TinyPhono - small SMD based phono

Hi all,

I've created some pcb's for a small phono stage - straight from the OnSemi application note (AND8177/D here - Figure 3).

I've changed some values around to some more common values; and it works out well. It's mostly SMD (except for the virtual ground caps and the DC-blocking cap); and I've taken care to split audio ground from the power supply ground. You can then either couple it with a resistor / inductor / capacitor / whatever you like. I've used some 10Ohm resistors, works out well and keeps power supply noise out of the audio circuitry.

The reason for using SMD is to keep the feedback loop as small as possible. And it's nice to be able to practice SMD work.

Capacitor C1/C3 is 15nF - giving a small rise in treble. This works out nicely for the Audio Technica AT122E-P with a Jico Shibata. If you want a flatter response; change this to 18nF. I've attached a frequency response graph (the test tone on a test-record that I have goes from 200Hz to 15kHz).

I've tested this with a NE5532A which is perfectly fine, but you can use this board with faster op amps such as the ADA4898 as well. It will not oscillate.

You can power this from any power brick (single supply - connect to V+ and V-) or a dual supply. It all works. Cheap and cheerfull. Gerbers are attached (already has filename extensions for OSHPark and the likes).
 

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Hi Zero D,

Yes, there is further improvements to be made in tweaking the values (That's why I didn't put them on the silkscreen. Some might want more/less loading as well, or voice it a little different).

Here's a sim with a 1uF input cap; and the 220uF cap you suggested. :)
 

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In general, I try to avoid capacitive loading, as this moves the resonant peak down in the audio band. It's better to have low capacitance, and vary the loading resistor.

The objective for this specific preamp was to have a small phono stage. I have a different one that gives me loading options :) So yes, no DIP switches on this one ;)

NE5534 is good, but that would have upped the part count in this case as it's a single op amp. Take a look at the ADA4898. It's even better if you want low noise. (0.9 nV/√Hz Input Voltage Noise, dual op amp)