Leaderboard

I was going to name it 'Double the Carbon, double the voltage, double the fun', but I'm afraid that would be too wordy. Ever since I measured the output swing capability of the Carbon, I wanted to see if it can drive my ESL speakers. To do that, I'd need a beefed-up version that can output at least 1kVrms before clipping. That's 1414V peak, out of a ±750V to ±800V PSU. To simply scale up the Carbon amp and the GRHV PSU without major changes to the PCBs, a few hurdles would have to be overcome. First is the 900-V rated 10M90s in the cascode CCS that bottom out with ±450V PSU. When I was browsing the high voltage FETs at Mouser, I found the UnitedSiC UF3N170400B. It's a 1700V 6.8A SiC JFET, naturally in depletion mode, perfect for the upper device in the cascode CCS. The threshold is about 9V, which helps the DN2540 to get further into the constant current region yet keeps the power dissipation still in check (no heat sink needed even with the TO-92 package). The drawback is the package. The TO268-7 isn't too friendly for a DIY thermal solution. I had a few carrier boards made with aluminum-based PCB. According to simulation, the little board would give me 9 degree temperature difference from the package case to bottom of the board when the FET is dissipating 9W. I chose black solder mask, hoping to get a bit better heat radiation capability. 10 boards cost me about $3 at JLC. They also have copper-based PCB with a special process to have the base copper flush with the top surface for a much, much higher K. Too bad the NRE is about $150, so I chose the cheaper route with aluminum. The insulation is good to 3kV so this board can be bolted directly on the main heat sink without additional insulation. Isn't that great? The next bottleneck is the 600-V rated STN9360 when the PSU voltage reaches ±600V. I replaced them with the 900-V rated 2SA1968s. Thanks to the cautionary words from spritzer, I started cleaning up traces with high voltage differential that are getting too close to each other. I removed the middle pad 'A' in the 10M90s footprint, and re-wired a couple of traces on the back. With the bias changed from 24V to 13V above B-, the JFET can be used as the output device as well. At almost $10 a pop, they are considerably more expensive than the SiC MOSFET they are replacing. So the full-JFET configuration shown below is more of a proof-of-concept than anything else. The feedback dividers are changed from 200k:200 ohm to 440K:470 Ohm to maintain the gain and allow the output swing to double, without having the feedback current overtaking the idle current through the input JFET. Two 10pf 1KV caps are in series as a 5pf cap, since I don't have the proper 2kV rated caps. Not a great idea. I was lucky it didn't blow up. Technically the board is now ready for up to ±850V. I tested the SiC-JFET 'doubled carbon' config with ±400V PSU. The performance is slightly worse than the original Carbon. Is it worth the effort? We'll see. (To be continued...)

I just can't help it. There's something about him...

Finished up the week at Milo & Otis siding, screen & vent repair, in preparation for what may be an epic paintjob on Mayberry Manor.

sure. and i have 4 original esl63 transformers in stock. (2 transformers make a center tapped pair)

My GMT which I bought new in Jan 1990

Nick Cave and Warren Ellis all morning. La Panthère Des Neiges/Carnage/Ghosteen.

Egg, toast and potato cake from last night's left over mashed potatoes.

Went to see Wagner's opera Lohengrin last night at the Royal Opera House, Covent Garden, London. This was the final part of my awesome series of birthday presents - this one from my wife, long planned and two months afterwards. It was bloody awesome. Everything was perfect - the setting, the set and lighting, and an Internationally renowned top flight cast of singers. https://www.roh.org.uk/tickets-and-events/lohengrin-by-david-alden-details With various courses of an excellent meal in the intervals. Carole was not a Wagner fan initially - but I've converted her. She was in tears of emotion by the end of the overture to Act 1 (honestly - so was I!). Now Wagner the man was a loathsome individual. Anti semitic, hateful towards his contemporary composers, and impossible to work with - a micromanager from hell. He described Brahms as "That bastard, Brahms", and put it about that Brahms' music was inspired by shooting birds from his balcony with a "Tyrolean bow" (there is actually no such thing) and listening to their dying cries. His dreadful reputation was not helped by Hitler being a Wagner fan, and it representing the pinnacle of music for Nazi National Socialism. Putting the awfulness of Wagner to one side - he was one hell of a composer! You just have to divorce the man from the music.

I've had my eye on these for the last year or so but waiting for a cheap set to come up. There are three versions they sell and I found the cheapest one for sale, brand new in the box with the transformer adapter. I'll take some pics of the system tomorrow (shortest day of the year here so... yeah not great for photos) but I've at least a pic of the headphones and the internals of the transformer box. Here they are and I quite like the looks and the build quality. They are using mini XLR's which is not ok but questionable connector choices are a theme here. The stock cable is beyond crap (more on that tomorrow) so I'm using a Stax PC-OCC off my RR-1's. They feel substantial but also light and fit my head snugly at the largest extension. Carbon Fiber headband and the leather is nice. On their site they claim the Minima is supposed to have pleather earpads but these are clearly genuine leather. These look very similar to earpads I've bought from China in the past and nothing wrong with the quality. I shone flashlight through the driver to you all could see the structure, very unusual drivers here. Now onto the adapter box... yeah this is not good. That's it... and yeah there are so many issues here. Let's start with this gem: It's hard to capture on "film" but the IEC input and the fuse holder are completely uninsulated and mere millimeters from the metal frame of the transformers. Thankfully the chassis is earthed but yeah, this is not to code and an instant CE violation there. In the first picture you can also see there is no protection for the transformers at all and we will get to why that is an issue. Now the active parts: The bias supply is driven directly off the mains, no isolation between you and the wall. Now this was commonplace in the 70's but now... I'm not sure this meets any modern standards. The bias supply is a simple voltage doubler and for 117V they just add another doubler on top. There is then a 600V zener clamp to make sure the bias doesn't rise above that threshold. None of this has the elegance of the Stax bias supplies and frankly this is just sad. For instance the LED for power indication is driven directly off the mains, through one tiny resistor. Now you might notice those 3 pin XLR's there and yup, they are the stock outputs for the Euridiche, the Stax output is just for convenience. One of my biggest gripes is with using XLR's as they are in no way rated for these voltages, especially the cheap, no-name, units they are using. Also check out the clerances on that PCB.. bias and high voltage signals less than 1mm apart. Then we have what scares me the most, see those traces which go right to the edge of the board and into pin 3 of the XLR's...? Yeah that is the bias so 600V is sitting there, pressed right up against the chassis with exposed solder connections. Sure this is after the ballast resistors (one 4m7 for the Stax and separate 10M units for each side of the XLR's) but still... They have a lot of faith in the powder coating on the chassis. Finally the Stax socket, 3D printed and fed directly off the XLR sockets. Almost no way to actually cram a Stax plug in there but you know, I almost had to use a hammer. 😉 Then we come to the final issue, on paper these appear to be Stax compatible despite the stupid XLR connectors and similar bias supply but nope... they are so inefficient that my usual test amp (Icepower 50 module with a preamp tacked onto it) was at max volume to get these to my normal listening level. I plugged in my test SR-207's as well and they were at half volume using this transformer box. As seen in the first pic, I've fitted them with a Stax plug but they make the Carbon CC work for its pay so yeah, you need a very powerful amp to drive them. Now finally, how do they sound... pretty damn nice actually. 🙂 This is off the Carbon CC prototype in my rig right now and they are very balanced sounding, slightly dark sounding but very mellow and open. They are not overly forward or bright, unless when called to be and I can listen for a few hours with nothing bad to say really. Bass is plentiful and deep, midrange has a nice presence to it and the soundstage is pretty good. Top end is a tad dark but it is very mild and they make for a relaxing and pleasant package. So TL;DR... great headphones that are let down by being too inefficient, frankly unsafe transformer box and stupid cable/connector choices. Change the cable to Stax and drive them off a powerful amp and the sound is great.

Way to go, Kasparov...

vojne vojne

actually for 4cx250, maximum power supply would be +/-1000 volts and forced air cooling for the tubes 3-500z much better. maximum power supply would be +/-2000 volts no forced air cooling after that it gets really large really fast. all tube golden reference power supply is not that hard. custom transformers will have to use very high voltage wire. will look like flyback transformers from old crt color tv.

maybe it can direct drive Quad electrostatic speakers bypassing the speakers in built audio step up transformer 🙂 Kevin, maybe we need a super high current and super high voltage golden reference psu?

start with a megatron and change the 8 output tubes to 4cx250 then use +/- 3000v power supplies far more fun. and just a slight bit more dangerous.

A fun guilty pleasure listen.... Japanese Female Pop-Punk band, Otoboke Beaver. That Yakitori song repetitiveness reminded me of this old gem:

Picked up a gift certificate at a local spa for my wife for Mother's Day. I wanted to give the monetary equivalent of three 50-minute massages ($87 each). The person getting the GC for me asked her co-worker what 3 times the price was, and before she could even pull out the calculator, I told her the amount. They both stared at me in awe, the second one double-checked my "work" and proclaimed I was right. they spent the next few minutes completing the card, and talking about how good I was with math. Scary.... They certainly LOOKED lovely.... 😂

Said by the person that actually likes Houston summers.

Learned how to engrave with my milling machine today. It's an original Kevin Gilmore et. Al. DIY T2 amplifier with original parts.

If you don't like the personality of the forum, why the everloving fuck do you keep coming back? Seriously, stop fucking whining. We get it, you love the pile of hot garbage to the point you're willing to look like a paid spokesmodel. You posted a diatribe on shill central, and pointed people here to it. It was pointed out why it's hot garbage. You said you don't understand the words that were used, but you love the beautiful beautiful music. Cool. Now you're just urinating in the oscillator. If you wait out your time out, and have a reasonable conversation, then you're welcome to come back. This isn't head-fi. It's intentionally not head-fi. It was created by people that were more than familiar with head-fi, and moved over here to get away from walls of mindless drivel over equipment that is hot garbage. So piss off, take your time out, and come back if you want, or just fuck off.

Some folks aren't understanding the difference between something being publicly accessible but still not "a public space." This is a MODERATED forum. Over the years it has established itself to have a certain personality, for lack of a better term; and it is moderated to fit that personality. Yes, it can be exclusionary, but only to people who argue excessively about the personality and try to change it. Otherwise, we want it to be open. When someone is banned, it's not us being cowards, it's reducing excess noise from someone who doesn't respect what this forum is about. There are a good number of very technically-inclined and experienced people here. They freely give advice to those who ask, some design their own equipment, and overall have earned the respect they get. I have seen countless cases of people posting pictures and getting some great advice about what is good and bad about a design. As a group, we DO listen to a lot of music. There are dedicated threads for this, but there are also many threads for other things as well; we're quite an eclectic bunch. When it comes to equipment, though, we're not going to ONLY judge based on sound. As I mentioned before, sound is on par with build quality in this forum, and even if something sounds good but has potential build issues, it will get called out. That is part of the personality of this forum. I will read and respect someone's thought on sound, but will also read and respect good technical input, brash or not. If something is built well and sounds good, it gets praised. Otherwise, it's open season for criticism (based on sound or build). Again....this is the personality of this forum. Accept it, join and try to have fun. Or leave. But if you keep fighting it, you will be banned - to reduce the noise.

that is a right that has to be earned, this isn’t a public space.

Indeed, you have no clue what you are talking about and you come to us... and expect what exactly? This isn't Head-fi where nobody has a clue what the hell they are looking at, we spot BS from miles away and shills as well. You may think this stuff is as good as it gets but for me that just points to inexperience more than anything else. Nothing wrong with that, everybody starts somewhere but barging in and claiming you have a clue what is going on... it's not a good look.

This ain't just any ol' audio forum. Should have done your research before cross posting from HF, etc. Enjoy the ride!

Voja, I think you are seriously missing the point. The big problem with the transformer box is potential SAFETY issues. When spritzer talks about the construction not being up to code, what he is talking about is construction standards that are designed to protect the user from being SHOCKED, or worse, ELECTROCUTED. For example, he mentions that the XLR connectors are not spec'd for the voltages they are intended to carry, which is not aa good thing. The metal panels on the box are not all connected to ground which means that if a wire inside the box should somehow break and touch an ungrounded panel, and you then touch that panel, you would get a shock. That is why all modern appliances (including amps) with metal boxes have their outsides electrically connected to the ground wire on your three wire power cord, for your protection. You admit that you are not a technical person, so you should pay attention to someone like spritzer, who is. It doesn't matter a bit if the headphones sound absolutely perfect, if they could injure or kill you. End of discussion.

I tried to read that article... holy crap do you honestly believe those cables and idiotic footers make a difference? For fucks sake... Also first good point is build quality... sure. Thanks for the internal pics though as this thing sure is a hot mess. So you have a tube amp... and you could use that to directly drive the stators but nope, they went the worst of all worlds. They take a push pull amp, step that down to speaker level and then step it back up for the electrostatics. WHY!!!?? In what universe is that a good design choice, double up the transformers and cram it all in a small chassis... right next to the power transformer and the inductor. You would be much better off with a cheap tube amp off ebay (the China specials) and a SRD-7. That way there is at least some isolation. Same bias supply as the transformer box, despite this being a tube amp and thus safe, high voltage AC being present which is easy to step up. Hell, a dedicated tap off the transformer would suffice. I just love that one nut in the back right hand corner just not fully fixed. Shows the amount of care. All the same earthing issues as the other amps as it uses the 3D printed corner pieces which don't conduct.

The point is that things can potentially SOUND good, but if corners are cut there may be issues with usage and/or longer-term reliability. Some prime examples of this have been HiFiMan (QC issues with many of their phones but often sounded good; and "production" models VERY quickly upgraded to v2 or higher, which tends to mean the product wasn't even a fully finished product to start on first introduction), Cavalli (similar QC type issues and possible design shortcuts), and as an extreme example, Single Power (parts used that aren't in spec for voltages present, poor construction that could literally cause fires and failure; but boy they sounded great). This is not your normal forum, and while it's good to learn about new things there are colleagues in here that can tell many aspects of design and construction quality based solely on the pictures of the innards. So while your opinions on sound are worthwhile in some aspect, it is tempered by build quality questions; so many decide not to move forward and blindly accept sound impressions without more technical info. It could save $ and aggravation in the long run. The argument is that both go together, sound and design/build. So if one is clearly not up to par, then the other doesn't matter - at least to people here. I'm in no way saying these products are like Single Power, but a LOT of people got burned by him/that company.

I've seen detailed internal pictures of both of the other units and yeah... pure utter trash. Every corner has been cut, product which springs for ChangX capacitors... yeah they really care about quality. If I'm so wrong, post internal pictures and tell me how wrong I am using actual facts, not feelings.

I got the HV sections and bias up and they work perfectly Here's the board... I've already tested the GRLV boards and they work. I just have to build another set for this supply. The thermals above the IXCY10M90S regulators don't go above 99 deg. F. Very happy with the board so far.