Phono Preamp Gain

[MikeT.]

Not an electronics superstar but do have some basic knowledge of sensitivity, gain, dB ratios and the like but have a question. I am looking for a moving magnet phono preamp, ideally with a gain of less than 40dB to use with a SUT. I’m using a Denon DL103 with a custom SUT 1:10 or 1:14 switchable. I’m using on 1:10 now with a Schiit Mani 2 at 33dB gain. I was using at the standard 42dB gain setting but it seems to sound better at the lower gain setting.

I have seen a phono pre spec’d at 39dB dB @1kHz. Why the spec at that frequency? What does it mean for 30Hz, 18kHz?

Thanks in advance for any knowledge you can impar!

Mike

 

[NTK]

Because of the required RIAA playback equalization, the gain of a phono stage is different across the audible frequency range.
[Edit] SUT's do not perform the RIAA equalization function, and therefore their gain should be flat with frequency.

RIAA equalization - Wikipedia

en.wikipedia.org

 

[MikeT.]

Thanks @NTK ! Let me paraphrase. In other words if a MM phono stage gain is spec’d at 39dB @1kHz, will the gain be higher below 1KHz and lower above 1KHz? Most manufacturers seem to only quote gain in dB saying nothing about frequency.

 

[fpitas]

Thanks @NTK ! Let me paraphrase. In other words if a MM phono stage gain is spec’d at 39dB @1kHz, will the gain be higher below 1KHz and lower above 1KHz? Most manufacturers seem to only quote gain in dB saying nothing about frequency.

That's because the RIAA compensation is assumed. See the Wikipedia link above.

 

[fpitas]

If you're looking for a phono amp, a lot have been reviewed here:

Turntables, Phono Amplifier, Cartridges Review

Review, measurements and discussions of LP format

www.audiosciencereview.com

 

[MaxwellsEq]

Thanks @NTK ! Let me paraphrase. In other words if a MM phono stage gain is spec’d at 39dB @1kHz, will the gain be higher below 1KHz and lower above 1KHz? Most manufacturers seem to only quote gain in dB saying nothing about frequency.

The phono preamp has to apply the RIAA equalization time constants.

To answer your question, then, above 1kHz the amplifier gain is reduced and below it, the gain is increased. If you had an imaginary unity gain amp at 1kHz, the higher frequencies would require attenuation and the lower frequencies would require amplification

 

[MikeT.]

Thanks @MaxwellsEq , @fpitas and @NTK ! You have expanded my knowledge greatly in this area.

 

[DVDdoug]

Most manufacturers seem to only quote gain in dB saying nothing about frequency.

The reviews here show how closely the equalization matches the ideal/theoretical RIAA EQ curve. The record is cut with recording EQ and when the complementary playback EQ is applied by the phono preamp you have flat response.

The RIAA EQ is usually pretty good... Better than most records & cartridges. The capacitive loading on the cartridge (from the cables and preamp) also affects frequency response.

 

[Balle Clorin]

http://www.rothwellaudioproducts.co.uk/html/mc_step-up_transformers_explai.htm

My MC cartridge with 10ohm internal resistance gives 0.32mV and with A 26db SUT +MM/47k at 36dB I get a level out of the RIAA that corresponds exactly to the MC setting of 61dB , that gives 1db insertion loss… theoretically it is 0.8dB
Measurable noise significantly lower with SUT.

 

[egellings]

Thanks @NTK ! Let me paraphrase. In other words if a MM phono stage gain is spec’d at 39dB @1kHz, will the gain be higher below 1KHz and lower above 1KHz? Most manufacturers seem to only quote gain in dB saying nothing about frequency.

1kHz is an industry standard accepted frequency at which the gain of phono preamps is given. You're about 20dB above that at 20Hz, and about 20dB below that at 20kHz in a phono preamp.