Megatron Electrostatic Headphone Amplifier

[kevin gilmore]

updated Megatron schematic.

If you manage to figure out what the stax mafia is doing, please let us know.
We are having a hard time keeping track of it all

[Victor Chew]

Will this measure up in performance against the T2 and the BHSE?

It has has more power than the KGSShv, with lower voltage swing but more current?

This is tempting to build. Less worries with fake semiconductor parts, at least for the amp part.

Edited June 18, 2012 by Victor Chew

[eggil]

I agree with Victor.It really sounds very tempting if it compares favorable to the KGSSHV. Even if it doesn't, I'd like some experience with tubes.

[RudeWolf]

My newbie eye tells me that it may be simpler to build than a KGSSHV. Then again I haven't seen the PSU.

Edited June 18, 2012 by RudeWolf

[kevin gilmore]

This is absolutely at the T2/BHSE level. Remember that 50% of the output tube heat

is filament heat, only 10 watts per tube goes actually goes to make audio.

(ONLY)

Because of the feedback, the prototype actually does .15% thd, and slew rates

of over 100 volts per microsecond.

The power supply is the kgsshv power supply at +/-450 volts. Or the simpler one.

The auto dc balance requires very stable power supplies, so if you build the simpler

one, the output dc will drift over temperature. A triple kgsshv power supply, +300, +/-500 would

give this thing even more output swing. I can do that later. I suppose that you can go completely

unregulated if you want to do really simple.

[RudeWolf]

And there I was hoping for a simple build that would allow me not to hunt for a good SRM1-MK2... That and also tubes.

Btw, isn't that thd a bit on the high side? I know that thd doesn't necessarily show the whole picture but still. In that sense it seems to be "something different".

[Victor Chew]

Looks very exciting.

Will the 6ca7 have to be matched given that it is a parallel pp?

Any chance the attenuator can be incorporated into the circuit to reduce the amount of floating wires?

[kevin gilmore]

.15% for a tube amp? Pretty low... (notice the . )

what i may do later is flip around the input stage and put a pot

in the middle. Rk50/dact is easy.

Board is going to get bigger.

[Victor Chew]

Any name for it yet?

[Horio]

what i may do later is flip around the input stage and put a pot

in the middle. Rk50/dact is easy.

Board is going to get bigger.

I like that idea! A high quality board mounted pot or DACT attenuator sounds great to me.

[spritzer]

The THD is on par with the 727 so not bad for a tube amp. Tube matching is critical so matched octets would be a good idea.

This could be the simplest high end amp anyone can build. The PSU is complicated but it's also pretty forgiving of mistakes so it would be a good noob amp. I do think I could cram the amp section in a 1U chassis but it will not be easy...

As for a name, well we'll have to think about it...

[kevin gilmore]

Any name for it yet?

The Quality goes in before the Name Goes On.

(i've been waiting 35 years to use that one now that it is no longer trademarked)

And you really only have to match pairs.

Edited June 18, 2012 by kevin gilmore

[spritzer]

Pffft... start with the name and demographic then work from there...

[RudeWolf]

Must be all the Dynalo iterations I've seen lately playing with my THD expectations.

[kevin gilmore]

actually someone suggested a name over there for another product. But i like that name for this one.

http://gilmore.chem....du/megatron.jpg

Only the RK27 will fit, both the RK50 and the dact are both much bigger.

i'm having trouble finding the datasheet for the quad, so if someone can find it.

otherwise the board has to get longer.

The pot is at the back near the inputs, and a shaft goes to the front. Same as the T2.

Edited June 18, 2012 by kevin gilmore

[spritzer]

Love the name.

[livewire]

@KG - Here you go:

http://www.familygat...7114_10KDX4.pdf

FWIW, I also have one that I tore out of my KGSSHV when I installed the DACT. (if you desire other physical info about it)

Edited June 18, 2012 by livewire

[kevin gilmore]

Perfect. Sometimes the web is not cooperative.

Will check the fit later.

[deepak]

KG why not use the quad Alpha pot since Birgir has plenty of them?

[justin]

pcb layout tip - if the amp can accept unbalanced inputs, then wire the first 2 sections of the pot for L+ and R+. that way if someone only has a 2-gang pot and only intends to have RCA inputs it will still work

[Victor Chew]

I believe he is now out of them for sale, with a few left for his own use. Besides, this looks like a mega amp with exceedingly high level of performance which deserves the "best" attenuators. Not saying that the Alpha is not good but this just deserves the top notch.

[deepak]

I believe he is now out of them for sale, with a few left for his own use. Besides, this looks like a mega amp with exceedingly high level of performance which deserves the "best" attenuators. Not saying that the Alpha is not good but this just deserves the top notch.

Well it has an RK27 in the latest board layout...

Understandable if Birgir has run out and it can't be used.

[Victor Chew]

Would it be appropriate to have a dedicated thread for this megatron amp once a name is chosen?

[Inu]

I think electorlytic capacitor 220uF/100V is too close to the hot 6CA7.

I know mounting these on other side but...

[Horio]

I believe he is now out of them for sale, with a few left for his own use. Besides, this looks like a mega amp with exceedingly high level of performance which deserves the "best" attenuators. Not saying that the Alpha is not good but this just deserves the top notch.

I'd be fine with the board getting a bit longer to fit an RK50 or DACT (I'll probably use the latter if its an option).

Love the name and I like where this build is heading.

Edited June 19, 2012 by Horio