I generally only see this in early to mid '70s units. This is two 741 op amps in a single package released not long after the 741. Like the 324, this op amp accepts inputs down to V-, so a substitute needs to be able to do the same. General purpose dual op amp, as far as I know the dual version of the 324, also 1972. The low power and low voltage specs also mean this chip has worse noise and distortion performance than others, but these factors are often of no consequence in a guitar pedal.Ĭommon quad op amp in '70s and '80s battery powered effects. The last feature makes this type of op amp not interchangeable with op amps that can't allow their inputs to come close to the power rail (TL0XX, for instance cannot get close to the V- rail) if the circuit requires such inputs. It uses little power, can work off of low voltage power supplies, and you can give it input voltage down to the V- rail. The 324 came out in 1972 and was a very popular quad op amp. These crop up in the Gretsch effects and the ARP 2600. This was originally available in 14 pin packages, with 6 unconnected pins. Like the 101, these require an external compensation capacitor. The 748 is an early single op amp released in 1969 as an answer to the LM101.
![bass microsynth daisy chain bass microsynth daisy chain](https://hariharimusik.id/wp-content/uploads/2020/09/cobra-daisy-chain-1-600x600.jpg)
(National numbering: 1XX = Mil spec, 3XX = consumer grade) Limited slew rate/"slow" frequency response is a often cited reason for its popularity in distortion circuits. This was notably at the time for having a respectable input impedance with bipolar inputs, but it has a slew rate even lower than the 741 at 0.3V/µs typical. LM741 was National's version, and you can many other variations of XX741 out there.
BASS MICROSYNTH DAISY CHAIN PRO
While this limited the 741's acceptance in pro audio designs, a poor slew rate appears to be a good thing when purposefully overdriving the chip for a distortion effect. The slew rate is given as 0.5V/µs typical. The amplifier is very similar to the LM101, but includes a 30pF capacitor internally which proved to be a popular decision with designers (one less component to deal with adds up!). "♚" stands for "micro amplifier." Due to the lack of a "µ" character on most keyboards, a "u" is often substituted when looking for the original chip online. µ is the Greek letter mu and it is used as an abbreviation for micro (as in ♟ for micro farad). The 741 was introduced by Fairchild in May of 1968.
![bass microsynth daisy chain bass microsynth daisy chain](https://sep.yimg.com/ay/stringsandbeyond/snark-5-pedal-9-volt-daisy-chain-adapter-cable-12.gif)
Check the datasheet to confirm any questions about suffixes. The device suffix letters are also generally unimportant except that they may indicate whether you are ordering a through hole (DIP or SIP), surface mount, or metal can (TO-99) package. This is usually unimportant, but may change the typical slew rate spec (believed to be important in distortion designs). The device prefix indicates the manufacturer.
![bass microsynth daisy chain bass microsynth daisy chain](https://i.pinimg.com/originals/41/ed/ba/41edba0e9f91e036948124d6aa0b3adf.jpg)
BASS MICROSYNTH DAISY CHAIN PLUS
Some descriptions of the very common devices follow, plus some notes on famous or notorious op amps (like those associated with Tube Screamers). BJT input and FET inputs are also interchangeable, but I usually stick to the same input type when swapping. Single op amps in circuits, especially where the offset pins are being used (rare in pedal effects), need a closer look at the datasheets before subbing. As for pinouts, dual op amps in 8 pin packages have a nearly universal pinout. A notable exception is rail-to-rail and "single supply" type op amps that accept a wide range of input voltages: subbing an op amp with limited input range may not work. For the most part, op amps are pretty interchangeable so long as the pinouts match.