Rolling OpAmps In The Elekit DAC ~ In Search Of Cheap Best 12Mar25

I renamed the living room stereo to EleFrugalKit and relocated its amp to a more secure location... and now there is plenty more experimental rolling fun afoot.

Rolling DAC Op Amps... The Blodgett Living Room (BLR) stereo based on DRC FH3 FrugalHorns is awesome, but is any audio guy ever done? Next up toward "DIY cheap best" is rolling the opamps in the Elekit PS-3249R 16bit/48KHz DAC. The op amps in this circuit are the gain stage to drive the line out. This DAC includes a 8 pin DIP socket for a 2 opamp circuit 8pin IC... the circuit layout is the same for all these ICs, as shown for the OP275. I bought some appropriate alternatives to the stock NJM4580 for about $8 each in single quantities...  Analog Devices LT1364, TI OP2132, TI OP275, Analog Devices AD8512. I looked for low noise, pinout equivalence, and solid audio frequency performance and linearity. For the last AD one I needed to also buy a 8SOIC to 8DIP package converter as it didn't come in a PDIP pkg. Here I will characterize and hopefully measure the differences that these alternatives make in the sound from the whole kit, and settle on the best opamps.

The discernible differences among contenders was subtle. Frequency sweeps and distortion plots don't offer much ~ with the exception of the re-packaged 8512. It was noticeably noisier with higher distortion than the other opamps. Who knows if it is my repackaging to a viable carrier to plug in the socket, or the IC itself. Whatever, it was the 1st to be eliminated. The room, cabinets, and drivers dominate the SPL frequency sweeps and distortion measurements. My ear is the guide here both from the FH3s and from headphones, and LT1364 and OP275 were just better than the stock 4580 and OP2132. The 2132 though is quite good but with higher noise & distortion (the distortion graph below is the 2132); it is the 2nd eliminated. The LT1364 & OP275 were clearer and sparklier in voices and and strings, they each sizzled nicely across the freq range. The ultimate winner is the Linear Technologies LT1364 ~ it was just more coherent and rounder sounding to my ear ~ and it delivered a smidge more thump from the FH3s.