Friday, 19 April 2013

Magnus Modulus

With 8 knobs and 3 switches I really didn't need to keep the size of this one down, but it will fit in a 1590B if anyone is utterly insane :o)  You can shave off another column if you solder D1 and D2 in the same hole and move the 1u cap over to the left into the hole vacated by one of the diodes.  But there probably isn't much point in saving the space when it's going in a 1590BB (at least) anyway.

Another mod would be to make the bottom left 100u cap switchable to change the speed range available from the LFO, but I'll leave experimenting with that one up to you.

From Nathan Alexander Smith's original project document:

The Magnus Modulus is another PT2399 based DIY echo modulation effect pedal. I wanted to make a digital delay and liked the idea of adding modulation ala Echo Base. I decided to use a stage from the BYOC Ping Pong with the LFO from the Tremulus Lune for maximum modulation control.  I didn't reinvent the wheel here, just a bunch of other ideas put together into one awesome effect. 

The delay lengths are controlled via a voltage controlled oscillator in the PT2399 at pin 6. The nominal delay length is set by R9 and Delay Time pot. The modulation is coupled on top of this DC value via R10 and C13. There is no need for a variable resistor (transistor, LDR). While I had the LFO and buffers already on board I decided to add a tremolo coupled into the output amplifier stage with a J201 acting as a switch.

This project is intended as a DIY effect and hopefully an evolving one.  This is a highly modifiable circuit, hopefully you'll find the setup you like the most. The values in the schematic and layout are my personal favourites, your taste may differ so I'd suggest a few mods. The project fits in a 1590BB if you have skills

MODS: Delay filtering - I have a really hot bridge pickup in my Les Paul and it can make the delay section distort (I use both pickups and designed the pedal using the middle one, it sounds awesome) I increased the values of C11 and C18 to filter more of the highs. Capacitors you can play around with to change the filtering are: C5, C6, C11, C18.

I used 240k resistors in the LFO, the original has 220k, you can add a "Fine" rate control as well.

The tremolo could be inlplemented with an LDR, I used the J201 as it is pretty common. There is a bit of charge injection that is only really noticeable with the space (or smooth, can' t remember) knob is turned down, the tremolo sounds really good and smooth when that control is set properly though.

You can use less knobs, the gain knob could be a trimmer if you don't want a booster.  Taking out the limiting diodes will increase the output significantly during self-oscillation and is not recommended


  1. There are these....
    if you're absolutely insane. I am not.

  2. Mark, are you going to do a Mutron III layout? I'm building Harald's one this evening, and you seem to publish your layouts on the next day I build the circuit :P (and I prefer your layouts for sure :P Harald's ones are great but highly density populated ones)


    1. I do it on purpose just to annoy you! :o)

      Yes I've got the Mutron in my to do list.

    2. Yeah.. what little I've built of Harald's circuits, he does seem to like his resistors standing up and the boards really cramped.

      No complaints, though! He has some interesting circuitry and responds quickly.

      Mutron? Perhaps a Meatball? :)))

  3. Which would be C5,C6, C11 and C18 on this layout? I'd like to try getting a darker sound on the repeats as they die away.

    1. C5 and C6 are the 2n2 caps at pins 13-14 and 15-16 of IC1. C11 is the 47n to ground via IC1 pin 14 > 1K. C18 is the 15nF cap to ground at the top left at Tail Sw1.

  4. Thank you for your prompt reply IvIark. I shall let you know what results I get from substituting these for higher values.

  5. How could I rig status leds for tails and tremolo? DPDT switches? Thanks in advance, this is not a one-nighter for me, that's for sure.

    1. Yeah, DPDT or 3PDT, whatever you have in stock. And no, is not a nighter :P I built the layout about 15 days ago, and just on friday was in the mood to do all these dammned wiring :P

    2. Thanks a lot, I think that's what I'll do. Now to decide if I'll try to fit this into a 1590bb or get something larger...

  6. I wish I could exclaim VERIFIED! But alas, not yet. Apparently the PT2399 works, as the effect oscillates at max feedback. I'll get back to this tomorrow, but thought that a few pairs of fresh eyes might see something I dont. The pin voltages are

    Pt2399 pin voltages
    1. 5,03
    2. 2,51
    3. 0
    4. 0
    5. 2,90
    6. 2,50
    7. 0,7
    8. 0,7
    9. 2,56
    10. 2,51
    11. 2,51
    12. 2,5
    13. 2,55
    14. 2,55
    15. 2,5
    16. 2,49

    Tl072 (substituted for Tl062)


    Apparently something is pulling down the voltages of the 5532, but I couldn't find any shorts. The red cut in the first picture ( lower left corner) is a mistake I think I fixed with a jumper that's visible in the upper left corner in the second pic. From pin2 of IC2 over the 1M resistors. The jumper doesn't short to any component that I could find.

    Thanks in advance for any and all help


    1. There must be a physical issue with the build. You're getting 7.91V on IC2 pin 8, but only 0.19V on IC3 pin 8 and they are connected directly by the copper link. Something is either misplaced or maybe a cold joint somewhere.

    2. Sorry I got the IC numbers the wrong way round, you're getting 7.91V on IC3 pin 8, but only 0.19V on IC2 pin 8. The misplaced link is why you're getting a higher voltage on the output (pin 7) of IC3

    3. Thanks Mark, there was a cold joint in the link at pin8 on ic2. That got the delay working, but somethings still wrong with the tremolo. I've only got 0,67V at the Gate, but 0 on Drain and Source...

      Most likely more cold joints, but now I'll really have to get some shuteye.

    4. Hmm. The rate led is not flashing, but is continuosly on. Where should the switching happen? At the J201?

    5. Oops, just saw your later messages, mark. Thanks a bunch, I'll check the link at IC3.

    6. Yeah, the link was indeed in pin7 of ic3, fixing that fixed the led, it now flashes according to the rate pot. Alas, no signal. And no steady pin voltages on pins 1-3 and 5-7. I'll have to get to work, I'll get back to this tonight or tomorrow.

      Thanks for the help Mark.

    7. Check the voltages again and post them to see where that leaves us.

  7. Yeah, I'll do that tonight. I bet i got the links manhandled to touch each other under ic2, grounding the power to the 5532. we'll see tonight.

  8. 5532:
    1. 3,89
    3. 3,73
    4. 0
    5. 3,88
    6. 3,89
    7, 3,9
    8. 8,95


    1. 2,42-6,08
    2. 2,43-6,02
    3. 2,43-6,02
    4. 0
    5. 2,58-6,09
    6. 2,64-6,08
    7, 1,35-8,14
    8. 8,95

    Pt2399 same as before.

    1. We've got signal. I Had accidentally ripped the input wire off the board... No tremolo, though :(

    2. It's alive! Just had to play with the adjustments a bit to get the tremolo to work :)

    3. Awesome, so is everything working as expected?

    4. Yeah, tremolo, delay and even the modulation switch work as advertised.


  9. Tag it :) Thanks for your help, Mark.

    The gain seems to be reversed, it's loudest while all the way counter-clockwise.

    I think there was nothing wrong with the tremolo, it just takes a bit of getting to know.

    1. Awesome, I'll swap over the gain lugs and tag it. Nice one matey!

    2. By far the most fun effect I've built this far. Have to figure out something great for the box.

      Here's now:

  10. Just finished wiring this and the tremolo is reversed. Counter clockwise is FAA as clockwise is slow.

    Anyways, it sounds really really good and is worth the size and effort. However I'm having noise issues with the delay side and a little bit from the tremolo. I can hear the PT2399 noise and it changes when I turn the time knob. Turning the delay level up increases noise a lot. If I turn it much past halfway, I'd say it's unusable. I can hear some leakage of the tremolo coming through as well, even when the trails are turned off.

    I have only gone through about 4-5 PT2399 chips and the first one was very noisy and it improved a little when I swapped. I'm gonna go through a few more as I've got 100+ of them. I'm hoping its just the chip.

    To be fair, when you're playing, you can't hear the noise unless you turn the delay level way up. I'd just like to tame the noise a little more.

    1. Stupid autocorrect on my phone! "counter clockwise is fast and clockwise is slow" was supposed to be there.

    2. On Harald's version, the rate knob work the same way, so maybe's designed to work like this, just like in the Deep Blue delay (same behaviour with speed knob).

      I built mine (Harald's one) and he tells lin pots. I believe that the behaviour shoud be clearly better with antilog ones as stated by Mark on Rate and Depth (in this position is clearly mandatory). In Time knob would be really useful too and on gain wouldn't hurt a log.


    3. I had the same problem. Too Much noise and no tremolo at all but i still can hear the heartbeat of the tremolo anyway. The Feedback knob and the Delay knob makes all the noise. Tonight i'm gonna see whats going on... Is there someone who has the same problem and has solved it?
      So far... is a very fun pedal already


  11. Boxed!

    Still have to fix the leds for delay and tremolo, but it works :)

    1. Done :)

    2. Puavo,

      Wich resistors have you used for the leds?
      And do the leds work now for the delay and tremolo? How did you fix it?


    3. I used a 4k7 resistor for the blue (delay), 2k7 for the purple (tremolo) and (I think) a 3k3 for the green at bypass.

      I hooked the tremolo and delay leds using 3pdt footswitches, as you can see in the picture. A DPDT is all thats needed. I hook the + of the led to the hot in the dc adapter via the resistor and the - of the led to the terminal next to switch 1. Terminal next to switch 2 is then connected to ground. This way you make and break the led circuit simultaneously while switching tremolo or delay.

      Hope this helps.

  12. Cardboard build completed. Sounds great after I finally found the cut I forgot to make at C6,R16 - IC1-Pin 6. Without it, no flashing LED, no Tremolo, no Modulation, but LOTS of frustration, cursing and painstaking troubleshooting. As always, thanks for the great job you and Mirosol do with these boards layouts and the support from your followers. I did find one variance from the original schematic, where it shows Time 2 & 3 are connected instead of Time 1 & 2 as shown here. Does it matter?
    Again thanks. Pete

  13. This was a really nice one, verified once more! One of the most exciting pedals to build out there, i just wish i didn't get a heartbeat sound on the tremolo rate when i don't play at all :) otherwise it's a very successful build and vero :)

  14. I built this one last night and it all seems to work but with a few issues...

    I also get the 'heartbeat' sound from the tremolo in time with the LED when the depth is turned up past half way. The delay repeats seem to be very short and a bit noisy. Any ideas on how to correct this? Anyway can get some really nice lush modulated tones from it despite these problems.

  15. To have the 'tails' switch on all the time i just connect the 2 tails wires together right? When i try it it doesn't work? I'm missing something obvious here...

  16. Hi, trying again and again and again....:-) Next than first repeats are too low or it goes to the oscillation. Tried to tune resistors around 2399, changed pots (audio, linear, different values), not helped. 2399 is O.K., I´ve built Deep Blue Delay (the best naturally sounding delay I ever owned IMHO, and I have had DMM long years) and when I swap the chips, DBD works as before and MM the same:-( Any ideas?

    1. We need the IC/regulator/jfet pin voltages to have any chance of helping

    2. P.S.: PCB verified maybe 15 times, inspected for short connections (both multimeter and "x-rayed" with lamp), parts measured. Circuit works, chorus is great, but repeats excl. first are weak.

    3. Pin
      1: 5.01V,
      2: 2.50,
      6: 2.37,
      7 and 8: 0.79,
      9 - 16: 2.51.
      I see the problem somewhere in the loop from delayed signal (13 and 14 via resistors) to the input of 2399 (15 and 16 via resistors), but everything seems to be O.K. Around these pins I have got 1n capacitors ´cos of cleaner sound, not 2n2. Slapback echo (1st repeat), chorus and tremolo are O.K., but next repeats are hearingly weak, muddy, very unnatural.

  17. Problem solved thru changing parts for "known good" one by one. Cap on pin 10 and one 1N4148 wrong - not certainly bad, but out of parameters.

  18. "This was a really nice one, verified once more! One of the most exciting pedals to build out there, i just wish i didn't get a heartbeat sound on the tremolo rate when i don't play at all :) otherwise it's a very successful build and vero :)"

    I have the same problem, how do you clean up the heartbeat sound? please help, i love this little beast.. but the heartbeat noise keeps getting in the way..

  19. Hi, I need some question. My english is not perfect, I try to say my problem.
    I built the MM, but the tremolo works bad. The depth control does not work, only at the end, when I scroll up the pot. There is the max. depth, and if I scroll down a little, the sound becomes "linear". My friend told me, that the bias of the J201 is wrong. That's all, so if anyone has an idea, please tell me. Thank you, Steve.

  20. Hi, just finished my built, but only the tremolo effect seems to work. Pots and switches of the delay and modulation are not making any difference. It works as if it is a plain tremolo effect. The voltages I measure are

    1: 3.62
    2: 3.45
    3: 3.38
    4: 0
    5: 3.59
    6: 3.64
    7: 3.64
    8: 8.22

    1: 5.02
    2: 2.51
    3: 0
    4: 0
    5: 3.07
    6: 2.51
    7: 0.82
    8: 0.89
    9: 2.55
    10: 2.51
    11: 2.51
    12: 2.55
    13: 2.51
    14: 2.43
    15: 2.56
    16: 2.51

    1: 3.25
    2: 3.25
    3: 2.51
    4: 0
    5: 2.55
    6: 4.9
    7: 3.4
    8: 8.22

    I: 8.23
    G: 0
    O: 5.04

    D: 0
    S: 0
    G: 0.66

    Rate LED is flashing normally.

    Could anybody tell any possible mistakes? I double checked for short circuits.


    1. The voltages don't look too bad to me. At first I thought the TL062 voltages were a little strange around pins 5 to 7, but we know that IC must be working because that is for the LFO which we know is good because of the LED flashing and tremolo working.

      Did you socket the ICs? Some PT2399's are temperamental and so it may be worth seeing if you have the same issue with a replacement IC. Either an error around the PT2399 or a faulty IC are the likely causes with that chip being responsible for the delay and modulation.

    2. Thanks for the quick response! Yes, the IC's are socketed. I tried 4 different PT2399s. No luck. Removing the IC makes no difference at all.
      Here's my board

      Comparing it to Puavos

      I find two differences. On the right side of TL062 there should be an electrolytic 100uF, and the 240k resistor at the bottom strip should connect to the pin 6 of the TL062. How could it be working for him?

    3. Ok, solved it. Just another silly mistake. I put two 1nF capacitors instead of 1uF. Everything works great, thanks once again guys!

  21. Hello, not much to ask if it would give me a hand, I want to put 3 footswitch wiring and togleswintch , but do not really understand how I haccerlo , someone who can help me , greetings

    1. I don't understand. Do you mean you want to use 3 stomp switches instead of toggle switches? Is so then the wiring remains exactly the same. The switch numbering doesn't change, just the method of actuating the switching.

    2. want to use a footswitch to bypas , one for tremolo, and one for the delay, and it is just a togleswitch , something like the picture, but do not quite understand the wiring

    3. This comment has been removed by the author.

  22. Hi and thank you for all the work; I've just built this one and it is absolutely best modulation thing I have ever played with!

    I have just a little problem anybody can may help me with. Everything works OK in my build instead of the tremolo. Delay section is OK, modulation section OK (detune/chorus/vibrato effect), all the pots in LFO works as expected and indication LED flashes. But when only the tremolo switch is on, no reaction. Any ideas?

    1. PS: I used BF245C instead of J201 (I could not get it here).

  23. One more verified.
    Very nice delay, and very nice layout, works first time. Thanks Mark !!

  24. hey guys , just fin this build . im having trouble with the trem .. there is none . no pulse just clean sound while change in the trem section pots . the rate led blinks and changes with the rate, works fine to change the mod/chorus but nothing when trem switch is active. Also the rate led dims with the depth pot .. is that normal ?
    gonna dive into it component by component bit later ... any advise where the issue could be or where to start would be very helpful

    1. im getting voltage oscillation till the gate of J201 .. then nothing from the drain . replaced the Jfet no diff . 3 jfet s . im mi missing something else here .. or maybe a bad batch of J201 s..? :(

    2. ok .. of the 5 j201 only 1 gives A pulse on the drain side ..done a run through with an audio probe ..cant get trem working .. got the pulse beats till aft 100u aft Q1 til 10k .. other end of 10 k is clean audio .. no trem ...
      any thoughts..

    3. done and done ....this was a modulus 'madness' . but got it all working ..whew.
      thanks guys for putting up all these veros

  25. Hi,

    If i understand this right, i can put a 3PDT for bypass and one DPDT for delay, which in fact is connected to "tails sw 1 & 2" ? I see "delay" written on enclosures but never "tails"
    In that case when engaged without delay engaged it only acts as boost ?


    1. Yes , As boost or as a tremolo if u have that switched on or mix . Delay / tails is same thing here .its quite handy to keep delay on with some boost ...n activate main 3pdt when soloing

  26. Hi is there a schematic to wire 3 3PDT or 1 DPDT and 2 3PDT instead of SPSTs?

    Thank you !

    1. You can just ignore terminals.

      1 3 LED +
      2 4 LED -

      1 4 LED + 7
      2 5 LED - 8
      3 6 9

  27. This comment has been removed by the author.

  28. After doing three major mistakes(5532 and tl62 upside down,replaced both, a couple of cold joints, resolder half the board just to be sure, AND a wrong capacitor value,0.022mf instead of 220nf, corrected) I can say: WOW! What a project this was! It was a pain in the... to connect all the wires, but it's sound is interesting, at least. It was my second build, after the Deep Blue Delay, which worked at once. So a big thanks to all of you who posted theese layouts, and you that had problems with them and discused them here, so we can have a starting point in troubleshooting.

  29. was there ever a wiring diagram for the leds? seems tails led is always on ? is this correct?

    1. Do you mean the rate LED? That should pulse in sync with the LFO but will be permanently on as long as there's power to the pedal

  30. Probably a silly question but can I sub a 50k lin for the weird 40k lin pot. Can't find one anywhere!

    1. Yes that would be no problem. It's just acting as a variable resistor anyway, so you could set it to exactly 40K if you wanted to

    2. Hi Ivlark, just wanted to say thanks for all of the layouts, I must’ve built like 30 different pedals from this site, and I couldn’t have done it without all the hard work you guys here have put in. It’s incredible, seriously!

      So, I’ve built this circuit and I get the raw input okay, but when switched on, I get the guitar sound with none of the effects. Suggests to me an issue with the PT2399 possibly but I’m not sure. Sounds like the Op-amps are doing their job (or at least one of them is, I don’t know).

      Voltages are as follows:
      IC1 – PT2399
      1 – 4.94
      2 – 2.48
      3 – 0
      4 – 0
      5 – 2.96
      6 – 2.47
      7 – 0.72
      8 – 0.72
      9 – 2.5
      10 – 2.5
      11 – 2.5
      12 – 2.5
      13 – 2.5
      14 – 2.5
      15 – 2.5
      16 – 2.5

      IC2 – NE5532
      1 – 4
      2 – 3.84
      3 – 3.84
      4 – 0
      5 – 4
      6 – 4
      7 – 4
      8 – 9.24

      IC3 – TL062
      1 – 6.55
      2 – 6.55
      3 – 7.5
      4 – 0
      5 – 6.92
      6 – 8.41
      7 – 8.65
      8 – 9.24

      I noticed when testing the rate LED came on briefly, I think. I was testing around the TL062, I think the 8.41V (pin 6) started dropping but not sure if was just poor connection between test lead and board.

      Thanks again for all the help.

    3. Forgot to say I subbed the J201 for a 2n5458, had a look at the Voltages on Q1:
      D - 0V
      S - 0V
      G - 0.6V
      This looks odd to me. I cannot see any short between Drain and Source. The mulitmeter sees a 228 ohm resistor between the 2 legs. And the drain capacitor has around 4V on its positive leg, and 0V on the negative leg. Don't know really.
      Thanks again

    4. Sorry thought I had posted my IC Voltages as well but maybe the comment was too long or something.

      I - 9.24V
      G - 0V
      O - 4.94V

      IC1 - PT2399
      1 - 4.94V
      2 - 2.48V
      3 - 0V
      4 - 0V
      5 - 2.96V
      6 - 2.47V
      7 - 0.72V
      8 - 0.72V
      9 - ~2.5V
      10 - ~2.5V
      11 - ~2.5V
      12 - ~2.5V
      13 - ~2.5V
      14 - ~2.5V
      15 - ~2.5V
      16 - ~2.5V

      IC2 - NE5532
      1 - 4V
      2 - 3.84V
      3 - 3.84V
      4 - 0V
      5 - 4V
      6 - 4V
      7 - 4V
      8 - 9.24V

      IC3 - TL062
      1 - 6.55V
      2 - 6.55V
      3 - 7.5V
      4 - 0V
      5 - 6.92V
      6 - 8.41V
      7 - 8.65V
      8 - 9.24V

      I may have missed the ground pin connection for the TL062. May have fried it as now its voltages are bouncing around a lot. The voltages posted above were before I saw I missed that connection... Will try changing it for another maybe

      Thanks again!