Wednesday, 18 April 2012

Merlin Blencowe's One Chip Chorus

Another one of these nice little PT2399 projects to try out.  This was a from a schematic posted by Merlin Blencowe and it seems to give a nice range of vibrato and chorus sounds for such a simple design, using just the PT2399 IC and nothing else driving it. 

Clip made by Merlin (he posted that any noise was due to his recording setup and not the effect).

Yes the chips can be temperamental, but the results can be great for some of these effects.  Just don't forget to buy 10 x PT2399's and keep trying them until you find one that works :o)


Posted by at 00:28
Tags: , , ,

40 comments:

  1. mirosol31 May 2012 at 05:38

    Battled this for a while yesterday, and can't seem to get it right. I get the signal through, but it's just kind of an strange overdrive. Tried on all my PT2399s, but that's not the problem. Transistor can be unplugged, and that changes nothing. Should the led be illuminated? Mine isn't.

    I'll continue debugging procedures on this once i have the time...
    +m

    ReplyDelete
    Replies
    1. IvIark1 June 2012 at 17:39

      Just been over the layout mate, and I've got the 100n from IC pin 8 going to the wrong row. It should go to pin 3 not pin 4. Layout updated.

      Delete
    2. mirosol1 June 2012 at 19:15

      Nah. Didn't change a thing. Forgot the say earlier that the rate pot also does nothing.

      There might be something else wrong with m,y build too, since i don't think that the voltages on the right hand side are healthy:
      Pins 1-8: 4,99|2,48|2,16|4,97|2,49|0,09|4,60
      Pins 9-14: 2,48 (yes, all of them)
      Pins 15 & 16: 4,49

      We got guests, so i have to stop for this evening.. :(
      +m

      Delete
    3. IvIark1 June 2012 at 20:04

      Grounding problem mate. Pin 3 should definitely be 0 volts, it's linked directly to the ground rail, and so if it isn't then either the soldering of the link is dodgy, or the ground rail isn't grounded. Did you put the double link under pin 3?

      Delete
    4. mirosol1 June 2012 at 22:01

      Yes double link is ok.. I just notices that the piece of paper i wrote the voltages do read:
      Pins 1-8: 4,99|2,48|0|2,16|4,97|2,49|0,09|4,60 - so i just forgot to write 0... There's only 7 voltages on that earlier comment.
      +m

      Delete
    5. IvIark1 June 2012 at 23:03

      Post a front and back pic mate. I've been over the layout a few times and it certainly looks right to me

      Delete
    6. mirosol1 June 2012 at 23:41

      I think there is something else badly wrong where. I have broken boards before by letting them have too much voltages in the wrong places. I'll rebuild it...
      +m

      Delete
    7. IvIark2 June 2012 at 00:01

      I've just been reading the "One Chip Chorus" thread on DIYStompBoxes and there is a post on there by Brymus which sounded very similar to what you describe. And a couple of pages later someone else posted that they had the same problem but swapping the PT2399s cured it.

      I'm confident the layout matches the schematic now, but I haven't read any other positive outcomes from Merlin's schematic other than from Merlin himself so I don't know if the schematic is 100% correct. He did make some corrections in the thread but the image didn't seem to change so I'm not sure what happened there.

      Maybe this is one to put on the backburner for a while until I can confirm a few things with Merlin.

      Delete
    8. mirosol2 June 2012 at 08:37

      Silly me. I could have read that thread too.. :)

      It's not that importantat circuit to me right now. I have built perfectly working Little Angel v4, which is more than enough. This just seemed like fun little board to try out. I thought about naming it "[sic]" as in "single ic chorus" :)

      If he confirms, let us know!
      +m

      Delete
  2. JonasL23 June 2012 at 08:38

    Any news on this? I really want to make it :)

    ReplyDelete
  3. pinkster5 July 2012 at 01:47

    i built a few different versions of this, but none of them seem to work. it's VERY temperamental as to 2399's...the last incarnation i built was working, so i boxed it up.

    sucker never worked again. i DID get it to be a one slap echo messing with it some, but so far i've found 2399's to be really problematic in general...no consistency to their quality control.

    i've bought from tayda, smallbear, ebay...all of 'em seem to have issues, and they all seem to randomly lock up.

    ReplyDelete
  4. mirosol29 September 2012 at 18:07

    Hmm. If you're using the schematic from merlinblencowe's photobucket, it seems to have 10µ from IC pin2 to ground and not 47µ. Pin2 is labeled REF, so that could be it. I might rebuild this to try it out.
    +m

    ReplyDelete
    Replies
    1. IvIark29 September 2012 at 18:19

      Copy and paste syndrome! :o) I suspect it won't make any difference though. It's an internal vref and so it's just like the difference in using 47u or 100u for filtering in various other layouts. Both will work and higher values will have more of an affect.

      Delete
    2. mirosol29 September 2012 at 19:33

      I just built it per schematic, using 47µ for filter and 10µ for vref.. It's pretty ugly pitch bending phase/chorus :) Tried on all my PT2399s and at least it is consistent, as all of them work exactly the same :)

      I'll go through any mistakes i may have there tonight.. Right now i need to do something else :)
      +m

      Delete
    3. mirosol29 September 2012 at 19:34

      Oh. I had only one deviation from the schem/layout. The 91K resistor that sets the range of range pot - i used 100K, but that shouldn't contribute to pitch bending...
      +m

      Delete
    4. IvIark29 September 2012 at 20:22

      Someone on DIYSB mentioned it was more extreme than the other one chip chorus, so your description probably makes sense. So was the 47u to 10u the only change and can this be tagged?

      Delete
    5. IvIark29 September 2012 at 20:38

      Another thing to try by the way mate which is something that caused problems in the Deep Blue Delay until I made the change, is to ground pin 4. That's supposed to be a digital ground derived internally, but until that was attached to the board ground the IC kept locking up. Certainly worth soldering in a temporary link to see if it makes any difference anyway.

      Delete
    6. mirosol30 September 2012 at 00:16

      Ok. So, "extreme" means just bad sounding modulation... And i just now compared my circuit with the demo above - and it is just like that. Probably should have listened to that link earlier on... (Personally wouldn't exactly call that a chorus, but a "bad space junker")

      So 10µ was the only change and yes. It can be tagged. LED might want a + sign on top lead...

      I also grounded the pin 4. That didn't change anything.

      Are we likely to see that other, James Howard's "One Chip Chorus" from DIYSB? Demo of that sounds like it could be better...
      +m

      Delete
    7. IvIark30 September 2012 at 00:19

      Cool I'll tag it and I'll check out the other chorus. Cheers matey

      Delete
    8. mirosol30 September 2012 at 09:11

      Ooh. I just checked my wiring, and the depth is in reverse. I noticed that yesterday, but there was other hazzle going on.. So i forgot to say it...
      +m

      Delete
  5. Unknown13 August 2013 at 17:39

    problem solved? did not work here ..... what could it be?

    ReplyDelete
  6. Unknown13 August 2013 at 17:46

    my changes: 91k - 100k
    820k - 840k (620k+220)
    not work ... anyone succeeded?

    ReplyDelete
  7. Unknown11 November 2013 at 21:04

    Hello, I wanted to build this circuit and also the little angel chorus, to use with bass guitar. Is this reasonable or should they be modified in some way, like input caps etc? thanks

    ReplyDelete
    Replies
    1. pinkster12 November 2013 at 01:54

      miguel, double the values of the coupling caps in the audio path and you should be good bro.

      Delete
    2. Unknown16 November 2013 at 17:10

      Thanks. Which would those be? I can imagine that the input 100n and the output 10n but I don't know if there are more in between.

      best

      Delete
  8. pinkster12 November 2013 at 01:55

    guys, i got this in an email the other day from one of the gents at bob keeley's site.. i hven't tried it, but just passing it on!

    Subject: Re:_Jimi_Pocius_Dot_Com

    Hey Pinkster,

    We were doing some searching for the PT2399 latch-up issues and found your problems on the tagboardeffects website and we had the same problem as you with the latching up everytime we powered it on and only after unplugging and waiting to plug it back in did it start working again…. We may have found a fix which is a 0.01uF capacitor across pins 2 and 3 of the PT2399. Worked for us anyways.

    Let me know if this fixes your problem!!

    Craighton Hale

    Keeley Electronics, Inc.
    www.robertkeeley.com
    1733 S. Fretz Ave. Suite C
    Edmond, Oklahoma 73013
    405-341-2025

    ReplyDelete
    Replies
    1. IvIark23 March 2014 at 02:41

      Sorry Jimi, I'm going through some threads because I keep coming across posts that I missed last year when I was away at various times, and this is one of them. Did you try the cap and did it solve your issue?

      Delete
    2. pinkster14 February 2015 at 20:19

      nope, it just killed the only working build i had of this kinda thing (little angel).
      it's the fucking chips. they just plain suck!!

      Delete
  9. Peeps18 December 2013 at 17:09

    Breadboarded to save vero & solder... No overwhelming ticking and doesn't break up with humbuckers. I like it- it's like a lofi memory man set to slap back.

    ReplyDelete
  10. Unknown22 December 2013 at 18:54

    Hello, this one built, no ticking problems, but I have a volume loss with the circuit engaged. Is this normal?

    ReplyDelete
  11. Peeps22 December 2013 at 23:10

    Depends on the depth pot a bit- deeper setting can sound a bit lower in vol. I've tried SHO & Tillman preamp circuit after for vol recovery, preferring the Tillman.

    ReplyDelete
  12. Peeps22 December 2013 at 23:13

    I should also note I am using a 500kc pot for speed (slower) & I raised the input resistor to 1M to increase headroom (does cut vol a little).

    ReplyDelete
  13. Unknown27 December 2013 at 17:59

    anyone use a tranny diff than BC337?

    ReplyDelete
  14. Ark Angel HFB21 June 2014 at 15:43

    Just thought I'd pop in and saw that a 10ohm or 20ohm resistor from pin 4 to ground should stop almost all lockups...

    ReplyDelete
  15. Anjang19 February 2015 at 09:53

    This is verified layout ??? Somebody explain please...

    ReplyDelete
  16. VLTRA3 January 2017 at 17:31

    Two times tried, with no success :/ There must be something wrong because if you short circuit the led with another one or make a bridge draining some extra voltage you have an effect that could be near to a chorus, but nothing else. The normal effect it does is some kind of echo, not suitable for playing anything :/ I'll try another design.

    ReplyDelete
  17. Dave2514 June 2018 at 00:10

    This comment has been removed by the author.

    ReplyDelete
  18. Dave2514 June 2018 at 03:00

    Ok so I answered my own question. The pin out of the 2n3904 is different from the bc337. My question now is the circuit is working perfectly but for some reason it sounds like a fuzz chorus any ideas? Oh and I cut the diode could that be the reason?

    ReplyDelete
  19. Steve22 October 2018 at 04:38

    I just built this and it does kind of work. However, it's wobbly sounding. Like it's pitch bending... Kind of funny really, like a drunk guitar. :-)

    ReplyDelete

Subscribe to: Post Comments (Atom)