[ATAT]

looks fantastic... damn this makes me want to spend the school budget on CNCing the bport.

It would be even cooler if you waterjet the headphone profile out
and you put an acrylic peice in there... of course now I'm just being crazy eh?

Tell us how it goes..

 

[velmeran42]

Quote:

Originally Posted by ATAT looks fantastic... damn this makes me want to spend the school budget on CNCing the bport.

The shop instructor was saying that the kit to do DRO and CNC on a standard mill was around $8k, but that the TRAK K3E (only two axis) come in at around $17k. For $17k the TRAK mills are pretty sweet machines, but sadly not three axis capable.
Quote:

Originally Posted by ATAT It would be even cooler if you waterjet the headphone profile out and you put an acrylic peice in there... of course now I'm just being crazy eh?

That is a highly interesting idea, I might just have to run that by the shop instructor to see if he'd let me run a few test parts to see what it'd take to get a good press fit. We have one of the new Chinese manufactured Flow systems, so we don't have the nifty self correcting head unit. If you cut too slow you end up w/ a slightly flared cut (we're talking a few thou unless you do something really odd, but noticable still on a press fit I'm sure)...... It's too bad the waterjet costs about $2.50 a minute to run (in consumables, not to mention power consumption).

I'll keep posting as things come up.

 

[Nordic]

I would suggest you find some way to seal the bottom of electrolytics with something that will prevent the epoxy from touching the rubber stopper as the epoxy will eat through that stuff...just like many other chemicals.

 

[velmeran42]

Quote:

Originally Posted by Nordic I would suggest you find some way to seal the bottom of electrolytics with something that will prevent the epoxy from touching the rubber stopper as the epoxy will eat through that stuff...just like many other chemicals.

Thanks for the warning. I still need to ask my electronics packaging TA what he can grab me for encapsulating everything. I can always just coat everything in a layer of Elmers Blue School Glue first, that stuff is pretty tough.... I could probably just use that by itself really... more thought when the time actually comes, first I have to make the case and solder it all up.

 

[MASantos]

I don't mean to be a PITA, but if you are investing so much in such a nice case and battery charging system, why not go witha more complex( and possibly better sounding) amplifier design. You could certainly go with a opamp + buffer design such as the pimeta or even with something similar to the pint. IMHO these are much better designs than the Cmoy and will give you much better sound.

You can also board mount the pot, jacks, so you don't have wires to mess with.

Since you are machining your case, you can adapt the board to the case and vice versa.

 

[ATAT]

Dont go for a press fit with that, press fitting acrylic is a PITA, you'd probably want a slip fit + loctite..

(acrylic tends to shatter when pressed)

 

[velmeran42]

Quote:

Originally Posted by MASantos ....why not go witha more complex( and possibly better sounding) amplifier design.... ....You can also board mount the pot, jacks, so you don't have wires to mess with.

I'm sticking with a CMOY for the low part count (and therefore smaller space). I've only got about $60 into the parts for this thing (yeah, spendy for a CMOY, but cheap enough for a headphone amp). I would have considered a PINT, but Tangent stopped selling boards for it since people were having isues with it. Since I've already ordered the parts, I'm sticking with it.

I' also don't intend to board mount anything since the pot and jacks need to be on different planes (and orientations) to maximize use of space. I'm planning on doing it p-p, which I've done for several GainClone amps and other projects (yes, it's a nightmare, but it works if you're careful).

Thanks for the input though.

Quote:

Originally Posted by ATAT Dont go for a press fit with that, press fitting acrylic is a PITA, you'd probably want a slip fit + loctite..

I was going to shoot for a <0.002" press and chamfer the back edges of the plex to aid in insertion, but a slip fit w/ CA glue would work just fine by me too. I'm all for learning by proxy though, so I'll just aim to slip and glue if it looks doable (still haven't tried cutting thin acrylic on the waterjet cutter, it was only put in a little over a month ago).

 

[velmeran42]

Ok, so slight change of plans. I checked the specs on the waterjet cutter we use... Not going to cut it, + or - 0.010", but I suppose that's what you get for buying the basic series. I can't afford that much variance on my plexi parts, so I'm just going to scrap the plexi mid section. So now I'm planning on just using two pieces of 1/2" stock and cutting the headphone logo into the case and then backfilling with epoxy (yes, the middles of the cups have connections to the main body still). I've updated the models to reflect it. I think it will be better looking with a glowing headphone logo for the power indicator.

 

[velmeran42]

My goodies have all shown up.

The Lipo in the upper left hand corner is 400mAh @ 11.1V w/ a protection PCB.
All other goodies are pretty typical except the AD8620 OpAmp (spendy little bugger), which was purchased for it's low cut off voltage (lower than the 7.8V cut off of the batteries).
There are 5 of the pocket clips so I have enough to mess up while trying to slot and pocket one to make it look cool.

More to follow (machining ought to start next week)

 

[tomb]

Ya gonna air-wire those SMD parts

, or did I miss something?

 

[velmeran42]

Quote:

Originally Posted by tomb Ya gonna air-wire those SMD parts , or did I miss something?

You got it right on the nose, point to point all the way on this build

. I've done the same or worse in the past. I will be filling the amp with polymer encapsulant (provided by my electronics packaging TA) once the circuit has been built and tested to satisfaction. I won't be soldering anything until after I complete the case work, so it'll be a week at least.

 

[Seaside]

Where's eletrolytic caps?
Are you going to make custom PCB for SMD?
Do u mind telling me the part numbers, especially for SMD capactior chips, stereo jacks (is it 1 kind or 2 kinds? They looks good anyway) and the black plastic thing that looks like a battery holder? Thanks.

 

[velmeran42]

Quote:

Originally Posted by Seaside Where's eletrolytic caps? Are you going to make custom PCB for SMD? Do u mind telling me the part numbers, especially for SMD capactior chips, stereo jacks (is it 1 kind or 2 kinds? They looks good anyway) and the black plastic thing that looks like a battery holder? Thanks.

No electrolytics, tantalums for power (I assume that's where you were expecting electrolytics). No PCBs, point to point as stated multiple times before. The stereo jacks are switchcraft jacks (mouser part 502-35RAPC4BH3), there's a 2.5mm mono jack (also switchcraft) being used for power, and the "black plastic thing" is the lithium polymer battery pack mentioned in the text below the photo.

I'd have to dig out the invoices to remember the part numbers on everything, but none of the parts are overly spectacular or amazing.

 

[tomb]

It looks like his power caps are those tiny rectangular cubes in the SMD tape (SMD tantalum). That was over and above the already obvious SOIC 8620 (only way it comes, though). That's why I asked the question about air-wiring SMD parts.

No offense, but it certainly fits your tagline.

 

[velmeran42]

Quote:

Originally Posted by tomb No offense, but it certainly fits your tagline.

None taken, I would definitely classify this as an unusual project. My projects tend to be fairly out there, but that's the point. I'm trying to use this project to showcase some of my skills that a company might find useful above and beyond my basic mechanical engineering ones, since I'm graduating this quarter. I view this project as a sort of "portfolio piece". I'm also building an Alien DAC as soon as the board shows up (not nearly so ambitious really, only hard part is the main IC), it too will receive a nice aluminum home assuming shop time permits.