[zolkis]

Was wondering the same thing when I saw the for sale post of the kgdt. Tempting at those prices which includes the 007 sz1 versions...yay or nay?

 
Yay, big time. It's a fair and good deal. I am pretty sure the amp drives the 007 well enough - the similar Erik Konka amp did as well at similar price, and Mjölnir make is probably the best you can choose for Stax. I don't want a 3rd 007, so I stay clear, but I must say it's tempting to buy just for trying it and then selling on .
 
Additionally, you can improve (or at least tweak) the sound of the 007 to your liking by
- playing with fit (bend the headbands for proper fit),
- by experimenting with taking out the springs from the ear pads,
- by reversible-modding the earpad stuffing (cutting the 4 mm white foam disk off from the yellow foam and optionally replacing them with thin carbon foam disk or crescent moon shaped pieces),
- by buying 009 pads (and mod them too). There are a lot of options, and most of them are described in the mods thread, anyone can try them.
I haven't played with the SZ1 series yes, but based on what I heard about alleged differences between the SZ1 series and 70xxxx series, it is possible that after mods they may sound even better than the early models.
 
So far the only headphone I could not make sound quite much better with (earpad) mods is the 009 - although I could make it sound warmer with more bass and less 1-4K mids, in the end I think the original sounded closer to the truth (with classical and instrumental), and it felt like a sacrilege using the 009 just for fun. A reference ought to stay a reference .

 

[astrostar59]

Was wondering the same thing when I saw the for sale post of the kgdt. Tempting at those prices which includes the 007 sz1 versions...yay or nay?

I would never say buy it as I haven't heard it. Also why so few of this build? Is it the KGST is better? Too many if's and don't knows. 

 

[sarora]

 
I would never say buy it as I haven't heard it. Also why so few of this build? Is it the KGST is better? Too many if's and don't knows. 

 
I explained why it's not that popular. KG/Birgir @ Mjolnir-Audio who makes the amps doesn't have unlimited time. He sells what he has in stock...I've talked to him about it when I purchased the amplifier (KGDT). The KGST was in active production and the KGDT was drawn up by Kevin Gilmore and Birgir and then released on Head-Case where they are very active, not here. You will find more info about things there..anyways, at the time he was moving and had as stuff was sold, he would remove it off the site. If you see my post a few back, I quote some stuff where Birgir explains the KGDT -- it is the sister amplifier of the KGST. It is very similar, but has the option of tube rolling. All of Mjolnir-Audio's stuff is excellent, no doubt, and the constant current source design allows your headphones to actually be able to utilize up the 600Vpp / ~380Vrms swings that the KGDT provides. Before I even bought the amplifier it was advertised as having very good control over the 007 MK1.
 
However, the slight compromise is that there is less current than the sister amplifier (KGST) which was already known, and thus the KGDT is warmer.  Again, here's a direct quote: 
 

The amp was designed around the ECC99/12BH7A and the 6N6pi/6CG7 but others will work assuming they have similar specs and the same pinout.  The circuit board has a simple toggle switch to select single 6.3V heater or a center tapped 12.6V setup.  Now some slight compromises had to be made to accommodate  these tubes so the rail voltages are a bit lower than on the KGST and there is a bit lower current running through the output stage.  This is done so that the tubes can’t be run way too hard and thus not last long.
The sound of this amp is very similar to the KGST and so is the performance.  Great control of even tricky phones like the SR-007 Mk1 plus the ability to alter the tone of the amp with different tubes.  117V or 230V are no problem as the amp has a switch inside like all my new amps.

 
 
The amplifier, as all of his work, is very well designed...and it's very similar to the KGST. However, from an economics standpoint and limited time in a day/opportunity costs, the demand for the Carbon (which is $4600 vs. $2200 - what I paid for the KGDT - and the KGST is $3000 for reference) as well as the highest-end amplifiers they make is very high as you can see it if you go on Head-Case or read the company site, as you see with many flagships that are excellent....and if you have the money and setup for it, it's an amazing amplifier no doubt.
 
But I am certain he is focusing his attention on building and stocking the Carbon as well as improving designs for the future with Kevin as they often do for projects. You can see that just looking at their activities on the forums of Head-Case..not here.
 
Anyways, tl;dr -- in my opinion the amplifier lives up to what it was advertised, and has the quality of his other products - build/chassis, component quality, craftsmanship, proper design (constant current source here, AC heaters) and things like easy switchable mains power for 115/230V and the passive XLR outputs to extend or connect the audio chain easily -- all of these things are found in their other amplifiers and that is certainly not lacking with the KGDT.

 

[paradoxper]

What a sales pitch. 

 

[sarora]

What a sales pitch. 

Glad you liked it!

I'm allowed to speak my experience, correct some information if it becomes relevant, and it indeed becomes relevant when someone puts off work from an otherwise very reputable group that you would agree with no problem - just because not many people here talk about it and so it must be terrible. The KG designs are all very good and they're all respectable people that aren't going to sell garbage even if I paid $2200 and not $4600 for the top of the line amplifier which they make and no one would say a word about.

And my sales pitch is explaining how I feel about it with actual data said by the guy who designed the amp himself...most of it was stuff I got clarified *before* I even bought it, so if anything I'm defending the product.

I don't expect any of you guys to buy this; I assume you have your own Stax rigs. But I will chime in when something is said like this is off limits because "who knows?" when you can find stuff from an owner of the product like me, the designer's comments directly, and things from where they mostly hang out...on head-case (not here).

 

[paradoxper]

Glad you liked it!

I'm allowed to speak my experience, correct some information if it becomes relevant, and it indeed becomes relevant when someone puts off work from an otherwise very reputable group that you would agree with no problem - just because not many people here talk about it and so it must be terrible. The KG designs are all very good and they're all respectable people that aren't going to sell garbage even if I paid $2200 and not $4600 for the top of the line amplifier which they make and no one would say a word about.

And my sales pitch is explaining how I feel about it with actual data said by the guy who designed the amp himself...most of it was stuff I got clarified *before* I even bought it, so if anything I'm defending the product.

I don't expect any of you guys to buy this; I assume you have your own Stax rigs. But I will chime in when something is said like this is off limits because "who knows?" when you can find stuff from an owner of the product like me, the designer's comments directly, and things from where they mostly hang out...on head-case (not here).

You take the cheeky much too serious.

 

[astrostar59]

  You take the cheeky much too serious.

My view. just get a KGST if he wants tubes, bigger user base, known sound quality. Or go for a KGSShv Sanyo as I know that is a great amp. as I had one.

 

[sarora]

  You take the cheeky much too serious.

 
Probably. Been awake longer than I should working so excuse my defensive language, lol. 

 
 
And yeah the reason this is just coming up is simple price....sure if price is no object go for it. I am not forcing anyone to do anything here. Just trying to justify my price. And forgetting about any one person here, I think it is pretty fair considering the prices for those amplifiers you just mentioned what I'm asking for with respect to the stuff I told you about the experience as well as the similarities and direct quote from the guy who made it....nothing new here. I was just getting the feeling that half of you think that the amplifier is worth about $500 and is essentially garbage from an otherwise excellent company because no one speaks about it on Head-Fi yet that isn't really a fair thing to say.

 

[JimL11]

   
I am pretty sure the amp drives the 007 well enough - the similar Erik Konka amp did as well at similar price, and Mjölnir make is probably the best you can choose for Stax.

I haven't heard the Konka Nebuchadnezzar amp, but based on an internal pic of one that sold on Head-Fi within the past year, it appears to be a variation on Gilmore's all triode amp from the 1990s, which is a completely different design from the KGDT and KGST.  The all triode amp is all tubes, with output plate resistors.  The Woo GES is, as I understand it, a similar topology.  Neither the all triode amp, the GES or the Konka have constant current loads on the output tubes, and so will not have the drive capability of the KGST or KGDT.

 

[astrostar59]

I hope it issn't anything like the Nebuchadnezzar amp as that got dissected / slated by Birgir.

 

[sarora]

The GES from Woo has/had a potential issue with the bias supply ballast resistor where it was incorrectly done or just not there in some of the older models at least, so over time your Stax headphone diaphragm would be in danger of destruction to put it nicely...

Birgir fixed the issue and added a few tweaks for balancing and power delivery with The Ocatave amp which they still sell and is his take on the GES.

As mentioned by Jim, KGDT/KGST aren't the same at all. They are essentially hybrid amplifiers and they don't have the issue that the all-triode GES had. I don't think The Octave has any issues as he wouldn't be selling it if it did, and I know it's modified from the old Woo GES design.

The Octave was described to me as being very warm and not ideal for the 007Mk1 as they're very picky, so I didn't buy it. Originally I was actually going to go with The Octave as I like tube designs (when done right). But yes, the KGDT and KGST have much more control over the voltage swing due to their design and constant current source. There is absolutely no noise even at maximum volume on the KGDT and I'd assume the same for the KGST.

By the way, there does seem to be one person who had experience with the KGDT besides me: http://www.head-fi.org/t/769105/mjolnir-audio-electrostatic-amps/15#post_11660846 but he hasn't posted recently. However I would agree with what he's saying re: the option to tube roll if you want to tune and the price (you can't tube roll by design with the the KGST).

 

[CalvinW]

Does anyone have any idea what volume pot Mjölnir amp uses? 

 

[Tinkerer]

  Does anyone have any idea what volume pot Mjölnir amp uses? 

Depends on the amp, but usually an Alpha or an Alps pot.

 

[sarora]

I believe he started to use Alpha potentiometers as he said they perform better in his testing for all his amplifier builds (read that on Head-Case) going back to at least the beginning of this year.

 

[Pale Rider]

My Carbon CC [built this year] has an Alps RK50 pot in it.