1 TheNocturneBrain.com 3 years ago As a lover of both the TIM/Timmy pedals and the Barber Burn Unit/ Small Fry/Tone pump pedals I often like to fool around with a smorgasbord of op-amp chips I have collected over time. folks go round and round about what chip sounds better in tubescreamer variety overdrives but most of these pedals are not made very well and dont even have an op amp socket in them so one can readily fool with the gain textures of their favorite pedal... in anycase my pedals I mentioned above DO have opamp chip sockets and are much fun to "chip swap".. if you have lazy turkey weekend time you should start experimenting in your tone kitchen. Whats in your cupboards?? If you are a geargeek/audiophile type you might enjoy this descriptive list of various chips swap options I find helpful. CHIP DESCRIPTIONS JRC4558D – Made by Japan Radio Corporation (JRC). Used in the original TS808s and TS9s. Ibanez later changed the chip used in their pedals. The JRC4558D is actually a very inexpensive chip that’s not considered Hi-Fi and was chosen because of its inexpensive cost and not for the tone it produced. It just happened to sound great when used with the Tube Screamers original circuitry. This chip has a little bit smoother gain than the RC4558P which is considered a more Hi-fi chip. I like the JRC4558D in the SD-1, it's smoother gain in the top end helps to offset the extra hair in the SD-1's gain. I prefer the RC4558P in a Tube Screamer because the Tube Screamer circuit produces a smoother gain and the RC4558P has a little more high end grit than a JRC4558D. Currently installed inOD-3 JRC4558DD – Made by Japan Radio Corporation (JRC). This is a Higher Gain & Smoother version of the JRC4558D (notice one has one "D" and the other two "DD"s). It's less Hi-Fi and has a smoother gain structure with a slight rounding off in the highs. This "DD" chip sounds surprisingly good in an SD-1. This is the stock chip you'll find in most SD-1s and TS7s. This is a good match for my SD-808. Try it and I think you'll agree. My SD-808 has clearer top end and more hair. The JRC4558DD tames the SD-808 a bit in the highs. Depending on your amp you might like this chip better. I have a few of these. Contact me if you want one, I don't have these listed for sale on my pedal mods page because most people write them off as being a bad chip. But, who cares what others say, the proof is in the tone and I say they sound great with some SD-1 setups. Of course, YMMV. RC4558P – Made by Texas Instruments. Also used in the original TS808s and TS9s. Ibanez later changed the chip used in their pedals. The RC4558P is also a very inexpensive chip but considered to be a bit more Hi-Fi than the JRC4558D. It just happened to sound great when used in a Tube Screamer circuit. These are still very popular today and are a great sounding chip. Very similar tone-wise to the JRC4558D, has a little more high end grit. RC4559P – Made by Texas Instruments. This is a more Hi-Fi lower noise chip than it's brother the RC4558P. The EQ and gain structure is a bit different than the RC4558P. I like this chip because of it's lower noise when used in a GE-7. I also like this chip in a SD-1 and Tube Screamer circuits. This chip changes the EQ of the gain and helps tame the mids in a Tube Screamer. LP353 - Made by Texas Instruments. Very similar tone-wise to the JRC4558D and RC4558P. Maybe a little less gain but an excellent sounding chip. Subtle differences. This chip sounds excellent in a Tube Screamer, Daddy-O or SD-1. This is a very popular chip with pedal modders. NE5532 - Made by Texas Instruments. Very similar tone-wise to the JRC4558D and RC4558P. This is a more Hi-Fi, lower noise chip than both the JRC4558D and the RC4558P. I really like the tone and gain of this chip. In some ways I like it better than a JRC4558D or RC4558P. Rich, smooth gain with nice overtones. This is a very popular chip with pedal modders. TL072 - Made by Texas Instruments. Very similar tone-wise to the JRC4558D and RC4558P. This chip has a very interesting tone. A little more complex than any of the other chips I sell. Very defined harmonics, especially at higher volume. This chip is very Hi-Fi with low noise and a great sounding gain structure. OPA2134PA – Made by Burr Brown. This is the most expensive op-amp chip I sell. This is a very popular chip with audiophiles. It’s low noise and excellent sound properties make it a popular choice with pedal modders. I especially like this chip in a Boss SD-1. It has a little more edge than a JRC4558D or RC4558P and is a tad cleaner with a flatter EQ which makes it a great chip to tame the mids of a Tube Screamer or SD-1. Very rich and defined gain with excellent harmonics and note detail. You can’t go wrong with this chip. Highly recommended. LM308N – Made by National Semiconductor. If you want that Vintage RAT tone that made the RAT one of the most popular distortion pedals of all time then you'll need to replace the stock raspy sounding OPO7DP. The LM308N will give the circuit a very warm and smooth fat gain structure.