ADA4625-2 bifet
from Analog Devices is 3.3nV/rootHz at 1kHz, and 5.5nV/rootHz at 10Hz. Current noise 4.5fA/rootHz at 1kHz
The OPA828 JFET has 4nV/rootHz at 1kHz, 7.5nV/rootHz at 10Hz, and 1.2fA/rootHz current noise. Available as a dual OPA2828. Surface mount of course.
And the only bipolar opamp to beat the NE5534 is the OPA210. 2.2nV/rootHz at 1kHz, an amazing 2.5nV/rootHz at 10Hz, and crucially for MM cartridges current noise of 400fA/rootHz (same as for the NE5534). It is just better in all respects than the Neanderthal NE5534.? And available as a dual OPA2210.
If you put it into my RIAA amp spreadsheet, for typical cartridge R and L the OPA210 only finds you 0.6dB improvement in SNR as compared to the NE5534. For a factor of 5 times greater cost. But distortion is vanishingly low, it only draws 2.5mA quiescent, and inevitably is only surface mount. And cheerfully drives 600 ohms with no degradation in distortion.
Craig
------ Original Message ------
Date 08/04/2025 03:55:22
Subject Re: [MicBuilders] FET OPAs for mikes
Look at this one:?? One of my reasons for choosing the OPA1642 was idle current. The OPA1633 ?has >10ma which for a phono preamp with external supply is not an issue?
Best Regards,
Jules Ryckebusch?
On Apr 7, 2025, at 21:32, Richard Lee via groups.io <ricardo_lee@...> wrote:
?
It's actually for a Jurassic application with of no modern importance;? RIAA MM preamps in DIYaudio.? I'm surprised that NE5534 is still one of the best for this; slightly beaten only by $$$ OP627 or Unobtainium NJM2068.
?
In theory, a FET OPA with <3.5nV/rtHz & low 1/f, popcorn noise bla bla should trounce 5534
