Sound & Comfort MC/MM Phono preamp

Dear DIYaudio community,

after building several phono preamps, i have still new ideas.
Today i started to draw a new design.
I combined some projects from my past.
The sound signature of the OPA627 opamp i combine with the spatial sound of the 2C51 tube. For comfort i use arduino mega with color touchscreen and remote to control the preamp.

Next i will design the PCB's.

Some spec's to start with:

- 3 inputs
- MC and MM
- Remote input, gain and cartridge loading switching.
- Color touchscreen

Ronny :)


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  • Comfort&sound - Schematic.pdf
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The two IC pinouts are drawn wrong. Pin 2 is inverting input not pin 3.
If it is wired like your schematic, where is the feedback loop on the ICs?

Thanks, my fault.:ashamed: I will change it.

Will you have some extra boards to part with if it is successful

No, i only make my own boards. But i will publish gerber files so you can order/make your own pcb's.
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Today i designed the preamp PCB to test the prototype.

You can devide the PCB in two. Between preamp and powersupply.
Tubesockets can be mount on bottom or top side.

Changed schematic with better anode supply for tubes.



  • Comfort&soundamp - SchematicA.pdf
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  • Comfort&soundamp - PCBA.pdf
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Today i had time to complete the soundpart. Tested it with my thorens TD160 mk2 modded and a ortofon 2m blue mm cartridge. One thing i noticed direcly, background is death quit. Like a battery operated preamp. Riaa frequency respond is within +/- 0,5db. First soundimpression without impedance tuning, tight, dynamic and big sound stage. Very promising. Hopely i can compleet the comfort part in the next view weeks.

The transformer which is custommade works great.


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This afternoon while listen to Eva Cassidy and Ray Charles i designed the comfort part. See picture below.

After rolling some opamps and tubes i prefer the AD847 and Bendix 2C51 combination for the sound part.

The phonopreamp is ideal for rolling opamps and tubes.

Next i build the comfort part and program the software for the Arduino Mega.


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  • comfort2.jpg
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I have build the comfort PCB. Still listening every day to the sound part. Next i test the comfort PCB just with manual control after that i need to program the arduino software. I have a arduino mega 256 with colourtouchscreen.
The housing i also need to make myself from 25mm mdf. I think i still needs 1 or 2 months to complete this project.

I shall try to publish some photos.

My time for this project is some what limited because I have at the moment 6 other projects with higher priority.