Posts Tagged ‘circuits’

On the Breadboard

May 30, 2016

Maybe this will be a recurring series. It should be possible if I’m actually Making Things.

Bazz Fuss

Information about the Bazz Fuss can be found here.

A few years ago I tried out the Bazz Fuss and was very disappointed. Being careful with transistor and resistor choice seems to be much more crucial than People on the Internet imply.

I actually fried one transistor by using a variable resistor that was allowed to vary down to zero. Was quite amusing to turn it down, then up again, only to find the tone was drastically different. Somewhere in the middle of this process I made an instagram video. Bazz Fuss fried video.

The “best” version I created consisted of a clean boost followed by a standard BF with high gain, then a tone stack, then a BF with lower gain and emitter degeneration added. This allowed bizarre octave-up effects with tone high and big muff-esque tones when low.

Double Bazz Fuss with Tone video.

Chance that I’m develop this further? It *was* pretty high before I built the next Thing. Now, slightly less.

Harmonic Percolator

The Interfax Harmonic Percolator is an legendary (or at least notorious) fuzzbox mostly associated nowadays with the music of Steve Albini. Albini has several youtube videos on the subject. There’s some info here.

Tried out a Harmonic Jerkulator, an all silicon Percolator clone developed by Tim Escobedo. Details available here. It sounds amazing. It doesn’t sound Albini, but neither do “faithful” clones or any other variant I’ve heard, so whatever. Sounds like a germanium fuzz-face to me except despite being boomier it never gets muddy enough to where you can’t hear all the notes.

IMG_2353.JPG

Chance that I’ll develop further? 100% chance I’ll youtube it, 50% I’ll box it up, 20% I’ll try and market it.

Ruby

The Ruby amplifier, from runoffgroove.com.

Built this LM386-based 0.25W amplifier. It sounds suspiciously good. Even when plugged into my upcycled computer subwoofer. I’m definitely gonna box this up. This is an extremely high-margin Thing if it were ever to be Etsy’d.

100% chance it’ll get boxed up. I’ve never sold on Etsy before so … if I ever decide to this’ll probably be the first thing I do.

IMG_2352

Anyway, those are the three ideas I’ve been monkeying around with over the past week.

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DIY PCB Etching process pictures

March 22, 2014

My first etch! It’ll be a single transistor overdrive for guitar, maybe.

Nail polish on copper on fiberglass:
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Ferric Chloride solution:
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Etching:
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Nail polish dissolves in acetone:
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Finished etched board:
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Now … drilling is next. How exactly I will drill 40 holes in that, we’ll find out later. :)

Update, lots of DIY thoughts, not much DIY progress

March 13, 2014

Sorry for no update. Really not that much going on.

Haven’t touched my diy-guitar amp. It still sounds great but no change. Haven’t recorded with it yet. I have a few things I need to do before I am capable of recording anything at all.

I’m thinking about using some hart pine my dad has to construct a cabinet for the amp head. IDK exactly what I’m doing in terms of DIY joinery, but it’s worth a shot. Main problem is that the best tool I own is a dremel. Worst case scenario I just use lots of brackets and screws. Also I have never finished wood. Anyone know the best way to finish hart pine?

Another problem with finishing the amp is that I’ll need to completely disassemble it in order to repaint the chassis. Should have done that first instead of last… oops.

I also just bought materials for etching my own PCB. I’m going to try and throw together a single-transistor dirtbox sometime that I planned a layout for.

I haven’t touched the antique tube radio I bought on ebay. I’ll post about that sometime. It’s going to take quite a bit of work to get restored.

I’ve gotten heavily into a new hobby: mining and trading cryptocurrencies. For the scope of this blog, the less said about it the better, I’m sure. I guess I actually mentioned it in passing last time. I taught myself python so that I could write an automatic daytrading bot. It’s been making me an average of a dollar or two per day, so that’s cool. Python is exactly like how xkcd described it. It makes programming fun again.

I always WANT to blog more and I WANT to record more music and I WANT to make youtube videos but sometimes these things just don’t happen. I scribbled down some music today at least, but unfortunately I have to do things to my computers before they can even record at the quality that I have in mind.

Here, listen to a cover I recorded three years ago:

Oh Sheesh (school, guitar amp, dogecoin, etc.)

February 5, 2014

I don’t seem to blog much right now. Since school has started again maybe my routine will work out so that it happens more. School is dumb this semester. I was too anxious to talk to all the right people to get signed up for the difficult things I need to do to graduate, so I’m just doing the easy things. Despite the things being easy, I am currently writing this post while procrastinating on something due at 8AM tomorrow. Such is life, I guess.

I finished the amp from last post. It is wonderful and it is loud. It still needs a tiny bit of troubleshooting:

  • Hum, probably from heater current. DC elevation didn’t fix it, nor did switching out the center-tap ground for a virtual ground. The heater wiring can be shortened but I haven’t gotten around to doing it. I could also reduce the total current.
  • The preamp plate-starve control does nothing. It varies the preamp supply voltage from 300V down to 150V as I planned–however this doesn’t affect the sound AT ALL. Apparently none of the amp’s distortion is actually coming from lack of plate headroom. It’s also possible that this control is bleeding hum into the signal, but it seems unlikely. This control will be removed, but I might put a master volume in its place.
  • The “snappiness” control is wired backwards, it seems. I’m gonna leave it.
  • If the second boost switch is enabled and the volume or tone is set at 8 or higher, very loud crackling and feedback occurs, in addition to small white sparks visible at the top of the power tube. Adding series resistance to the bypass capacitors didn’t fix the problem. I’m thinking about adding series resistance to the power tube grid to see if that helps. If it doesn’t, I’ll just rewire the knobs so that 8 is the new 10. :)

Soon I will take pictures and possibly video and make audio recordings, but I’d kind of like to fix these issues first.

The other thing I have been “into” recently is dogecoin mining. I’m getting about 100KH/s but I only made a $50 investment into gear, so whatever. So far I’ve made back about $15 (actually Ɖ11,000)  but I’m planning on holding until the price goes up. The inflation rate is going to halve in almost exactly a week, so that’s interesting.

What have you guys been “into” recently?

DIY guitar amp in progress pictures, 5F2A inspired

January 13, 2014

Here are some pictures of my amp in progress. Tooling a steel chassis with nothing but dremel is kind of way too much work bit for my first build ever it’s still worth it.

Here’s the first batch of parts I got in:

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Vacuum tube power! This is the power amp tube, a 6V6GT made by Electro-Harmonix:

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And here is the preamp tube, a 12AX7, also from EHX:

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This is the power supply soldered on the turret board… Next time do wires first and components second, self. Of course at this point my 600V wire hadn’t come in the mail yet.

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Power Transformer holes on chassis:

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And here’s where the output transformer will be:

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Finished turret board in place for reference, no wiring yet lol.

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Finally got the tube socket holes dremeled out. Never again, lol.

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Power tube (temporarily) in place next to power transformer. Panel drilled and (temporarily) populated.

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All front panel and board wiring done. All socket wiring done except for whatever goes to the transformers.

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All I have left is drilling the output jack, drilling the output transformer wire holes, dremeling the lamp hole, then wiring the output and power connections. Then I can rock out! Oh yeah I do need to finish wiring my old combo as a cabinet before then, but that’s basically done already.

I have spent about $170 building this amp–a new replica would cost at least $600 (and wouldn’t have any of my extra features ;)). Of course I’ve also put at least 10 hours of work. Maybe 15. And that’s not including planning which is probably another 15 or 20. So if I was selling it you could say I was paying myself about $9/hr. Better than I thought! Of course to actually get $600 it would have to be painted and mounted in a nice wooden box with a panel decal, etc.

I was hoping to finish before school started (which is today) but no dice. I might not get to put any work into it until tomorrow, and even then I might only get an hour or two. Hopefully by the weekend I’ll have it knocked out.

Tube Guitar Amp Design

December 28, 2013

I haven’t been “active” recently (Thanks school!), but I’m about to start on a fun project that I’ll hopefully get to write a bunch about before school starts up again. I’m building a guitar amp! If you don’t care for technical mumbo-jumbo, skip ahead to the question at the end of the post or something.

I’m building a guitar amp head based on the Fender 5F1, 5F2, and/or 5F2A circuits. These are Class A single-ended 5W tube amps made in the late 50’s, sold under the names “Champ” and “Princeton”. Mine is based on a Champ from 1958. Here’s a block diagram:

5f1-champ-block

The 5F2 adds a simple low-pass tone control after the volume. The 5F2A adds a bypass capacitor to the first triode’s cathode resistor. This gives a little extra gain and brightness.

Here’s a preliminary schematic from LTSpice. I’ve been running LOTS of simulations, lol.

spice-champ

Here is a list of features I’m adding to the 5F1:

  1. Switchable cathode bypass capacitors
  2. Adjustable negative feedback
  3. Tone control
  4. Speaker impedance selection
  5. Output transformer open-circuit protection
  6. Adjustable preamp anode voltage
  7. Adjustable power tube voltages (probably not!)

Also I’m going to be using a solid state rectifier instead of a tube rectifier, but some might have a point of contention with me calling that a “feature”.

So let’s go through those. First, switchable bypass capacitors. I’m adding a switch to select between two different bypass caps for both triode’s cathode resistors. The 5F2A uses 25μF, which is overkill. Mine will have the option of no bypass, 2.2μF, or 0.22μF: The lower value will give a more distinct treble boost without boosting the overall gain too much. The boost from the 2.2μF option isn’t much different to the 25μF. Using the first stage’s boost should result in more triode distortion, while using the second stage’s boost should result in more distortion from the power tube. I hypothesize that since the power amp is Class A this shouldn’t be a dramatic distinction, but it should be noticeable. However, this is before negative feedback is taken into account. The second triode’s bypass cap effectively removes all negative feedback from the circuit.

Second, adjustable negative feedback. In these amps, there is a 22k resistor tied all the way between the speaker output and the second triode’s cathode. There is very little current through it but just enough to give the sound a little extra clarity. Of course, this reduces distortion, so some people like to remove it. I figure making it variable from 10k to 100k would be more interesting. There should also be a different effect depending on which speaker impedance is being used, and as mentioned above, any feedback at all has less effect if the second triode’s cathode resistor is bypassed.

Third, tone control. I’m considering using the 5F2 tone control as-is. If I wanted to create more work for myself I might use the Baxandall tone stack, which I have some affection for, but honestly it’s probably too much work for little payoff. The way I play my amp now is either dimed or with the highs rolled back, so I might as well be using a basic LPF like the 5F2 anyway.

Fourth, the output transformer I acquired has taps for 16, 8, or 4 ohms. I should either make the taps switchable or use separate jacks.

Fifth, output transformers hate being run without a speaker hooked up. Since I’m building a head instead of a combo, I should really design some kind of protection. Putting 220Ω from the 16Ω tap to ground should prevent say… a fire, but if I want even better protection I should find out what kinds of shunt diodes or MOVs or whatever else are out there. There is probably a jack available that switches to a dummy load when unplugged as well. Who knows if such things are trustworthy–more research is required.

Sixth, the triode plates are run at 275V. This can be decreased as much as I want without anything bad happening. In general, lower voltages sound bad but they give one the option of increasing distortion without increasing volume. Who knows, perhaps there will be an undiscovered sweet spot.

Seventh, the same as the above could be applied to the power amp tube. Unfortunately, it draws significantly higher current, and for safety, one shouldn’t change the plate voltage without changing the screen grid voltage as well. So while the triode voltage mod can be done with a single potentiometer, the power amp voltage mod would require the design of some kind of power BJT or MOSFET circuit. I’ve attempted to design a few of these that should work, but the parts are relatively expensive and I really doubt the work would pay off.

The biggest change I’m making isn’t an addition, it’s a substitution: silicon diodes instead of a rectifier tube. Some people claim that tube rectifiers sound better because they “sag” and others claim that they promote tube longevity because they take longer to turn on. Either of these design goals can be achieved via resistor and capacitor selection, so it’s kind of a non-issue.

So there, that’s a description of my goals. I need to come up with a task list so I guess I’ll do that right now. (Not including research. For me, research seems to just HAPPEN. I have something like 45 open tabs in Chrome, and that’s only on my phone…)

  • Test power transformer with multimeter
  • Test output transformer with multimeter, dummy loads
  • Design solid state power circuit
  • Make list of special parts needed–power resistors, HV caps, etc
  • Determine cable current requirements
  • Order passive components (digikey)
  • Order tube sockets, tubes, chassis, board (ebay)
  • Build power circuit
  • Test power circuit
  • Build amp circuit
  • Populate chassis
  • Test bias voltages
  • Rewire old combo as cabinet
  • Test amp with guitar
  • Do some cabinetry
  • Mount chassis in cabinet

I might have left something out…

I already started writing a post (which actually became this post instead) about the power circuit design, but it needs some work before it’s readable.

So yeah, that’s what I’ve been thinking about recently. Have any of you DIY-guys ever built a guitar amp? If any of you non-DIY guys have a guitar amp, what do you like about it?

(Absence of) Progress — school project, pedal projects, monotron simulation

October 19, 2013

I haven’t been present here for the past couple of weeks… I’ve had one alright post I’ve been working on but have had to spend a little too much time on school stuff to actually finish it.

Anyway, Korg made the schematics for the Monotrons and Monotribe public, so I’ve been working on an LTSpice simulation of the original Monotron. I have the VCO and VCF working, but I haven’t made any cool samples or anything. I’m hoping to use the simulation to fix what is widely perceived as the Monotron’s worst bug–a popping sound that occurs at the beginning and end of notes.

I’m at least two weeks behind on my project for school, but at least I finally have 90% of the parts in. I’m at a coffee shop right now designing the motor driver. It’s gonna be a giant pain and take up two Arduino proto shields. I have no idea if I’m going to require heat sinks or not either, and if I do, I have no idea how I’ll get them or make them or whatever.

Another problem I had was getting the motors attached to the wheels. The bit of aluminum that is supposed to connect to both was too small to fit the motor shaft inside it so I had to drill it out. Then the screw holes for screwing into the wheel were spaced too far apart to fit my wheels, so instead of using them I just covered the whole thing in epoxy and stuck the wheel on. They’re going to wobble a little but at this point I’m beyond caring about that. A post I could easily make tomorrow would be a photo post of my progress. Good idea, self.

I also breadboarded a Tube Screamer and have been rocking out with that, even though I never finished building the other guitar effect I was building. I’m having a hard time deciding if I should finish the as-of-yet-unnamed “black dirtbox with big switch on it” or start working this TS clone into a box. The black dirtbox has its board about 70% populated but as usual everything is way too close together and I’m not sure if I’m going to be able to make any of the connections on the bottom properly.

For the TS clone, I’m planning on using a case that I tooled for an older TS-inspired design I dreamed up. That one I gave up on when I had just started populating the board–again because I tried to cram way too much crap onto it. Because I’m removing all the extra features I’d added it’s going to have four giant holes with nothing in them. I’ll have to at least shield it or something. *shrug*

I guess I should post some pictures of those guitar projects too. I’m not currently in a state where I can make any recordings to show you what they actually sound like. Even my playing consists of just one chord over and over while I change one value on the breadboard, so when I say “rock out” I’m really using that term loosely.

Anyway, that’s what I’ve been up to, Nothing is EVER FINISHED but I’ll try and get a few pictures posted tomorrow anyway.

Steiner-Parker VCF simulated

September 22, 2013

I spent Friday night at my internet-less grandparents, but I still got some work done on simulating some schematics I already had laying around.

I saw this schematic for a filter inspired by the one from the Steiner-Parker Synthacon, and was taken by both its simplicity and its unique design. I haven’t really done a lot of analysis of it, other than that it uses a string of eight diodes as voltage-dependent-resistors to vary the cutoff frequency.

Unlike many multimode filters, each mode has its own input but the filter has a single output. Most filter modules you regularly see have a shared input for each mode, but with separate outputs. This one looks the most similar to a filter topology I’ve seen in school, the SAB or single-amplifier-biquad, but I haven’t really given it an in-depth look.

Anyway, the schematic can be found here. Props to Ken Stone for his work. I might buy some of his PCBs sometime.

I made a crappy sawtooth oscillator (perhaps a post on that later) and then loaded Ken’s schematic into LTSpice, then fed the oscillator output into the filter’s low-pass input. I set up a piece-wise-linear voltage source to drive the oscillator with an eight-step sequence and summed three slow triangle-wave voltage sources to drive the filter’s cutoff. I hard-set the resonance to max–in my simulation this didn’t cause oscillation as Ken’s website noted. *shrug*

Image

Here’s the 64 seconds of synth-filter sound that I coaxed LTSpice into dumping out:

This filter’s squelchy goodness is really remarkable. When I ever get around to buying some CGS PCBs these will definitely be on the list.

WordPress Tags/Topics

September 17, 2013

The “circuits” topic here on WP is about 50% arduino and 50% fitness. I’m new to ardunio, and it’s fun, but what I’m really into is all analog. The “analog” topic, of course, is about 90% photography and 10% music, but no circuits. “electronics” is pictures of iPhones.

Not to mention, “modular” is less than 5% synthesizers.

So yeah, if anyone sees anyone blogging about non-digital circuitry, lemme know. Still looking for more people to follow.

Or if there’s something about the topic system that I’m misunderstanding.

SesquiAPC Atari Punk Console “mod”

September 16, 2013

This is an idea that I vlogged about approximately a million years ago. I finally built one into a more permanent enclosure.

(Sesqui means one and a half.)

I used something called “dead bug” construction. This refers to gluing components upside down to a surface with their legs in the air, then soldering directly to the legs without a circuit board. It’s kind of like a really crappy quick-and-dirty version of point-to-point wiring, except it lets you use more modern package types that aren’t intended for that.

I made a video demo last night. I currently lack a decent audio interface for recording. Please just bear with the static and crackles:

Here’s a rough schematic. I had to make it from memory… there are probably quite a few differences between it and the one in the video. All of the crossfade resistors are encased in heat-shrink stuck directly to the pot’s legs, for instance. And I can’t read the values on these caps without a magnifying glass, so I just didn’t.

sesquiAPC

Basically, the top 1/3 of the circuit is a narrow pulse oscillator. The first capacitor charges through R1 and R2. When it reaches 2/3 of the supply voltage, the 555 does its magic and lets the capacitor discharge through just R2 until it reaches 1/3 of the supply voltage, then the process starts over.

Every time this happens, a pulse is generated on the “OUT” pin. This pin is connected directly to the “trigger” pin on the 2nd and 3rd 555. These are set up to only let only one cycle occur every time they’re triggered. However, if they get triggered twice (or more) before the the capacitor finishes charging, then they still only output one pulse for all of the triggers that happened in that time.

Basically this means that if the first part is generating a 600Hz pulse wave, the second part is capable of outputting a wave at 600Hz, or 300Hz, or 200Hz, or 150Hz, etc. And the third part does the same thing, but these two frequencies are selected separately, which means that musically useful harmonies can made between them.

The original only has one of these dividing stages. I see a lot of people building TWO of the original in one box together, but it is my opinion that what I’ve done is about 50x as musically interesting and useful as that, and also has less parts.

If you think this sounds interesting enough to make your own, I could try going a little bit more in depth with a how-to. The original APC is one of the simplest things you can build that has a really impressive sound, and my SesquiAPC isn’t that much more involved.