Earspeakers

Where can you order them from?

I can vouch for these chassis, I've got two and am finishing the first built. Well worth every penny, would cost many times this in a finished product.

I also heard from another friend in the business that they're using 2sc6127 on the output. The electro harmonix input tubes have me interested. I love the 600LE with it's 6922, maybe this'll sound similar - very energetic. Yeah DAC or phono makes sense, the industry has abandoned diffuse field I think. If the DAC wasn't just another delta-sigma clone I'd be thrilled, maybe a R2R. Heresy but personally I don't mind the lack of regulation in Stax power supplies, curious to hear from Jude what the story is here. It's less accurate but does give a nice looser character which I appreciate for a lot of music. But for a amp of this class I'd expect regulation. Spendy, but I'm a stupid sucker for Stax, will surely pop for one. I'll post a write up in that case.

Maybe a diffuse field equalizer like the ED-1, but tailored for the 009? I believe the later headphones strived to build the equalization into the headphone, but at that point you're fighting physics so I wonder how much can be accomplished. Anyhow it looks like a 20 pin connector from the back, and since it has it's own power supply, I'd guess DAC and possibly eq. I love the ED-1/Pawel/Monitor eq personally, would love to see that option.

I'm in the near final stage of my GeorgeP cased T2 and talked to a EE hardware manager on my team at work about heat sinking. The discussion was useful so thought others here might like to hear what he said. Turns out he has a lot of experience with heat management, since dealing with every mW is his biggest issue on the platform and they've struggled with it for years. What they found is that the the only factor with heat sinking is air gaps, since air is an insulator. Torquing is only specified as a poor mans way from the manufacturer of trying to ensure there's no gaps. Beyond the normal smoothness you find on a heat sink that also makes no difference - it all comes down to having a thin layer of compound (ideally it would be zero but obviously we have to suffer with minimal compound) with no air gaps. It's so important for them that they x-ray every one, and they use no hardware to clamp the parts down - just normal soldering. The key is good technique in applying the compound and placing the part. If you do that right torque, lapping or anything else doesn't help. I explained my project and showed him pictures. On hardware he didn't like the idea of using steel screws with the HV silicon - he recommended going with the Peek screws for arc safety and again - using good compound application technique with the screw there just to hold everything together. Further on having all that aluminum and parts screwed together (IC's, brackets, sinks) he was concerned with creep. Ideally you attach to a 'hard' surface, meaning one without creep. A thin PC board is fairly hard, but aluminum isn't - he described it as 'mushy'. You can screw to it but over time the aluminum under the screw points will "flow" away from the pressure point. So, what they do (because everybody has to suffer with aluminum sinks) is to use a wide steel washer under the clamping bolt. This works well to ensure the bracket/sink stays together with thermal cycling. Otherwise he suggested a yearly physical inspection of IC to bracket and bracket to chassis to ensure a continuing tight fit. So, he recommends PEEK screws, don't over torque (or worry about torque at all), but be fanatical about compound application, such as using a non silicon based compound like AOS 52022KH for long term stability if you like. For attaching sinks and such he recommends using a wide steel washer (not a 'lock' washer) to spread out the pressure point. FYI -

Too busy, hey it's your fault Kevin, you keep coming up with these amp designs that are eating up my free time

I can recommend a Metcal station with desoldering gun, you can build a kit off eBay for cheap (I got the gun new for something like $100). Just hook it up to an air compressor, get a few tips and it beautifully makes rework easy. Weller and others have similar solutions.

I have access to both

Sounds good. I'm stupid enough to be building a second one in parallel so can do both.

Darn, I'm in the latter stages of my build and used Takman for the battery 390k/820k. And as things turned out (and a little help from my friends ) got Xicon 390k/820k. It would be easier to pull now rather than later, should I swap them? Or just give them a shot?

Perfect, we have a quorum.

We're doing a quick moving T2 board set group buy; there are two members and we have a quote for two more (but will go ahead regardless). Specs are ... FR4Blue solder MaskWhite silkscreen2.36 mm thicknessENIG3 oz cuIPC-class 2100% e-TestedThe buy consists of a set of the full sized boards; one power supply and one amplifier board, $225 for the set + shipping and PayPal fees. Post interest here and we will close the buy in one week. If we have more then 4 participants the price will be lower.

No, making a 'wood thing' is exactly the kind of things real engineers do when starting out. We hack something together best we can to get an idea of what we're doing (do searches for prototype Google Glass for an example). But not having any engineers on your team is dubious, which necessitates you coming to forums for help. Without engineering how will you do the CAD? Measurements? Testing? Design for production? I'd recommend you find an engineer first.

What's the status of the GB, any updates ?

I thought you might have meant that but didn't parse. Current production silicon T2? Didn't know there was such a thing. This one is using out of production (original T2 design) silicon, or the original T2 design at least (2SK216, 2SJ79, 2SC3381, 2SA1486, 2SC3575 etc). Any links appreciated.

No sand, just the PCB's. We've done a run of 4 boards already and the PS has been built out and tested as mentioned and the Gerbers have been previously fully built out and verified by others. Correction to above, these are not the shortened boards.

Interest check for a group buy for T2 boards. I have a quote from Custom Circuit boards for $125/amp, $100 PSU, ENIG, 2.36mm, 3oz copper, 100% e tested in quantity 4 each. These are the shortened boards, GeorgeP has verified the PSU is good (we've already got a set each). I want one, if three others are interested I'll do the buy. PM me if interested, if I don't get enough interest here I'll do a separate post to call it out.

Got it, so the brackets go on the the PCB top, the silicon is bent horizontal to bolt to the angle bottom, and the angle vertical then bolts to the side mounted heatsink. I've only finished the KGST and KGSST so far with the on board heatsinks, got a Megatron board done except the final silicon (PS has the offboard heatsink), and a DIYT2 so haven't figured out how the offboard heatsinking is supposed to work. Makes sense, thx

Just a sanity check - angle brackets for the heatsinks? How big of a bracket, as big as is reasonable? Confidence that will produce enough ability to radiate heat?

I missed this thread somehow too, anyhow added myself if still open for 2 filled and 2 bare.

FWIW my VF display is fine. Not new brightness but more than usable, as long as I don't leave it on 24/7 it should last years. But yes that is definitely a possibility with these older DMM's, as I'm guessing these were used in a Korea production line and so were probably just left on.

Yet Another Group Buy: Keithley 2015 THD Multimeter Except I won't participate as I have one already. The person I bought it from (in Korea) has many more for sale. Shipping is separate, so presumably you could buy them in lot and have them shipped individually to everybody from the source, pretty convienant. Pricing: (Used and functional units) more than 3 : USD $270 eachmore than 5 : USD $250 eachmore than 10 : USD $220 each It needs a central person to manage the money and information. If there is interest in a Group Buy and a leader who wants to take it, I'll forward the contact information. Please indicate your interest (how many) and whether you'd be willing to lead it on this thread for a rough interest check.

Got it. I have scopes at work I can use (haven't bothered to buy one as I can borrow one that costs as much as my house), but I'll leave that alone.

Good tip, just so I know what I'm getting into if I have to resort to that, why should doing it be avoided? Thanks.

Good ideas, I'll check the belt. I read somewheres that there might be POTS on the board to twiddle for adjusting the tracking, I'll be on the lookout.