NEED TO KNOW ____WHAT IS AN ____OpAmp with diodes doing in a Dirt pedal. ????

WTF IS AN OpAmp DIRT BOX

First I am going to over simplify. All needless jargon and rocket science surgically
removed, This a need to know explanation. 

OPAMP

First an OpAmp is basically a little preamp that takes the guitar signal and makes it louder. Like anything there are different qualities and ALL will color the signal. Some sound a bit better than others but in the real world of Rock guitar the differences are negligible. In guitar folk lore a really old shity OpAmp is better because it highly colored and that color is prized. 
The reason old all prized OpAmps were discontinued as they were meant for the consumer products like a radio where the buyer wants clarity first. If a manufacturer could make an OpAmp, 

smaller, cheaper and cleaner, they did.

For our purposes consider them nano amplifiers with only a clean sound. 

Lately the 'most transparent' OD is the fashion. These use state of the art OpAmps beyond dead clean and color free. So what's better? Vintage crap or NASA/Military spec. I own both, LOL.

WHAT YOU USUALLY GET

Nearly all pedals including the made in China ones use a 'reliable' well made OpAmp with a spec much higher than needed for the mid range voice of a guitar PU. 

 Why ??? Simple, most of these products are now made by high tech machines that can boot out up to 2000 pedals a day and the product HAS to be reliable or you can hundreds of failures. Low return rates are OK ...high ones will sink the company.

DIODES

Diodes are meant to cut the signal going thru. So if you have your OpAmp up full you
and it goes through an Diode that is rated too low for it it will chop off the top of the signal and distort it. More small equals more dirt. Add to that different diode types are more nasty then others.

Finally, the signal has a positive and a negative signal. You need a pair of diodes to make it work. If they are the same value you get a more transparent sound but if they are unequal you get more dirt. Real tubes are more like a pair of unequal diodes. Tubes do not make the kind of distortion that matched diodes make. 

Surprise, surprise, 99% of all matched diode OD's are Tube Screamers no matter what bullshit name is printed on the enclosure, lol. 

All the others with mismatched diodes are basically a Rat if high gain or if medium gain a Boss SD-1.

The only other OD/Distortions of consequence are made by using a tube amp design and substituting the tubes with JFET transistors.

Fuzz pedals use germanium or silicon transistors or they too can use an OpAmp. There are rare exceptions but they all sound like crap.

Endless new pedals come out all the time.Most are same old. They add new high tech NOS parts or blend designs together, go crazy with EQ or give you switches to swap out diodes or add a pre amp for a boost.  Considering analog is a  very limited tech it is surprising with a lot of ingenuity some new pedals really sound better than others.