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Megatron Electrostatic Headphone Amplifier


kevin gilmore
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Other than European equivalents such as the ECC83 or the British CV4004 and M8137, there is the 7025 which was a premium type designed for low filament hum.  There are also rare industrial types such as the 12AD7, 12DF7, 6681 and 7729.  Some tube rollers will also use 5751 tubes which were originally designed for the military as 6SL7 equivalents.

 

As for the 12AU7, industrial tubes that can be substituted include the 5814,5963, 6189, 6350, 6680 and 7730.  The 6CG7/6FQ7 can also be used other than the fact that they are 6 volt filaments only.

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sorry for the spam, but the coupling shafts just came in. I'm aesthetically finished, just waiting on a mains relay now. I've been using it without a delay like normal but I imagine it would unnerve anyone else who used it...

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feels good man. this thing took forever because I was too busy listening to it

the aspects didn't turn out exactly how I wanted but I met the space/density goals. it kind of reminds me of a Manley amp with the way the tubes are oriented, except nicer boards

overall I'd give it a 3/10 because the knob isn't made of obsidian

 

I think I'm going to get someone to take real pictures of the thing before posting ad pics on head-fi

 

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Other bits of information

 

It gets pretty warm inside the case. I think the top plate gets to ~55C after 8 hours or so. Underside isn't a problem, top plate worries me a bit but it doesn't seem to be hurting anything. 

 

I switched out the quads, CCS tubes are on the outside iirc so orient your quads that way if you're mix and matching

 

I might be a fan of Supremes now, I'd shake my first at Birgir if it wasn't dead from screwing and unscrewing things

Edited by nopants
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i have sent MEGATRON to Beijing with SR-009 and SR-OMEGA for a big flagships party.

 

And the He1000 ,Abyss 1266 ,Jade(Winny will come) , SR-009 , SR-OMEGA has already for the PK. ::)  

 

My friend in Beijing has a BHSE,and he is waiting to do AB test between MEGATRON and BHSE.

Edited by xianghao
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  • 3 weeks later...

Uploading :

 

that is the vcap version MEGATRON with RK50 what i am working for.

 

the original PCB is`t have much space for the V-CAP so spritzer`s version(see before) must be a better. 

 

Oops.i forget to make a report about the Beijing party.

 

here are one conclusion: to AB with BHSE. MEGATRON is BHSE level questionless or even more higher.

 

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some pictures about party:

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6rV3JMp.jpg

 

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  • 2 months later...

Hi everyone and thank you all for the wealth of information here.

My electronics knowledge is average, but I'm trying to build myself a nice Megatron using a board from Birgir and would welcome all advice and criticism. I do have someone a lot smarter than me giving a bit of advice.

I'm using the KGSSHV power supply, even though I know it's not the number 1 choice anymore.. simply because I had a board and a lot of the parts already. It'll be 450v with offboard heat sinking.

So the questions: The board uses 12vdc for the front end, so I planned on switching the 7815 to a 7812 and increasing the 16-0-16 output of the transformer to 750mA (for a bit of headroom above the 600mA required for heaters). Is that a logical approach ?

Secondly, the main transformer.. the BOM says use 420v secondaries for 450v, but someone here suggested that was too high for a Megatron build. My buddy has suggested that in order to ease the work and heat from the FQPF8N80Cs, I could probably get away with 380v secondaries. Mains voltage where I live (Western Australia) is 250+, so his suggestion was a custom transformer with Primary: 230v/250v. Secondaries: 2 x 380v/200mA, 16-0-16v/750mA.

Thanks in advance for any input, and thanks again for the great forum.. especially Kevin and Birgir for all their efforts in helping dummies like me build themselves a decent amp.

 mega_zpshecgp4du.png

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