So I often find myself just sitting at the computer surfing EE sites, data sheets, etc. and thought it would be cool to have a thread to share good tidbits of lernin'.
Here's a paper on what to do with unused opamps in a design. (http://www.electronicproducts.com/Analog_Mixed_Signal_ICs/Amplifiers/Properly_terminating_an_unused_op_amp.aspx)
The idea is to avoid wasted power, stress and noise, you should make sure it has a reference voltage and give it feedback. So something like this:
(http://cl.ly/image/1v2y100X2o1J/Screen%20Shot%202013-02-27%20at%2011.58.37%20PM.jpg)
Like the idea of this thread. Isn't this already one of the nerdier corners of the internet? ;)
I'd like to share these transistor charts:
http://www.beavisaudio.com/techpages/Transistor-Pinouts/index.htm
not only does it help with pinouts, it gives hfe/gain ranges
-tip on what I've learned: don't underestimate low gain transistors, especially in fuzzes and wahs. Vintage transistors were low gain. Modern transistors are high gain. Try low gain transistors where you're going for a "vintage" sound
Quote from: jtn191 on February 28, 2013, 07:01:06 AM
Like the idea of this thread. Isn't this already one of the nerdier corners of the internet? ;)
well at least we've got the musician-thing going for us, haha.
i thought i'd share these design notes on active filters (https://focus.ti.com/lit/ml/sloa088/sloa088.pdf). published by texas instruments. very mathy but lots of good info, especially on the different filter implementations.
Quote from: jtn191 on February 28, 2013, 07:01:06 AM
Like the idea of this thread. Isn't this already one of the nerdier corners of the internet? ;)
Hell no! What we do here is usable in the real world on a day-to-day basis! For a really small portion of the worlds population, but still usable..... ;) I really like this thread-idea, hope to contribute something soon!
Paul
Quote from: jubal81 on February 28, 2013, 05:05:40 AM
The idea is to avoid wasted power, stress and noise, you should make sure it has a reference voltage and give it feedback. So something like this:
Diagram A is what we'd be doing most of the time.
But you might as well use that output as VREF for the rest of the circuit, instead of just tying it off. Buffered VREF is more stable and can be less noisy in some applications.
In the Box of Hall and Tenebrion reverb circuits, that's exactly what I did. Only needed three op amps for the audio, so I used the leftover amp to buffer VREF.
Quote from: culturejam on February 28, 2013, 07:57:46 PM
Quote from: jubal81 on February 28, 2013, 05:05:40 AM
The idea is to avoid wasted power, stress and noise, you should make sure it has a reference voltage and give it feedback. So something like this:
Diagram A is what we'd be doing most of the time.
But you might as well use that output as VREF for the rest of the circuit, instead of just tying it off. Buffered VREF is more stable and can be less noisy in some applications.
In the Box of Hall and Tenebrion reverb circuits, that's exactly what I did. Only needed three op amps for the audio, so I used the leftover amp to buffer VREF.
That's definitely some good thinkin'. I'd noticed that when I saw your schematic because I do love my reference buffered.
Came across a fun toy at Analog devices.
This web app designs filters to your specification. (http://www.analog.com/designtools/en/filterwizard/#/type)
You choose the filter type, components, etc. and it shows you the circuit. Neat stuff!
(http://img708.imageshack.us/img708/8150/thir.jpg)
Quote from: stecykmi on February 28, 2013, 07:43:27 PM
...
i thought i'd share these design notes on active filters (https://focus.ti.com/lit/ml/sloa088/sloa088.pdf). published by texas instruments. very mathy but lots of good info, especially on the different filter implementations.
That's a great reference. I used it to learn how filters worked back when I was only doing digital stuff just so I could get a better understanding. In general, TI's got a ton of really good application notes. I posted a link to this one on op amps in another thread, but it is worth sharing here too,
http://www.ti.com/lit/an/slod006b/slod006b.pdf (http://www.ti.com/lit/an/slod006b/slod006b.pdf).
If you are into the history of this stuff, TI has this great paper on op amps which has to be one of the earliest papers on op amps. It's written by Thomas Brown, the Brown in Burr-Brown.
http://www.ti.com/lit/an/sboa092a/sboa092a.pdf (http://www.ti.com/lit/an/sboa092a/sboa092a.pdf)
Quote from: jubal81 on June 21, 2013, 12:45:28 AM
Came across a fun toy at Analog devices.
This web app designs filters to your specification. (http://www.analog.com/designtools/en/filterwizard/#/type)
Awesome. It's like a top-down version of this:
http://sim.okawa-denshi.jp/en/CRhikeisan.htm
Quote from: midwayfair on June 21, 2013, 12:55:58 PM
Quote from: jubal81 on June 21, 2013, 12:45:28 AM
Came across a fun toy at Analog devices.
This web app designs filters to your specification. (http://www.analog.com/designtools/en/filterwizard/#/type)
Awesome. It's like a top-down version of this:
http://sim.okawa-denshi.jp/en/CRhikeisan.htm
These are both really useful. I've bookmarked them both. Thanks!
Just picked up this interesting nugget on opamp noise and design: (http://www.analog.com/library/analogdialogue/anniversary/8.html)
"The amplifier's own voltage noise is always amplified in the non-inverting mode; thus when an op-amp is used as an inverting amplifier at a gain of G, its voltage noise will be amplified by the noise gain of (G+ 1). For the precision attenuation cases, where G<1, this may present problems. (A common example of this is an active filter circuit where stopband gain may be very small but stop-band noise gain is at least unity.)
Only the amplifier voltage noise-and any noise developed by the noninverting-input current noise flowing in any impedance present in that input (for example, a bias-current compensation resistor)-is amplified by the noise gain."
This is breadboarding like a sir. Tons of great tips.
Nice! I thought I was a half decent breadboarder until I watched this :D
Gotta give some of those tricks a whirl.
Thanks for sharing!
Josh
Quote from: jubal81 on July 12, 2013, 12:12:34 AM
This is breadboarding like a sir. Tons of great tips.
This makes me feel inadequate. :p
Yeah... I thought I was pretty good at it too.
Now I know I'm not.
Jacob
Well, not having started breadboarding at all, I now know what not to do, plus a whole bunch of good advice to start doing it. The only thing I didn't like was when he was talking about throwing stuff away..... I just can't do that! If it's not completely wasted, I'll hang on to it......
Paul
He shows the exact breadboard wire set I bought. And said to throw it away. Lol.
That guy sure does some tidy wiring.
Sent from my Nexus 7 using Tapatalk 4 Beta
Quote from: DutchMF on July 13, 2013, 08:55:36 PM
Well, not having started breadboarding at all, I now know what not to do, plus a whole bunch of good advice to start doing it. The only thing I didn't like was when he was talking about throwing stuff away..... I just can't do that! If it's not completely wasted, I'll hang on to it......
Paul
Um, I like those little short guys that are all cut to exactly the length that you need for almost every connection. Why would I throw them away? Does he throw every wire he used away after he's done with a project? I do understand about the waste of information involved in having the colors correspond to lengths instead of something meaningful though.
My biggest change in how I breadboard things now is that I've taken to etching boards for common modules that I find myself using repeatedly. That make things much easier.
Quote from: RobA on July 14, 2013, 12:38:14 AM
Quote from: DutchMF on July 13, 2013, 08:55:36 PM
The only thing I didn't like was when he was talking about throwing stuff away.....
Does he throw every wire he used away after he's done with a project?
Isn't that exactly the kind of advice this world needs? ;)
Quote from: RobA on July 14, 2013, 12:38:14 AM
My biggest change in how I breadboard things now is that I've taken to etching boards for common modules that I find myself using repeatedly.
Like buffers, boosters, generic transistor stages, muff stages, whole overdrive/distortion sections, variable low pass filters, mid cut/boosts, tone stacks, phaser stages, LFOs, charge pumps, right? What else?
Quote from: kothoma on July 14, 2013, 09:49:04 AM
[...]
Like buffers, boosters, generic transistor stages, muff stages, whole overdrive/distortion sections, variable low pass filters, mid cut/boosts, tone stacks, phaser stages, LFOs, charge pumps, right? What else?
Pretty much, yes to buffers, boosts, tone stacks, phaser stages, charge pumps (and other power supply). I haven't done any work on anything distortion/overdrive/fuzz related since I started this idea. So, none of those modules. The others are various modulation targets, tremolos, etc. The main thing I've been working on is CV control, so modulation targets are the natural thing.
Quote from: RobA on July 14, 2013, 11:29:52 AM
Quote from: kothoma on July 14, 2013, 09:49:04 AM
[...]
Like buffers, boosters, generic transistor stages, muff stages, whole overdrive/distortion sections, variable low pass filters, mid cut/boosts, tone stacks, phaser stages, LFOs, charge pumps, right? What else?
Pretty much, yes to buffers, boosts, tone stacks, phaser stages, charge pumps (and other power supply). I haven't done any work on anything distortion/overdrive/fuzz related since I started this idea. So, none of those modules. The others are various modulation targets, tremolos, etc. The main thing I've been working on is CV control, so modulation targets are the natural thing.
I see. Just a few more: mixers/panners/balancers, envelope detectors (for noise gates, compressors, auto filters/wahs, envelope phasers, detune delays...)
Yep, auto-wah and compressor modules are next on my list of things to etch.
I'm still looking for a way to use such little modules not only for breadboarding but also for actual builds. Just can't find the right geometry and mechanics for this.
Quote from: kothoma on July 16, 2013, 05:35:00 AM
I'm still looking for a way to use such little modules not only for breadboarding but also for actual builds. Just can't find the right geometry and mechanics for this.
If they are small enough, then I arrange them like a DIP module and then use these,
http://www.taydaelectronics.com/connectors-sockets/pin-headers/40-pin-2-54-mm-single-row-pin-header-strip.html (http://www.taydaelectronics.com/connectors-sockets/pin-headers/40-pin-2-54-mm-single-row-pin-header-strip.html).
If they are too big for that, then I just put some of these http://www.taydaelectronics.com/connectors-sockets/pin-headers/40-pin-2-54-mm-single-row-female-pin-header.html (http://www.taydaelectronics.com/connectors-sockets/pin-headers/40-pin-2-54-mm-single-row-female-pin-header.html) on and use jumper leads between the breadboard and the module.
Quote from: RobA on July 16, 2013, 09:07:56 AM
Quote from: kothoma on July 16, 2013, 05:35:00 AM
I'm still looking for a way to use such little modules not only for breadboarding but also for actual builds. Just can't find the right geometry and mechanics for this.
If they are small enough, then I arrange them like a DIP module and then use these,
http://www.taydaelectronics.com/connectors-sockets/pin-headers/40-pin-2-54-mm-single-row-pin-header-strip.html (http://www.taydaelectronics.com/connectors-sockets/pin-headers/40-pin-2-54-mm-single-row-pin-header-strip.html).
If they are too big for that, then I just put some of these http://www.taydaelectronics.com/connectors-sockets/pin-headers/40-pin-2-54-mm-single-row-female-pin-header.html (http://www.taydaelectronics.com/connectors-sockets/pin-headers/40-pin-2-54-mm-single-row-female-pin-header.html) on and use jumper leads between the breadboard and the module.
Yeah, that would be possibilities. But I'd like to avoid sandwiches as height usually is an issue.
Truly excellent filter calculator right here:
http://www.ampbooks.com/home/amplifier-calculators/coupling-capacitor/
Thanks to Thelonius on DIYSB for the tip.
I was watching this new video from SparkFun this morning on PBC layout tips (https://www.youtube.com/watch?v=NJKZZArjdg8 (https://www.youtube.com/watch?v=NJKZZArjdg8)) and there are some good tips in there. He mentions at one point a site that has a calculator for computing trace widths. I looked at the site and there are a few other calculators that might prove useful as well http://circuitcalculator.com (http://circuitcalculator.com).
Simple circuits reduce regulator noise floor (http://www.edn.com/electronics-blogs/the-practicing-instrumentation-engineer/4422750/Simple-circuits-reduce-regulator-noise-floor)
The "capacitor multiplier" circuit looks really interesting. Wonder how viable of an idea it is to replace large power supply caps with say a 10uF ceramic, a resistor and a transistor.
The title of this article grabbed me. Why, no, I had no idea that LEDs have intrinsic capacitance.
This little tidbit got me wondering:
"The threshold, or knee, voltage rises higher as the LED wavelength becomes shorter. All PN-junction diodes, including LEDs, have capacitance due to depletion and diffusion profiles."
Wonder if that principal applies to multicolor LEDS - and of course - can you alter the threshold dynamically in a clipping configuration?
Linky (http://www.edn.com/design/led/4368392/An-LED-s-intrinsic-capacitance-works-in-a-650-mV-LRC-circuit)
Already had a nother thought. That capacitance value probably affects the clipping characteristics. Wonder how much of a factor when two diodes with the same FV sound a bit different as clippers? Which dialectic materials have more and less capacitance? And how much high end is getting sucked to ground?
Quote from: jubal81 on October 17, 2013, 09:55:56 PM
Simple circuits reduce regulator noise floor (http://www.edn.com/electronics-blogs/the-practicing-instrumentation-engineer/4422750/Simple-circuits-reduce-regulator-noise-floor)
The "capacitor multiplier" circuit looks really interesting. Wonder how viable of an idea it is to replace large power supply caps with say a 10uF ceramic, a resistor and a transistor.
Interesting stuff there. I wonder how the other characteristics of large caps come in to play and how these multipliers work with it. It seems it would be useful for power supply applications in SMD settings if it works well.
I did some playing around with using an op amp based capacitance multiplier to make the high shelf circuit of a parametric EQ movable. I remember it working pretty well. Which reminds me that I need to go and play with that some more.
I forgot to post this little bit of experimentation here back when I went through it.
First, here's an extended discussion.
http://www.diystompboxes.com/smfforum/index.php?topic=104341.0
Here's the results of my experiments:
I got some time to do some experimentation with the FETs I have here. I used a 10K for the source resistor for the tests just to get a sense of what they did. The supply voltage was 18V and the gate bias resistor was 2.2M. No positive bias on the gate.
I tested:
2n5457 (fairchild from Smallbear and the mystery ones from Tayda)
2n5458
2n5485
2n5952
J201 (fairchild from Smallbear and the mystery ones from Tayda)
MPF102 (fairchild from Smallbear and the ones from Tayda that seem to be the real thing)
2SK30
2SK170
MPF102 ended up with the highest source voltage, about 3.5V (all were above 3V out of the ones I had). I was a little surprised by this based on the datasheets.
The second best was 2N5458, about 2.5V.
2n5457, 5485, and 5952 all ended up around 1.5V-1.7v, despite the differences in Vgs on the datasheets. 2SK30/170 were a little closer to 1.5. The supplier didn't seem to matter in this usage even though I know that many of the Tayda ones have less output when used in a booster.
J201 was all the way down at .7V! And I could indeed hear it distort with some humbuckers.
MPF102 is fairly common, but the 5458 is a little cheaper.
I went back to an MPF102 on the breadboard to mess with the source resistor some, and no matter how big I make the source resistor it never got above a certain level (about 3.6V). None of the other FETs I have on hand get anywhere close to that.
Okay, I know that 3.5V is VERY BIG for a guitar signal, and anything in front of the buffer that might be creating a signal that big is probably a dirt pedal, so any buffer distortion is not likely to be too noticeable or objectionable. But it's certainly nothing like the half supply you guys have mentioned. I don't exactly have a huge collection of FETs, but these are a fairly wide range.
----
Also, Brian at Runoff Groove suggested 2N3819, which ends up with an even higher emitter voltage (over 4v).
------
Hope some people find this useful. In particular, you might want to consider swapping out J201s in your input sections for a different FET as noted here. For instance, I've been using MPF102s for buffered bypasses (one in my Fatpants 2013 and one in my Zen Drive because that circuit sounds like ass unbuffered).
Thanks Jon, that's very useful.