Nanotube: the newest electrostatic amp by Kevin Gilmore!

[Music Alchemist]

Most exciting news I've heard all year: Kevin Gilmore has designed a new electrostatic amp called the Nanotube!
 
You can read some of the background info in various posts here.
 
I'm thrilled about this amp! DIY only, of course, but by the time I can afford it, it should surely be readily available. (People are speculating that it will cost $10K, $15K, or more!)
 
Anyway, I suppose this thread would be the most convenient place to discuss it and eventually post impressions.

 

[Earspeakers]

I'm not clear on all the details, Kevin if you could help me
 
The Nanotube is a SiC Circlotron from what I understand.
 

1. Is this the latest known working PS board?
   circlotronhvpowerdualnewer2.ZIP

 

 

1. Is this the latest known working output board?
   kgsshvcarboncirclotron.ZIP

 

1. And latest known working driver board?
   kgsshvcarboncirclotrondriver.ZIP

 
 

1. Are these ready for experienced DIY?
2. Who supplied your trafos? Any special notes
3. Any special build notes other than
   1. single chassis as we're near kV
   2. mil-spec teflon wire
   3. HV DMM probe
   4. ceramic heatsink standoffs where needed
   5. lift resistors
   6. any special component notes - resistor/cap specs?

 
Thanks so much, as always I look forward to the build
 
Edit: For reference Kevin's notes
 

all of the circlotron boards have now been published and i believe that they are all
final versions. There were a couple of very minor changes in the last few weeks
related to moving connectors to various places etc. i'm super happy with it.

there are a total of 4 floating high voltage power supplies, 2 high voltage power supplies
referenced to ground, 2 low voltage power supplies referenced to ground, and a bias
supply also referenced to ground. Then there are 2 driver boards and 2 output boards.

the final piece of the design is an opto isolator controlled adjustable output stage
bias. likely similar to the nelson pass design that uses an opto isolator for bias
control, although i have never seen that design. As designed, 20ma minimum,
25ma maximum, although the bench prototype has been tested to 50ma.
This amplifier will do full voltage swing at 20khz into a standard headphone load.

what is a circlotron output stage..

a fully balanced push pull output stage with 4 devices.
2 of those devices are (npn,mosfet,jfet,tube)
and the other 2 devices are floating power supplies

this is the first production push pull otl electrostatic amplifer
that i know of

a circlotron output stage has no voltage gain, but has
lots of current gain. it could be class AB or class A.
(sumo9 was class A, my amp is class A, the atmaspheres are AB)

a circlotron output stage is VERY fast. hundreds of volts per microsecond.

a circlotron output stage is very low distortion, cancelation of 2nd harmonic
distortion exceeds 6db.

the output dc voltage is fixed at 1.8 volts with respect to ground.
For an electrostatic amplifier, this is of no concern. I could add
a bunch of extra parts to deal with this issue, but there is no
reason to.

this amp is as much fun for me as when i listened to a T2 for the first time.
the tendency to crank it to 11 cannot be ignored.

and the best part, 100% available mouser parts and it fits in
a standard chssis (the 5U thing) 

 

[Music Alchemist]

Since we're posting notes here, I'll share the rest of them, in case anyone doesn't want to bother reading through the thread they were originally posted in. Hope that's alright.
 

circlotron is capable of more than double the output current
(subject to heatsink size) up to 50ma per driver
 
lower distortion by a little bit
 
faster in general with a very extended frequency response
(>250khz)
 
Lots more parts
 
4 floating ONE THOUSAND VOLT power supplies
 
basically a Ragnarok on steroids.
 
Jason might want to comment about doing a circlotron at
these kind of voltages. (or he may run away screaming)

lots of people built T2's.
 
this is less parts in total, and they are all available.

 
And my favorite part:
 

works with every electrostatic headphone.
koss and he90 included.
 
amazing on sr-002

 

 

[kevin gilmore]

The form factor of that dual 900v supply does not fit the box.
 
There is a singles version of the power supply (you need 2 per channel)
that is form factor compatible with the 5U amp chassis. The latest version
of the singles 900v supply also includes the layout for the 4 wire mundorf
electrolytic caps, which are very sweet. (non magnetic, copper wires etc)
 
This really needs to be a one box amp for safety reasons.
 
There are also the "fat" versions of the ground referenced hv supplies
that are also suitable for the 5U chassis.
 
if you want to get even more silly, there is the goldenreference ultra
accurate, ultra low noise power supply, which was just tested
and works as designed. this replaces the standard dual low voltage
power supply.
http://gilmore.chem.northwestern.edu/goldenreferencedual.jpg
 
in addition I'm working on an ultra low noise, ultra stable, and fully
adjustable digital bias circuit.  (electrostatic bias)
 
the output stage adjustable bias circuit control will come later, currently
its a pot that you set once, 10v for 20ma and 8v for 25ma.
(yes its upside down to make the servo simpler)
 
The 900v power supplies use the 1kv connectors, and require
1kv rated Teflon wire.  But very short distances between the
supplies and the output board.

 

[Music Alchemist]

@kevin gilmore
 
If it's not too much to ask, could you post photos of your Nanotube amp?

 

[kevin gilmore]

I do not post pictures of hand wired prototypes that run on stacks of
bench power supplies. Sorry, don't want people trying to duplicate
stuff like that.

 

[Music Alchemist]

  I do not post pictures of hand wired prototypes that run on stacks of
bench power supplies. Sorry, don't want people trying to duplicate
stuff like that.

 
Ah, I see. Guess I'll have to wait until the later stages then, when others have started building it. Really hoping Birgir will, since I don't know where else to look for it.

 

[kevin gilmore]

you can look back to the T2 project to see how this is going to progress.
the only difference is that I'm not doing custom chassis, because
 
1) I don't need to this time
2) I would rather not up front $35k and loose $2k in the process
 
I will be supplying drill files for the heatsink etc. So in the end, this
will be as easy to build as a T2.
 
if you want to build it earlier, and you have the abilities to do the
chassis work, then by all means make it easier on me.
 
I still have 2 dht amps to finish.

 

[Music Alchemist]

Someone I used to talk to on a frequent basis is building a T2...very slowly. Since the parts for the Nanotube are apparently easier to get, I have high hopes that the DIY builders out there will create an environment that will allow those of us interested in buying the amp to do so. (I certainly don't have the knowledge or skill to build one myself!) What I'm confused about, though, is how the DIY T2 and Nanotube will compare in terms of sound. Ultimately, I just want the best amp available, but perhaps it's not so simple. Maybe they both excel at different things...

 

[kevin gilmore]

complete production board set (ok, I forgot the stax jack board)
 
http://gilmore.chem.northwestern.edu/circlotronboardset.jpg

 

[wink]

Noice....!!!

 

[Earspeakers]

I and others have got boards in hands, but this will take some time and care. Queued behind other projects too. 

 

[bmichels]

Nanotube, Circlotron, Megatron.... so many exciting "high end" variations ?  
 
will some be available other than DIY ?? 

 

[theboch]

  Nanotube, Circlotron, Megatron.... so many exciting "high end" variations ?  
 
will some be available other than DIY ?? 

 
Those mentioned are all pretty complicated designs. So If someone would build one "on order" it will be pretty expensive...

 

[soren_brix]

For those interested, a few sets of Circlotron boards from the Group Buy at 'the other place' is available here
 
All PCBs are from PCBNet: 3oz copper (ALL boards to build the Circlotron is included)
 
4 x HV900 Golden Reference High Voltage Power Supply boards 
2 x Driver Boards
2 x Output Boards
1 x Split Golden Reference High Voltage Power Supply includes BIAS supply (580V)
1 x Split Golden Reference High Voltage Power Supply includes low voltage supply
 
16x 470uF/550V, for the HV900 batteries
4x 680uF/550V for the HV PSU
 
(This is excess from a recent Group Buys, so not a whole lot in stock)
 
 
The kit can be used for building a KGSShv Carbon, as the driver board is almost similar to the Carbon v5 amp board although it takes a few tweaks in rgrds to servo and feedback loop.
 
/S