Balanced input all DC coupled RIAA preamp

[sek]

Originally Posted by FdW

The Ultiboard and Multisim files are in the attached zip archive.

Here they are, thanks FdW.

The archive needed splitting up due to the forum's attachment size limitation.

The (EW) archive contains the Ultiboard files, the (MS) archive the files for Multisim, respectively.

Cheers,
Sebastian.

[FdW]

Originally Posted by sek

The archive needed splitting up due to the forum's attachment size limitation.

Sebastian,

So that was my problem, the zip file was to big. Thanks for solving

Regards,
Frans.

[tubewaller]

I really like the quality of the craftsmanship. Comment on using a single opamp as an "instrumentation amplifier": The input impedance into the non-inverting input will always be R53 + R54 (188.2 K ohms). But, the input impedance into the non-inverting input will vary with the signal conditions. When the signal into the inverting input is equal to (R51/(R50 + R51)) times the voltage into the non-inverting input, the input impedance into the inverting input will tend to infinity.
Both R50 and R53 are in series with the signal and will add Johnson noise (actually, quite a lot of it). One approach to consider is the use of either a 2-opamp or 3-opamp instrumentation amplifier with a gain of 10 for MM or 100 for MC with the loading resistors (23.2K each for MM or 5-50 ohms for MC) to signal ground. This initial voltage gain overcomes the noise introduced in the following RIAA equalization stages. Splitting the RIAA equalization into 2 inverting stages (to produce overall non-inverting output) produces a better step response but at the cost of a slightly increased noise figure (compared to a non-inverting RIAA stage) because of the necessity of the "feed-in" resistors. Best Regards, tubewaller