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Guy's Phono Amplifier
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Author:  randy warren [ June 18th, 2013, 12:51 pm ]
Post subject:  Re: Guy's Phono Amplifier

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

Author:  High Transconductance [ June 18th, 2013, 1:13 pm ]
Post subject:  Re: Guy's Phono Amplifier

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!!!

:violence-swords:

Author:  randy warren [ June 18th, 2013, 1:48 pm ]
Post subject:  Re: Guy's Phono Amplifier

agreed!

Author:  Guy [ June 18th, 2013, 3:52 pm ]
Post subject:  Re: Guy's Phono Amplifier

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.

Author:  High Transconductance [ June 18th, 2013, 4:01 pm ]
Post subject:  Re: Guy's Phono Amplifier

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.

Author:  rock4016 [ June 18th, 2013, 4:07 pm ]
Post subject:  Re: Guy's Phono Amplifier

and I thought my 75 min commute was long! :(

Author:  Guy [ March 21st, 2020, 12:14 am ]
Post subject:  Re: Guy's Phono Amplifier

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!

Author:  Roscoe Primrose [ March 21st, 2020, 12:27 am ]
Post subject:  Re: Guy's Phono Amplifier

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

Roscoe

Author:  ratbagp [ March 21st, 2020, 8:49 am ]
Post subject:  Re: Guy's Phono Amplifier

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

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

ray

Author:  Guy [ November 30th, 2021, 2:33 pm ]
Post subject:  Re: Guy's Phono Amplifier

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! :roll: 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! :crazy:

Attachments:
File comment: Power Supply Guts
Power_Supply_Inside.jpg
Power_Supply_Inside.jpg [ 139.17 KiB | Viewed 7972 times ]
File comment: Power Supply Rear Panel
Power_Supply_Rear.jpg
Power_Supply_Rear.jpg [ 83.19 KiB | Viewed 7972 times ]
File comment: Front View of Power Supply
Power_Supply_Front.jpg
Power_Supply_Front.jpg [ 97.01 KiB | Viewed 7972 times ]

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