Megatron Electrostatic Headphone Amplifier

[nopants]

Thanks for the info spritzer, I will keep that in mind my wallet recovers enough to consider rolling these tubes. I went digging around for 6ca7's on ebay and happened upon this:

 

http://www.ebay.com/itm/171112790336

 

He gave me a bit of a discount for purchasing 8 so I figured the price delta over the various reissues was worth my curiosity. Leaving the link here for anyone else interested.

[nopants]

Well the rest of my parts and come in tomorrow, I should have something functional by the weekend...luckily I ordered the necessary parts before before an untimely car accident 

 

here's to hoping this thing doesn't explode

[Victor Chew]

What transformers specs are you using nopants?

[nopants]

everything is from antek except for the hv transformer, which is the hammond 269GX- 450V + a single 6.3 filament which seemed like a natural fit for the psu and front-end.

 

25VA / 2x6.3 x 3

25VA / 2x15 x1, based on the kgsshv requirements for the LV secondaries

 

I should be able to stack these to save some space and mitigate hum issues based on past experience. I was envisioning a one box build where the amp board sits on top via standoffs,with some kind of cage around it. Sounds pretty dumb in my head, but I'm no less averse to casework than when I did the kgsshv...

[RiStaR]

nopants you're using two of those Hammonds?

[nopants]

Actually I might not even be able to roll two of those....they don't supply enough current compared to the custom transformer from sumr right?

 

2 x 420V (@125mA output ea) secondaries

 

addendum: I am a dumbass

Edited September 6, 2013 by nopants

[RiStaR]

Yep. And you need two windings at the minimum.

 

Trying to go all overkill on this one since the tubes draw so much more power... toroidy is having difficulty with shipment to where I am

[eggil]

I assume the KGSSHV PSU built for the Megatron should be at +-450V?

And use 2 instead of one?

Edited September 7, 2013 by eggil

[spritzer]

400V or 450V will work and two PCB's?  No but you need to modify the one PSU to output more current. 

[chiguy]

With the KGSSHV PSU able to be built for 500V output, is there any point or advantage in running the Megatron at 500V (assuming that it's capable)?  Any downsides?

Edited September 7, 2013 by chiguy

[spritzer]

You can do that if you like smoke rising from the amp. 

[nopants]

I thought that feature came by default, I was going to cure my fish and meat with this

[eggil]

Now that would make Kevin truly furious...    Did you ever see the inside pictures of that amp?  So he didn't want to spring for a +/-15V supply but the amp was filled with Z-foil resistors... 

Z foil resistors! Man, that would be more expensive than gold. Where the screws encrusted with diamonds?

A titanium knob, well I could see Kevin doing that

Edited September 7, 2013 by eggil

[spritzer]

Well this was in 2003 and they were cheaper back then. 

 

The Ti knob has been done, it's on my T2. 

[nopants]

For anyone interested I got a quote from SumR for a 6 x 6.3Vac @ 2A / 76VA transformer, $98 each before shipping.

 

Encapsulated into container, leads out lower side for flush mount: Container  OD:  4 1/8”, HT: 2 1/8”.

Edited September 10, 2013 by nopants

[kevin gilmore]

 

A titanium knob, well I could see Kevin doing that

 

Don't forget the titanium hammer with the 24k gold replaceable tapper

which was shown at CJ010.

 

I specialize in goofy.

[livewire]

@KG - When are you gonna machine some of them demon core hand warmers?

 

(a more compact version of the original pictured here)

 

 

You can see he is warming his left hand with the device.

It had a fatal flaw though, he slipped with the screwdriver and the 14 pound plutonium orb that was inside went critical.

He was walking dead after that. The experiment was known as "tickling the tail of the dragon".

 

http://en.wikipedia.org/wiki/Demon_core

Edited September 11, 2013 by livewire

[chiguy]

For anyone interested I got a quote from SumR for a 6 x 6.3Vac @ 2A / 76VA transformer, $98 each before shipping.

 

Encapsulated into container, leads out lower side for flush mount: Container  OD:  4 1/8”, HT: 2 1/8”.

 

I'd be interested in the quote.  Thanks!

[wink]

 

"tickling the tail of the dragon".

Ignorance is not always bliss.

[eggil]

I did not realize base and collector are linked in the 1486 that sits alone.

After soldering, I thought I had created a bridge and removed the transistor.

Lesson: look at the schematic and a bare PCB if you have one to compare.

In the older PSU, they were connected by a trace. Now they are linked, and that makes it look like a solder bridge.

[eggil]

Waiting for parts

 

Edited September 26, 2013 by eggil

[livewire]

Oooooh! Wanna see more!

[eggil]

Bought a Cannon macro lens, but I am not a very good photographer.

3 cold solder joints fixed.

[nopants]

I'm mostly done with my stuff,waiting on the transformers. I haven't touched it in a while so I need to revisit it in detail for errors and such.

 

Also bought some mundorf supremes for coupling between input and output stages, any suggestions for other candidates I might use? Maybe I'll socket those spots...

[spritzer]

Do not under any circumstance use those rectifier diodes!!!  Use the ones printed on the board.  The board always overrules any BOM.