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PMA 27th December 2012 01:20 PM

OPENAMP1 - MM phono preamp open project
For those who might be interested, I have prepared an open project of the phono preamplifier for MM cartridge. It has very low noise and very low distortion. Gain is 40dB/1kHz. Output is capable to drive 50 ohm load, so one may directly connect headphones via 100 - 220 ohm pot. Please feel free to download documenation from

Preamplifier for MM cartridge

Mooly 27th December 2012 01:33 PM

It looks really good Pavel (and all immaculately presented too). The buffers seem an unusual addition (in a good way) and should make for total compatability. Nice...

Thanks for sharing with the forum :)

MLStrand56 27th December 2012 01:48 PM

Is this available as a kit? Price? Shipping?



PMA 27th December 2012 01:53 PM

Mooly, thanks for the kind words.

MLStrand56, not yet as a kit. But PCBs will be available by the end of January 2013. I have been very busy this year with industrial automation projects, namely plasma spraying, and have had almost no time for audio. Now in December I finally got some time for audio projects. Let's see, at the moment I cannot promise the kits.

PMA 27th December 2012 01:58 PM

1 Attachment(s)

Originally Posted by Mooly (
The buffers seem an unusual addition (in a good way) and should make for total compatability.

The buffers make 2 or 3 improvements:

1) feedback network may use lower impedance resistors (100 ohm between -IN and GND) to get lower noise. This results in higher capacitances, that are easily driven with buffer.

2) buffered output is much less sensitive to output cable type and length.

3) output is able to drive headphones.

To demonstrate buffer capabilities, please see attached distortion measurement of this MM preamplifier into 50 ohm load.

Mooly 27th December 2012 04:40 PM

Thanks for the explanations and distortion plot. Impressive for 50 ohm loading.

Joachim Gerhard 27th December 2012 05:33 PM

Hello Pavel. If you like i can contribute an MC head.
It is super simple and works very well.

PMA 27th December 2012 05:42 PM

Hello Joachim, thanks, we may put it together.

Joachim Gerhard 27th December 2012 05:56 PM

1 Attachment(s)
Here we go.

Joachim Gerhard 27th December 2012 05:57 PM

The servo will even be not necessary.

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