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Megatron Electrostatic Headphone Amplifier


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Finally got around to finalize my Megatron, fitted into one chassis with GRHV.     

Did some fine tuning on my Megatron. Bring the regulated HV down to 430VDC rails and changed one resistor from 21K to 15K to supply 300VDC to the front end tubes. In my case the front end tubes draw a

I made some modifications to my Megatron. Most of them are under the hood. changed the CCS tubes filament supply transformers from 25VA Antek AN 0206 to 50VA AS 0506 (one for each channel). Now

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Inu must be playing with spice biggrin.png

yes it would have to be a 2sa1968, because nothing else is stable at 500 microamps.

or a 2sa1486. The 10m90s won't work. Actually the real number is 450 microamps.

Neither of these are in current production. Could probably get away with ksa1156.

dn2540 also won't work because leakage at likely temperatures is more than 500 microamps.

and with the 12ax7 in the first stage, the gain is a bit high at 65db. so i'm playing

with a 12au7 at the moment. brings the gain down to 52db.

removing the pot probably does not help with the space needed for the current sources.

We will see...

Edited by kevin gilmore
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The voltage gain of the 6SN7 varies from 13 to 16. If the source provides 2V (a CD player), the second stage grid, U3 (U4), could receive 26V. With R8 of 300K, and R7 of 1K, 400V for B+ will provide an adequate bias of U3?

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Which BC560 is the correct one for the Megatron? I don't think there is a BOM or a schematic yet. is there?

http://www.mouser.co...key512-BC560CTA

or this one?

http://www.mouser.co...lkey863-BC560CG

Also, I assume these ones are correct:

http://www.mouser.com/Search/ProductDetail.aspx?R=KA7812ETUvirtualkey51210000virtualkey512-KA7812ETU

and

http://www.mouser.com/Search/ProductDetail.aspx?R=KA7912TUvirtualkey51210000virtualkey512-KA7912TU

Edited by eggil
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Birgir,

Are you guys at all worried about having at least one of the filaments connect so close to the pot/input? Seems like a place for noise to get in early on unless one is very careful. The power supply must be a bit of a beast as well.

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That filament was always supposed to be DC powered but 12VDC operation would have been a better idea in hindsight or even running them at 25V.

 

My plan for this one is to run it off a BH power supply with it and the power transformer in a separate chassis.  The amp chassis will also have to have mains running to it as the filament windings for the CCS tubes need to be as close as possible to the tubes.  So that will be 4 transformers for this one and all in the largest Galaxy cases.  Half the size of the ESX for a far more complicated amp... should be fun.... :D

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