I want to bypass everything before the ADC on my Korg MR-1000. It uses the njm2737 ic, which I have seen reported as having a poor bandwidth and slewrate. I, however, don't think the passive parts can be changed due to all-SMD constraints, so I am looking for a electrically equivalent drop-in replacement. SMD to DIP adapter probably can be found and fitted on the PCB, but other than that, I believe, I am stick with the existing circuit.
OPA1612 when bipolar can be used but it is SOIC8. This opamp is a way better performer but make sure to check decoupling on the PCB. SOIC8 to DIL8 converters can be used but use good ones. LME49860 is a nice bipolar DIL8 replacement too. IMHO it is optimal to use SMD opamps when the original was also SMD and DIL8 when the original was also DIL8. Above all you should know beforehand what the power supply voltage to the opamp is exactly as NJM2737 is a special low voltage use part with normally 6V supply voltage so the new opamp should work OK with 6V too. If they used 5V for instance then a replacement opamp is harder to find. Beware of my advices when 5V is used as then you will need rail to rail input AND output opamps!! A simple solution would be to up the supply voltage just 1V and be able to use lower noise opamps that are not rail to rail input/output... It seems worthwhile to change the situation as NJM2737 is a poor performer in all aspects except ultra low voltage use. Without knowing anything of Korg MR-1000 we can probably determine that NJM2737 was solely chosen as there was 5V already in its vicinity...
BTW active parts can not correct what mediocre passive parts destroy.
BTW active parts can not correct what mediocre passive parts destroy.
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It is a pity but I see you are already trying to do something in the device? Old fashioned practice to use parallel TH caps for decoupling. It really would have been better to use SMD parts and then X7R or even tantalum or film types.
Anyway you could draw the schematic what regulator feeds the 5V to the NJM. Then find out its input voltage and of course if nothing else is connected to the 5V output voltage. Then change the regulator to a 6V type and the opamp itself too.
Since I regret seeing devices modified non optimally/laymen style I am out of this thread. Good luck with the modifications.
Anyway you could draw the schematic what regulator feeds the 5V to the NJM. Then find out its input voltage and of course if nothing else is connected to the 5V output voltage. Then change the regulator to a 6V type and the opamp itself too.
Since I regret seeing devices modified non optimally/laymen style I am out of this thread. Good luck with the modifications.
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the Wima parts in (parallel?) is part of Busman mod, along with replacement of 4580 to something looking like AD8022. I bought the unit modded at ebay, and have unmodded one. The modded sounds more true to the source, that is for sure.