ECC83 Phono Stage

[Primalsea]

Now happy with tthe way this is turning out, so time to post a few pics. WD Phono 3 clone but with a twist. I do own a Pre 3 and the PSU, but for the phono stage I decided to try out an inverter supply. The unit will be powered by an external laptop PSU outputting 19V. I done something similar with a guitar pedal and the results were very good and with very little noise floor. If it all goes to pot not too much of an issue as I can just use the WD PSU.

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The PCBs are prototyping boards that I bought from valvewizard.co.uk a while back. These are no longer available, which is a shame as they are really good.

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The boards are bolted to the Alu strips that are held to the chassis by screws. What I do need to get some longer bolts so I can change the height of the boards so that the valves poke out further through the top.

One of the back
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Just needs a bit of tidying up and also waiting for some 8.2nF caps to arrive so I can get those in and wire it all up. Also need to lash up a MC step up amp so I can test.

[Puffin]

Nice.

[Primalsea]

A bit more work today. The PSU is almost completed:



And the 8.2n caps have been installed and the boards mounted to the sub chassis using longer bolts that I made by connectinf two shorter bolts using heatshrink.





The PSU has been tested and works. A nice feature of these PSUs is that it takes a while for the HT to reach full voltage while the 470U cap charges, but the LT heater supply works immediately after switch on. This makes a nice soft start.

[Primalsea]

I have now managed to get this up and running, sort of...

The circuit boards wired and now fitted with plug connectors for the HT and LT supplies




Had some problems with some dodgy capacitors that were passing DC current and causing the resistors in the power supply to smoke. Managed to solve this and fit it all together. It works and the plate and anode voltages all seem OK but its very noisy on both channels. I think the SMPS power supply and inverter may be a step too far. Doesnt seem to be mainshum,just a broad band noise which I think is due to the power supply injecting too much noise onto the signal ground..

I may have dig out the WD PSU...

Anyway almost there and will probably to solve the SMPS issue first, If I can.

[Primalsea]

Now finished and initial testing looks good. The noise was from the laptop-style SMPS. I lashed up a 19V DC linear supply and all was fine. Just some valve noise and a small amount of hum if its too close to a source of mains noise, such as a transformer or TT motor. The base is well screened so I think the valves could do with some cans over them.

The PSU is housed in this rather snazzy money box.


It does look a bit agricultural but I can spray it up later in a more pleasent colour. £6 for a metal box, it had to be done.

The finished phono stage.


Just waiting for a few bit to be delivered so I can knock up a MC head amp and then I can give it a more thorough testing.

[smithie]

looks brilliant and great work.
of course the blue £6 metal box is just the icing on the cake