Transformer coupled electrostatic amps

[n_maher]

Good lord, Frank, that's just beautiful.

[Emooze]

Good lord, Frank, that's just beautiful.

My words exactly. That picture is my new computer background.

[nattonrice]

That looks awesome!~

Did you do each Cu pipe with hand tube benders or do you have a roller?

Crazy uniform =S

[HeadphoneAddict]

That is pretty awesome looking. You are an artist.

[boomana]

Gorgeous.

[crappyjones123]

amazing work sir. truly beautiful.

[FrankCooter]

I really appreciate all the positive comments and encouragement! It's definitely part of what inspires me to keep building these dinosaurs.

This was kind of a two phase project. I was attempting to build the simplest possible all DHT electrostatic amp, but I was also interested in exploring a new chassis concept.

The chassis is solid Gabon ebony with a 1/8" copper top plate. Tubing is plain old Home Depot 3/8" copper water tube. The tubing was cut and bent with basic hand tools. Not a fun task, and I have a pile of pieces that didn't quite fit. I polished them in a drill with 400 grit wet/dry, then spray laquered them. Kind of crude, but it worked.

The design emerged out of my affinity for all things Art-Deco. In this particular case, the inspiration was a movie theater marquee. I've been looking for something more rounded and organic, more "tubelike", than the rectilinear forms I've previosly used. I wanted something that was "retro", yet at the same time modern and futuristic. I like this sort of style and intend to explore it further. One of my "pet peeves" about the age we live in is the death of industrial design. Where is Raymond Lowey when you really need him?

The amp is still a "work in progress". I'll have more about the circuitry and sonics later.

[Voltron]

This amp better be at MOA II! The look achieved all of your design objectives and more Frank. That is really something.

[morphsci]

That amp belongs in an art museum. That is a beautiful design Frank.

[Dusty Chalk]

The design emerged out of my affinity for all things Art-Deco. In this particular case, the inspiration was a movie theater marquee. I've been looking for something more rounded and organic, more "tubelike", than the rectilinear forms I've previosly used. I wanted something that was "retro", yet at the same time modern and futuristic. I like this sort of style and intend to explore it further.

Thanks for the explanation, I do think you captured that look well.

And I know what you mean -- one of my music loves is synthpop. And sometimes, when I'm waxing eloquent about it, and talking about its purity, I'll say something to the effect of, "it's what the future sounded like back then, and it still does". "Futurepop" is one of the terms that they used to describe one of the subgenres now, and I mentally always prefix it with "retro-".

[Torpedo]

Really wonderful Frank. Very few pieces of gear become artworks like that

[manaox2]

Geeez, that is amazing looking Frank. I definitely wow'd.

[FrankCooter]

This one's going on the shelf until I can afford a second set of proper magnetics. As is, it's not something I would take out in public. There's some promise, but in addition to the restricted bandwidth, there's a bit of flatness and lack of resolution compared to the D3A/7403 zebrawood amp. I'll try again when I'm able. And no matter what, it was definitely a valuable learning experiance. The big lesson is that electrostatic headphones, because of their low sensitivity if nothing else, are quite compatible with DHT's. Even with a gain of over 400, no special measures were required reduce hum and noise to acceptable levels. Building an all DHT dynamic headphone amplifier for something like a Grado is much more challenging in this area.

A valuable find was the 2E22 directly heated pentode that was used for the second stage. This tube is the big brother of Pete Millet's favorite 307A. Triode wired, this tube is a very interesting substitute for a KT88 or EL 34. Premium European examples run only about $40.00. I'm going to convert the 7403 in the original amp to a 2E22 and see what happens. If it works out, then I intend to install a switchable CCS load for the D3A. I think it would be interesting for the listener to switch between a classical interstage transformer and a modern CCS plate load. Maybe there could be a blind "taste test" between the two topologies at the next meet.

Thanks again for all the kind words! I'll be back with something new in the not too distant future.

[doc]

Hello to All,

this is my first post here.

I was looking for such a thread for a long time.

I can read about/look at very interesting, inspiring things here.

There is very little on the web about SE Amp driving a electrostatic headphone and I don't know why, since I believe that if you split the signal at the beginning of an amp, the following stages will change the symmetry of the signal.

I recently got myself a Stax Lambda Nova Classic/SRD7mk2 and feeding this through my "EL84 direct coupled to 2A3" Amp (http://www.tubemaster.de/e-diy-EL842A3.html) and a modified Revox B226 CD player with tube out, so there is only one capacitor (V-Cap CuTF) in the direct signal path from the DAC to the Speaker.

It is very exciting to listen to and the sound is very good and it is plenty loud - more than enough for me.

So at the moment the signal from the 2A3 is being transformed down by the OPT and then up again by the SRD7mk2.

My question to all the experts here is:

Would I gain sound quality by modifying my amp with a (interstage ?) transformer (1:2 ?) to connect the primary to the 2A3 and the secondary to the elctrostatic headphones?

I guess I would.

I am hopeless with transformer coupling and their specs, but willing to learn.

Could I use a Lundahl 1677? Maybe a amorphous core 1677?

Or should I get a custom transformer from Electra Print and what would be the specs to ask for? Bandwidth should be 25Hz-20kHz.

How will my 2A3 see a 3k load when on the secondary there is "only" the Stax phones?

This is what I don't understand.

Hoping for some help and hints.

Torsten

[doc]

Hello to All !

This is my first post here.

I was looking for such a thread for a long time.

I can read about and look at very interesting, inspiring things here.

There is very little on the web about SE Amp driving electrostatic headphones and I don't know why, since I believe that if you split the signal at the beginning of an amp, the following stages will change the symmetry of the signal.

I recently got myself a Stax Lambda Nova Classic/SRD7mk2 and feeding this through my "EL84 direct coupled to 2A3" Amp (http://www.tubemaster.de/e-diy-EL842A3.html) and a modified Revox B226 CD player with tube out, so there is only one capacitor (V-Cap CuTF) in the direct signal path from the DAC to the Speaker.

It is very exciting to listen to and the sound is very good and it is plenty loud - more than enough for me.

So at the moment the signal from the 2A3 is being transformed down by the OPT and then up again by the SRD7mk2.

My question to all the experts here is:

Would I gain sound quality by modifying my amp with a (interstage ?) transformer (1:2 ?) to connect the primary to the 2A3 and the secondary to the electrostatic headphones?

I guess I would.

I am hopeless with transformer coupling and their specs, but willing to learn.

Could I use a Lundahl 1677? Maybe an amorphous core 1677?

Or should I get a custom transformer from Electra Print and what would be the specs to ask for? Bandwidth should be 25Hz-20kHz.

How will my 2A3 see a 3k load when on the secondary there is "only" the Stax phones?

This is what I don't understand.

Hoping for some help and hints.

Torsten