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Guy, I am building that circuit, so it should make for a good comparison!

Randy and Guy:

By the time you get your phono stages assembled, I should have my rig back in service. My Kalman phono stage (EC8010/6AM4/6SN7) and Izzy Wizzy (D3a pentode/6AM4/LL1660) should be both available. I'll need group opinions on my two, so this looks to be a great phono stage meet!

PS, the winner goes up against Charlie's best!!!

agreed!

Maybe we should drag Charlie's over to the shoot-out? Where would we do this? My basement is a wreck and not conducive to a club meeting, and my system is not up to par yet.

Hop in a jalopy and drive the 85 minutes to my house, where my rig will be up in less than a month! Will your preamps be ready by then? If not, we will do it when it works for all!!! There will be good food and drink!!! Club meet. Think carpool! It ain't that bad of a drive, I go every day from York to DC. ~91-105 minutes in morning rush.

and I thought my 75 min commute was long!

This has been in a coma for years, but it's coming back, I swear!

Question: I thought to use tube rectifiers for the power supply to give me a slow turn-on, but it looks like the best I can do is 170 mA with a 5U4GB. Can anyone verify this or tell me I can't read datasheets?

Thanks!

A pair of 6AX4GTBs will get you a real slow turn-on and 330mA...

Roscoe

For phono, these possibly might be overkill, but it would definitely look cool.

https://en.wikipedia.org/wiki/Mercury-arc_valve

ray

Holy crap, it's been over 8 years since I started this project! I think It's time to resurrect it.

It's funny how much time a project can consume. I now have a pair of red-oak boxes to house both the phono pre-amp and its power supply. Both have aluminum top panels and perforated-steel bottom panels that mount to the boxes using tapped angle aluminum. The power supply attaches to the pre-amp chassis using a six-foot umbilical made up of a set of shielded twisted-pair cables ending with a military-quality 19-pin Bendix twist connector. A power switch enables the supply, which then waits for a signal from the pre-amp to energize the pre-amp circuits. The power supply is finally together so I can move on to the pre-amp.

I built the pre-amp's first two stages on a slab of Delrin, not stopping to think that it will sink my tubes into the chassis. This is significant for the 2nd-stage tubes, which are 6AM4s (pretty short single triodes.) A switch on the pre-amp front panel tells the remote power supply to energize the amp circuits. I used gas regulators in the pre-amp (if I didn't provide schematics earlier, I'll plan to in the future,) which require more than the regulated voltage to start. This would mean that I have 45V more across my current regulators than I planned, making them dissipate a lot! To cover this, I installed a current monitor in the power-supply chassis to detect when the gas regulators fire off: when the current steps up, a voltage-dropping resistor is placed in series with the B+ supply that drops the voltage down to the levels I planned.

Anyway, I'll post more status when it gets juicy, and hopefully sooner than 8 years! I attached a few pictures of the power supply and pre-amp. With all the things I screwed in underneath, the top looks like a crazy riveter got loose!