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OPA1652: Need to replace RC4136 in active audio filter with lower noise part. Is OPA1652 a good choice?

Part Number: OPA1652
Other Parts Discussed in Thread: OPA2134, RC4136, OPA1678, TINA-TI

Have an active audio filter in an older piece of equipment that uses RC4136s. It is quite noisy. OPA2134 has been suggested as replacement,  as well as OPA1652. What is best choice from standpoint of noise? From standpoint of noise performance/$ ? I have necessary adaptors for modern footprint. Thank you for any comments.

  • Hi Wally,

    The RC4136 is a legacy op amp and the electrical performances of today's TI audio op amps easily exceed that of this older device. I suggest the OPA1678 for high performance, low noise audio applications where cost is a major consideration. You can find the OPA1678 datasheet here:

    http://www.ti.com/lit/ds/symlink/opa1678.pdf

    Regards, Thomas

    Precision Applications Engineering

  • Hi Thomas,

    Thank you for your answer.

    OPA1678 is indeed low-cost.

    If one had budget for devices costing a few dollars/each, which might be used, and what would typical improvement in noise performance be?

    Wally

  • Hi Wally,

    Certainly, the circuit design in which the audio op amp is applied will influence the ultimate levels of noise and distortion that can be achieved by a particular device. Probably the fastest way to give you some idea of the levels of performance that TI's best performing audio op amps can achieve is to direct you to one of the SoundPlus web pages:

    http://www.ti.com/amplifier-circuit/op-amps/audio/soundplus.html

    It breaks down the audio op amps performances in three performance levels; Essential, Premiere and Ultimate. When you select a particular op amp to review you can scroll down the page and the 1 ku pricing information is provided. Even with Ultimate audio op amps it becomes a challenge to pay more than a couple of bucks for the op amp!

    Once you have an idea about the audio op amp you would like to use in the audio filter it is an easy step to set the circuit up in the TINA-TI simulator and find what sort of response and noise performances can be achieved. The modern audio op amp Spice models are quite accurate.

    Regards, Thomas

    Precision Amplifiers Applications Engineering

  • Thanks again Thomas for the good suggestions.

    Wally.