Compressor Burn-In??? (Engineer's Thumb)

[poojalooba_cow]

So I just finished a build of Merlin's Engineer's Thumb compressor, and I had some interesting experiences along the way.  I was just wondering if anyone experienced the same or if they could shed some light on the phenomenon.

I made the five-knob version of the compressor.  When I first prototyped it on stripboard, it was NOISY NOISY NOISY. I know Merlin advertised it as being much quieter than a Dynacomp, so I wasn't too impressed and I let it sit for a few days while I did other stuff. Then yesterday I soldered it on perfboard (I don't etch PCBs, I use point-to-point soldering), and it wasn't quite as noisy, but a couple of the controls did weird stuff. For instance, the release knob would distort (clip) and boost the signal anytime it got below ~130 kOhms. (Mostly fixed that by adding 100k in series). And the attack would sound all harsh anytime it wasn't on its fastest setting. And the ratio knob would boost the pickup hiss on my strat like crazy once the release had worn off. The strat is shielded inside and has Texas Special pickups, which humbuck in positions 2 and 4, but it would still boost whatever residual hiss it could find to ungodly-high levels. It sounded fine as long as I kept playing and didn't leave quiet spots, so I decided to just finish up the project today and put it in is box and close it all up and then maybe never use it again.

So here's the even weirder thing: after I got it all put into its box and had been fiddling with it and my guitar for about an hour, I realized that the compressor was no longer exhibiting any of its previous weird behaviors. I couldn't get the distortion from the release knob at <130k , the attack was much smoother, and the ratio knob, even at both extremes, didn't really add any signal noise at all, even when I wasn't playing. And with all of those problems seemingly resolved, it's actually a pretty awesome compressor now!  It's got some really sweet tones in it.

So somehow, though, the compressor "fixed" itself? It was still distorting and making weird noises after I put it in the box at least for a little while, so I'm pretty sure it wasn't just the transition to a shielded, grounded box that helped it out.

So that's the reason for the title of my post: Does anyone know if compressors exhibit a "burn-in" period like headphones, speakers, and amps do? After a certain amount of usage after they're brand-new, do they magically respond better? I'm pretty sure the answer is "no" because the Engineer's Thumb is just two TL072s and an LM13700 OTA, but what other explanation could there be?  I'm pretty mystified myself,  but I'm at least happy that the build finally turned out so nicely and that the compressor sounds so great.

[bluebunny]

Does anyone know if compressors exhibit a "burn-in" period . . .

Nope. 

[~arph]

Why are you mistified?  I makes total sense that  it becomes less noisy when you put it in a shielded box. Also all sorts of things com into play, like wire length, wire layout, shielding, perf/stripboard layout, component placement, bad solder joints, etc. etc.

[alfafalfa]

bad solder joints,

Imho you must have touched something to turn a bad connection into a good one ( for the time being), I would go over all the solder joint and wires once again.

[bool]

So I just finished a build of Merlin's Engineer's Thumb compressor, and I had some interesting experiences along the way.  I was just wondering if anyone experienced the same or if they could shed some light on the phenomenon.

.... .... ....

So that's the reason for the title of my post: Does anyone know if compressors exhibit a "burn-in" period like headphones, speakers, and amps do?

No, we don't know. So you be the first to find out. Treat it with a zippo and report back.

[blackieNYC]

The combination of noises found in an unboxed unshielded circuit, and the things a compressor will do, could give you some strange results.  In breadboarding other, simpler kinds of circuits, I think I'm starting to be able to tell a noise that will go away when boxed, from a noise that's going to stay with me.  There is a leap of faith there, such as when you decided to solder it together even though it was acting weird - maybe based on your faith in Merlin and some other talented folk who have built the thing.   
Someone in the forum puts their breadboard in a big grounded metal box. Then there's the whole "noise goes away when I turn down the guitar all the way" thing.
But if you are sure it improved after being in the box for a while, it sounds like you have intermittent contact going on somewhere.  Even though it's sounding good right now, there is no burn-in benefit, so you should probably open it up and poke around your solder connections with some pokey tool and a magnifier.

[FiveseveN]

Nope. 

And for the record, headphones, speakers and amps don't either.

[bool]

And for the record, headphones, speakers and amps don't either.

Highly debatable with shitloads of real world user experience suggesting otherwise. But hey you know better...

[poojalooba_cow]

And for the record, headphones, speakers and amps don't either.

Yeah, I know I know I know.  Burn-in is not a real thing but audiophiles swear by it, and it's the closest thing I could think of to explain what my compressor experienced.

Thanks for the responses thus far, guys.  I think we'll go with "the shielded and grounded box made everything better" for now, and if we need a fallback explanation we'll go with "there's an intermittent connection happening once it got squished down into the box".  I double-checked the layout and the solder joints and then I hot-glued the bottom of the board to insulate it from anything else, but there always possibly could be something making a different connection in the box.  It sounds so good right now, though, that I think I'll leave it as it is unless there's a problem in the future.

[PRR]

Loudspeakers do soften-up in the first hours of hard-work.

Whether they get better or worse depends on the speaker.

I do suspect that much "burn-in" is in the user as much as the system. We are wired differently for "new" and "familiar" objects. It takes some time to move from "new" to "familiar".

As for the compressor: there should be NO gross changes. Obvious suspects are change of box, bad joints, possibly incorrect capacitor polarity, bad joints, and bad joints. While in this case "bad" turned to "good", if you do not know why then it is sure to go "bad" again, and probably for That Important Gig.

[Perrow]

I experience burn in every time I change from my Koss Porta Pros to the cheap in-ears that came with my phone. The first fifteen minutes they sound awful, then they sound half descent til I use the Kosses again.

[FiveseveN]

Adding to what PRR said above, see http://en.wikipedia.org/wiki/Neural_adaptation