A Couple Compressors

Discussion in 'Burnt Fingers DIY Effects' started by zippofan, Apr 16, 2019.

  1. zippofan

    zippofan Tele-Afflicted

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    I've been doing a little of this, that and the other thing lately, including modding some builds with different op amps, diodes, and rewiring the heaters on my MOD tube amp, quiet as a mouse now :cool:.

    In the meantime I've had two compressors on my bench. A FET based comp from 1776 Effects, the Bear Hug, and the classic 5 knob Engineer's Thumb, the PCB is from DeadEnd FX.

    Drilled the box tonight for the Bear Hug, starting assembly now, gotta figure out a good graphic decal for it.

    BearHugInProgress.jpg BearHugGutprogress.jpg
    Giving the GuitarPCB 3PDT switch board a try, just with a standard LED this time. The SPST switch has been waiting patiently in my parts drawer for about 30 years now, lol.

    The Engineer's Thumb is a big board in a 1590C box, so I gotta print out some templates before I go drilling willy-nilly.

    More to come...

    Z
     

    Attached Files:

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  2. awasson

    awasson Poster Extraordinaire

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  3. Urshurak776

    Urshurak776 Tele-Holic

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    @awasson what did you use for an LDR?
     
  4. awasson

    awasson Poster Extraordinaire

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    Well, I'm glad you asked :D

    I have a few really compact LDR's I picked up some time ago from a company called Parallax. I just checked and they no longer carry LDR's. I paired up the LDR with a pair of green rectangular LEDs and put them in heatshrink. I don't have any loose green ones but they look like the ones below.

    IMG_4467.jpg IMG_4468.jpg
     
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  5. zippofan

    zippofan Tele-Afflicted

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    Decals printed and cleared, drying in the corner in the basement with the door open, thankfully it's warm enough to do that!
    Found some cool fonts to use, no crazy artwork, just straight up labels for these two. I think they'll look good, hopefully they'll sound great (I have a feeling they will...)

    Edit: Decals drying now...

    IMG_0504.jpg
     
    Last edited: Apr 20, 2019
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  6. mictester

    mictester TDPRI Member

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    Thanks! That's my design!

    There is a Karmic Law of Unintended Consequences: The "Really Cheap Compressor" was designed to fulfil a need for a really simple, but effective guitar compressor. It's not perfect, but the effect of the Karmic Law worked in my favour: The slowness of the response of the LED / photo-resistor combination actually works FOR the device. The basic envelope of the guitar signal doesn't get altered until AFTER the initial attack, so the basic character of the guitar sound remains. The compression only really starts to act in the "decay" phase of the note, increasing the gain of an op-amp in quite accurate inverse proportion to the reduction in level of the note - this extends the decay of the note, giving us the "Sustain" that we want. I found that the net effect of the device at medium compression was to make a guitar seem more "sensitive" - it wasn't louder, it was just more responsive. At maximum compression, you can get the awful "duck and swell" effect so beloved of dance music producers!

    In the intervening years since the pedal was designed, I've experimented with improvements and changes, but none of them really improve the basic design to a significant extent. There's one mod that is worth doing, though, which was to add a CR network in parallel with the input resistor to give some passive "treble boost", and then add a similar filter to the output to flatten out the response. This has the net effect of improving the signal-to-noise ratio, since most of the noise is at higher frequencies, and you can buy a 6dB S/N improvement for just a few pennies. The details of the modification are on the Freestomboxes.org thread where I publicised the original circuit.

    The other change that I have made in the ones that I've built recently for people is to use the LCR0203 or LCR0202 https://www.alibaba.com/product-detail/Pure-Resistor-opto-coupler-LCR0203_511182349.html
    These are an LED and a photo-resistor ready packaged, and they give very consistent results. I've also used them in pseudo Univibe circuits with great success ( the secret is to pulse-width modulate the LED at ultrasonic frequencies to give smooth changes in brightness), and I've been playing with a split-band compressor design for bass guitar, which uses three of these devices. I bought them from Shenzhen for about £0.02 each!

    Many guitarist friends of mine use the RCC as an "always on" pedal in their effects chain, usually as the first effect in line (unless they have a Fuzz Face). It lives up to its name - it's really cheap to construct, and the results are worthwhile - pretty quiet compression for guitar at little cost, and without colouration (unless you wanted to mess with the frequency response!).

    PS: The "Engineer's Thumb" is a very good compressor, and can be built with the full set of controls for the inveterate twiddler. However, it's more expensive to construct, and works about as well as my RCC, so you can make your own choice. Jon Patton's "Bear Hug" is also a very good compressor, but requires a bit of part selection and some tweaking for minimum noise.

    Cheers

    Mictester

    Long live Open Source design!
     
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  7. awasson

    awasson Poster Extraordinaire

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    Fantastic! Thanks for the details and history about your RCC. I recognized your screen name from the circuit.

    Originally when I decided to get a compressor, I decided I would buy one on the used market through Craig’s list. In rapid succession I attempted to buy a Milkbox, a Dynacomp an Ibanez CP10 and a Boss CS3. For some reason all 4 CL sellers flaked out so I decided I would just have to build one myself. The RCC was the perfect build because I had everything for it on hand. The resulting pedal is extremely quiet and sits right after my wah pedal on my board in the always on position.

    It really is my always on pedal. I’ll have it just on at the 2 o’clock and 9 or 10 o’clock positions to smooth my playing out and add some sustain and a year later it’ll still be on. I’ll switch it off for a few days and on it goes again.

    Thanks for the tips about improving the S/N ratio and the optocouplers. I think I’ll put another together to experiment with.

    Thanks again,
    Andrew
     
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  8. zippofan

    zippofan Tele-Afflicted

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    Just completed the Bear Hug, and I did have to go through some different JFETs before I got one that I thought sounded good. I tested all the remaining devices in my stash (except for the SMDs that I've yet to solder) and picked one that ended up testing right around typical for Idss current. It's fast but subtle, not unlike the Love Squeeze that it's partially based on, though maybe a little more squish at full compression. If you like un-squishy but usable compressors, the Bear Hug or the Love Squeeze (Rullywow Love Smush board) are worth building.
    BearHugComplete.jpg

    As I was closing the back the USPS showed up with some goodies (including a Weber 12A125A speaker, I'll let you guys figure out what that's gonna be for :D), something I've wanted to do for awhile.

    Last week I did some rewiring in my MOD 102+ to remove a little residual hum. Worked like a charm, and it's a sweet sounding amp. It always bothered me that the top was wide open as it's down here with me in the 'man cave' aka basement, which means dog fur, dust and all the other junk in a typical basement. It's no longer wide open:

    cage.jpg

    More on the Engineer's Thumb, final assembly begins later this week.

    Cheers,
    Z
     
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  9. FenderLover

    FenderLover Friend of Leo's

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    I think you'll really like the Engineer's Thumb. It's a different design that works well, and is very quiet. One of my favorites. Looking forward to your build.
     
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  10. zippofan

    zippofan Tele-Afflicted

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    Now that I had a capacitor bonanza from Mouser I can button the Engineer's Thumb up!

    I made a slight mistake drilling the output jack about a 1/16th of an inch too close to a cap :eek:. Stubby capacitors to the rescue, and I laid in a supply of Nichicon audio grade electrolytics in the usual values too. Love all those gold and black electros on board :cool:

    Just gotta get through parents' night at Scouts tonight, then back to the bench!
     
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  11. zippofan

    zippofan Tele-Afflicted

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    The Engineer's Thumb is complete:

    EngineerComplete.jpg EngineerGuts.jpg

    Talk about infinitely adjustable, I'm going to be tweaking this for a week! So far it can be as subtle as the Love Squeeze/Bear Hug, or as squashed as a Dyna Comp, with the ability to adjust every setting in between. As I mess with it I see it possibly kicking my Tone Press off my bench chain, or at the very least replacing the Whirlwind Red Box on my actual pedal board.

    After the last two builds, I think I can safely say I'm done building compressors. I have an optical unit that I use now and then (DOD), couple flavors of OTA including ones with blend (Tone Press, EP Compressor), FET comps and a set and forget Orange Squeezer (Henretta Orange Whip) which is sweet but a bit noisy.

    Thumbs both up for the Engineer's Thumb!

    Z
     
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  12. jimilee

    jimilee Tele-Afflicted

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    I would agree, that is a great compressor. I’ve built a couple myself. It works exceptionally well for bass.


    Sent from my iPhone using Tapatalk
     
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  13. cruisemates

    cruisemates TDPRI Member

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    I personally prefer the opto compressors to the other ones I have tried. They just seem to have the smoothest and most usable compression response. I have not tried MICTestors yet, although it looks great. I have built the Diamond and the LA-2A from tagboardeffects, - I really like them both but the LA-2A seems especially natural while the Diamond is more versatile.

    And I use the LDR and LED combination. The LDRs I have seem to have a very wide range of response (I'm guessing from 0 to well over 100k) so they work in most situations assuming the LED is bright enough and the LDR is placed well. I usually bend the LDR and the LEDs over sideways and use shrink wrap to make a small dark tunnel. I say just get some LDRs and give it a try, I have ordered a few different lots and they all seem to work about the same (as long as they look like the ones pictured above).
     
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