My own version of the EAR 834P Clone

[Algar_emi]

I'm building my own version of the EAR 834P Phono preamp, using the modified Thorsten version. Here the schematic I'm using.

[Algar_emi]

It is mounted using point to point. Here the preamp section. It used normal carbon film resistors, Nichicon HV caps bypassed by Wima MKP for the supply. The passive feedback network used Caddock MK132 resistors and 1% Silver Mica caps. The coupling caps are a little bit more fancy. I used RelCap for the first stage, then Jensen paper in Oil, bypassed by a small 0.1uF Musicap, for the final output cap.

The final tube can be a 12AT7 or a 12AU7. It is selectable by a jumper that change the cathode resistor, see schematic.

[Algar_emi]

Here my detailed parts list.

[Algar_emi]

This is some other user schematic with typical voltage readings. It can be useful for troubleshooting.

[Algar_emi]

This is Thorsten mods guide for the original EAR834P. His schematic has all these mods included.

[Algar_emi]

My own schematic that I used to build the preamp section. It matches my Parts List.

[Algar_emi]

And the supply schematic. It is using a EZ81 Tube rectifier and CRC pre-filter for the HV. The filaments are DC, 12V using Soft recovery rectifiers and LV regulator IC. The Filaments voltage is lift over ground by about 30V, using a voltage divider connected to the HV section for better noise reduction. I may use an adjustable potentiometer instead of R309, R310 as some users reported even better adjustable noise reduction.

The actual supply schematic is using only CRC filtering for the HV. I'l try to use dual mono Shunt HV Regulator using my own PCB.

[Algar_emi]

The Supply schematic specifies an HV Transformer Hammond 270X. But I found a very nice surplus transformer with slightly higher voltage (better for the Shunt regulator application). It is fully encapsulated. Here this beauty.

[vinylkid58]

Very nice build and excellent documentation.

Is this design quieter than an octal based pre with choke loaded PS?

Thanks for posting,
Jeff

[Algar_emi]

I'm in the process of building it, among other projects

Still working on the supply section. I'll try first without the shunt reg PCB, then I'll try them.