My DIY headphone amplifier design

[cetoole]

I have been working on designing a new DIY portable headphone amplifier lately, it is actually a heavily modified Mint amp, new layout, heavy 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 nearly all SMD parts.
http://img.photobucket.com/albums/v323/cetoole/DIY%20Amp/CEMMRender.png
http://img.photobucket.com/albums/v323/cetoole/DIY%20Amp/CEMMBeta10silktop.png
http://img.photobucket.com/albums/v323/cetoole/DIY%20Amp/CEMMRenderBottom.png
http://img.photobucket.com/albums/v323/cetoole/DIY%20Amp/CEMMBeta10silkbottom.png
http://img.photobucket.com/albums/v323/cetoole/DIY%20Amp/cemmbeta11.png

[zabomb4163]

how much does it cost for custom boards?

[cetoole]

Olimex, the company I am going to use, is $33 for a single double layer eurocard size board, plus shipping. Eurocard is 160 mm x 100 mm (6.3" x 3.9"), and since my board is 21mm x 48mm, I should be able to fit 14 of them. They offer free panelization, so they will split my boards apart for me for free. This is a very inexpensive company, and their boards are not quite as nice, but most of the major fab houses are really set up for large orders, and cost ~30+ each for single boards, with prices becoming more reasonable in larger quantities.

[nn_step]

wouldn't a 7805 (+5V Fixed-Voltage Regulator) work better than 4 Caps for voltage control of the powersupply?

[cetoole]

wouldn't a 7805 (+5V Fixed-Voltage Regulator) work better than 4 Caps for voltage control of the powersupply?
No, those arnt smoothing caps, they are the main power reservoir capacitors. The 3 leg IC in the center of the power supply section of the board is a TLE2426 virtual rail splitter, it takes the voltage from the batteries (9.6v), splits it to equal positive and negative rails (+/-4.8v) and the caps are used as reservoirs. They are also known as rail capacitors. When I start working on the NiMH fast charger for the amp, I will probably end up using a LM317 for the regulation, as it is much less noisy than the 78xx regulators, and the adjustable ability will be convenient. I am not sure what charge controller IC would be ideal yet, need something that detects negative slope voltage, the OnSemi MC33340 is the most promising so far, but I am still looking.

[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, I am pretty excited.

[cetoole]

Look what arrived today:
http://img.photobucket.com/albums/v323/cetoole/DIY%20Amp/allpcbs.jpg

[STickGuy]

Keep us up to date on the project

[Magnj]

sounds sweet, will you be selling them as kits or already soldered or not at all and how much $?

[P_1]

Look at what I built over the past few days:

http://img526.imageshack.us/img526/3664/img09771ud.jpg

http://img525.imageshack.us/img525/444/img09783mq.jpg

http://img525.imageshack.us/img525/9831/img09795yh.jpg

http://img525.imageshack.us/img525/3808/img09806ab.jpg

http://img503.imageshack.us/img503/6635/img09813ii.jpg

http://img503.imageshack.us/img503/9507/img09825qq.jpg

http://img503.imageshack.us/img503/8346/img09835sb.jpg

http://img503.imageshack.us/img503/5418/img09844nx.jpg

(these are cmoy amps btw)

[Magnj]

haha nice boxes