Wednesday, 23 March 2016

Madbean Glam (Chorus)

Here is Brian's new PT2399-based chorus.
You can find all infos from his website here.

Here is a video by Ciaran:


61 comments:

  1. any other jfet opamp that could work in here you know of by chance instead of teh tl062?

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    1. im guessing the tl072 will work just fine ..we will find out soon !

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    2. As seen elsewhere:

      - TL062 is the low power version of the TL082.
      - TL072 is the low noise version of the TL082.

      TL062 draws less current from your supply.

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    3. The TL062 is often chosen for the LFO in effects like this because its low current draw makes it less likely to induce noise in the power supply which could be audible at the output. A TL072 would probably "work" but you might hear a thumping or clicking noise that corresponds to the chorus modulation rate.

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  2. Replies
    1. Bwahaha. I think he should be the one to verify any pt chorus pedals after how amazing his little angel came out. :p

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    2. Son of a bitch...

      PT2399 Chorus... we meet again.

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    3. haha. heath, don't worry, it's nowhere near as finicky as your favorite little bastard chorus.

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    4. Time to sprinkle my soldering iron with holy water, sharpen my dremel, and trying hunting--er... building this thing...

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  3. I totally just got the PCB for this and was waiting to build it as it requires 1/8 watt resistors and I had to order them. Nice timing! Might try this layout if I can't wait any longer.

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    1. Hi Ralf, don't take Madbeans' parts list as a case of "must be these values". They specify the MINIMUM voltage ratings for resistors and capacitors, in order to get a successful build.

      In other words, if you have 1/4 Watt resistors, you can happily use them - you could use 5 Watt resistors and it would still work.

      You can happily use 1/8 Watt or 1/4 Watt resistors for ALL of the 9V and 18V circuits on here.

      The same applies to capacitors. If Madbean specify (for example) 47uF 16V you can happily use any voltage higher than that, so if you only have a 100V cap, use it - it will not make any difference.

      Just remember when dealing with electrolytic capacitors that you want to use one rated at (roughly) twice the supply voltage. In other words if you building a 9V circuit, the caps should be 16V or higher, and if you are building a 18V circuit, 24V should be your minimum rating.
      You don't want them exploding in your face!

      You don't have to worry with film, box and ceramic caps - most are rated at 50V.

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    2. Yep and the Madbean layout is quite tight, hence why it calls for 1/8W resistors. They are very small.

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    3. Good info Breaker. I meant 1/8 watt resistors are required for the Madbean PCB layout as it is is quite small, designed to fit in a 1590G enclosure.

      Wattage and voltage, why and when, were things that confused me when I started building some months ago. I've learned a lot from the comments on this site. Keep up the good work.

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    4. Sorry, I did not realise there was a size issue on the PCB - I should have checked first. The PCB should still be possible with 1/4 Watt resistors, but will not look as neat - you might need to stand the resistors.

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  4. Hi Alex. All built up but currently the LFO isn't working. I'll start looking for the usual suspects now. Depth is doing what it should and audio passes just fine. But the Rate pot does nothing and all voltages on the IC are steady at 4.50v ish.

    I'll keep you posted. Cheers

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    1. Tag it VERIFIED lad. The top right link was only soldered on one side. Time to book an opticians appointment methinks.

      Sounds great! There's no denying its a PT2399 based effect. They're not as fast as BBD chips so you get the slightest (and I mean slightest) feeling that its lagging behind a bit. It's not as "lush" but has a sound I would call its own. Can easily pull off some 80's Mark King type sounds. Its definitely getting a box anyway!

      I'll try to get a demo recorded once I get it in a box and send you the link.

      Cheers again lad.

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    2. Cool!
      Thanks Ciaran!
      A video would be great!

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    3. Hi Alex. Short demo found here...

      https://www.youtube.com/watch?v=-W4uEJiIiS8&feature=youtu.be

      Cheers again lad.

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    4. Thanks Ciaran!
      It sounds great!

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  5. If you feed the pt2399 6 volts it clocks faster and you get less of a delay.

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    1. Found this info: Delay times for pt2399

      with pin 6 grounded,
      5V supply = 24ms
      6V = 18ms
      6.5V = 16.5ms
      7V = 15ms
      7.5V = 14ms
      8.5V = dead chip

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    2. Good info Sean cheers. The data sheet makes no mention of any other supply voltages but 5V, so I've never really considered giving it any more.

      Don't get me wrong though...when playing normally there's no hint of latency...just when you really scrutinise it one note at a time. It doesn't put me off at all. It's not filtered as heavily as some BBD designs so it really shimmers. Loving that!

      I suppose the circuit would really benefit from a dry signal mixed in at the end. I may try that at some point but I'm quite happy for now.

      Cheers

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    3. I want that dead chip tone so I'm gonna feed it with 9V. B)

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  6. Have not built that many PT2399 choruses, but damn this sounds sweet. You can almost forget that it's on... But when you turn it off it's back to cold, ugly dystopia we know as reality.
    +m

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    1. Haha! Somebody needs a hug...and an Easter Egg

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  7. Hi all. Does the (-) leg of led 2 just go to any ground? or even with the
    (-) leg of led 1 going to the 3pdt sw?

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    1. Yeah so if you want the speed LED to be on even when the effect is bypassed, just take the speed LED cathode to a ground. The LED will always be on and lit up even when the effect is bypassed.

      The bypass LED will have it's cathode to the 3PDT switch at the LED ground spot. This will be ur usual indicator LED.

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    2. Thank you Charles. If I want the rate light off when effect is off, how is it wired?

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    3. I would put the - led 2 lug to the 3pdt switch along with the on/off led - wire. Right?

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    4. I did away with the LED 1 (bypass LED) altogether. I took the LED 2 cathode to the usual spot on the bypass switch so when you kick it in, it lights up AND pulses to the rate. No popping. The 1K is its CLR so I would play with that to get your desired brightness.

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    5. Thanks C.
      Great idea. 1 led 2 functions. I'll do that. I finished this and it seems noisey. Good effect but a kind of 'rush' behind the effect. Is yours dead quiet? I am waiting on 2399's. Might be that causing the noise. Thanks from Terre Haute, IN., USA.

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    6. Sorry I missed this Jeff. Yeah, there is a slight "rush" as you call it behind the notes. You can hear it in the demo I just posted to Alex above. I only had 6 chips left and this was the quietest one of the bunch.

      I'd deffs recommend buying a large stock and auditioning them. Some are quieter than others.

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  8. Is it verified? No LFO noises?
    Thanks

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  9. My attempt came out as a warbling distortion, anyone else run into this?

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  10. Really liking this one. Have only the slightest hint of noise. Thanks all.

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    1. I just double-checked all of the little caps by the 2399 and now it works great. I is easy to get them confused down there. This is one of the nicer choruses I think even if it is not very versatile.

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  11. The 1N5817 is use as polarity protection, and can be replaced by an other diode ? Or must be exclusively a Schottky diode?

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    1. It is just a series polarity protection. Any diode will work. Schottkys just have lower voltage drop than other types. But. Any will work.
      +m

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  12. Mine seems not to work properly. I get the sound out and clean (a bit saturated if I strum too powerfull, but I think that's pretty obvious), but both the pots do nothing. From CCW to CW I get the same sound out, that has very little chorus on it. Double checked the solders, the voltages on the ICs and transistors and changed the pots, but I have no idea what to do now.

    Anyway, I still don't have any chorus working, a little frustrating eheh

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  13. Hi Dan,

    Might be "PT2399 lock out" - symptoms are similar to what you describe (ie no delayed signal) - though connecting pins 3 to 4 to ground, which is the case with this layout, should stop this happening. You didn't miss the link under the ic, did you?

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  14. Against my better judgement (and past experience) I went ahead and gave this one a shot.

    First of all the effect is very nice. Like Miro said, it can be left on and you'll forget it's there until you turn it off and things go "ugh..."

    HOWEVER... mine is noisy as hell. I tried over 30 different PT2399 chips and they all sounded exactly the same, so I don't think it's that chip doing it. It's almost like a fuzzy buzz clinging to every note. Dead quiet until I hit a string and then there's this layer of buzzy noise all over it. As a matter of fact, play the low E string high up on the neck gives an almost synth type sound, like an ugly brother of a Green Ringer.

    Anyone got any idea what could be causing that? I spent the last few hours going through PT2399 chips and it got late. Tomorrow I'll try tracing it with a probe to see where the buzziness starts coming in.

    No one else got anything like this?

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    1. Not constant, but when strumming hard.

      Check your voltage on pin 7, if above 2v the PT is being overdriven. If so, put a green LED from pin 7 to ground, should help.

      I've done this on every PT build. I usually see the LED flicker when playing so it seems to do the trick for me.

      I think Jon Patton is credited for the idea.

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    3. I'll give that a shot. Mine is dead quiet until the strings are touched. Once I'm generating any sound whatsoever through the circuit, there's an "aura" of fuzzy noise clinging to it. It's very hard to describe. I'll try to record it.

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    4. the solution of the green led between the pin 7 of the pt and ground is correct, after putting it it has eliminated the small distortion that he was dreaming of every note, thank you Michael, now the pedal sounds very well, I have used tl082 instead of tl062

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  15. Replies
    1. That's a 50k trimmer to bias the jfet. Be sure to check the build doc for instructions.

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  16. Got mine working today, nice but I think I'm going to try and up the PT voltage to 6V for shorter delay times as noted by Sean Caskey.

    6V = 18ms
    6.5V = 16.5ms

    Also, I think the LED on pin 7 is a must if using humbuckers or other hot pickups. Mine was also noisy without it.

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  17. I tried 5.7v, 6 and 6.7v.

    Seems like the chorus progressively tightened up but also got a bit darker and less lush. It seems like the depth is backed off somewhat with the higher voltages.

    I think there may be some tweaking needed for the higher voltages. 5.7v was still pretty good as is.

    Going to see if adjusting R18 and/or R19 evens it back out with 6.7v supplied to pin 1.

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  18. Finished mine, works well but I have a continuous high frequency noise, like a biiip.
    I used a TL072 until TL062.
    I tried differents trimmer position, but nothing to do, this high sound is continuous.
    Have you any idea where can come that sound?

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  19. Just wasted my day debugging a noisy Glam chorus I built today. Turned out it as a crappy power supply. Sounds great and I don't have any noise at all

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  20. made it and works great. just a silly question.
    what's the purpose of D1? i have the same result with and without it.

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  21. I've built this, and it works as a chorus, but if I strum normally it starts to distort. The green LED lights up very prettily. Any ideas? Otherwise, it's clean, but that distortion is quite a nice crunch... It also boosts the volume a touch, but my little angle did that too.

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    1. Should mention I only have the Green LED connected, LED 1 or 2 hooked up. Also using a TL072.

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    2. The IC is the part of the LFO and not in the audio path, but I would change it to a TL062 just to be safe. Using high output pickups? You could add a pad resistor 100K? on your input...or up the right 10K (next to the 2 20Ks) to something like 100K and see if that helps.

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  22. Ok, I tried all these things:

    Pads across input to ground, started at 100k, went to 33k (getting there) to 10k and 2k (inaudible signal)

    Changed that 10k to 100k. Some difference in overall volume (it decreased)

    What fixed it was removing the green LED, which shall now be known as the clipping diode!

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    1. Just to be a little clearer, I changed the 10k next to the 20k resistors to 100k which caused the volume decrease. I was also using a 2n5484, and the test guitar used a JB pickup.

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  23. I'm losing signal at pins 14 and 16. Voltages check out in the LFO and on the 2399 within reasonable variation. I've audio probed the signal path and retain signal to pins 13 and 15 (lpf ins). Checked the caps around the 2399 and everything seems fine. Auditioned about 4 chips and the problem persists for each. Chip removal results in signal retention at the output, albeit very attenuated. Scratching my head on this one. Any ideas?

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  24. Hi
    Tnx For the Pedal
    I need a mix volume for this pedal can somebody help me ?

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