Diode Cliping - Pro co Rat2

[RatBrat]

Hey guys!
I want to do different tests in my rat, but i want tips and ideas! I did the LED mod already it was preaty good

I couldn't figure out the way do put a mosfet where the diode was suposed to be...

Tryed a zener diode too, i couldn't see any difference...


Thanks!

[seedlings]

I like regular silicone 1n400X (X is 7 in my case).  Also really like Schottky diodes (1N60) if you can't get Germaniums.  If your Zener was more than 4 volts or so, that may be why you didn't hear a difference.

CHAD

[RatBrat]

Thank you mate! I'll try lower voltage zener, and germanium diodes..
And what about Mosfets, how do I connect?

[seedlings]

Thank you mate! I'll try lower voltage zener, and germanium diodes..
And what about Mosfets, how do I connect?

I googled and got this result:
http://www.diystompboxes.com/smfforum/index.php?topic=90474.0

CHAD

[tubelectron]

I want to do different tests in my rat, but i want tips and ideas!

A very good one is to change the OP-Amp from the stock OP07DP to an LM308N (original 1981 RAT OP-Amp) - if it is not already done.

You'll find probably a great improvement in the distortion tone and harmonics - like I do...

I stayed with the original clipping diode, therefore.

A+!

[RatBrat]

Well, I've tried the 7.5V zener (1n4737a) and I got different result! Something like a 'not much too much drive' boost!

And i kept the LED, while using a spdt switch so I can choose between LED clipping and zener...


The zener gave something like the mighty mouse...

But I'll look for a on/off/on switch and use no diode to...

The LED clipping is cool, because it starts glowing when you play :B It's kinda obvious, but is really cool lol.

About the LM308:

I'll put a socket, so I can try different op amps. I just can't find the LM308N/LM308AH where I live :/

Wich other opamps you guys think will give me a cool result?


THANKS GUYS, you are really helping this electronics newbie!

[RatBrat]

Any one?

[ashcat_lt]

I used tl080 with good results.  Needs a different compensation cap.

A couple people (myself included) like the lm324, but that wont be a straight swap.

[RatBrat]

Hum... What is a straight swap?

Wich comp. cap to use?

[the3secondrule]

I really like a LM741 in the Rat - especially with assym mosfet/bat41 clippers.

Beavis Audio Research had some great clipping mods for the rat - hopefully it's back online soon

[RatBrat]

With lower zener voltage, l get more gain?

I'm keeping the LED and 7,5V zener, I liked it 

Thx for the tips guys! I'll try the LM308n, cause it will be reeeeally easier for me... It is getting hard to find components around here... :/

[ashcat_lt]

Hum... What is a straight swap?

Wich comp. cap to use?

LM324 is a quad opamp, so pinout is different.  It won't even fit in the same socket as the others.

With the 080, I think I used 180pf comp cap.  Just followed a suggestion from the board, didn't really experiment.  But it sounds good!

[Gus]

How did you wire the Zeners?

If you used them in parallel they will clip like a regular Si diode.

[RatBrat]

I'm sorry, but what means parallel and asymetric clipping?
If I use the Diode with positive in the negative it win't work, right?

[Jdansti]

I'm sorry, but what means parallel and asymetric clipping?
If I use the Diode with positive in the negative it win't work, right?

I've recently  educated myself on the same questions you have.  The following is a very basic/simplified explanation:

1) Your music signal is an alternating current (AC) voltage.    
2) Diodes only allow the signal to pass in one direction.   That is why you usually use two of them in parallel with their polarities reversed. 
3) Diodes "turn on" when the forward voltage reaches a certain value. This causes the AC peaks and troughs to be clipped before they reach their full amplitude. This is what causes the distorted sound. 
4)  Different types of diodes turn on at different voltages.   Two that turn on at the same voltage will cause symmetrical clipping. If one turns on at a different voltage than the other, you have asymmetric clipping because one peak/trough has a different amplitude than the other. 
5) Different types of diodes also cause different wave shapes. Some sound better than others. 

The following articles have great explanations and pretty pictures.  They will help you get you up to speed:

What is clipping and different types of clipping:  http://www.geofex.com/effxfaq/distn101.htm

Clipping with mosfets and zeners:  http://www.muzique.com/lab/zenmos.htm

Controlling harmonics in clipping:  http://www.muzique.com/lab/warp.htm

Clipping tone circuits:  http://www.muzique.com/lab/tclip.htm

Once you read the above articles, you can go crazy trying different circuits to see what you like best. Good luck!!!

[RatBrat]

Thank you very much!
I'm reading it now! I'm sure it's going to be helpful!

[RatBrat]

I'm drilling the box now
That's it by now



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