Author Topic: Introducing the "One Chip Chorus"!  (Read 148078 times)

Govmnt_Lacky

Re: Introducing the "One Chip Chorus"!
« Reply #60 on: August 01, 2011, 07:47:36 AM »
Has anyone built it on to a pcb yet?

Waiting on this as well. This whole project looks very promising  ;)
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of ‘up to and including my life.’

askwho69

Re: Introducing the "One Chip Chorus"!
« Reply #61 on: August 02, 2011, 09:14:23 AM »
do we need some mix on this? for more versatility?
"To live is to die"

anchovie

Re: Introducing the "One Chip Chorus"!
« Reply #62 on: August 02, 2011, 09:22:26 AM »
Replacing the two 10K mixer resistors with a pot was mentioned earlier in the thread.
Bringing you yesterday's technology tomorrow.

Kearns892

Re: Introducing the "One Chip Chorus"!
« Reply #63 on: August 03, 2011, 09:31:37 AM »
R13 on the vero is listed as 10K while on the schematic it looks like it is 100K. What is the intended value?

anchovie

Re: Introducing the "One Chip Chorus"!
« Reply #64 on: August 03, 2011, 10:05:33 AM »
Well spotted! Should be 100K as per the schematic.
Bringing you yesterday's technology tomorrow.

Govmnt_Lacky

Re: Introducing the "One Chip Chorus"!
« Reply #65 on: August 03, 2011, 10:30:57 AM »
Has anyone verified Scruffie's or Kearns' PCB layouts on Page 2?
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of ‘up to and including my life.’

anchovie

Re: Introducing the "One Chip Chorus"!
« Reply #66 on: August 03, 2011, 10:59:39 AM »
Has anyone else got this working on a breadboard, even?  :-\
Bringing you yesterday's technology tomorrow.

merlinb

Re: Introducing the "One Chip Chorus"!
« Reply #67 on: August 03, 2011, 11:03:32 AM »
Here's another take on the one chip chorus. This one has deeper modulation, so it generates a very thick warble, more like the deep settings on a LA. It also has an improved latch-up fix that may be useful for other projects.

Scruffie

Re: Introducing the "One Chip Chorus"!
« Reply #68 on: August 03, 2011, 12:29:36 PM »
Has anyone verified Scruffie's or Kearns' PCB layouts on Page 2?
Don't think so, atleast no one's mentioned it to me.

I'll verify it if you wanna etch me one  :icon_lol:

Here's another take on the one chip chorus. This one has deeper modulation, so it generates a very thick warble, more like the deep settings on a LA. It also has an improved latch-up fix that may be useful for other projects.


Damn that looks nice... looks like i'll be making another PCB layout this evening... and using the breadboard if I can clear some space.

Has anyone else got this working on a breadboard, even?  :-\
Same as above, if I can get some space on the breadboard i'll try tonight... it's kindaaa full at the moment.

Slade

Re: Introducing the "One Chip Chorus"!
« Reply #69 on: August 03, 2011, 12:59:11 PM »
Just saw this thread...
I'm amazed... Congrats on this new design!

Thomeeque

Re: Introducing the "One Chip Chorus"!
« Reply #70 on: August 03, 2011, 01:51:55 PM »


 Is this drawing correct? I'm trying to figure out how the LFO works here and I don't see it.. LTSpice neither.. Thanks, T.
Do you have a technical question? Please don't send private messages, use the FORUM!

Govmnt_Lacky

Re: Introducing the "One Chip Chorus"!
« Reply #71 on: August 03, 2011, 01:55:02 PM »
I wondered if it would be possible to make a chorus effect using a PT2399 and no external op-amps and the answer is yes! Instead of using the internal amplifier intended for the output mixer, I've given it a new role in a phase shift oscillator. I originally intended to use the LFO output to modulate delay time, but the nice surprise was that there was no need - the oscillator uses the chip's Vref pin (famously exploited by frequencycentral in the Little Angel as a place to inject modulation) as its ground point and, just by being there, it makes the PT2399 wobble.

This is how he did it Thom  ;)
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of ‘up to and including my life.’

Kearns892

Re: Introducing the "One Chip Chorus"!
« Reply #72 on: August 03, 2011, 02:04:18 PM »
I was going to try and etch my board today, but I am not sure I have enough PTs to complete this and the other PT based projects I'm rushing to finish.

Thomeeque

Re: Introducing the "One Chip Chorus"!
« Reply #73 on: August 03, 2011, 02:04:44 PM »
I wondered if it would be possible to make a chorus effect using a PT2399 and no external op-amps and the answer is yes! Instead of using the internal amplifier intended for the output mixer, I've given it a new role in a phase shift oscillator. I originally intended to use the LFO output to modulate delay time, but the nice surprise was that there was no need - the oscillator uses the chip's Vref pin (famously exploited by frequencycentral in the Little Angel as a place to inject modulation) as its ground point and, just by being there, it makes the PT2399 wobble.

This is how he did it Thom  ;)

 Well, that's how anchovie did it, but I'm asking about Merlin's magic, that's completely different circuit ;) T.
Do you have a technical question? Please don't send private messages, use the FORUM!

Govmnt_Lacky

Re: Introducing the "One Chip Chorus"!
« Reply #74 on: August 03, 2011, 02:12:06 PM »
Well, that's how anchovie did it, but I'm asking about Merlin's magic, that's completely different circuit ;) T.

SLAPS FOREHEAD PROFUSELY!!!!!!  :icon_redface:  :icon_lol:
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of ‘up to and including my life.’

merlinb

Re: Introducing the "One Chip Chorus"!
« Reply #75 on: August 03, 2011, 03:33:51 PM »
Is this drawing correct? I'm trying to figure out how the LFO works here and I don't see it.. LTSpice neither.. Thanks, T.
Pah, there's always something! Resistor in the wrong place- drawing has been corrected. (If it still looks the same try going directly to http://i81.photobucket.com/albums/j207/merlinblencowe/OneChipChorus.jpg)
It's a relaxation oscillator, just like in most modulation effects, e.g. Phase 90.
« Last Edit: August 03, 2011, 05:29:55 PM by merlinb »

Govmnt_Lacky

Re: Introducing the "One Chip Chorus"!
« Reply #76 on: August 03, 2011, 03:42:59 PM »
What resistor was moved and where? I do not see a change even after clearing history  ???
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of ‘up to and including my life.’

Thomeeque

Re: Introducing the "One Chip Chorus"!
« Reply #77 on: August 03, 2011, 04:26:21 PM »
Is this drawing correct? I'm trying to figure out how the LFO works here and I don't see it.. LTSpice neither.. Thanks, T.
Pah, there's always something! Resistor in the wrong place- drawing has been corrected. (Clear your browsing history if it still looks the same)
It's a relaxation oscillator, just like in most modulation effects, e.g. Phase 90.

 Actually, integrator capacitor 4u7 is in wrong place, it should lead to pin 13 not 14 of PT2399 (I see only thumbnail in your gallery corrected, full picture is still the old one - some photobucket issue I guess).

 Funny, this LFO works only thanks to weak internal reference voltage divider :) If it was harder, it would not tick (voltage at positive input of LFO op-amp must be alternated for this type of oscillator).

 Problem is, that you don't get triangles on the reference voltage this way (triangles are only at the integrator capacitor) - what you get there are rounded squares*..

 

 That's why it sounds as you describe it (it generates a very thick warble) probably..

 T.

* Edit: But now I see that it can be rounded almost to sinusoidal wave (when increasing C1 and C3).. and of course I don't know how exactly internal reference voltage source looks..
« Last Edit: August 03, 2011, 04:59:26 PM by Thomeeque »
Do you have a technical question? Please don't send private messages, use the FORUM!

frequencycentral

  • Awesome!
  • ****
  • Posts: 4962
  • Total likes: 130
  • Virtue signalling keyboard warrior since 2020.
    • frequencycentral
Re: Introducing the "One Chip Chorus"!
« Reply #78 on: August 03, 2011, 09:51:03 PM »
Here's another take on the one chip chorus. This one has deeper modulation, so it generates a very thick warble, more like the deep settings on a LA. It also has an improved latch-up fix that may be useful for other projects.


I *think* this is based on the updated version. Please check before attempting - it's late - I'm tired.


« Last Edit: August 03, 2011, 10:19:27 PM by frequencycentral »
http://www.frequencycentral.co.uk/

Questo è il fiore del partigiano morto per la libertà!

David

Re: Introducing the "One Chip Chorus"!
« Reply #79 on: August 04, 2011, 06:48:38 AM »
How crucial is it to use a BC337?  Would substitution with a 2N series transistor be possible?