I think the problem is using a quad IC. It's the only difference from the breadboard.
Now the LFO buffer/gainstage shares the same chip as the input and output stage..
I will have to try and confirm this on the breadboard, and most likely change the PCB layout into dual opamps.

Or maybe I'll go back to my original idea to have a dual opamp LFO, insted of using the CD40106 for this.

/ Freppo
Title: Re: PWM phaser in the works
Post by: Freppo on October 11, 2014, 11:08:45 AM
Oooh, nasty when that happens.

Your layout looks sensible - LFO's all in one corner and wiring to pots & switches close by. Have you boxed it?

Try feeding the 40106 +ve supply pin 16 via a resistor before the filter caps. Say 270ohm?
If the pots have metal bodies, try fitting a ground wire to them - those can radiate quite badly if not screened.
Twist the wires to the LFO controls. Screened wire on ALL audio.

Last Vibrato I made had horrible ticking before boxing it (but didn't on the proto board). The foot-switch body was picking up off the LFO speed & depth pots - then injecting via stray capacitance to the switch contacts and into the high impedance (1M) input! Was fine once boxed.


Thanks, I'll try with a resistor from pin 16 of the CD40106 to V+.
I'm have hooked up the PCB to a breadboard using small trimmers for pots

I'll report back
cheers / Freppo
Title: Re: PWM phaser in the works
Post by: Kipper4 on October 12, 2014, 07:10:54 AM
So I've been looking at the chips for this and noter rthatthere are two varieties
CD40106BNC and CD40106BE

CD4066BNC and CD4066BE

Which should i use.
I'm guessing one is a buffer version?
Title: Re: PWM phaser in the works
Post by: Freppo on October 12, 2014, 07:20:50 AM
I'm using the BE versions :)
Title: Re: PWM phaser in the works
Post by: anotherjim on October 12, 2014, 07:24:31 AM
I'd say the BE, but I don't think the other kind is radically different - they're all buffered series (Hence the B). BE are the usual vanilla plastic DIP package. UBE would be un-buffered versions (if they existed).

Title: Re: PWM phaser in the works
Post by: Kipper4 on October 12, 2014, 07:55:44 AM
Thanks. time to order the chip then.
Title: Re: PWM phaser in the works
Post by: duck_arse on October 12, 2014, 10:18:02 AM
the 4066 "quad analog switch" will/might have buffering on the erm, lever? throw? control? input, but the switch is analog, so no buffers.

the 40106 is a schmitt, so it will have extra internal junk that will equate to buffers, even if it doesn't have straight-out buffers
Title: Re: PWM phaser in the works
Post by: Kipper4 on October 13, 2014, 11:24:13 AM
Erm yer.
I'm not familiar with theses two chips the 4066 switching and 40106 schmitt.

Looking at the pinout for the 4066 I guess Vdd (pin 14 on TI pdf) is +9v ?
and VSS (pin 7 on the TI pdf) is ground correct ?

also seen here
http://en.wikibooks.org/wiki/Practical_Electronics/IC/4066
Title: Re: PWM phaser in the works
Post by: anotherjim on October 13, 2014, 02:51:10 PM
Yep. Vdd = pos and Vss = neg are the power supply names on CMOS chips.
Title: Re: PWM phaser in the works
Post by: Kipper4 on October 13, 2014, 03:06:01 PM
Thanks Jim another bit of brain fodder for me. I never knew that for CMOS chips


Ok another question
Is it ok to leave the unused pins on the CD40106 unterminated ?

I'm nearing completion on my pad per hole layout.
Title: Re: PWM phaser in the works
Post by: armdnrdy on October 13, 2014, 03:30:02 PM
I'm nearing completion on my pad per hole layout.

Wouldn't it be a better idea to wait a bit until Freppo comes up with a working drawing that he's happy with?

His last few posts outlined a ticking issue and possible changes in ICs. ;)
Title: Re: PWM phaser in the works
Post by: Kipper4 on October 13, 2014, 03:36:13 PM
Yer I was going to wait Larry.
and my layout refers to his earlier breadboard schematic.
I know Freppo Is busy doing his test.
I'm just trying to get my head around some of these new to me chips. and learn some more about best practices in layouts.
No offense meant.
Title: Re: PWM phaser in the works
Post by: armdnrdy on October 13, 2014, 03:55:58 PM
No offense meant.

I think you took this wrong...I am not offended in anyway...how could I be?

and I didn't intend my last post to be taken in a demeaning manner.

I was purely making a suggestion from my observation.

I know that when I....and just about everyone...is working out a project...there can be many changes until it has reached fruition.
I didn't want to see you waste time on an unfinished design.

Imagine if someone did a layout every time Rob (deadastronaut) posted a new drawing! Hi Rob! ;)

There would be fifty wrong layouts floating around before the final drawing hit the thread!  ;D

Title: Re: PWM phaser in the works
Post by: GodSaveMetal on October 13, 2014, 04:38:26 PM
Yer I was going to wait Larry.
and my layout refers to his earlier breadboard schematic.
I know Freppo Is busy doing his test.
I'm just trying to get my head around some of these new to me chips. and learn some more about best practices in layouts.
No offense meant.

Me too; I made a redrawing of all waiting for the test!!! I stay TUNED!!!!
Title: Re: PWM phaser in the works
Post by: bluebunny on October 14, 2014, 02:44:53 AM
Is it ok to leave the unused pins on the CD40106 unterminated ?

Tie the unused inputs to VDD or VSS, otherwise it'll go bonkers.  You can leave the outputs unconnected.

Imagine if someone did a layout every time Rob (deadastronaut) posted a new drawing! Hi Rob! ;)

Ha ha!  With three or four schemos per page and forty or fifty pages in a thread, the world would run out of components!   :D
Title: Re: PWM phaser in the works
Post by: deadastronaut on October 14, 2014, 11:59:34 AM
oi!..this is cyberbullying..i'm telling the administrators :)

 ;D

i get there in the end eventually though eh.. ;)


Title: Re: PWM phaser in the works
Post by: armdnrdy on October 14, 2014, 12:31:37 PM

i get there in the end eventually though eh.. ;)


Two years in the making....may I introduce to you....the One Knob Fuzzerator!  ;D
Title: Re: PWM phaser in the works
Post by: Freppo on October 14, 2014, 05:37:15 PM
Lol guys.. that's mean (but funny)  :D
I suspect this phaser will go through a few revisions too before the final version

Unfortunatly the phaser project will be on hold for a little while now.
Work, relationship.. life, you know...  :icon_neutral:

Hopefully I can pick it up again in a couple of weeks and present a good layout not long after that.
Stay tuned! :)
Title: Re: PWM phaser in the works
Post by: bluebunny on October 15, 2014, 02:58:31 AM
oi!..this is cyberbullying..i'm telling the administrators :)

You know we love ya really, mate!   :D

Quote
i get there in the end eventually though eh.. ;)

You do indeed.  And that's why we love ya.
Title: Re: PWM phaser in the works
Post by: deadastronaut on October 15, 2014, 05:35:19 AM
 :-*

 ;)
Title: Re: PWM phaser in the works
Post by: anotherjim on October 15, 2014, 06:58:54 AM
Personally, I find those blow by blow, watch it develop threads, very entertaining and educational. Keep at it Rob!

Freppo, l'll look forward to seeing your next moves soon I hope.
Title: Re: PWM phaser in the works
Post by: Freppo on October 27, 2014, 12:30:02 PM
Hey folks

I've been playing around with the phaser for a couple of days now.
I decided that the dual LFO thing didn't really work out so I ditched it
So now i'm back almost where I started, with a fairly simple version.
The big difference is that I changed the LFO. Now it has a better sweep.
It should be dead quiet aswell, no ticking or noise. :)

(http://forumbilder.se/DEC5T/parasite-phaser-final.png) (http://forumbilder.se/DEC5T/parasite-phaser-final)

Sorry about the tiny size. My website editor is down at the moment, so I can't upload files.
I will share a fullsize image when it is online again.

I have made a new PCB layout, just need verify it... :)

/ Freppo
Title: Re: PWM phaser in the works
Post by: Kipper4 on October 27, 2014, 01:45:00 PM
Bravo Freppo.
Can't wait to see the pcb.
Title: Re: PWM phaser in the works
Post by: GodSaveMetal on October 27, 2014, 03:31:06 PM
I stay TUNED on this; FREPPO take your time man!!! THANKS!!!!!!!!!!!!
Title: Re: PWM phaser in the works
Post by: deadastronaut on October 28, 2014, 01:54:59 PM
Where's the other 15 schemos.... :icon_mrgreen:

Can we add a depth. Resonance. And  a vol ...and a switched speed cap to get

Ludicrously slow sweep option.... :icon_ :icon_idea:
Title: Re: PWM phaser in the works
Post by: Kipper4 on October 28, 2014, 03:16:29 PM
Are you not forgetting something Rob?
Title: Re: PWM phaser in the works
Post by: deadastronaut on October 29, 2014, 04:24:58 AM
Pulsing led of course...a must have... ;)
Title: Re: PWM phaser in the works
Post by: bluebunny on October 29, 2014, 04:44:41 AM
Pulsing led of course...a must have... ;)

Just the one?   ;)

(http://stream1.gifsoup.com/view3/1424411/led-cube-o.gif)
Title: Re: PWM phaser in the works
Post by: deadastronaut on October 29, 2014, 07:15:17 AM
Hmm...ive just setup my living room with rgb smd 5050 reels...20metres of the stuff...

Mrs Astro decided to have a Halloween party Friday...so I put that up...very cool..

But the best bit is I have a few metres spare so have been tinkering... :icon_mrgreen:
Title: Re: PWM phaser in the works
Post by: bluebunny on October 29, 2014, 09:00:56 AM
. . .  so have been tinkering... :icon_mrgreen:

That's not like you, Rob.

Can't wait to see the results.  I have my welder's mask at the ready.   ;)
Title: Re: PWM phaser in the works
Post by: Freppo on October 29, 2014, 04:01:14 PM
Ok

Here is the new layout and it's verified!  :icon_biggrin:
http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parasite_phaser_pcb.pdf (http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parasite_phaser_pcb.pdf)

A demo video is coming.. but I want to box it up first, so it will take a while

Sorry, no LED rate indicator  :icon_razz: It's because LED needs to be buffered and inverted..
But I'll make a optional daughterboard for that on vero later..  :icon_wink:

/ Freppo
Title: Re: PWM phaser in the works
Post by: Kipper4 on October 29, 2014, 04:28:57 PM
File damaged and could not be repaired message.
Adobe wouldnt open it.
Sorry Freppo
Title: Re: PWM phaser in the works
Post by: ~arph on October 29, 2014, 04:30:55 PM
I can open it on my ipad just fine
Title: Re: PWM phaser in the works
Post by: GodSaveMetal on October 29, 2014, 07:02:49 PM
I SEE IT THANKS IS FINE; GREAT FREPPO!!!!!!!!!! AWERSOME!!!!!!!!!!
Title: Re: PWM phaser in the works
Post by: bluesdevil on October 29, 2014, 07:28:08 PM
That's awesome!! Oh hell, I don't have CD4066 chip here!
I've been having a Freppo fest here all week building up the Ray Gun Chaos Fuzz and Black Current pedals.... good stuff.
I think I will try to put all the circuits in one box as a tribute build. :icon_twisted:
Title: Re: PWM phaser in the works
Post by: deadastronaut on October 30, 2014, 03:22:35 AM
@freppo...nice one.. 8)

do you have the updated schemo, i'd like to bread this first..
Title: Re: PWM phaser in the works
Post by: Freppo on October 30, 2014, 06:13:37 AM
do you have the updated schemo, i'd like to bread this first..
Of course :)
schematic: http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parasite-phaser-final.pdf (http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parasite-phaser-final.pdf)

I've been having a Freppo fest here all week building up the Ray Gun Chaos Fuzz and Black Current pedals.... good stuff.
I think I will try to put all the circuits in one box as a tribute build. :icon_twisted:
Haha, that's awesome! :)
Title: Re: PWM phaser in the works
Post by: deadastronaut on October 30, 2014, 06:33:00 AM
cheers man.. 8)
Title: Re: PWM phaser in the works
Post by: Kipper4 on October 30, 2014, 10:47:04 AM
Nice  work Freppo.
I'm away for a few weeks but I know I'm doing this as soon as possible.
I got all the PDFs working on iPad too. Lord knows why the PC won't open it.
Thanks mate and keep up the good work. It's high time there was a reasonable alternative to matched jellybean phasers.
Title: Re: PWM phaser in the works
Post by: bluebunny on October 30, 2014, 11:24:31 AM
Also on my (very long) list.

It's high time there was a reasonable alternative to matched jellybean phasers.

But if you want an alternative, Rich, check out Rick's "Causality (http://www.diystompboxes.com/smfforum/index.php?topic=80456.0)" 13700-based phaser.
Title: Re: PWM phaser in the works
Post by: deadastronaut on October 30, 2014, 11:34:49 AM
^ i tried that on bread...it was more like wah filters to my ears, rather than phasey whoooshyness... :)
Title: Re: PWM phaser in the works
Post by: Kipper4 on October 30, 2014, 12:57:02 PM
Sound clip please Rob.
Thanks for the link Marc. looks intresting too.
Title: Re: PWM phaser in the works
Post by: psychedelicfish on October 31, 2014, 04:27:43 AM
Sorry, no LED rate indicator  :icon_razz: It's because LED needs to be buffered and inverted..
Why not run it off the PWM signal? It would probably benefit from a BJT buffer, but that would still only take 3 extra components.
Title: Re: PWM phaser in the works
Post by: mykaitch on November 01, 2014, 03:12:36 PM
So what am I missing?
PWM - pulse width modulation.
The analogue switches have two states, on or off. They turn on with about 3v on the enable so what is this triangle stuff all about?
In a phaser with FETS the ramp will ramp the FETs and hence the op amps.
Can't see where/why PWM is any use. We need a ramp or triangle, I thought. Won't just banging the ref volts up and down produce a sort of
clicky sound? Sorry, I don't geddit.
Title: Re: PWM phaser in the works
Post by: anotherjim on November 01, 2014, 03:35:32 PM
The analog switches are acting as variable resistors. The resistance they present is proportional to the duty cycle of the switching control. PWM is varying the pulse width of the switch control and hence varying the average resistance through the switch. A long On time compared to a short Off time amounts to a low switch resistance - A short On time compared to a long Off time is a high switch resistance. The switching frequency is well above the audio range so you don't hear them switch. The triangle LFO is modulating the pulse width of the high frequency clock oscillator.
Title: Re: PWM phaser in the works
Post by: Freppo on November 01, 2014, 03:57:11 PM
I suck at explaining tech stuff. But I'll try... It's really simple once you understand it.

It's true that the switches are either on or off. But, take for example PWM controlling the brightness of an LED:
The flow of current to the LED turns on/off rapidly in pulses, giving us the illusion that the LED is constantly on.
Narrow pulses gives us a lower current over time then wide pulses... so the LED gets stronger with wider pulses, since it's more "on"

This is exactly how it works with the CD4066 switch.. it turns on/off very rapidly and gives you the same effect as a resistance
So the pulse width determines how long the switch is open (so narrow pulses=more "resistance" then wide pulses)

Remember that these pulses are very often fast (over the audiable range 20K +)
And for example 20 000 hz is 20 000 swings per second (please correct me if i'm wrong)

In this circuit the CD40106 makes a pulse width oscillator (with very high frequency, about 90K)
It also works as a narrow pulse widener, modulated by a triangle wave LFO.

/ Freppo
Title: Re: PWM phaser in the works
Post by: Freppo on November 01, 2014, 03:58:45 PM
The analog switches are acting as variable resistors. The resistance they present is proportional to the duty cycle of the switching control. PWM is varying the pulse width of the switch control and hence varying the average resistance through the switch. A long On time compared to a short Off time amounts to a low switch resistance - A short On time compared to a long Off time is a high switch resistance. The switching frequency is well above the audio range so you don't hear them switch. The triangle LFO is modulating the pulse width of the high frequency clock oscillator.

Anotherjim beat me to it :) Much better explanation then I could ever give. Cheers!
Title: Re: PWM phaser in the works
Post by: Freppo on November 01, 2014, 05:25:00 PM
Why not run it off the PWM signal? It would probably benefit from a BJT buffer, but that would still only take 3 extra components.
Yes, but I couldn't find room for there extra 3 components without making the PCB larger.  :icon_rolleyes:  :icon_razz:
But running it directly from the PWM signal is a nice idea and should only require a simple RC filter. I'll try that. :)

cheers
/ Freppo
Title: Re: PWM phaser in the works
Post by: Cotoletta on November 01, 2014, 05:49:14 PM
Nice idea. I'm having some issues with a JFET based phaser, way too much distortion using humbuckers. Does your design solve this problem?
Title: Re: PWM phaser in the works
Post by: psychedelicfish on November 01, 2014, 06:47:08 PM
Why not run it off the PWM signal? It would probably benefit from a BJT buffer, but that would still only take 3 extra components.
Yes, but I couldn't find room for there extra 3 components without making the PCB larger.  :icon_rolleyes:  :icon_razz:
But running it directly from the PWM signal is a nice idea and should only require a simple RC filter. I'll try that. :)

cheers
/ Freppo
You don't even need the RC filter, persistence of vision will take care of any need for filtering, especially if your PWM is running at 90kHz.
Title: Re: PWM phaser in the works
Post by: Freppo on November 02, 2014, 04:28:28 AM
Nice idea. I'm having some issues with a JFET based phaser, way too much distortion using humbuckers. Does your design solve this problem?

This design doesn't have any distortion, even when using hot humbuckers.
Sorry to hear you are having problems and I hope you can solve it!
I had the same problem with a Phase 90 that I built on a tonepad PCB.

/ Freppo
Title: Re: PWM phaser in the works
Post by: Freppo on November 02, 2014, 04:33:11 AM
You don't even need the RC filter, persistence of vision will take care of any need for filtering, especially if your PWM is running at 90kHz.

Tried it now. It kinda works directly from the PWM signal, but with a limited range. It never turns off completely.
With a filter in front it goes from off to fully lit, making it much more visable and usable. And it's only two components extra :)

I made a new PCB with the added LED stuff. :)
http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parasite_phaser_rev1_pcb.pdf (http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parasite_phaser_rev1_pcb.pdf)

cheers / Freppo
Title: Re: PWM phaser in the works
Post by: Cotoletta on November 02, 2014, 09:02:22 AM
Nice idea. I'm having some issues with a JFET based phaser, way too much distortion using humbuckers. Does your design solve this problem?

This design doesn't have any distortion, even when using hot humbuckers.
Sorry to hear you are having problems and I hope you can solve it!
I had the same problem with a Phase 90 that I built on a tonepad PCB.

/ Freppo

Good to hear! I have a bunch of 4066, tomorrow I'm grabbing some 40106 and give it a try.
Title: Re: PWM phaser in the works
Post by: armdnrdy on November 02, 2014, 09:34:45 AM
Great job!

I have a question.

I know that your goal was to keep this design low parts count and light on controls but...

Is there any reason why you didn't include a depth control?

A depth control will give you the option of dialing back the effect which is especially useful in the upper speed range.

One can always dial back the feedback but...that is a different parameter.

The feedback path reinforces the notches...the depth or width control adjusts the range (amplitude) of modulation from a narrow to wide wave.

If I'm looking at your schematic correctly...it would only take the inclusion of a pot (lug 3) at the output of IC5B, the wiper connected to the 4.7K resistor, and lug 1 connected to ground or Vr.
Title: Re: PWM phaser in the works
Post by: mykaitch on November 02, 2014, 10:23:09 AM
Weird. Analogue switches do what they say on the tin. Look at the data sheet. It may be that they could work as var R in the same way that a 7400 for example can work as an op-amp, but I have to ask why???
Title: Re: PWM phaser in the works
Post by: Freppo on November 02, 2014, 11:19:16 AM
Great job!
Is there any reason why you didn't include a depth control?
If I'm looking at your schematic correctly...it would only take the inclusion of a pot (lug 3) at the output of IC5B, the wiper connected to the 4.7K resistor, and lug 1 connected to ground or Vr.

Thanks! I didn't include a depth control because I don't think that it is really necessary. The effect is subtle enough until you turn up the feedback.
Also, the filter at the output of the LFO smooths out the waveshape, reducing the depth and keeps it from sounding wobbly or unmusical at high rates. :)

But you could always add a depth pot if you wanted to, just as you discribed.

cheers
/ Freppo
Title: Re: PWM phaser in the works
Post by: anotherjim on November 02, 2014, 11:41:58 AM
I think the point of using CMOS switches as variable resistors is because the multiple stages will track each other very closely and it is cheap.

The alternatives are to use JFET's as variable resistors or Vactrols BUT both types need to be closely matched in order to get decent tracking. Very expensive and tedious to do. If you don't have close tracking of the phase shift stages, the effect is less noticeable than it should be.
 
This diagram...
(http://sound.westhost.com/articles/vca-f11.gif)
Shows a VCA using 2 switches forming a potentiometer. With the clock pulse width at 50% it's dividing the input by 2. The inverter between the 2 switch controls means that as the PWM pulse-width increases (but frequency remains constant), one switch increases resistance as the other decreases. In this case, the switches are directly in the audio path, so an output low pass filter is shown to remove the clock frequency.

If I ever get around to building a Phaser, I will definitely try this scheme.
Although I do have a bunch of 2SK30A JFETS that were long ago pulled from a dead Roland Jet Phaser. Hmmmm.....
Title: Re: PWM phaser in the works
Post by: Freppo on November 02, 2014, 01:31:24 PM
My goal with my phaser was to avoid FETs and Vactrols for the reasons you discribed. :)
I have pulled my phaser off the breadboard now. I want to try other things for a while.

But soundclip / demo is coming soonish. :) Maybe I'll do a vero layout aswell..

BTW, That's a neat schem!
Title: Re: PWM phaser in the works
Post by: Cotoletta on November 04, 2014, 05:33:03 PM
Anyone tried to build this? Just built mine for the second time and I'm having a strange distorted sound, no phasing at all. Checked every connection, seems all good. I can hear the LFO ticking if I disconnect from ground the unused triggers inputs so I know it works.
Title: Re: PWM phaser in the works
Post by: Freppo on November 04, 2014, 07:54:38 PM
Sorry you hear you have problems.
I built it and it works  fine. I wouldn't share anything I didn't test first.

Can you post IC voltages?
Title: Re: PWM phaser in the works
Post by: Cotoletta on November 05, 2014, 07:38:50 AM
Sorry you hear you have problems.
I built it and it works  fine. I wouldn't share anything I didn't test first.

Can you post IC voltages?
I know your circuit is tested (well, we have also a video!), maybe I just did something wrong  ;) I also re-did the PWM part of the circuit and now I have a clean signal, no strange noises.
Also if I connect from the pin 8 of the 40106 instead of the 9, I have a slightly volume boost but and a little distortion but still no phasing.
I'll post some voltages.
Note that I have a few differences from your schematic: didn't have a TL022 so I used a LM359 or TL072, but same result. Used two TL072 instead of one TL074.

Voltages:

CD40106 (signal to 4066 from pin 8 )
1  GND
2 4,49V
3 GND
4 4,49V
5 2,76V
6 0,14V
8 0,001V
9-10 4,49V
11 1,13V
12 4,49V
13 0,145V

HCF4066:
1 4,49V
2 4,49V
3 4,49V
4 4,49V
5 4,49V
6 4,49V
7 GND
8 4,49V
9 4,49V
10 4,49V
11 4,49V
12 4,49V
13 4,49V
14 4,49V

(looks suspicious?)

Input/output TL072 buffer:
1 4,49V
2 4,49V
3 4,02V
4 GND
5 4,49V
6 4,49V
7 4,37V

The phasing stages I think are fine, tried connecting some JFETS (with an LFO) instead of the 4066 and I have phasing.
Title: Re: PWM phaser in the works
Post by: Freppo on November 05, 2014, 07:59:49 AM
I'll check my voltages later today, but those 4066 values look a bit strange.
Pin 14 of the cd4066 should be connected to +9v

/ Freppo
Title: Re: PWM phaser in the works
Post by: Cotoletta on November 05, 2014, 08:30:40 AM
I'll check my voltages later today, but those 4066 values look a bit strange.
Pin 14 of the cd4066 should be connected to +9v

/ Freppo
Uh I'm a dumbass haha. I was powering both 40106 and 4066 from the +VR line.
Corrected this I still have no phasing. If I feed the 4066 from pin 8 of the 40106 again I have a volume boost but this time no distortion.

*EDIT x2: everything works. Sounds great!
Title: Re: PWM phaser in the works
Post by: mykaitch on November 05, 2014, 02:27:24 PM
I really want to get my head around what you're doing because I've just built the phase90.
Your scope pic shows what I would expect,sq waves.
The anal sw needs a logic level to control it and turns on or off.
In the sch it seems that a set voltage is switched.
SO...PWM what???

In the orig p90 there is a simple osc and a charge cap.The cap will charge in a crude sort of ramp.
When the gates to the FETS are turned on by this ramp they will exhibit a changing resistance and this
'sweep' the opamps. We can see all this with a scope.

So my Q still is, just what is being controlled by means of PWM because ultimately those cmos switches will only turn on or off.
Please don't misunderstand me, I want to know what I am not seeing here.
You have to have some sort of linear control to sweep the phase. If you just switch it is only going to be in phase or out,albeit changing at the LFO rate, and probaby clicking....
Title: Re: PWM phaser in the works
Post by: Freppo on November 05, 2014, 05:03:14 PM
*EDIT x2: everything works. Sounds great!

Awesome! I'm glad to hear you got it working. :)

Please don't misunderstand me, I want to know what I am not seeing here.
I think you are a bit confused about how PWM works. The pulse oscillator is not to be confused with an LFO.
The PWM signal turns the switches on/off at a very high rate (about 90 000 times per second in this case)
That is why you don't hear any clicking. It's above the range of our hearing and what our equipment can reproduce.
The video demo I did in my first post shows the PWM signal very "zoomed in", at something like 0.002 second.

The width (duty cycle) of the pulse determines how much time of every cycle the switch stays in either state (on or off).
So with a narrow pulse the switch is mostly closed each cycle, which translates into a high resistance.
And a wide pulse keeps the switch mostly open each cycle, which gives us a very low resistance.
Remember that each cycle is repeated 90 000 times per second, but the effect of changing the pulse width adds up "over time".
This way it's possible to go inbetween fully closed (infinite resistance) to open (only a few ohm's of resistance) using PWM.

Check out this video
https://www.youtube.com/watch?v=mVx02s1fHIY (https://www.youtube.com/watch?v=mVx02s1fHIY)

The width of the pulse however is modulated with a regular LFO. :)
If I scoped the LFO output insted we would see a triangle wave at only a few hz per second.

I hope that helps. Maybe someone else can chime in a explain this better then I can.  :icon_rolleyes:
Cheers / Freppo
Title: Re: PWM phaser in the works
Post by: Cotoletta on November 05, 2014, 08:33:43 PM
Hey Freppo,
Just added two extra phasing stages and sounds all cool.
One question: I think the phasing is a little bit uneven. Looks like the PWM signal goes to a lower duty cycle too fast, as can be seen your videoclip. Any plan for modifying this?

Btw great circuit. Sound very similar to the phase 90 clone I have in my other breadboard without the distortion issue.
Title: Re: PWM phaser in the works
Post by: Freppo on November 05, 2014, 08:57:08 PM
One question: I think the phasing is a little bit uneven. Looks like the PWM signal goes to a lower duty cycle too fast, as can be seen your videoclip. Any plan for modifying this?

Cool. I'm glad you like it :)
The latest schematic doesn't have the same LFO as my first video, so the sweep should be better now.
But you can try to offset the Vref of the LFO to change how much time it spends at either ends of each sweep.
Try a 20K trimpot between +9v and ground, insted of the 10K and 12K resistors coming for the LFO IC.

Here is the latest schematic again, in case you missed it:
http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parasite-phaser-final.pdf (http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parasite-phaser-final.pdf)
The feedback pot numberings are backwards and I haven't added the LED rate indicator stuff yet..
It's a 22K resistor from the CD40106 pin 9 that goes to the LED anode and to a 100nF cap to ground.
LED cathode to ground.

Cheers / Freppo
Title: Re: PWM phaser in the works
Post by: Cotoletta on November 05, 2014, 09:22:00 PM
Cool. I'm glad you like it :)
The latest schematic doesn't have the same LFO as my first video, so the sweep should be better now.
But you can try to offset the Vref of the LFO to change how much time it spends at either ends of each sweep.
Try a 20K trimpot between +9v and ground, insted of the 10K and 12K resistors coming for the LFO IC.

Here is the latest schematic again, in case you missed it:
http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parasite-phaser-final.pdf (http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parasite-phaser-final.pdf)
The feedback pot numberings are backwards and I haven't added the LED rate indicator stuff yet..
It's a 22K resistor from the CD40106 pin 9 that goes to the LED anode and to a 100nF cap to ground.
LED cathode to ground.

Cheers / Freppo

Yap, that's the schematic I used.
Just tried the 22K trimmer, it is possible now to adjust how much time the duty cycle stays at higher values, but the transition to low duty cycle looks like the same.
Title: Re: PWM phaser in the works
Post by: mykaitch on November 06, 2014, 07:03:22 AM
The PWM signal turns the switches on/off at a very high rate (about 90 000 times per second in this case)
That is why you don't hear any clicking. It's above the range of our hearing and what our equipment can reproduce.
The video demo I did in my first post shows the PWM signal very "zoomed in", at something like 0.002 second.


Thanks for the reply, yeah I figured you might be doing that, obviously you need to switch at a much higher rate than your bandwidth -- and you do. I have two ICs on my board, I think I might use a PIC out of interest and hook it on to my board to see how it goes. You have more board to cover (unless its SMD) for the sake of 4 fets but then, you have a lot more scope. With a PIC I should be able to do all kinds of stuff  :)

I use PWM in some of my lighting effects but to avoid FETs etc I use digital pots and let the software sort it out.
Good luck with the project.
Title: Re: PWM phaser in the works
Post by: Freppo on November 15, 2014, 07:50:40 AM
I finally boxed up this one!  :)



At about 3:25 I switch "mode", which makes it sound very different. Sorry about my crappy playing.
I think it turned out good, and I probably won't tinker with this one much more :)
But if I am building this one again I'm going to reduce the maximum speed (raising the 330K and 1.5 resistors),
or at least use a log pot to have more control over the slow rates.
Other then that I'm pretty happy. I hope you like it!

You can find the latest PCB layout and schematic at my blog:
http://parasitstudio.weebly.com/building-blog/parasite-phaser (http://parasitstudio.weebly.com/building-blog/parasite-phaser)

Cheers / Freppo
Title: Re: PWM phaser in the works
Post by: anotherjim on November 15, 2014, 08:45:16 AM
Bravo! Sounds just like a Phaser ;D

My opinion is any LFO faster than 8Hz sounds silly with most modulation effects. My own personal taste is for about 7Hz tops.

I've never experimented with phasers - is there a limit on how slow the LFO can go before the effect disappears?

Title: Re: PWM phaser in the works
Post by: Kipper4 on November 15, 2014, 09:01:15 AM
Just started mine this morning. Should have it done today
Thanks for the clip Fredrik. Sound excellant.
Excited or what!!!!!!!!!!
Title: Re: PWM phaser in the works
Post by: Freppo on November 15, 2014, 05:40:20 PM
Bravo! Sounds just like a Phaser ;D
Thanks, it does.. :P All those hours and just regular phaser sounds. feels alittle underwhelming lol.
But it's nice to make something really useful for a change and it does sound nice.  :icon_smile:
Now i'm back experimenting with synthy noisy stuff, it's much more fun!

is there a limit on how slow the LFO can go before the effect disappears?
Not really. It can get extremely slow, but the sweep gets wierd. I think a sinewave or hypertriangular LFO should suit better for a slow sweep phaser.

Btw.. If anyone wants to slow down the overall range of the LFO try changing the 330K resistor to a 470K. :)

Just started mine this morning. Should have it done today
Thanks for the clip Fredrik. Sound excellant.
I'm glad you like it! :) Good luck with your build.
Title: Re: PWM phaser in the works
Post by: bluebunny on November 17, 2014, 02:57:04 AM
Cool demo, Fredrik.  I may have said this was on my build list.  I think it moved up a notch or two!
Title: Re: PWM phaser in the works
Post by: Kipper4 on November 17, 2014, 03:39:21 AM
Mine's done. Thanks for all the hours Fredrik. It was worth it because now we can make phaser without having to match fets.
I used a 50k trimmer with a 47k in parallel because that's all I had. There's a very narrow margin for biasing as I expected.
I redrew Frederiks layout for perfboard. Now verified. So if you want the perf version pm me.
Thanks again good work
Rich
Title: Re: PWM phaser in the works
Post by: anotherjim on November 17, 2014, 04:25:03 AM
"All those hours and just regular phaser sounds. feels a little underwhelming lol."
That may be, but you've helped to publicise an alternative method, and that's all to the good.
Title: Re: PWM phaser in the works
Post by: Kipper4 on November 21, 2014, 02:43:44 PM
I just did the LFO range mod by putting a 150k in series with the 330k on a spdt switch so I can have either the 330k alone or the 330+150K.
lots of room on the board for the mod and
No popping issues with the switch. sounds good.
Thanks Freppo
Title: Re: PWM phaser in the works
Post by: Jem on November 24, 2014, 05:53:30 AM
Very cool and innovative use of PWM - thanks for sharing!

It would be tempting to use the PWM in a small PIC to generate the sweep and add a bunch of waveforms and tap tempo.

Just for fun I was also wondering if you could swap the op amps for CMOS inverters biased for linear operation and have an all CMOS phaser - is this feasible?
Title: Re: PWM phaser in the works
Post by: anotherjim on November 24, 2014, 02:11:21 PM
Not really possible with inverters such as they are. A phase shift network uses 2 paths and they are either fed into a differential amp (the opamps here) or produced from a transistor phase splitter (like Uni-vibe). The CMOS inverter can't do either trick.

If you really wanted (for the hell of it!) to use CMOS, the MOSFETs in a CD4007 might be able to make a uni-vibe type phase shifter, possibly  getting you at least 2 stages out of one 14pin IC!
Title: Re: PWM phaser in the works
Post by: snap on November 25, 2014, 01:34:09 AM
Not really possible with inverters such as they are. A phase shift network uses 2 paths and they are either fed into a differential amp (the opamps here) or produced from a transistor phase splitter (like Uni-vibe). The CMOS inverter can't do either trick.

If you really wanted (for the hell of it!) to use CMOS, the MOSFETs in a CD4007 might be able to make a uni-vibe type phase shifter, possibly  getting you at least 2 stages out of one 14pin IC!


you might as well take a look at this topic: http://www.diystompboxes.com/smfforum/index.php?topic=87949.0
Title: Re: PWM phaser in the works
Post by: anotherjim on November 25, 2014, 06:34:03 AM
Doh! Silly me. Of course you can split phases with an inverter - input and output.
For that matter, you can make a diff amp with 2 inverters and some resistors (invert one input and mix).

You still get the usual hit's with inverters in linear mode. High current consumption and noise.
I go back to mention the CD4007. There may only be 3 inverters, but you can insert some resistance in series with each of the complementary pairs to limit the current draw.
Title: Re: PWM phaser in the works
Post by: Kipper4 on December 09, 2014, 01:37:04 PM
Hey Freppo
Where should I hook up the oscope to see what you had in the video please.
Title: Re: PWM phaser in the works
Post by: Freppo on December 09, 2014, 02:44:25 PM
Hey Freppo
Where should I hook up the oscope to see what you had in the video please.
From IC3 (CD40106) pin 9.

cheers / Freppo
Title: Re: PWM phaser in the works
Post by: Kipper4 on December 09, 2014, 03:23:51 PM
Cheers man
Title: Re: PWM phaser in the works
Post by: Freppo on December 23, 2014, 08:58:21 AM
Savvas over at the tagboardeffects forum made a vero layout that is verified. :) Thanks!
http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parphaser.png (http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/parphaser.png)

/ Freppo