Mjolnir Audio electrostatic amps
May 26, 2015 at 4:15 PM Thread Starter Post #1 of 82

goobicii

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I am deciding what amp to buy for SR-009....   I narrowed it down to  KGSSHV,BHSE and maybe T2 DIY,atleast I thought so,I was looking where to get the KGSSHV and found this website called  Mjolnir Audio that makes KGSSHV but also some of their own new designs based on BHSE/KGSS....
 
1. KGST  "Just finished another KGST.  This amplifier has been called the mini BHSE and it is a fitting name.  This is a hybrid amplifier and the circuit is similar to the BHSE in many ways.  The power supply is similar and so are the first two amplifying stages.  The main difference is with the tubes used and how they are used.  The KGST uses the tube in a more traditional nature but with the same constant current source as the BHSE.  The tubes used are the 6S4A and they handle the output directly with no extra stages needed.  There are no external heatsinks and the tubes are fully enclosed in the chassis.  Sound wise they are very similar but the KGST is warmer and more forgiving making it a better match to the SR-009.  Like the BHSE it runs very warm so it needs a lot of air to breath.  Similar to the KGSSHV this one has a servo which monitors and corrects the output so warmup is less of an issue."
 
 
2.KGDT "Here is a new amp design from us, the KGDT.  As the name might suggest this is a sister amp to the KGST.  The goal here was to allow to tune the sound more by tuberolling.  On the KGST you can just use 6S4A’s and only them, on the KGDT you can use many of the larger 9 pin dual triodes.  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 comporimisies had to be made to accomodate 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."

 

 

theres more interesting stuff on that website I highly recomend you to check it out.. my question is this,is this legit/high quality? is it build properly as if Kevin Gilmore made it? how does new models sound?   I am looking at amp with loudest sub bass but aso high detail,he says the KGST is warmer that BHSE that sounds interesting,it says "The tubes used here are the 6S4A and they handle output directly with no extra stages needed"  this will probably sound stupid but does that mean its kinda electrostatic equivalent of OTL? make it simple direct and raw to preserve signal quality?

 

BTW feel free to tell me how various amps compare in SR-009,especialy KGSSHV,BHSE and T2 DIY,I want to have LCD x,pre fazor LCD 2 bass from stax,that would be dream come true

 
May 27, 2015 at 2:47 AM Post #2 of 82

paradoxper

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Mjolnir Audio is as legit as you can get. 
 
May 27, 2015 at 4:45 AM Post #3 of 82

nassq8

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Mjolnir Audio is as legit as you can get. 

 


+1 ......

I also stumbled upon Mjolnir Audio a couple of months ago as a newbie looking for electrostatic amp. And I'm glad I did that.

I have Mjolnir Audio's "KGSSHV-mini" and "Dual Differential Amp" all hand made by Birgir (really a very committed guy and a wiz at electrostatic stuff!). I can assure you that the quality of his product is extremely high.

For the performance, well KGSSHV-mini is really an overkill for 009, which has indescribable performance with KGSSHV compared to what I have in my headphone inventory.

For the Dual Differential Amp, it is not as powerful and transparent as KGSSHV , but it has more euphoric impact over 009 sound.

Overall, you will not go wrong with their amp. The guy behind Mjolnir Audio is for sure not a hobbyist but a professional with serious products that other makers should closely watch. But still he does not have a strong commercial presence as other. Strange!
 
May 27, 2015 at 5:03 AM Post #4 of 82

NoPants

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In case it hasn't been made too clear, that is spritzer's site where he sells his absurdly plentiful stock of electrostatic amplifiers. He and Kevin Gilmore designed/implemented most of what he's selling, so you can't really get much more legitimate than that. 
 
KGSSHV < BHSE < T2, each one is roughly double the cost of the last. Whether you want to translate that to better sounding is probably up to your wallet. I think I wrote some other post in the stax thread but you also have
 
KGST = KGSS/HV input stage, tube output with CCS
KGDT lower voltage KGST with different tube choices, similar CCS
Megatron = all tube
Carbon = Silicon carbide mosfets, same CCS
 
I probably listed those in the order of increasing rarity
 
Among the offerings on his site I would probably pick up the KGSSHV in the recycled chassis because I could care less about cosmetics. The 6cg7 looks nice too but Spritzer can tell you if it's appropriate for all the Stax models
 
May 27, 2015 at 12:40 PM Post #5 of 82

goobicii

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Thanks for clarification


I decided I will go with SS amp for my SR-009... I have very little knowledge about these amps I would like if you help me out and educate me a little about how they sound.

Solid state T2 DIY? I constantly reed that T2 is best amp ever made,someone mentioned it could be made into SS,thats very interesting,my inner hipster likes that nobody else have it and it will be best SS amp for Stax right?

Full size KGSSHV..... there is some on board ,outboard,some Sanyo something that is supposedly warm sounding,exactly what I want,I am confused,what should I ask for to get KGSSHV thats perfect for me? I Want maximum warmth and high resolution.Theres some 450w and 500w


and lastly there this new Carbon from Kevin Gilmore,never heard about it before,never saw it,how much it cost,how does it sound,how it works inside how it is different to kgsshv?
 
May 27, 2015 at 12:48 PM Post #6 of 82

paradoxper

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Thanks for clarification


I decided I will go with SS amp for my SR-009... I have very little knowledge about these amps I would like if you help me out and educate me a little about how they sound.

Solid state T2 DIY? I constantly reed that T2 is best amp ever made,someone mentioned it could be made into SS,thats very interesting,my inner hipster likes that nobody else have it and it will be best SS amp for Stax right?

Full size KGSSHV..... there is some on board ,outboard,some Sanyo something that is supposedly warm sounding,exactly what I want,I am confused,what should I ask for to get KGSSHV thats perfect for me? I Want maximum warmth and high resolution.Theres some 450w and 500w


and lastly there this new Carbon from Kevin Gilmore,never heard about it before,never saw it,how much it cost,how does it sound,how it works inside how it is different to kgsshv?

Sanyo parts are supposedly sweeter sounding than the IXY. Is it really noticeable? Ask those who've had both. I'd say get your feet wet with a HV or KGST.
After, if you've found you like stats, investigate a MT, T2 ,BHSE or whatever else. 
 
Lastly, good luck finding a T2/MT builder. There may be a run of T2's sometime, maybe in the future, possibly. Kevin threw out a rough north $10k figure.
AND please be diligent in picking out your builder - making sure he's skilled enough and honest. There have been people that have been ****ed over with commissioned builds.
 
May 27, 2015 at 3:01 PM Post #7 of 82

NoPants

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You haven't specified your budget, and for most intents and purposes the SST2 doesn't exist
----------------------------------------------
I've had both IXYS and 1968 HV's, the difference is not as much as people would have you believe. In a nutshell the 1968 has slightly better extension and the IXYS has a bit more "edge" in the transient decay. I've tweaked the currents for a short period of time, not that big a difference in my experience. I'm sure someone could convince you it changes everything including your clothes if you look hard enough. 
 
KGSSHV onboard vs offboard is just a matter of how the amplifier boards are built. The idea is that the offboard  heatsinks gives the builder the ability to dissipate more heat than the onboard version. As an end consumer your concern is that the offboard version is more expensive because it's harder to build. If you decide that the output current is your top priority then that's what dictates this decision. 
 
450V vs 500V also very little difference, it's more or less a loudness thing. Typically you want to lower the voltage and up the current. In my experience -/+ 400 is more than enough for most stuff. 
 
For the record I have an onboard 1968 and offboard IXYS that are in build progress atm
 
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You're not getting an SST2 unless you spend quite a bit more than 10k imo (like 2x+). The people who are capable of getting it up and running typically don't take commissions. Since you sound pretty new to this I highly doubt you are well-oriented enough to manage a commission of that scale. The most immediate thing is that you're not familiar with what the conversion to SS entails, it's really easy to take advantage of situations like that as the builder.
 
You're better off getting a Carbon if you're married to the idea of "hipster SS", the output devices are the same ones used in the SST2 I think. I've only seen 2 or 3 units. Maybe Birgir is interested in selling his first completed unit, you should message him directly. Should fit your needs if you really need to go solid-state. I wouldn't really call SS the "hipster" choice, but the Carbon certainly could be classified as such because of how new/rare it is. The cost of parts for the build I'm looking at is more expensive than a KGST, due to the need for offboard heatsinking.
 
It sounds like what you're after is the KGDT, all things considered. You might be able to fulfill some hipster desires by seeking out some obscure tubes that can be used in the amplifier. There are tons of choices for 12BH7/6CG7, and there's a much longer list of usable tubes. Pretty sure the 009 doesn't require higher voltages than -/+300. You also only need 2 tubes, and matched pairs are easy to come by.
 
The real hipster options for Stax amplifiers are the all-tube solutions in my opinion, because Kevin Gilmore has popularized so many DC-coupled amplifiers.
 
Maybe I'll make a flowchart for this BS
 
May 27, 2015 at 3:21 PM Post #8 of 82

goobicii

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NoPants,I was joking with the hipster part,what I am really trying to find is whitch of these amps have most sub bass,whitch one is warmest,I am comming fro audeze x and I want sr009 to get closer by getting some warm amp... I heard sanyo HV is warmer than BHSE,also its SS thats perfect combination,but what about T2 and Carbon and Megatron,how warm are these?
 
May 27, 2015 at 3:56 PM Post #9 of 82

NoPants

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Everything is warm, but less than 65 C if nothing is amiss
 
the KGST is "warmer" than the KGSSHV. It shifts some of the mids closer to center stage and takes some of the edge off the treble that the 009 is known for. Pretty sure only ~2 people have heard the carbon, so to paraphrase Birgir it seeks to achieve similar goals as the KGST but in solid state form.
 
I can't comment on the T2, just that it's unobtanium- to the degree that you shouldn't consider it a viable option unless you're going to build it yourself. 
 
Megatron is probably the "warmest" and you get to control a lot of the presentation with the ability to swap 12au7 and 12ax7 in the amplification path
 
May 27, 2015 at 4:06 PM Post #10 of 82

kevin gilmore

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Birgir, Joachim and I have working carbons.
I really like mine. Its close to a solid state T2 without
the massive amounts of parts. Grounded Gate.
 
Joachim actually machines his own circuit boards and has
a mirror image pair, board files on my site.
 
Newest version has the wide range servo. No adjustments.
Just set the balance once, and done.
 
That servo is going to show up in everything at some point.
 
The megatron is the warmest amplifier of the bunch, great
for those cold winter days
tongue.gif
 
 
Ebony knobs required.
 
(finally after 5 years got a perfect piece of very dry and very old ebony enough for about 5 knobs)
 
The Circlotron is going to be late. BECAUSE... all these upgrades and modifications
including new micro sized step attenuator, ssdynalo and ssdynahi surface mount version, Current feedback amp 2,
zero feedback balanced amp,tube/solid state dynamic... keep eating up time.
 
board pictures from the other thread
http://gilmore.chem.northwestern.edu/kgsshvcarbonservo.jpg
http://gilmore.chem.northwestern.edu/kgsshvcarbonstereo.jpg
 
May 28, 2015 at 10:43 AM Post #11 of 82

customcoco

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What would you think about the KGDT if it was to be used with an O2MkII ?
 
May 28, 2015 at 12:12 PM Post #13 of 82

kevin gilmore

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for safety reasons the circlotron has to be in one box.
 
otherwise there would be an umbilical connector capable
of 8 x 1000v+ connectors. (those things are brutally expensive)
 
the lemo version is about $400, and you would need 4 of them.
 
whether its actually one circuit board or not is still under discussion
 
May 28, 2015 at 1:31 PM Post #14 of 82

NoPants

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Can you enforce this by drawing a monolithic psu+amp channel board? Free dual mono marketing
 
May 28, 2015 at 1:35 PM Post #15 of 82

NoPants

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  What would you think about the KGDT if it was to be used with an O2MkII ?

 
Birgir said it works fine with 007s, for the KGDT running at 300V. I myself have tried the KGSSHV at 350V and I had no problems with headroom/volume.
 

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