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Megatron Electrostatic Headphone Amplifier


kevin gilmore
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Working on the amplifier chassis. Used 6 mm aluminum for everything except for the front panel, which is 10 mm.

The filament transformers will be hanging down like bats. That's what the outer holes are for. That way all the wires will be in the same plane.

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Edited by eggil
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Working on the amplifier chassis. Used 6 mm aluminum for everything except for the front panel, which is 10 mm.

The filament transformers will be hanging down like bats. That's what the outer holes are for. That way all the wires will be in the same plane.

 

Looks beautiful, and looks like a design I'd like to do. Please post your FPE files for us. 

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Thanks Kerry.

I'll post the FPE files as soon as I can. I am on a PC not my MAC currently.

Just assembled part of the chassis to make sure everything fits, and it does.

Never mind the front panels are upside down. Easy fix :)

The LED's are on top. Made 4 holes for them.

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Edited by eggil
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  • 2 weeks later...

After running the amp for about 30 minutes, a low hum develops in one channel. If I turn it off it goes away when I try I later on. I wonder if the temperature is too high inside the case. The top panel gets hot.

The thing is, when I just turn it on even a few minutes later, it sounds great without any noise whatsoever.

Edited by eggil
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Not sure I understand your question, but those circled headers are the right ones if you don't use the RK27. If you used an RK27 and it's mounted then yes, because they are connected to those headers the mounted attenuator will affect it. 

 

Even with the RK27 fully open (max volume) you're still getting channel imbalance? [you should be able to measure the attenuator with a DMM to see if it's bad - at max volume setting especially] I assume you also tried to swap the tubes around to make sure it isn't the tubes?

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Not sure I understand your question, but those circled headers are the right ones if you don't use the RK27. If you used an RK27 and it's mounted then yes, because they are connected to those headers the mounted attenuator will affect it. 

 

Even with the RK27 fully open (max volume) you're still getting channel imbalance? [you should be able to measure the attenuator with a DMM to see if it's bad - at max volume setting especially] I assume you also tried to swap the tubes around to make sure it isn't the tubes?

 

Even with the max volume,imbalance still happen. About the tube, i try my best to swap them,i don`t think they are bad.    Based on what you say,measure will be done tomorrow(maybe).

 

Anyway,thanks RiStaR.

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Even with the max volume,imbalance still happen. About the tube, i try my best to swap them,i don`t think they are bad.    Based on what you say,measure will be done tomorrow(maybe).

 

Anyway,thanks RiStaR.

 

Not sure I'm helping... just suggesting some stuff :) Just to be clear, I meant to swap left channel tubes to right channel tubes as a check instead of swapping all of them.

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Well, I checked everything and could not find anything wrong. No more hums though. Not sure what it was.

The 009's sing nicely with it. Have listened to them for hours at a time without trouble.

And the temperature on the top panel is between 53 C on top of the transformers, 63-66 C between the big tubes, 51 C on the front and 57 C on the back of the top panel after a couple of hours.

Edited by eggil
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  • 2 weeks later...

I swapped to 12AU7 from left to right sides.
The intermittent hum still happens only on the right channel and it's intermittent of temperature or use time.
Sometimes it happens within 5 minutes and sometimes it takes 2 hours but invariable disappears when I shut down the amplifier, but it comes back again without regard of time or temperature.
Otherwise it sounds great in between humming episodes.
Any ideas?

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