Wednesday, 15 February 2012

Rothwell Love Squeeze

You don't come across this very often, but this is a fairly original compressor!  At 22 columns wide it will fit in a 1590B, but file the sides down as much as possible for extra space, and maybe use some electricians tape on either side of the box for insulation as a precaution.  I tried to get it down a bit more but that's the price I pay for wanting flat resistors.  Oh and watch for the shared hole at pin 8 of the IC.

Manufacturers info:

The Love Squeeze is a compressor designed simply to sound right with guitars, without any bizarre “pumping” effects and without any noise.
This has been achieved by designing a circuit from scratch instead of adopting the more common approach of using an operational transconductance amplifier (for tech heads, it’s usually the CA3080 chip) or simply copying an existing design (like some American boutique makers have done) and gives the Love Squeeze a sound of its own. Low level signals can be raised by as much as 20dB without boosting high level signals, so when used in front of distortion - either in a pedal or an amp - leads lines can be fattened up without chords sending the distortion into mush. When used with a clean sound the Love Squeeze can be set to just take off the ice-pick attack of single coil pickups for a tone a little easier on the ear. Like reverb (when used sensibly), this is a subtle effect which can go almost unnoticed until it is switched off - then you wonder how you could live without it.



53 comments:

  1. Hi Mark I have just made this. It works as I can hear compression happening but the output is really weak. I've checked the obvious cuts, jumpers, tracks and soldering. Caps and diodes around the right way. I've tried turning around Q1 it does have an effect but just makes a kind of on/off switch of the compression pot. I've Checked the IC is seated correctly. Does it matter how the LEDS are? I have left one + at the top and right one the opposite.

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    1. No as long as the LEDs are top to tail, it doesn't matter which way round they go. If the signal seems weak then it may be worth checking that you're getting continuity to all the points of ground on the board and offboard, and often reflowing the solder can help make a better connection if there is a bad joint somewhere. Can you post a high res front and back pic so I can see if anything else jumps out at me.

      And thanks for the layouts you've verified.

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  2. Works. Tag it.

    I noticed too late that i was out of 3mm red leds, so i put in clear orange instead. Didn't even socket them which i think was a mistake. Anyway, it's as loud as it should be. Not OD loud, but loud.

    There is a first time for everything :) Compression pot's behaviour felt like all the action was in the first 20-50% of the turn, so i swapped B10K for A10K, and the compression control came out much better.

    I reckon that those orange leds may be the cause of this, but attack seems to be a bit harsh. Not as smooth as i hoped. It's still nice non-optical compressor. Currently not as good as Mr. Squishy, but nice nontheless. If i feel like it, i might put in sockets for those leds and try on a variety of different combinations - to see if some other set of leds give out smoother attack. If i feel like doing it. :)

    So. If you have only clear orange leds - i don't recommend this one. Build the Squishy instead :)

    p.s. Only 15 more to go for 200..
    +m

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    1. Nice one matey. I've built a Forest Green Compressor and have been waiting for a pot coming for it which has now arrived, so hopefully we'll have another compressor verified soon.

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    2. I've been wondering if should build some MP/BJF stuff, but they are always using components that are not your everyday stuff - and nothing else seems to use the same components..

      Compressors are great for fattening things up. I'll be building more. I need to do some optical comp soon. :)
      +m

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    3. Bjorn does tend to use some weird E96 value resistors but in everything I've built I've just used the closest thing and they've worked fine. Of course it may not sound absolutely 100% identical to an original, but then he also uses some 5% carbon film in some of his pedals and with cap and transistor variation you may not get two of the originals sounding exactly the same either.

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  3. I notice a mistake of sorts on your layout - the two leds are shown being soldered across two rails (i.e four contacts per LED) which is incorrect - it should be the outer two connections only.
    Hope this helps,
    Philly

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    1. The top and bottom ones are the connections. The second and third rows are part of the LED symbol with DIY Layout Creator which I think is supposed to signify where the wire comes out of the LED body.

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  4. Is there no longer a shared hole at pin 8??

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    1. Well spotted! No I altered it but didn't remove the note

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    2. why did you remove it?!? does this change affect the sound?

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  5. Hi!

    Having a problem with this build.. when i plug in the power i can hear a crackle and the LEDs just light up for a second..the volume pot has no effect and the comp knob just makes the signal louder..

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    1. ok figured out i forgot to ground the volume pot.. now i'm having a distorted sound when i turn up the comp.. did i fry something?

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    2. What type of pickups are on your guitar? A few people have mentioned distortion at higher comp settings which is common in a lot of compressors and so it may be behaving as expected, particularly if you're using higher output singles or humbuckers.

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  6. i have P90s, one thing i forgot to mention is i had no 100pf so i paralleled a 51pf and a 47pf.. could this be the cause?
    i also just replaced the tl072 and the 2n5457 for fresh ones but had no luck..
    when i turn on the effect i cant hear nothing, only after i play a note i can hear the sound fading in distorted... strange

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    1. ok i have to correct myself, the sound just fades in wether i play a note or not..

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  7. i built this one yesterday and it sounds great. when i use it with a bass, if i turn the comp knob a little past noon i get a weird delayed fluttery distortion ONLY on notes on my low E string. i tried running it at 18v and it made it even worse. i also tried different transistors and opamps but to no avail. i ended upsolving it by replacing the lower right 10u electolytic with a 22uf one and it works perfect and didn't seem to change its tone or compression one bit. IMO, it's a great comp, and super quiet.

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    1. Excellent info thanks John. Jeez you must spend ages experimenting with these. Do you just change everything to see the affect or did something else point towards the cap?

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    2. well, since i make my pedals for use with a bass, i socket quite a few of the components so that i can test which values will work best. i already socketed all of the 10u caps so i could compare aluminum electro's vs tants, so since they were so easy to replace, replacing the one of the 10u's with a 22u solverd it. i also tried different diodes (1N270's, BAT41's and 1N134A's)but the 1N5817 was the one that works best in this pedal.

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  8. I built it and it sounds great, but it has considerable amounts of squish and "pop" sound. when picking you get that strat spank and nice compression. I used a 4.7 instead of 5.1 and blue led instead of red. Is that why? I also used 914 diodes rather than the 5817 is that why?

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  9. you must use the proper diodes (both the leds and 5817's)and the correct value resistors. they are an integral part of how the circuit operates. for example, 914's have a forward voltage of around .7 volts, whereas 5817's are at around .2 volts.

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  10. I'll order in a few diodes then, no biggie. Sounds pretty cool as is, but I'm down for a more transparent sound.

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  11. i've found this circuit sounds MUCH better running at 18v... especially with bass and high output pickups. I'd say 18v is NESCESSARY for active bass pickups. now to try a buffered blend circuit in there!

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    1. that's strange, i think mine sounds better running at 9V. i added a true bypassable blend to mine since i wanted to have the option of running the pedal with or without it. here's a pic of it:

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

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    2. How does it work with a buffered blend?

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  12. I'm getting a lot of distortion with this circuit, I made a few part subsitutions, 22r for 33r, 15n for 10n, 39k for 33k, 47k for 51k. They were the closest values I had, but it seems that I may have changed too much, as the comp seems to add bass, darken the tone, and distort as well. Halp?

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  13. IvIark, how would I add an attack control to this circuit?

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  14. I made it three times yesterday with new components at each time to be sure that I made it good.
    And the three ones I made distort the sound. I also tried with another layout (other site).
    I play it with bass guitar.
    Did anyone have this problem and resolved it ?

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  15. Perhaps there's a difference between TL072P (like the original) and TL072CN I put in ?

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    1. That shouldn't matter. The suffix usually denotes things like operating temperature ranges or the packing type the ICs are shipped in so that shouldn't make a difference.

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  16. I changed all components excepted mechanical parts (footswitch, LED indicator and jack in and out). I don't think that should be these parts.
    Anyway, it's a really good overdrive :-DDD

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    1. Are you using it with humbuckers? I've heard a few people say that it clips with higher output pickups so it may be one better suited to single coils

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    2. hmm??? I use mine with a bass and it doesn't clip at all.

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    3. (I've already said that in another topics but... excuse me for my perfectible english...)
      I've got a basic Precision Bass.
      Is it possible that my 3mm LEDs are not good ? I tried different LEDs but they are all from the same seller. I tried the one on the left with catode on top and the one on the right with anode on top and after I tried to do the other way (IvIark, I understood, as you said, that it doesn't matter but my disappointment told me to try this !).
      I tried three different 2N5457 and placed them as shown on the drawing. Is there a good way to put it to have a compressor and a wrong way to have an overdrive ?
      The wire "Comp 2 & 3" goes from the board to the "2" of my Comp potentiometer. Then "2" and "3" of the potentiometer are wired together.
      I didn't take account of the note "Note the 22R/100u shared hole at pin 8" as mentioned above.

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  17. Ok, the problem was with my 3mm LEDS that were clipping too much.
    I replace them and it sounds good but I notice a volume drop even with volume set at max.

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  18. Ive used 2n5459's and 1n4007's are these ok?

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  19. Is there an easy way to add extra compression to this circuit? Mine sounds great, but could use a touch more squish.

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  20. This one REALLY clips with humbuckers - it an average overdrive and even worse I built it wrong the first time in a way that was unfixable (I wasted four hours trying to troubleshoot it, but had it completely rebuilt in under 2 hours). It is just like a first stage in an overdrive (not a bad one).

    Anyway, I want a compressor so maybe I will try a different one. The demo to this one sounded great, though.

    By the way - many of us (siunce early 2015) are hanging out in the forums: http://guitar-fx-layouts.42897.x6.nabble.com/

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    1. Try replacing the lower right 10uF electolytic with a 22uF one (like jonhk said). It worked for me.

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  21. Busy building this but the TI TL072 op amps I bought don't have the notch to orientate them should I assume that writing should then be in the same orientation? Not keen to blow them cause I only ordered two.

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  22. I built this today using MPF102 and NJM4558. Sounded good, maybe a little soft for my taste. 3mm led color doesn't seem to matter. I decided to try different op amps. It sounds better with jfet input, such as TL082. I settled on NJM2082, which definitely broadened the sweep of the compression dial.

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  23. A decent compressor for bass. At very low compression settings the sound distorts some tho. I used 1n5819 instead of 1n5817 tho.

    I changed the lower right 10u to 47u. That gave me a bit less compression which I felt was to much before. I tried different values up to 100u, but 47u was my sweetspot. Higher values equals less compression it seems.

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  24. Am trying to build this and not having much luck. Have double checked the usual problem sources - bridges, cold solder joints, part misplacement etc. The 2N5457 and the TL072 have been reliably sourced.

    On tracing the circuit the signal with an audio probe the sound is fine till the 1N5817 diode pair. I actually get a nice volume bump from pin 7 of the opamp. From the diode pair en route to the 2N5457 JFET the signal gets weak and spluttery. Putting a jumper from the diode input to the 1M resitor (R16) connected to the JFET in the schematic produces distortion. Removing the JFET from its sockets doesn't change the sound in any way.

    What am I missing? Any help would be very appreciated. Thank you in advance.

    Also the 3mm diodes do not light up - is that a problem?

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    1. Ey, I've just rebuilt my Love Squeeze board and made a couple silly mistakes. I put the 1,5nf cap taking up three rows instead of four. Take a look a that kind of stuff.

      You could measure some AC voltages. At input, output, output opamp(pin 7), r11, r12... Record a loop with the guitar and let it playing while you do the measurements. That way it's fast and easy.

      For a 18mV signal input I got 36mV at the output with both pots all the way up.

      DOes your volume pot work ok? Do you get any sound? You're not clear about that!

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    2. Thank you very much Nono St for taking the time to reply. I will check these things and get back on here to report what I find.

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  25. The original unit uses BAT43 instead of 1N5817. I got some BAT43 and they are .270Vf. An 1n5817 is about .190Vf. That's what my tester says. It shouldn't be a dramatic change, but it might be noticeable in some cases. The lower the Vf is the more compression you got, so keep that in mind. Also check your 2N5457 from drain to ground, it should be between 300-400 ohms.

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  26. https://atomiumamps.tumblr.com/image/158975466951
    IT REALLY HELPED A LOT. NOW IT SOUNDS RIGHT

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  27. Speaking of compressors, here are my fixes for the Rothwell Love Squeeze circuit. It uses a JFET instead of an LDR in the feedback loop of an opamp. With no signal applied, the FET’s resistance is about 300 ohms and the stage’s gain is anywhere from unity to 10x, depending on the sustain control setting. When signal hits it, a P-P rectifier hits the JFET’s gate with a negative bias voltage in proportion to the input signal. The JFET’s resistance rises and reduces the gain of the first stage – compression. The advantage of the JFET is that its attack time is incredibly fast, limited only by the rectifier – half a wavelength of whatever fundamental frequency you’re hitting the front end with. The problem is that most people who build this circuit end up with distortion; it behaves like it has very little headroom.

    It has plenty of headroom, the problem is the way the sidechain blocks frequencies below 100Hz. It does this to avoid ‘pumping’ or overshoot on the compression envelope. But what you really get is phase shift in the sidechain at low frequencies, combined with lower drive and higher ripple on the P-P rectifier. So at a specific input level – right at the compression threshold – the circuit will snap in and out of compression very quickly, effectively acting like an LFO. It doesn’t do this at higher or lower signal levels, just at the threshold. You hear it as a blatty, sputtering decay on chords. It can be mitigated by increasing the release time (R11), but the only way to cure it is to let the sidechain run full-range. The changes above do that.

    (Note: you can get this behavior by simulating the circuit’s transient response in LTSpice, so it is definitely a design flaw and not a layout problem. In theory, certain selected JFETs might have curves that avoid the problem, so it’s not guaranteed to affect all builds… but why not fix it definitively?)

    There is a tradeoff, in that you will get some ‘pumping’ on big bass transients, but it is still far less noticeable than on more traditional compressors, because the attack time is so much faster. It seems possible to mitigate the overshoot by using a shelving filter in the sidechain amp instead of moving the highpass corner down. Maybe a -6dB filter below 100Hz. That might be a best-of-both-worlds solution, but I haven’t tried it.

    I replace R11 with a 25kB pot in series with a 15k resistor, which yields a much more traditional range of release times (roughly 100-300ms), with fewer intermodulation artifacts from rectifier ripple modulating the compression.

    Once this is done, there’s no reason to keep LEDs in the feedback loop, since only the absolute hottest pickups will distort the opamp, and only at max compression and for the first positive half-wave. It’s virtually inaudible.

    The other thing is that C12 should be no larger than 4.7nF, which attenuates treble above about 7.5kHz. The stock Rothwell uses 15nF (supposedly), which would explain why it has a reputation for being ‘dark’ sounding.

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    1. Yes!!! Thank you! I've done a lot of tweaks to this circuit and the darker tone was the only issue remaining. A 3.3nF cap works great :)

      I built a version with a Threshold pot and a couple switches for attack and release. Let me know if you want to know what I did.

      The transistor brand is very important. CEN good Farchild bad (far less volume)

      Cheers!

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  28. I've built this verbatim with the exception of socketing the LEDs and the bottom right 10uf electrolyric based on some user comments.

    I am using this pedal for bass and on my lowest string (d with the tuning my band uses) I was getting lots of distortion at 10uf, and still an annoying amount all the way up to 47uf. I ended up settling on 100uf in the bottom right. It still distorts a tiny bit, but it's much less noticeable. There is less compression but I want the attack this compressor gives, and there is still lots of snap there.

    The LEDs don't seem to make much difference, but I've only tried yellow and reds so far. Maybe I'll throw some greens or blues in to see if it affects the distortion. But for now I'm moderately happy with how it sounds.

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