Someone recently emailed me a set of questions that are way too open-ended and general for private email. I prefer that such answers go to public places so that more than one person gets to learn the answers, and others can chime in with their own thoughts.   I'm putting this here because the...

I recently started designing a new board. (Nothing on-topic for Head-Fi. Don't get excited.) I had a choice:   1. Continue using my old EAGLE 5 license   2. Upgrade to EAGLE 7   3. Try KiCad   I went with 3, because I'm a neophile.   KiCad's been getting a lot of attention in the maker...

I just got around to updating the copies of the EAGLE libraries I've been offering, here. The changes reflect all the PCB design work I've done in the past three years or so. Notable additions:   all the dual thru-hole/SMT footprint stuff from PIMETA v2 (Rs, Cs, Ds, op-amps...) LMH6321M...

Make yours today.  

In the initial version of my resistor matching article, which I finished back in mid-summer, I baldly stated that Agilent owned the bench DMM market, and Fluke owned the handheld market. At the time, Fluke only had two bench DMMs, one of which cost more than my first four cars combined, and...

The site never tells you whether they have the item in stock or not. You'll see why in a bit. I ordered three items from them on June 1: a current shunt, a temperature probe, and some clip leads. They quickly sent out an email saying they'd received my order. That's all I heard until two...

The PPA is a circuit board for a high-end headphone amplifier. You can make a stationary amp with it, or you can add a NiMH battery board to get a "transportable" amp. The battery board has an on-board charger which tops the batteries back up when you plug in external power. The PPA boards...

The PIMETA is a small circuit board for portable and small home headphone amplifiers. It uses a circuit similar to the PPA with changes in favor of small size and low power consumption. This project is just above "entry level" in terms of build difficulty. There is no kit, but all of the...

I just read an article that gave many examples of what can be done with just over 17 bits of resolution. Read it, so that the next time you're trying to compare the relative merits of an 18-bit DAC to a 20-bit DAC, you'll have an idea of how silly such specs are.

No, really! The 2005 South-by-Southwest music festival happened a few months ago, and this year they're giving away a collection of ~750 high-quality MP3s for free. It's a "featured artists" kind of thing, so no doubt the idea is to get you to buy more of the music you like. ...and tempt you...

I've been looking into making a circuit you can add to a PPA battery board type NiMH fast-charger circuit to prevent the battery from being over-discharged. Here's what I've come up with: Schematic, PDF, 20KB The first comparator circuit compares the divided-down battery voltage to a 2.5V...

I've recently been thinking of buying a new calculator. But first, the Genesis of calculators in my world: That's the story as it stands today. So far, I do prefer the native Palm-based calculator to an emulated 49G, but a lot of that has to be because shrinking a 49g down to Palm screen...

Many manufacturers in the electronics industry have free samples programs where you can get a few parts just by asking. The purpose of this program is because the manufacturer knows that if you use their part in a product, they're likely to get an order for thousands or even millions of the part...

I've been thinking about low battery indicator circuits lately. So far, the only thing I've seen on these forums is ppl's zener/CRD circuit, used in his personal amps and then adopted into the PPA and PIMETA. Just shutting the LED off when the battery is low is kind of weak, though: it isn't...

I've started an archive of parts for ExpressPCB and EAGLE with parts you can download here: http://tangentsoft.net/elec/parts/ You can also upload your own components for inclusion in the archive. Think "open source for PCB layout". So far, all of the parts are either mine or Morsel's...

After 2 years of virtually no change, I've gone and updated my op-amp reviews article. Some of the highlights: - Several chips reviewed (nothing new...just ones that should have been reviewed long ago) - New objective clipping test methodology, instead of the listening test I used before...

I dunno how many people this will interest, but here's the new measurement preamp I'm working on. (Schematic.) It's primarily intended for testing linear-regulated AC power supply noise, which on a decent good linear supply is way below the noise floor and/or resolution range of typical hobbyist...

Just this little thing I whipped up... Panel by FPE, knob by DACT, chassis by PAR Metals. ...and inside: Left front, a DACT CT-2. On the board, OPA637/627s driving Glassman v3 buffers. Power supply...no, it isn't a STEPS.

In making the PPA battery board one of the innovations was allowing it to charge more than 16 cells, the limit of the highest-voltage charge controllers we could find. Since we couldn't find a controller that would directly charge 18 cells, we studied the available charge controllers to see...

A neat little takeoff on a headphone amp: It solves the problem where the car stereo has a front-panel input and you want to use a low-output portable source. Say the portable has only 1/2 line voltage, so you have to fiddle with the volume knob when switching between the aux input and...

On the PPA battery board, R4 and R5 form a voltage divider across the battery pack. The batteries discharge through this divider, so it contributes to the speed at which the pack self-discharges. Previously, my configuration calculator kept the resistor divider in the tens of Kohms range, but...

Something that's been going around for years in various forms: The Ten Commandments for Technicians [list=1]Beware the lightning that lurketh in the un-discharged capacitor, lest it cause thee to bounce upon thy buttocks in a most untechnician-like manner. Cause thou the switch that...

Can anyone tell me by looking at the AD797 datasheet what the gain bandwidth product is? On the front page, they claim that GBWP is 8MHz at g=10 and 110MHz at g=1000. They say the same thing in the data table. Sooo....bandwidth goes up as gain goes up? I'm supposed to believe that? I also...

There's been some demand for me to put the Sulzer and Jung regulator history that I traced out a few weeks ago up on my web site. Naturally I couldn't leave well enough alone so I added a bunch of material. It should serve as a good introduction to this type of regulator now. It doesn't replace...