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Friday, 18 January 2013

Bearhug FET Compressor

Jon Patton's Bearhug FET Compressor (Yeah! That's the same cool dude who demoed Valvewizard's Engineer's Thumb a while back!) As requested.

From Jon: The Bearhug is a (fairly) low-parts-count, quiet, tonally transparent compressor using only transistors. It can do subtle peak limiting or squishy sustaining, with a decent amount of boost (probably ~6-12db).

 Notes & mods:
- The hold cap is the reversed 4.7uF. This sets the overall compression and decay. The 10K + 47K in parallel with the hold cap set the decay. Larger values may be used, but these were the most natural sounding overall.
- The High/Low switch is there for "more." A 100K instead of the 47K would provide a much more dramatic change.
- You can use substitute Schotkey, germanium, or other diode with forward voltage under ~.35v for the 1N60Ps.
- The best tone control for this circuit, if you want to add one, is Jack Orman's version 2 of Mark Hammer's SWTC.
- The 100pF cap is primarily to eliminate noise and can be adjusted to change the overall brightness.





Turned out pretty compact. I've been through it a few times, but you should still grab the schematic for reference from DIYSB...


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52 comments:

  1. Kinski18 January 2013 at 22:21

    Nice! That was FAST! it will be a few days till I can slap this together as I am probably missing some of the parts needed. Very much looking forward to checking this out. I've been on the long search for the right compressor.

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  2. Geiri21 January 2013 at 12:11

    So the switch is an SPST?

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    1. Unknown21 January 2013 at 15:48

      Looks like it, here is a good BOM...
      https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Bear%20Hug%20BOM.pdf

      Delete
    2. mirosol21 January 2013 at 16:21

      Added notion about the switch...
      +m

      Delete
  3. Unknown21 January 2013 at 15:46

    Been waiting for this one to be designed for veroboard! Thanks!

    Questions, what does the double link signify? Link from a link from row 1 to row six as well as a link from row 6 to row 11?

    Thanks again!

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    Replies
    1. mirosol21 January 2013 at 16:17

      Hi. That means that two links are sharing one hole.
      +m

      Delete
  4. Unknown13 February 2013 at 15:30

    Oh, neat, I didn't know you did a layout of this one until someone told me they built it. Thanks! :)

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  5. Unknown17 February 2013 at 21:41

    It looks like this layout is missing a 10k resistor in parallel with SW1/SW2, right?

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  6. Unknown17 February 2013 at 22:04

    Dan, the 10K is in series with the switch. The 47K is in parallel with the switch (i.e., bypassed).

    However, the 47uF cap from Comp 1 & 2 to ground is backwards. Should be - to ground. I'll let you guys know if I see anything else.

    -Jon

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    1. Unknown17 February 2013 at 22:17

      Yup. I see that now. For some reason, I saw "R10" as 10k on the schematic....

      Delete
    2. mirosol17 February 2013 at 22:18

      Thanks forr noticing.. I'll reverse it right away.
      +m

      Delete
  7. Unknown23 February 2013 at 16:20

    This one can be marked, finished the other day and works like a charm!

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  8. kod2nd15 March 2013 at 17:51

    When i connect the 9V and ground wires to my power source, my power source seems to shut off and my amp starts rumbling. Any ideas?

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    1. mirosol15 March 2013 at 17:53

      Definitely a short somewhere on the board. Knife the strip gaps and check everything visually - maybe with a magnifying glass.
      +m

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    2. kod2nd15 March 2013 at 17:54

      could it be that my 9V and ground are connected together somewhere?

      Delete
    3. kod2nd15 March 2013 at 18:16

      Doh! Had a micro solder bridge somewhere. Problem Resolved!

      Delete
  9. kod2nd18 March 2013 at 05:32

    I seem to get clipping when i play hard, is that normal?

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    1. kod2nd19 March 2013 at 03:40

      Could it be the FETs causing clipping?

      Delete
    2. mirosol19 March 2013 at 06:49

      Possibly. Did you use a socket so you can swap it? All FETs seem to been not than consistent... Your symptoms point to that, especially now that Adam and Kinski built this successfully.
      +m

      Delete
    3. kod2nd19 March 2013 at 15:59

      A bad solder joints on one of the capacitors was the problem. Resoldered, it sounds great!

      Delete
  10. Kinski18 March 2013 at 20:51

    This thing sounds great. i just built it. FINALLY got the parts order in that I needed. I've been looking for a good, clean, quiet, smooth compressor for a while now. I've build a ton, and this one is the best for sure. At least for my purposes.

    I might leave off the switch and keep hard-wired in the "high" position. We will see see...

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  11. Unknown16 September 2013 at 15:03

    I'm adding some recent changes to this design here. I don't know if Mirosol will see these, but these changes make it sound about twice as good. Briefly, these give a larger compression range (both more and less compression) and much, much more output.

    1. The 2.2K connected to the drain of Q1: Change this to 4.7K (or slightly higher. Target voltage on drain is 5V-5.5V).
    2. Remove the 1K in the bottom right.
    3. Use a 1KC for the comp pot. It'll be much easier to dial in.
    4. Use 1N4148 (or any other generic silicon) for D3&D4.
    5. The 1M in the lower right, connected to the gate of Q3: Make this 1K. This is a MAJOR change and you must change D3&D4 when doing this!
    6. The two resistors in the top right, 10K and 47K, set the decay. I prefer 22K and 100K for these now. It sounds much more natural.
    7. Finally, I prefer 47pF rather than 100pF for the bypass cap on Q1 for a little more sparkle.

    Here's a demo of version 2.0:
    http://www.youtube.com/watch?v=WPm8x4hEwZ4

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  12. bart19 September 2013 at 20:55

    Reporting from the battle field: I have just built version 2.0 with all values suggested above by Jon himself. Works and sounds excellent but:

    - the switch doesn't seem to do much - I'll continue debugging/experimenting
    - I used 12v Zener but I doubt it may have any effect on the sound.
    Bart

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  13. Unknown13 February 2014 at 20:19

    Ola sou brasileiro fiz o pedal e gostei so gostaria se poder mandar o esquema do pedal pra mim obrigado

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  14. BK30 March 2014 at 13:43

    Bart, the switch is pretty subtle but you can hear or 'feel' the difference in compression,especially at higher compression settings.

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  15. bart30 March 2014 at 15:51

    Hi Bill, I finally figured that. Once I tried the compressor at a bit higher than bedroom volume, the change was indeed noticable. Great compressor.

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  16. jaredmcohen31 May 2014 at 23:19

    To anyone else who's built this... is this about the subtlest comp ever? I built it, tested it, and spent an hour trying to figure out what was wrong because I had output just fine, but no compression. Then after swinging the comp knob back and forth a couple dozen times I *think* I can hear a very slight difference between the two ends of the spectrum. Sound about right? If there's supposed to be some serious compression, I'm missing it completely, somehow.

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    1. levis1 June 2014 at 18:14

      Try converting it to version 2.0 specs.

      Delete
    2. jaredmcohen2 June 2014 at 00:56

      levis, thanks man. I must have seen the changes somewhere else because I'd done some of them, somehow... but I went through and did the rest, and now everything is perfect. It doesn't seem like those changes could have been such a big change, so maybe I had a solder bridge somewhere I accidentally got rid of.

      Great pedal, very versatile. Everything from a light comp, to a total clampdown (with the comp maxed and the More switch on).

      Delete
  17. Unknown23 June 2014 at 23:16

    I am getting a pronounced drop in high frequencies that I can't pinpoint, could it possibly be the input cap value that is cutting them out?

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    1. IvIark23 June 2014 at 23:46

      No the input capacitor acts as a high pass filter so it won't affect high frequencies, and will only cut bass. Try removing the 100p cap and see if that helps, that'ss a low pass filter and so will be cutting some top end.

      Delete
  18. jaredmcohen8 July 2014 at 20:57

    Going a little nuts here. I've got this wired up properly. Checked it a dozen times. And it's wired to the 3PDT properly. Somehow, the volume control is controlling the volume of my guitar when the pedal is on, and when the pedals is OFF! I don't know if I'm just not seeing the forest for the trees, but I can't find anything wrong. Any ideas on that one?

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    1. jaredmcohen8 July 2014 at 23:32

      Well I opened the pedal up and everything works as expected. Perhaps when the back of the pedal was on, something was touching that shouldn't have been. But I still don't understand the pedal being off and the volume control working... Goes against everything I thought I knew about true bypass... I'll put it back together very carefully.

      Delete
  19. Unknown17 December 2014 at 01:32

    I spotted something that is causing me great confusion with my limited knowledge. There appears to be some discrepancies with this board layout above and the schematic and perf board layout at DIYSB. In the circuit above, and in the schematic at DIYSB, the Comp pot has no direct connection to ground, but in the other schematic that is linked from the DIYSB page and on the perf board layout it does. Also, the perf board layout at DIYSB and the linked schematic show the ground connection to the Comp pot on different pins, the perf board layout shows it to pin 3, the linked schematic shows it to pins 1&2.

    I am very keen to build this with all the mods added so would like to know which circuit is correct, please help.

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  20. Unknown17 December 2014 at 13:33

    Something else I forgot to ask, where do you connect the LED? It isn't shown in any of the circuits

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    1. Unknown18 December 2014 at 14:33

      Didn't know that all my questions have answers in the thread at DIYSB, so having read through it I can now see that the discrepancies are all due to mods being made. I also figured that the connections to the Comp pot can be reversed without any effect as it will still reduce the resistance to ground when turned clockwise no matter which way around pins 1&2 and pin 3 are connected to the circuit. I also figured that by using a 3PDT foot switch I can achieve true bypass and use one pole to power the board and use a 4.7K resistor to power an LED.

      So, I have solved all my queries, but please correct me if I have anything wrong. Have not messed with any electronics for about 20 years, so this is a good refresher course.

      Delete
  21. Unknown5 January 2015 at 10:11

    Does someone know if mods like threshold, ratio or attack could be added? The switch and associated restistors could be replaced with a decay control from what I discovered so far.

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  22. Unknown13 October 2015 at 17:15

    Hey all, having a bit of trouble with this build. I've built it as per the schematic and checked it a bunch of times over, I'm not getting any signal whatsoever when plugged in. Oddly enough, when I remove the power jack, I get a really strange rising pitch (it sounds like Sonic the Hedgehog jumping, if that rings any bells!). I assumed it was a capacitor discharging, but all of the polarised ones are oriented correctly and there are no shorts. It's the original schematic posted above, so I haven't implemented the mods that Jon suggested yet, but I should be getting something. Going to go through it with a probe and see where the signal is dying this evening, but I thought I'd post up in case any of the more experienced of you were able to diagnose it straight off, or suggest something specific to look for?

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    1. Unknown13 October 2015 at 17:18

      I should add, the 1 uF capacitor below the 10 uF electrolytic on the left hand side is a tantalum (oriented in the same direction as the electrolytic and D1) as it's all I had to hand, and D3 & D4 are 1N34As as I didn't have the 1N60P. Could this be it?

      Delete
    2. Unknown5 November 2015 at 14:00

      You should definitely implement the mods suggested by Jon. They will make it more "compy". Not sure about your other weird issues, probably just a stuff up somewhere!

      Delete
  23. Eli_Klngsmkt9 November 2018 at 01:46

    Built it and am very pleased with the result.
    At first I did all the mods Jon posted above but with humbuckers I wasn't able to dial in a subtle effect. So I put the 1M resistor back in and changed D3 and D4 back to 1N60P diodes.
    This way I can go from very subtle to quite squishy. Also the switch makes it more versatile than I expected.

    Thanks for this good sounding box and easy & fun build!

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  24. abie12 May 2020 at 13:45

    I've got it all built but I'm getting a weird glitch – there's little or no sound, but when I put a finger on the back of the board (solder side) under Q1, the signal comes in strong. If I take my finger away, after a short pause (~1s) the signal fades out again. Any idea what this could be? Here are the voltages I was able to measure:

    Q1 (2n7000) G=5.7V, D=4.823V, S=4.823V

    Q2 (BC549B) C=8.58V, B=672mV, E=19mV

    Q3 (2n5457) G=~300mV, D=~2mV, S=~1.5mV

    The voltages on Q3 were not stable. I know 2n7000 has a different pinout than the BS170 in the original layout and I made sure that it is oriented correctly.

    Pictures of both sides of the board: https://imgur.com/a/gWyWyXb

    Any help would be very much appreciated. Thanks!

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    Replies
    1. Diegotto26 September 2020 at 15:38

      Happened me a couple of times before.Check your solder! a broken solder might be hiding somewhere and the parts get in contact every time you press the board.

      Delete
  25. Tom25 January 2022 at 07:03

    Nice subtle compressor. Sounds best with Jon’s amendments listed in the comments. Posted “unknown” 9/16/13 above. Thanks guys. And thanks Jon for the recommendation.

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  26. Tom26 January 2022 at 01:52

    I just noticed that volume 1 & 3 are backwards. Thought I was losing’ it.

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  27. Tom26 January 2022 at 01:53

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  28. Tom26 January 2022 at 01:56

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  29. Tom26 January 2022 at 01:57

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  30. Tom26 January 2022 at 02:05

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  31. GarbB25 August 2023 at 22:33

    Hello! Has anyone got any experience using this with higher output pickups at a higher operating voltage? I read one of jon's comments on his youtube video for the 2.0 version and said that increasing the operating voltage to, say, 18v can actually drive the signal and harder and get you less headroom, not more. Is the reverse also true, giving you more headroom at lower voltages?

    I'm wondering if the 2.0 version is perhaps less suited to higher output pickups, but I don't want to have to build two basically identical versions of the same pedal just because I'm switching between different guitars often. Thanks.

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