So I had to find out for myself why people don't engrave small one-off circuit boards. In my delusional fantasies I figured the tool would cut like butter, it would be like writing with a felt tip pen on nice paper, and I'd be done before the next guy could set up his light box and etching...

Can a current mirror be used as a very low overhead trickle charger? This is about as primitive a version as I can draw, that doubles the current through R. There are more sophisticated similar circuits, with more parts and/or higher overhead. This circuit won't have a dead flat charge...

I'm part of a design effort to build an inexpensive analog controller for BBQ pits. I keep Art of Electronics handy, but 'in over my head' is where I generally like to be, and where I probably am right now. If anyone would be amused to comment on this circuit, I'd be grateful. But first...

Has anyone A/B compared the AD8620 to using two separate AD8610 opamps, in the PIMETA? Tangent has the best price for either of these. Putting two singles on a BrownDog adapter is marginally more work than soldering a dual, and at his prices the cost comparison is basically a wash. My...

I attempted to use BrownDog's Single-to-dual Op-Amp Adapter (p/n 020302) (from Tangent's Audio Parts Shop) with a pair of Burr Brown OPA627 op amps, in an Assmann Electronics Op Amp IC Socket .300 8 DIP GOLD, Digi-Key AE7313-ND. It barely seated on my first try, enough for me to...

Here are some pictures of my bloodwood PIMETA. The end panels are 1/8" bloodwood, as described in the thread Exotic Hardwood End Panels: The Hammond J16 case just fits in a sturdy pocket: The battery pack is a set of three RadioShack 270-413 AAA battery holders, holding 12...

I've always bought the party line on power cap voltages, but now I find myself wanting to fit 12 NiMH AAA cells into my Hammond J16 PIMETA, to give me a bit more voltage before the AD843's start clipping as the battery runs out. However, I used 16V caps, and 12 NiMH cells briefly reach 18V fully...

I am experimenting with PIMETA output resistors, not to reduce hiss, but to convert my Etymotic 4p earphones to 4s. Many of us who bought the 4p did so to be able to use them directly with, say, an iPod. We waded through reviews and manufacturer literature describing how the 4s, with 100 ohm...

RadioShack 23-349, 18V Charger, is on sale now at stores for $5, listed for $3 but out-of-stock online. At this price, hard to resist buying a bunch to use as trickle charge power supplies, so I bought one for testing. I can't tell if they're discontinued or just on sale. It has a fairly...

I'd like to find pins to make DIY boards in the style of BrownDog's SIL single-to-dual Op-Amp Adapter: What are these pins gripping the bottom of their board? Molex headers are too fat to fit into IC sockets. Does anyone know a source? Thanks!

Here's a 15x26mm surface mount layout for one MINT channel (the back side is a ground plane, with gaps as needed for holes that aren't ground): I couldn't find a surface mount CRD in stock anywhere for D2, so this layout uses the same through-hole part as the MINT. One solders the top...

I need to make a MINT board as thin as possible, on the resistor/IC/diode side (plan). I'm struck by the constrast in how little solder one uses in refined surface mount technique, compared to the tiny solder mountain ranges one sees on the solder side of through-hole boards. I have a good iron...

I've admired various projects I've seen here incorporating wood, so I want to share a source: Rockler.com thin woods I visit one of their retail stores, where of course, two of the three woods I bring home aren't even listed on their web site. From left to right above, Bolivian Rosewood...

As far as I can tell, Vishay Dale Military, MIL-R-10509 Qualified, Type RN55E_BB14 are the best available resistors that fit 0.3" spaced boards such as the MINT, PIMETA, PPA. They have 25ppm, 0.1% tolerances, and are sold through Mouser. However, Mouser doesn't list available values for this...

So many of us are on the brink of adding internal charging circuits to our amps, and will be in a position to swap them out later for more advanced circuits, if we fancy. If I were to simply specify the desired behavior and then build it, I'd want the power jack on the back to accept 2V to...

Does anyone know where to get jacks that fit the Apple 24V laptop plug? Or what the deal is with their various contacts? I've gotten as far as getting my DMM to read 24V, same as some of my Apple supplies are labeled. In this 24V format I have several international travel chargers...

This is a "by the book" charging circuit for NiMh 9V batteries, as found on its datasheet and as used in Tangent's TPM schematic. I am following standard advice by separately charging each cell, which is a good thing because at the moment they are at very different charge levels. There is...

For your consideration, here is a $1.30 charging circuit to go inside a PIMETA (or anywhere else one sees fit). My design goal is to use 8 AAA cells, and be able to charge either from an iPod power supply or from a generic 15V wall wart. Short of building a full-blown fast charge controller...

I raised this question first in PPA v2 Project Announcement, in reply to PPL's post The PPA 2.0 Buffer tech info. I did not intend my question to be a suggestion for revising the PPA, whose design I intensely admire, and whose size would not accommodate my idea. So I'm moving my question here...

Would it be easier to assemble a project using many surface mount components, if we could clamp a laser-cut frame over the PCB, drop in the components like a kid filling in a wooden puzzle of the fifty states, solder, and remove the frame? "Caching" and "Precomputing" are key concepts for...

Here is a design for a 36 step "volume, trim" stepped attenuator small enough to fit inside a Hammond 1455J12 case. Each rotary switch is 1/2" in diameter. I've spread out the parts for clarity, but they could easily be wired more tightly: The circuit is a nested pair of "series" type...

Does anyone have recommendations for surface mount resistors for stepped attenuators? All this recent talk about pots and attenuators got me thinking again. I want an inexpensive, practical stepped attenuator design for portable use in cases too small for the Alps Blue. I'd like to make a...

The largest electrolytic caps that fit in PIMETA positions C2, C3 are generally 12.5 x 25 mm, and one generally needs 25V or higher. I've given up on squeezing into a Hammond J12 case, the K12 gives me much more room to play with attenuator, charger experiments, so these are the constraints I'm...

My experience has been mixed with getting iPod line out to my CMoy amp, and I want to do better when I build my PIMETA. The particular SendStation PocketDock Line Out I bought sounded dreadful, with serious distortion. Who'd think you could botch the sound in such a short distance? They sent me...

I'm working through the Pimeta parts list. As I've said elsewhere, I'd love to fit into the Hammond J12 case using 12 rechargeable AAA cells in two RC battery packs. This limits my C2, C3 capacitors to 12.5 x 20 mm. A height of 25 mm won't fit. Ok, if I drop back to 10 AAA cells I can use the...