| cetoole |
I have been working on designing a new DIY portable headphone amplifier lately, it is actually a heavily modified Mint amp by Tangent, but new layout, decoupling, and changed parts, but the actual schematic is virtually identical, buffered opamps with jung multiloop. The board is about 1/2 the size of the origional mint, about 21mm high and 48mm wide. I am getting ready to send these files to Olimex to get printed, in a couple weeks, I should have ~14 professional PCBs back of my own design. Potentiometer with built in switch, Alps RK097, goes right in the center of the board, with the input/output jacks on either side of it. Dual mono opamps, each with their own buffer, with CRDs for Class A biasing, and capacitors for full decoupling, resistors for setting buffer bandwidth, four capacitors for the power supply, capacitors to limit opamp bandwidth to increase the stability of "stupid fast" opamps, and the parts on the board now are nearly all SMD.
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| motherone |
Colin,
Followed your work on the head-fi forum. Glad to see it come to fruition! |
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| bigmike216 |
Cool!
Will you offer your eagle files to those of us who would like to make one for ourselves? :) |
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| cetoole |
| Sure, just tell me where you want me to send them, I got no problem sharing, and I would love to see what you make. |
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| cetoole |
| Here is the preliminary BOM for the amp. |
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| cetoole |
| I just placed an order with Olimex for PCBs, gonna be getting 14 of them for $45 shipped, and they should arrive in a couple weeks, so I am pretty excited. |
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| bigmike216 |
| Awesome :) Thanks for the eagle files! I'll be etching my boards shortly... Then I'll build it up after I find some buffers! I've got all the other parts in my parts cabinet, except the buffers... I've got them in PDIP and TO220, but not SOIC. :( |
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| motherone |
| Congrats Colin. It must feel great to have your boards coming to fruition. I hope to get into PCB design someday so I can get some of my ideas etched down :D |
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| paulb |
| cetoole, have you had previous boards from Olimex? Their prices seem pretty good. |
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| cetoole |
bigmike216: The buffers, the biggest issue I have right now. TI is having trouble keeping them in stock, and they have been difficult to get. They had come in stock at Mouser a week ago or so, but are sold out again. I have 8 for my own use, so I am set, but I dont know about other people.
motherone: Yes, it does feel great to have my own boards coming, but I believe it will feel even better to have a working amp built using them.
paulb: I have not had any experience with Olimex before, these are my first boards ever, and I chose them because of price and because Sparkfun froze their ordering for a while. I will let you know how the quality is when I get the boards. |
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| paulb |
I also looked at EuroCircuits but their shipping options seem very expensive.
I'll watch for your results. Thanks.
Paul |
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| cetoole |
Paul, I wasnt able to complete my order with Olimex, due to their requirement for a faxed order form, and when I tried faxing, I couldnt get it to go through. Instead, I got my order added to someone else's panel, he is getting a full panel done, and boards are due sometime this week. I have been looking some more at the layout, and made a couple (relatively) minor changes, caps are now 8mm diameter, so for 10v Panasonic FM, quad 470uf caps fit nicely, definitly should be worth the extra 3mm length I feel. Also added a fuse, redid some traces, and a couple other minor things.
Intersil HA5002 Buffers
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| paulb |
Hi, thanks for the update. I wouldn't mind hearing more when you receive the boards.
Nice layout. What tools are you using? (you may have already answered this somewhere else, if so sorry). And where are you getting your Alps pots from? I got pricing of about US$28 for small quantities. |
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| cetoole |
| My tools include a $35 clone of the Hakko 936esd from Circuit Specialists, with an assortment of tips, usually just a fine conical and ultra fine conical, which have been fine for all of the work I have done so far, including a USB DAC using a PCM2702 IC in the SSOP28 package. Assembling this board will necessitate careful selection of the order that parts are installed, probably opamps, then buffers, resistors, bypass caps, CRDs and TLE, pot, electrolytics, and I/O wires, in that order. Just gotta be sure that you dont solder down something that blocks access to another part. I dont really have anything fancy in the way of tools, the rest of my stuff includes a Fluke 112, desoldering iron, desoldering pump, some dental picks, tweezers, locking hemostats, liquid solder flux, solder (Kester 2% Ag right now, might pick up a pound of Cardas soon), some alligator clips I use to hold smd ICs down while soldering, just position correctly, carefully clamp, and solder, and a Helping Hands. For case work, I have much less, a dremel, a drill with stepped bits up to 7/8", and a heatgun for heatshrink. Wire, I have about 1000' (yeah, I went crazy, bought a 500' spool of 22awg teflon coated stranded SPC, and the same, but in 28awg), about 500' 22awg enamled magnet wire, and some belden 24awg teflon coated copper Plenum rated cat5 cable. The 1000' of SPC was all NOS off ebay, paid around $40 shipped for all of it, none of the stuff was really that expensive. There is some stuff I am looking to get at some point, but only when I find it for a price that I am willing to spend, which isnt much, believe me. I need an OScope most, been keeping half an eye out for school sales of old khz range ones, kinda looking for a gas reflow system, but thats not high on the list, a dmm with accurate hFE tester, but I will just breadboard and calculate for that now, and a drill press. After making you read all of that, I feel it is only fair to share with you a cheaper source for the Alps RK097 switched 10k log taper pots that this amp was designed for, only $3 each from Tangent's Audio Shop, a very reputable store and person, same Tangent as the designer of the origional Mint, Pint, Meta42, Pimeta, PPA. That said, I have been thinking about starting an interest check for a group buy of these pots, to corrispond with, but not be exclusive to, the board buy. |
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| paulb |
Interesting, I have a META42 board right in front of me here.
The tool description is interesting, but I meant PCB layout tools. I like the 3-D graphics out.
Are you using guzzler's USB DAC card? I have one of those in front of me too.
I was looking at the Alps RK27, probably a step up from the RK097.
http://www3.alps.co.jp/WebObjects/c...RK271/RK271.PDF
I have a quote for 100-lot quantities around $8.
I'll check out tangent's store. |
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| paulb |
I see Tangent's got the RK27s (50K) for $16, very reasonable.
Ooh, and there are some SO-8 to DIP adapters for $3...maybe I'll place an order. |
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| cetoole |
| Ah, design tools. I use Eagle for the pcb design, and Eagle 3D for the renders, with POV-Ray to do the actual raytracing rendering. Yes, I am referring the the Guzzler USB DAC, I actually am waiting for 2 smd resistors and 2 tantalum caps that I dont currently have, a 10r 1206, 330k 1206, a 10uf tant, and 47uf tant, which I will be getting pretty soon. The RK27 is definitly nicer than the RK097, but take a look at the size differences. Also, RK27 isnt switched. |
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| cetoole |
Did some more work, really just working on routing improvements, and trying to make the groundplane more continuous.
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| paulb |
Would you consider selling any blank PCBs? Or perhaps I could order some through Olimex using your layout?
I have this concept of headphone listening stations throughout my house. Oh, and at work. |
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| cetoole |
| I plan to run a PCB group buy for this amp, you could get some boards then. Also, I would be willing to send you eagle or gerber files if you wanted to get some made up, or play with the layout a bit on your own. If you want the files, shoot me an email. |
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| paulb |
| Thanks, I can wait for the group buy. I'll stay subscribed to this thread if you post it here. |
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| cetoole |
| I just got a notification email that my protos are in the post, on their way to me :D. |
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| cetoole |
Sorry for the poor images, dont really have good lighting in here, and not so skilled with the camera. |
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| Evilsizer |
just a tip
turn off your flash on the camera and use the light above/near you. You could also try to tape a piece of paper over the flash so its not reflective.
looks nice .... how many you got there? |
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| cetoole |
| Took those photos in my room, which is kinda dark, only got a single incandescent light on the ceiling, and it was already dark outside, so the flash was necessary. What you see is what I got, 6 boards, 4 for BUF634u or OPA551, 2 groundplaned, 2 not, and 2 boards with groundplane for Intersil HA5002 buffers. |
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| Illusus |
| Looks very nice. I'm in if you get a GP rolling. I'd like to put together a more proffesional 'ChuMoy' than what I've now (it's a P2P mess, works well... but not very portable) . |
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| paulb |
Those look pretty decent. Hard to really tell until you start stuffing / soldering, and whether you find any hairline cracks etc.
Better than home etching, anyway. Maybe I'll give Olimex a shot sometime in the near future.
http://www.olimex.com/pcb/index.html |
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