Category making things

[This is a cross-post from here at diyAudio Forums:]

Well, the first five PCBs were ordered from PCBEX.COM a few minutes ago. The biggest changes since yesterday were moving the smoothing capacitor before the voltage regulator to 1000uF (13mm diameter, 5mm lead spacing footprint) which required a good bit of shuffling of parts in the power supply. (Some configurations, particularly those not needing to use the 5VDC output, can use a much smaller cap here. I’m recommending this value as a best-fit.) As part of this I also ended up moving all of the connectors to the front edge of the board, which I think is a rather good thing.

The boards are five-day turn, so I figure they’ll ship sometime around the end of next week. As PCBEX.COM batches their boards out to China I expect it’ll be another week or so before I have the boards.

Here’s how the part prices from Mouser breaks down:

All parts, except PCB, heatsink, relays, and audio terminals: US$10.46
5x 4PDT Omron relays and 5 place Phoenix terminals: US$57.10
5x DPDT Omron relays and 3 place Phoenix terminals: US$25.45
1″ Tall Heatsink: US$1.14
1.5″ Tall Heatsink: US$1.06

Of course, you can cut these prices down if you do things such as not fitting the boards to switch all five inputs, leave out some of the onboard power supply parts, etc.

The PCBs cost about US$16/each after shipping from PCBEX.COM. If I were purchasing for a group buy or something I imagine the price would be a good bit lower, although that obviously depends on the quantity.

So, I guess that’s about it for now… There is more info over at the main nuxx Audio Input Switch (as the device is now known) page.

One final question for everyone: Are any of you interested in purchasing some of these PCBs in a group buy?

I figure that I could probably handle doing a group buy for some folks. I’d provide a PCB and programmed PIC, and you’d just have to order the rest of the parts. Everything in there is very standard, so even if you can’t order from Mouser you shouldn’t have a problem sourcing the same (or compatible parts. I’m not in the position to offer kits or assembled boards.

Off the top of my head I’d estimate the total cost at being around $20, to cover the blank PCB, PIC, packing stuffs, PayPal fees, etc.

Anyway, that’s it for now…

1) I should be in bed.
2) The vent on an electrolytic capacitor is called that for a very good reason. That said, I’m surprised how long the 470uF 25V Nichion audio cap worked for while backwards. It even somewhat worked while backwards, which is probably why I let it go for so long. Whoops!

nuxx Audio Input Switch on a Breadboard

Well, that’s that. The nuxx Audio Input Switch is coming along nicely and things are working as expected. Except for not realizing that MCLR has to be externally pulled high (or disabled), causing me about half an hour of head scratching, the software has worked as hoped for.

I had to learn a bit more about how the driver works and thusly redraw parts of the PCB, but I think it’s all sorted out now. If you’d like to see the board layout, just take a look here. Of course, you’re also welcome to read through the nuxx Audio Input Switch page, which currently has a fair bit of misplaced / inaccurate information in it.

Here, have a PCB layout that I think it almost complete. I need to validate some parts and be sure the drivers work as I expect, but beyond that it should be all set.

Now I’ll be able to switch inputs on a headphone amp without plugging / unplugging things. Yay!

Yay! I just finished porting the software for my PIC-based audio input switch to the PIC16F630. Earlier this afternoon I got it feature-complete and worked out all the bugs I could find, then in the last half hour or so I got it running on the new chip.

Tonight I hope to get it working with internal pullups (should be trivial) and then I’ll give the power supply design some thought, along with initial parts selection for the PCB itself.

Since I haven’t mentioned it here before, it’s:

– 2-5 input audio selection switch (configurable via jumpers)
– Relays for switching audio
– Fail-safe design
– Switches balanced or unbalanced audio
– Next / Previous buttons
– Mute function
– Saves input to ROM so that last state is restored at power-on
– MIT-licensed software

I’ll post more info later. Now it’s time to go home and meet up with Danielle for dinner.

Assembled Alien DAC w/USB Power (Top)
(Click for more photos…)

I decided that I’m going to build another one of those Millett Hybrid Maxed headphone amplifiers, except this time I want to build one using a bit more specialized parts, stick it in a case with wooden end panels, and fit both a USB audio adapter and input switch in the housing. As you can see here, the two PCBs will easily fit in the case. (The Elna RFS / Silmic II capacitors can also be seen there.)

Today the Alien DAC kit arrived from Glass Jar Audio, so I set to work putting it together. It really wasn’t too difficult, most of the parts were either through-hole or 1206 / 0805 SMT. The SOT-8 voltage regulators were real easy to solder as well, and I had very little trouble with the SSOP28 PCM2702E. The board is reasonably well laid out, but there are a couple of things I would have changed. I’m really not sure what the designer was thinking (I think he wanted to save space / make things more compact), as hand-soldering SMT IC legs to ground without thermals is a huge pain in the ass. Regardless, it worked out.

Oh, and the bottom of the board can be seen here.