Tube Screamer IC Chip Change
Excerpts from Analog Man's Ibanez Tube Screamers page. with minor additions by Ashley.

I generally keep old circuit boards from effects or whatever so that I can hopefully find a resistor or capacitor to resuse when I need one. Lately, I was looking for a resistor to pull from an old DOD Digital Delay pedal and saw a chip with RC4558P on it. The numbers struck a bell and got me thinking about the chip in the Tube Screamer. I searched the web and immediately came to Analog Man's Tube Screamer Page. His History section gave me some good insight.
Early TS-808's have the Ibanez (R) "trademark" logo which some people seek. There is really no difference, although some of these that sound awesome have a Malaysian Texas Instruments RC4558P chip instead of the normal Japanese JRC4558 chip.

The Malaysian RC4558P chip was probably used to save some money as they were cheaper than a Japanese made JRC chip. We would be glad to use the RC chip in your mod if you would like. They have a little bit more grit which some people might like.
This sounded interesting so I added a socket to the TS-7 circuit board and tested the sound of each chip I had. The stock JRC4558D (with "43k" stamped into its underside) sounded thin to me, even after the other mods I'd done to the pedal already. I had another JRC4885D (with "TM" stamped into its underside) from a kit I bought to upgrade the pedal and it sounded better, more full, than the stock one did. The RC4558P sounded the best by far and is the chip I left in the pedal. Says Analog Man:
In AB tests, there is VERY little difference between the three chips [JRC4558, JRC4558D, RC4558P] although the JRC gives the strongest CLASSIC tube screamer sound- the sweet vocal midrange.
Well, I guess I don't appreciate the CLASSIC sound. I do appreciate the sound I have now though.



  1. PARTS: You'll need an 8-Pin IC Socket (99 cents at Radio Shack), a RC4558P IC chip, a soldering iron, and some solder.
  1. Open your pedal by taking out the four screws on the bottom. Remove the bottom cover and put it off to one side. Be careful not to lose the spring that will fall out of the switch end of the pedal.
  1. Remove the two screws holding the large circuit board to the pedal chassis.
  1. Carefully lift the large circuit board out of the chassis. The power adapter end will be connected to another board underneath. Pull gently to 'unplug' the large board from the smaller one.
  1. Locate the current IC chip on the circuit board and remove it. Be extra careful when getting the chip off of the board as you may want to put it back later.
  1. Solder the new IC socket into the eight holes left by the chip in step #5.
  1. Insert the new chip into the socket. Note that the little circle on top of the chip should be facing the center of the circuit board.

    I was testing back and forth with the chips when I took this photo. The chip that I kept in the pedal was the RC4558P.
  1. Put things back together and test it out.


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