D3A phono complete (almost !!)

This project took the longest time to complete, but it is finally done (almost).Still need to tweak for the input impedance - right now the default loading is at 50K. Maybe use a linear pot like Edwin did on his initial phono stage designs. My initial impressions are that it is quiet for a tube phono stage (no low-freq hum). It is also detailed sounding maybe a littled tipped to the high frequency, but I think I might be able to workaround with changing the loading impedance. This project is collaborative effort on diyaudio.com - the shunt regulated high voltage power supply is designed by Salas in Greece, the phono stage is designed by Andrea Ciuffolli in Italy and the PC boards designed by Quanghao in Vietnam. I'm using an enclosure from par-metal - nothing fancy but does the job for this project.













Some features I need to incorporate in the future :

1. Toggle Switch MM & MC
2. Install Altec 15095A
3. Loading option using a Dual Linear 100K Pot or Stepped Attenuator
4. Re-orient the phono board

D3A Phono Build - 0427

Connected Phono Board to PSU and hook'ed up to input and output RCAs Found that the on the input side, the "GND" silkscreen was reversed. Banged my head trying to find out why I wasn't getting sound only on one the left channel. Found that I had not connected B+ to the right channel. DOH !!! Ahh.. finally got sound out of both channels ! Amazing detail thru the Stax Lambda headphones using the iRIAA and iPhone. iPhone -> iRIAA -> D3A phono -> T-Amp -> Stax Lambda == Smiley Face


Next steps :

• Re-orient boards


• Run all joints thru a round of solder


• Install resistors on the secondary after parts get delivered


• Try mounting 15095A in the chassis for MC functionality (possibly MU metal shielding)


• Install switch for switching between MM/MC


• Install shielded hookup wire
  
• Heatsink solution for MOSFETs if they don't run cool even after installing the power resistors on and dropping B+ to 200 (current set to 220V)

D3A Phono Build - 0426

Tasks Completed :

• Bored hole for power switch on the face plate ; used 0.7" drill bit
• Completed wiring for power switch
• Completed extending secondary heater wiring
• Tested power on with switch - tested okay
• RCA female plugs are painful to tighten. Looking at Neutriks :





To Do :
• check ground wiring
• use hookup wire to hook RCAs
• solder terminal posts
• connect to main D3A phono board ; test B+, H+ voltages
• connect iRIAA and test