OP-SWAP, considerations in the op-ed market.

What are op-amps? Integrated circuits, typically with 8 pins, which provide in our case for audio preamplification, and which manage to compress costs considerably, since they replace outright at least ¾ of the circuitry required to make a stage, from phono up to the output circuits of a DAC and/or preamplifier. They are found far and wide in many, many realizations even of blazon, and only in hi-end products are discrete circuitry, that is, made from standard components, used instead. In fact, the op-amp replaces a good chunk of circuitry-20+ transistors plus accessory components-with the advantage of containing all the semiconductors in the same silicon chip, providing superior component similarity and more linear thermal behavior, the elements being very close together.

Op-amps, a history of nearly 100 years

The operational amplifier, whose name comes from the fact that it inherently can perform numerous operations on signals, i.e., sum, subtraction, derivative, integral, etc., etc., made its first appearance in the 1940s made with thermionic tubes, but it was an expensive and bulky device. The evolutionary leap came through solid-state semiconductors in 1963 with the introduction of the first integrated circuit operational amplifier, the u702 designed by Bob Widlar and made by Fairchild , followed by u709 in 1965. Bob later moved to National Semiconductors and there created LM101 in 1967, the first true op-amp in a metal package. A little less than a year later Fairchild responded to National with the uA741, which immediately caught on in the audio world as well. It took 10 years, however, for total clearance in our world with the TL071 debuting in 1975 and then to follow TL072, 081 and 082 from Texas Istruments, and later NE5532 (1977) and all others to follow to the present day. There are, just for the sake of disclosure to readers, single op-amps, i.e., which internally contain only one amplifier cell, and others contain two.

Does it make sense to replace one op-amp with another ?

The vast op-amp market, with thousands of models and dozens of manufacturers, allows the substitution of one particular type for another -within certain limits-. Beware, therefore, of changing (without being properly informed) one op-amp for another; you risk burning out the integrated and perhaps even the circuit around it. Then the reference must be respected, that central notch that is normally placed next to PIN 1, if you reverse the op-amp you will burn it out practically for sure, injecting the unfortunate person with the supply voltage where you would expect the input voltage instead. But that is another story. The rampant phenomenon of appearance marketing to which Fosi leans is to propose the replacement of op-amps subsequent to the purchase of the product. The op-amp, however, like DAC chips to varying degrees, needs a solid outline to work at its best. It is not necessarily the case that a relatively old op-amp sounds worse than a very modern one; there is the power supply circuit, the lay-out, the components, and above all the circuit design. The Chinese generally use schematics from the op-amp manufacturer’s application literature without any particular fancy.

MUSES02, one of the most cloned op-eds.

There are many models of op-amps that are normally used in the audio world. Starting with early TL071 and 072, to modern Sparkos, high-level discrete circuits that “simulate” the circuitry of an integrated. Interchangeable are the NE5532 with the MUSES02, the SS3602 Sparkos, and the OPA2134PA. Particularly for the MUSES02, there are very different prices and equally varied origins, some dubious. MUSES02 in fact is an excellent op-amp, which is manufactured by Nisshinbo Microdevices (which by the way also offers absolute level volume controllers, one even used in the Marantz Model 10) The Muses can only be bought on Mouser, Digikey and Profusion. Mouser’s price is 45€+VAT and shipping each, but they can be found on Aliexpress, for example, at prices ranging from 10€ to 25€ a piece, but here you have to be VERY careful about copies and scams. There could be another op-amp “inside” while the affixed label is that of the Muses, and sophisticated measurements would have to be made for the average enthusiast to notice. Less difficult is the 5532 market; one of the best manufacturers is Texas Instruments, and the product can “certainly” be bought true and to spec on Farnell, as on Farnell one can also find the 49720 also from Texas, and costing about 7.50€. Do those bought from Farnell branded Texas sound better than what comes with their own electronics ? It often happens to find in Chinese production components that only outwardly are “equal” to the original, and we are not referring only to op-amps, but also to capacitors for example. Red WIMAs are very expensive capacitances, now used everywhere, even where the economics of the product would definitely prevent it, how is that possible ? But then again there is almost no means-especially for a capacitance-to trace the actual origin.