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OK, so this is probably a really stupid idea, but...

I'm getting antsy waiting for the first PCB I did to come back from OSH park and I want to do a couple of more prototypes. I don't want to spend a lot of time laying out stuff that won't work, so I was planing on waiting until I had the first board back before I did the next one so I could make sure I was doing things the right way and my library was working. But, I've got to get started on the next stage. So, I came up with this cracked idea to make a double sided layout, burn them on two boards and then glue them together. I figure I might be able to get them aligned if I drill a couple of the holes very carefully and use this as a way to keep them aligned while gluing and then drill the rest of the holes after it's together.

Anyone ever try this? Or, is it just too silly?

I went looking for MIDI foot controllers again yesterday and was once again put off by the price, size, complexity, etc. of what I found. I've done this several times now. I have the Behringer tank/aircraft carrier thing, but it's, um a little oversized. (And I hate programming it.) So, I've got this idea in my head of building one using one of the little Arduino embedded boards as the brain. I think this part would be pretty easy. There's a decent MIDI library for Arduino and I've written a MIDI controller in software before.

If I'm going to do this, I'd kinda like it to be a useful project in general instead of just focused on the one thing I have in mind. So, I was wondering if there would be others here interested in teaming up to work on this.

The features I'd like to see would be:

• Compact
• Multiple foot switches
• Expression pedal or CV input
• Simple read out options, two line LCD or simple 7 segment numbers
• Battery powered with Li-Po batteries and onboard 9V recharging input

I think most of these would be pretty simple to include. The only on I can see being a bit of a problem is the battery charger because all these parts are SMD. They don't have a lot of pins though, so it wouldn't be too bad.

Anyone interested?

I'm thinking of making an Autobahn for my nephew. He plays bass and guitar. I'd be building this mainly for bass, but I'd like it to work for guitar too. I made one for myself and I really like the way it works for guitar. Are there mods that need to be done/suggested for bass? Input cap up to say 100n? Would it be a good idea to put the 22nF Filter caps on a toggle with say some 47nF caps?

Thanks,
Rob

I picked up one of these last night,

http://www.seeedstudio.com/depot/dso-nano-v3-p-1358.html?cPath=174

It's a tiny little thing. It does work well for effects type circuits. I mainly got it so it would be easy to look at LFO's and other CV circuits. It's great for doing this. It's also got a little square wave generator in it -- it looks to be pretty useful for debugging builds too.

http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/FJN598JCBU/?qs=sGAEpiMZZMv4z0HnGdrLjpo3FY8YkyPv%2foI%252b0yg3vWo%3d

I came across this through hole audio JFET, FJN598JC,  when looking around at Mouser. It's got decent specs for audio. It is end-of-lifed like every other through hole JFET. But, they've got 7000 of them in stock. I ordered a few and I think they are pretty nice. They work well for source follower buffers and overdrive nicely in tube simulation settings. The have an SGD pinout.

Anyone here ever try this method?

http://quinndunki.com/blondihacks/?p=835

The part where she talks about etching is way down the page in "Part V."

I'm looking for some advice on op amps. I'm finishing up the design of an effect that needs a rail-to-rail input and output op amp to do some filtering of signal for a microcontroller. I've got a couple that work well, but I'd like to be able to suggest other possibilities as well since these two aren't available at the more guitar DIY oriented shops as far as I can find.

The two that I have that I know work are the TS922IN and TS912IN. I've tested the usually suspects, TL072, 4558, TL2272, 2082, ... and most of them fail on both rails. The LM358 and TL2272 do fine on the negative rail, but can't reach the positive rail. Anyone have any suggestions for others that will/might work?

Thanks,
Rob

I've been looking for some ways to do audio routing and presets from a microcontroller and I came across this slick op amp, the NJM2121D. It's essentially a slightly beefed up 4558 with two input sets and a single switched output. I think it would be pretty slick for use in various effects, but I can't remember seeing it used anywhere. Does anyone know of an effect that uses one of these?

Here's the link to the spec sheet,
http://semicon.njr.co.jp/eng/PDF/NJM2121_E.pdf

Just wondering if anyone here is using KiCad.  I started working on what I hope will turn into an open hardware project a couple of months ago. So, I figured I should do the development with open software on a readily available computer. I decided to do all the work using KiCad on a Raspberry Pi.

It was a bit weird at first as I was coming from Eagle. But, I've gotten to the point where I actually prefer KiCad now. So, I was just wondering if anyone else is using it.

Rob

I need to get a heat gun for shrink tubing. Any suggestions?

I've tried to read through the various threads on the LowRider, but I'm still confused. Because I've actually got several 2SK30's and only a couple 2n5457's left that I've got plans for, I want to try the 2SK30's first. I'll socket them to make things easier to deal with, but I'd like to get the insertion right from the start. Anyway, here's the question;

The docs list the 2SK30 as the stock part and show them on the schematic, but when I try to follow the traces on the PCB it appears to me that the PCB is actually setup to take the 2n5457 by default. So, if I do try to use the 2SK30's, I'm going to need to do the leg bendy transistor yoga on them?

Thanks for the help,
Rob

I need to get a bunch of low profile jacks and Smallbear is showing zero stock. I've searched everywhere I can think of and I can't find them. Does anyone know of a source for them?

Thanks,
Rob

I was testing some JFET's using the test circuit from runoffgroove and discovered that an entire batch of 2N5458 transistors I recently ordered have strange Idss readings. Before I write and notify the company, I wanted to check to see if it is likely that something else might be up (like I'm doing it wrong).

I checked several other types of transistors; J201, 2N5457, MPF102, BF245A, and 2SK117GR's. These all were within the stated specs. For the 2N5458's, the Vp was within spec but the Idss was only about 0.1 to 0.15 mA where the spec sheet lists 2.0 to 9.0 mA.

Is it likely that these are either fakes or are just bad? Or, am I missing something in measuring these?

One other thing that makes me suspicious is that the face of the transistors is a slight bit rough. I haven't seen this before.

Thanks,
Rob

Since this is my first post, I've got to start off by saying thanks for making these PCB's available. I've built the Current Lover, Pork Barrel, and Slow Loris so far and they've all been great.

Now to the question(s). I've been playing around with a circuit that is essentially the negative voltage generation from the Road Rage. I've got a modified polarity protection scheme on the voltage input and I've changed the capacitors a bit. For the caps, I'm using low ESR electrolytics paralleled with smaller tantalums. Although, this doesn't really seem to have much to do with the issue since changing caps around doesn't fix the issue (other than changing the volume).  I'm testing with an op-amp based tone control circuit that can give about 20 dB of gain.

The issue is the oscillator frequency from the various converter chips. So far, I've tested the Microchip TC1044SCPA, Intersil ICL7660S, and the LT1054CP from TI. I've put a scope on the output and here is what I hear and see for the whine (frequency multipliers on) : TC1044SCPA 10800 Hz @ -68dB, ICL7660S fractionally below 20kHz @ -68dB, LT1054CP 38 kHz @ -64dB. I have either 2 or four samples of each of these and the numbers are pretty close.

So, the TC1044SCPA looks unusable on anything with much gain. The ICL7660S is usable but I'm a bit worried about marginal samples causing problems. The LT1054CP looks really good but is at the higher end price wise.

The TC1044SCPA's have a non-multiplied frequency of around 3kHz which is well below the spec'd typical value. So, I was wondering if anyone else had scoped any of these and had more data. 

Also, I see that Microchip has a device, the TC7660H that is spec'd at 150kHz at 20mA supply with a 10.5V limit. Has anyone tried one of these?

The last question I had was if anyone had tried using an external clock to drive the TC1044SCPA and if so what were your results?

Thanks, Rob