Thursday, 1 March 2012

Mad Professor Forest Green Compressor

Another request.  This was a bit of a pain to make 1590B friendly, especially with my aversion to standing resistors, but I just about managed it.  Had to do a couple of things I don't like to do, like the grey external link and the angled component avoiding link (make sure that one is insulated), and the legs on that 47n are spectacularly long, but needs must.

Anyway, the info for the original:

BJF design guitar and bass Compressor/Sustainer pedal

FOREST GREEN COMPRESSOR (FGC) is designed to meet the highest standards of guitar and bass compression.  There is extremely low noise throughout the range and a high overload margin, which allows also a wide dynamic input range at minimum distortion and noise.  FGC is equipped with a special tone control to fine-tune the compressed sound for most transparent tone and effect.  The pedal has a switchable compressor and sustainer mode.  In Sustain mode you can get a very dynamic, touch sensitive tone with a long sustain. Here the attack is not lost, making the pedal suit-able even for blues players and works great with slide playing.  Like all Mad Professor pedals FGC is hand made in Finland using only premium compo-nents, to give years of trouble free operation with superb musical tone.

Controls

LEVEL: in Compressor mode adjusts the overal volume and the FGC can be used even as a booster. In Sustain mode the Level no longer adjusts total output but the level of the sustained part.

COMPR.: Sets the amount of compression and sustain. Lower settings give mostly peak limiting, higher settings more compression and less touch sensitive response. At maximum the output will be heavily compressed, while still retaining clarity at almost infinite sustain.
A good starting point for this control is a bit below centre (ten o’clock) with most guitars.

TONE : Tone control on FGC is designed to fine-tune the compressed sound for most transparent tone and effect: Adjust CCW for full range compression and set at noon for tighter sound with a little less bottom end and turn fully CW to slightly reduce upper treble.

COMPRESSOR/SUSTAIN SWITCH: Attack and decay times are carefully fine-tuned and internally set for swift attack and slow decay. Sustain/Compression switch set for Sustain the attack is preserved allowing dynamic touch and ease of playing as the FGC amplifies the decay and weaker parts.
For standard compression set mode switch to Compressor.




Now verified:


92 comments:

  1. Nice! Another one for the To-Do-list.

    Cheers,

    m

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  2. Is this layout verified..?? Thanks. :)

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  3. Not yet, you could be the first and get all the plaudits! :o)

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  4. I will.. but not now.. :/ I have an overdrive to finish.. But, if i start it (one month from now), will i have help with the debugging..? I have some vtl5c2 sitting instead of the classic led-ldr combination..

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    Replies
    1. Yes of course, I'll always help out where I can to get the layouts verified.

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  5. Could you use a VTL5C2 in place of the LED/LDR? If you went with the LED/LDR, do you need to wrap them together? I'm a newbie to optical components.

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    Replies
    1. Yes the VTL5C2 has 1M off resistance which is similar to the popular LDRs so it would probably be a good choice. Considering the price of vactrols, I'd probably socket it to test first though just to make sure.

      The LED/LDR combo can be left untaped, but it'll cause you a problem to test it because it will only work properly in a closed box. Better to get some black electricians take and wrap them together so you know it's completely isolated from any external light. Again it's worth socketing if you use LEDs and LDRs because you may find the pedal reacts better with one particular type or colour LED and so you may want to experiment.

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  6. hi, i'd like to build this comp with your vero layout :) I have a noob question... Is da a status led? If not, will this be ok http://www.taydaelectronics.com/led-5mm-red.html ?

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    1. No, that LED is wrapped together with the LDR, it's the optical part of the compressor. That LED will be fine for it.

      I've already built this up and have been waiting for a pot to finish it off which has now arrived. So you may want to hold off until I get a chance to finish it off and verify.

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    2. ok! Thank you for the reply! :) I'm waiting for your verification then!!!

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  7. Hi Mark .. Do you have any news for this layout.??

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    1. Hi Stathis, put it to one side and totally forgot about it! :o) I've just soldered up the pots and switch and yes it worked first time. So this one can now be considered verified.

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    2. Thanks Mark.! I will give it a try..! :)

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    3. Incidentally, I used a 3mm diffuse red LED and the LDR was 10K to 1M. I haven't experimented with that combination at all but if you want to fine tune it and see what works best for you, it may be worth socketing them so you can swap and change.

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  8. I'm waiting for the components i ordered! Happy to see it is verified :D

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  9. Any Alternatives for 2sk170 & BC560C? Can I use 2N3819/2N5457/J201/MPF102 for 2SK170? and 2N3906 for BC560C?

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    1. The 2SK170 is the lower noise version of the 2SK117, but you'll need to check the pinouts and twist the gate and source around if necessary if you use something else. Bear in mind also that JFETs can be more awkward to substitute because they often need biasing differently and so I can't say for certain which if any would make a good direct replacement without tweaking resistors. The 2N3906 should work but it is lower gain than the BC560C, something like the 2N5087 may be more suitable but you can certainly give it a try.

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  10. Hi, a small consulting;

    Is fully compatible with the AD797 integrated NE5534?

    I find it a bit strange that you can put any 2 without any alteration.

    This verified that?

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    Replies
    1. They're the two opamps that people have noted as being in the Forest Green Compressor, but the scheme was put together from a tracing done on one with an AD797, so there is always the chance that other components also change with the versions with alternative ICs. But they should both work, they are both single opamps with only the inverting input, non-inverting input, output and power connections used.

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  11. i have a question. is SW 1b is the centre lug? im using spdt.

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    Replies
    1. You only need a SPST so use the middle lug and either of the other lugs, doesn't matter which.

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  12. Will the NSL-32 optocoupler work fine in this circuit?

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  13. hmm, I seem to be having a hard time finding a 285ohm resistor. I tried mouser, digikey and tayda and got nothing. I could probably run a couple in series if I had to....

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    1. I used a 270 ohm and it worked fine

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    2. ok thanks! I wasn't sure how much leeway I would have if I were to just approximate.

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  14. Hello all. I built this based on IvIark's layout... everything seems to work except the amount of volume I get. With the vol know completely clockwise, it's still slightly lower than unity gain. What section would be responsible for this? Any help is much appreciated!

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    1. Mine had plenty of volume so it must be a problem with the build or a component. A single cold solder joint could cause the symptoms you describe so you really need to check over everything and look for bad joints, unwanted bridges, shorts around cuts from burrs etc. If you post the voltages of the transistor and IC pins that may help pinpoint the problem area.

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  15. Here are the voltages

    NE5534:
    1) 6.82
    2) 4.12
    3) 3.74
    4) 0
    5) 3.49
    6) 4.14
    7) 8.93
    8) 6.85

    Q1:
    D) 8.64
    G) 3.72
    S) 4.8

    Q2:
    C) 4.0
    B) 1.59
    E) 1.02

    Q3:
    C) 3.33
    B) 0
    E) 0

    Q4:
    C) 3.33
    B) 0
    E) 0

    Q5:
    C) 8.06
    B) 8.06
    E) 8.64

    Thanks!!!

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    Replies
    1. Thanks for the prompt reply. Magnifying glass and razor blades used. No solder bridges. Any other suggestions?

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    2. Well if you're sure there's no build error or usual bugbears like the ones mentioned that only leaves a faulty or wrong value component(s). Post a high res front and back pic of the board and I'll see if anything stands out. The layout is definitely good though so a build error or component problem are the only things left.

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  16. Okay, photos uploaded:
    https://www.dropbox.com/sh/gghrjaq7eltxnob/KbPCO9Ta6R

    please let me know if you see anything. thanks!

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  17. Hi everybody!

    I need help, please!

    The 78L05 of my Green Compressor, after ONE second that i put it inside the socket, become hot!
    Very very very Hot!

    I've seen that even without this regulator the pedal works...
    Can I leave my circuit without it?

    What kind of problem do you think that it is?

    Thanks a lot!

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    Replies
    1. I don't know how the pedal would work without it, it would mean that Q4 wasn't getting any supply at all. It may be better to go for the TO220 regulators for the greater current capacity.

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  18. Thanks at first!
    So, you think that my Q4 is not working?

    I'll try to remove it to see if will there differences...

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  19. I am thinking about building this soon. One question - how did you wrap the LDR - LED combo - some shrink tubing or somthing else? Just wondering.

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    Replies
    1. Yes oversized heat shrink and my lighter did a good job and seemed to wrap it up well

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  20. Is it ok to substitute the BC550C and BC560C for a BC550B and BC560B from Tayda? -

    http://www.taydaelectronics.com/bc550-npn-low-noise-transistor.html
    http://www.taydaelectronics.com/bc560-bc560b-low-noise-transistor-pnp.html

    Will it make any difference?

    Thanks,

    Ian

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    Replies
    1. They're lower gain but should be fine

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  21. Hello everybody! I just built this one but it doesn't work as it should. Output is quite low, only at unity when maxed. Checked for solder bridges but found nothing. Also the voltages are close to what Edmund Moon had earlier in the comments. Any tips? I used nsl-32 instead of vtl5c2, but it shouldn't be the problem, right?
    Thanks

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    1. I can't remember the specs for the silonex vactrol.. Basically, if that doesn't offer suitable resistance with light/dark - then your symptoms could be explained by that... But i'm really not sure about the specs.

      Other really common reason for low output is wrong resistor value in just the right place. Have you tried probing it to see where the signal goes south?

      Niin outoa kirjoittaa maamiehelle englanniksi... :P
      +m

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  22. Alright gotta try with other vactrols when I get those.

    In the fsb forums someone else had the same problem and he noticed that the output resistor was 14.7K in the schematic, but 147K in this layout. So I gotta try that as soon as the iron is heated.

    Hah niinhän se on :) saapahan muut ainakin selvää mitä selittää :P

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    1. Yep, that solved it and now it works as it should. Now into some funk action :P

      Thanks ja tattis

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    2. That resistor makes sense. 14K7 will probably dump too much of the signal to ground where as 147K seems a lot better choice to me. Which value solved it? Or, which is correct?

      Mukavampihan se on, että muutkin tietää sitten jos tuossa leiskassa on jotain häikkää :)
      +m

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    3. It was the resistor to the left hand side of Q5 that was wrong but has been corrected in the layout. I originally had a 14K7 there and it should have been 147K, but I built it with a 14K7 and mine worked fine. The resistor at the output should definitely be 147K, so if it has fixed something, then you must have corrected a bad joint or something.

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  23. I used 15K at the output, so now it goes past unity.

    Mark youre right i mixed those two, the resistor left to Q5 is supposed to be 14.7K and the output 147K. I guess maybe I had something else wrong there and the 15K resistor "fixed" it. Oh well it works :D

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    1. No, the resistor next to Q5 should be 147K, I had a 14K7 there in the first place which didn't line up with the schematic and so the layout now posted here has already been fixed. But mine worked fine with a 15K resistor in there too.

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    2. You're totally right, dammit with these brainfarts :D

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    3. Happens to the best of us :P
      +m

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  24. what type of LED did you use in this one Mark? was quite a while since i worked with LDR's, last time i think i went with a blue one in a tremolobuild.

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    1. I used a conventional 3mm red LED, these ones:
      http://www.ebay.co.uk/itm/181135554960

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  25. I only have 2sk170-BL, not 170-GR.
    I get fuzzy sound. I believe 170-GR is the key.
    is it possible to use 170-BL by changing R-values?

    Thanks

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    1. If it's just a bias problem then you may get away with just changing the 10K source resistor for a trimmer. But I don't know for definite that just re-biasing will fix your issue.

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    2. Thanks for your kind reply.
      I checked the signal line, but the fuzzy(noisy) sound is coming right after the 5.6k near the input line way before the TR. I guess I need to check the solder joints further.

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  26. I think this could be a stupid question.
    If I put only the LED, will it lit when I strum the guitar?

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    1. Yes, but it wouldn't be a modulation compressor anymore because you'd lose the lfo by removing the ldr part of the vactrol.

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    2. What I meant to say is that it wouldn't be a compressor at all anymore... :)

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    3. Of course I'll use optocoupler and that is the heart of this project. I am having a difficulty in debugging and it's good to know that LED should lit. and mine is not at the moment....

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    4. What voltage are you getting on the led right now?

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    5. Well no wonder it's not lighting, it's most likely fried... :)

      No LED I know of can handle that, unless has a built-in resistor.

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  27. Hey Mark

    Built this the other night and I get a some hum from it when effect is on. Should I treat this compressor similar to a high gain pedal and keep leads short and avoid crossovers and/or use some shielded cable? The pedal works as it should but I just can't seem to get rid of the hum. All components are correct values and I can't see any bad solder joints. Would a failed electrolytic possibly cause the hum ie. not filtering out some noise?

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    1. Found the problem. It was a failing 9v power supply giving heaps of dirty DC out. Made a new power supply out of a computer psu nice clean 9v DC. This may be a similar issue on another couple of builds I was doing that i chucked in the too hard basket. Now I can resurrect them.

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  28. Hi there!

    Does the sustain mode is when the switch is "open" and comp mode when it's close or is it the contrary?

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  29. Hi Mark,

    I build this and compared it to the original Forest Green and it's completely the same - nice job!

    I just have one issue: When I use the compression mode, my sound gets fuzzy, when I strumm my strings to hard - this is only in comp mode - in sustain mode everything works fine and the sound stays clear.

    Also, the Tone control is only working in comp mode, in sustain mode there is almost no change of tone.

    Any ideas what the problem might be..? I checked the layout 10 times, everything is fine and the voltages are the same as posted above.

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  30. Having trouble finding a good LDR available in the USA to use. Anybody have any recommendations? I can get a KE-10720 from Tayda but I'm not going to pay int'l shipping for a $.24 resistor and I recently made a large order from them so I'm not really in need of anything else that I could use as a cart stuffer.

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  31. Finally got around to building this one, doesn't appear to do anything. My voltages are the almost identical (minor variations due to tolerance) to the ones Edmund Moon posted above. My 2SK170 looks to be working as well... 9V in, 5V out. Here's the behavior of the controls:

    - If you switch the Comp/Sus switch down, output to the amp is very faint with a slight hiss. If up, it appears to basically bypass the circuit... no tonal changes between the entire pedal in bypass and on, except for the slight hiss applied based on level.
    - Tone does nothing
    - Comp does nothing
    - Level doesn't change the output, but as you turn it up, a slight hiss is added to the output
    - LED on/off works
    - LED for optical compressor (3mm RED) does not light/dim with playing... it's always at about 25%

    I went through and double checked the offboard wiring, everything looks OK to me.

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    Replies
    1. Correction: my *VR* is 9V in, 5V out, not the 2SK170.

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  32. everything works...but there is a fizzy buzz tone all around when you strike the strings too hard. it's like it's a too high input impedance or something...what could be wrong? if i play with the volume a little lowered on the guitar, it is ok...please help. Which values should i check?(because obviously because of resistor tolerance, some which are in parallel or series don't give the exact resistance)

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  33. on single coils the problem almost goes away entirely. please tell me which value at the in or out of the pedal i should adjust . Thanks!

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  34. I just finished building this one yesterday. I tried 8 different LDRs and I seem to like my home-rolled one the best. I don't hear that much of a difference between the sustain and comp modes but it's there.

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    1. No I couldn't put my finger on exactly what the difference was between sustain and comp either.

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    2. did anybody ever get the sustain/comp switch to work properly? I've tried everything and there's no difference in either position. their instructions/maual, testimonials, reviews and demos all clearly say that it makes a big difference. there's absolutely no difference on mine. I don't intend to box mine up until I get that resolved. it's a great sounding comp, but it seems silly to install an extra toggle or rotary that does nothing. I also posted this on FSB a while ago but no one ever replied.

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  35. Just build this one, it's a great peal. In compressor mode, my Level knob acts as a volume knob: turning it fully ccw and the pedal goes silent. In sustain mode, that does not happen, and the pedal is overall a little bit louder. There is no real difference in voicing between the two modes. I have never owned or played an original fgc, but at least it seems to respond as described in the info for the original.

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    Replies
    1. Hi Marijn, i'm really glad that you posted how yours works. it made me dig deeper into troubleshooting mine. it turns out that I had a 10K resistor that read 'open' on the source of Q1 (no wonder it didn't work right!). it works perfect now. I've now completed it and boxed it up:

      http://johnkvintageguitars.homestead.com/Effects/Compressors/BJFE/FGComp-01.jpg

      gut shot:

      http://johnkvintageguitars.homestead.com/Effects/Compressors/BJFE/FGComp-02.jpg


      i'm really digging this one now.

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    2. Glad that I could be of help!

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  36. Doesn't this one require a 100p between pins 5 and 8?

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    Replies
    1. No, that was just used in the later CB version which used a JRC5534DD

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  37. Build one yesterday and almost got it running except it now works as a distortion. Used a 3mm red LED and a 10k to 1M LDR. Beside that and 2 swapped resistors I've build it like the schematic. Also the LED doesn't light up in any way, which could be due to fact it's getting 5 volt..

    Tried scraping for solder bridges and checked all the components twice but to no effect. Also tried to track the 5v from the LED. The whole 10th row is 5v but after that I haven't got the knowledge to find the source of it. Does anyone have an idea where or what to look for?

    Also as far as I could see there was no indication which way the led should be mounted. Does this mean it doesn't matter or could this be the problem?

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    Replies
    1. If you look closely there is a small white line on the bottom of the LED which represents the cathode. So yes that does matter. If that doesn't fix anything then post all the IC and transistor voltages so we can see where the problem area seems to be.

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    2. Thank you for your reply! The LED was indeed wrongly mounted but this doesn't change anything to the distortion when I hit the strings a bit harder. The distortion starts when I turn the volume up past 12 'o clock and gets progressively worse with higher volumes (even though the output signal is still less loud than the bypassed signal). The compression part now seems to work fine though. These are the IC and transistor values I found.

      IC
      1) 6,16 8) 6,17
      2) 3,88 7) 8,33
      3) 1,93 6) 3,88
      4) 0,00 5) 3,22

      Q1
      D) 8,11
      G) 1,29
      S) 4,55

      Q2
      C) 3,99
      B) 1,59
      E) 1,03

      Q3
      C) 3,30
      B) 0
      E) 0

      Q4
      C) 3,30
      B) 0
      E) 0

      Q5
      C) 7,59
      B) 7,57
      E) 8,12

      78L05
      O) 5,06
      G) 0
      I) 8,34

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  38. This comment has been removed by the author.

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  39. Greetings will the common gl5528 LDR work in this? Thnx

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  40. This comment has been removed by the author.

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  41. Perhaps a stupid question, but I'm new with LDR's.
    What type do I need?

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  42. I noticed the vero layout and the picture below it do not match. Are they both verified?

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  43. Hi ,i'm french,sorry for my english.
    I want to build this pedal but i have a newbie question:
    What means :volume 1?
    I think it's the first lug of the pot but left or right?
    Thanks
    Carlo
    PS: the vero layout is verified?

    ReplyDelete
    Replies
    1. http://tagboardeffects.blogspot.gr/2012/04/vero-build-guide.html

      http://tagboardeffects.blogspot.gr/2012/02/offboard-wiring.html

      hi.you need to read those links first.those will answer your questions.
      this ia a verified layout.
      it's taged that way at the end of the post

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  44. Hi Mark, I just built FGC today and I failed. Actually, it turned out very nice overdrive, creamy&crispy sounds like Vox AC amp. (I really love the sound.) Only nob working is "Compressor" which act as "Drive". I noticed that one diode came off from the socket and other diode and LDR/LED combo are quite loose in it's socket. But still nice overdrive sound is there. I soldered directly to the board but the same result. I wonder what possibly make this happen. Do you have any idea? I'm gonna re build this compressor, also I like to add Tone and Level for this happy accident overdrive. Any advice would be helpful.
    Thanks!

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