Friday, September 13, 2013


I'm thinking about blogging a little bit on Wordpress for a while. It'll be more casual than here. If you use Wordpress and aren't following me you should follow me and help me pick out a new handle.

Tuesday, June 18, 2013


Hello everyone who still might read this!

I am considering installing Disqus before resuming blogging here.

Please let me know if you  
  • like or dislike leaving comments using Disqus.
  • have or haven't installed Disqus on your own blog.
  • found it easy or difficult to install.
  • had any moderation problems.
  • have decided some time after installing it that it is worth keeping or not.
  • have any other suggestions for other comment systems.

Tuesday, September 25, 2012

Big Muff Tone Stack analyshenanigans.

So, I did a few crude experiments and have a few problems, but they've gotten me thinking about how difficult it to manage impedance-related losses in passive circuitry. Here is a more technical diagram of what I'm actually doing.

This is just a diagram of models. Basically I know that if a circuit fits a model, and the models work together a certain way, then I know that the circuits work together that same way. Every wire you see Zout in one stage, and Zin in the next stage, attenuation is occuring, and this time its unwanted. For a "perfect" transmission of voltage, Zout must be zero and Zin must be infinity. The problems with these impedance is that they change when you twiddle the knobs. If it was predictable it wouldn't be a big deal, but there are some variable resistors that have to be taken into account, so instead of saying Zin is a, we have to say Zin varies from b to c. It might take differentiation to find the min or max, depending on how you do it. Here's the schematic for the version of the tone stack I'm using:
To find Zin, we just see what the equivalent resistance to ground of the whole thing is, assuming no load. To keep life simple, we're going to just do a DC analysis, and assume that capacitors are open circuits.
There's only one path for current to go through, so the equivalent input impedance is trivial to find: just add up the three resistors. To find Zout, you see what the equivalent resistance going in BACKWARDS from the load is, assuming that the source is grounded. For this circuit, this means two branches which are effectively in parallel, and each one of them contains half of a potentiometer. bigmuffstack3 To really analyze this, we're going to have to split up the potentiometer. Let's call one half R and the other half (1M-R), since they have to equal 1M. So this means that the two parallel branches consist of R + 39k and (1M-R) + 8.8k. The formula for parallel resistance tells us that in terms of R, Zout is (R+39k)*(1008.8k-R)/1047.8k, a quadratic. It's easy to see that when R is 1M, Zout is approximately 8.8k, and when it's 0, Zout is approximately 39k, but when R is 484.9k, about halfway, Zout becomes its maximum amount: 261.95k. So there you have it. When I design the attenuator, it must be able to deal with this large change in output impedance by having an input impedance much large enough to be considered equally "larger" to both values. When I tested the circuit I plugged it directly into the 22k impedance effect return, and the result was that in the middle of the knob barely any sound came out, and it was crazy loud at the outside. Looking at the numbers, this is the result one would expect! More on attenuator design coming soon.

Monday, September 17, 2012

Getting the rig together--FX loop tube

So, I actually have a growing need for a working and/or more permanent guitar rig. For recording I've been able to hack things together as a kind of one-off, but most of the tones I got were things that I wouldn't be able to easily reproduce again, especially live, with the equipment I have now.

Anyway, one part of this is due to the fact that I rely on a (cheap) mic tube pre-amp to make my (cheap) solid-state combo amp sounds like an (expensive) tube guitar amp.

The problem with this is that to get the nice tone coloration out of a tube, you have to drive it hot, and it ends up being driven so hot that the signal level would be unsafe. So I just keep the volume as low as possible. I just nudge it up from zero until it sounds at all--and that's still usually too loud. I feel like if I turned it up any higher than that I'd blow my power amp or speaker for sure.

The combo I'm using is a Peavey Transtube Studio Pro 112, and the mic pre is an ART Tube MP Studio. Based on the specs, the amp nominally sends and receives -10dBV through the effect loop. The Tube MP has a maximum gain of 44dB, and a maximum output of about 20dBV. While it looks like I'd need a 30dB attenuator, I'd rather it be adjustable, so I'll probably end up testing several levels before committing to one.
Unlike a guitar amp preamp, the Tube MP also lacks any tone controls. I've been wanting to implement an idea for a new passive tone stack anyway, so I've decided to use it here. It consists of two Big Muff tone stacks, each with flat mids, but who have different cutoff frequencies. This would allow a wide range of mid cut and mid boost options in addition to regular Big Muff tone operation.

Both the attenuator and tone controls can be 100% passive, and since they're intended for the same device, I'm going to consider them the same project and put them in the same box, which with the ART TubeMP I'll hopefully be able to velcro somewhere on my amp.

Here's a diagram of how it would be.

rig Without the FX loop, the signal goes straight from the internal preamp to the power amp.

Next post I'll record a video of what it sounds like without the attenuator and tone stack (although I think I've done that before, but without really talking about it), and show what would have to hook up to what.

Thursday, March 15, 2012

Meta Mojo Remojonation Blog Meta Plan Post Blog

This blog needs some new mojo or something. New description etc.

Here's stuff I do that is "bloggable":

  1. Music Stuff
    1. Guitar Technician Stuff
      1. Basic Tech Stuff
      2. Tech "experiments"
    2. DIY Audio Recording Stuff
      1. Basic Audio Recording (in linux)
        1. LADSPA effects
        2. Software
      2. Recording technique "experiments"
      3. Noodling that results from recording technique
    3. Equipment "tour" Review videos
    4. Video Production Stuff
      1. Basic Video Editing (in linux)
      2. Video editing experiments
      3. Video encoding process (in linux)
    5. Actual full-fledged videosongs
    6. Songwriting
    7. Album reviews
      1. New Albums
      2. Old Albums
      3. Johnny Cash Albums
  2. Book stuff:
    1. Book reviews (including synth books)
    2. Book vlogs a la Fragment Friday
  3. Electronics stuff:
    1. Pedals
      1. Pedal Design
        1. Mainstream and/or Boutique pedals
        2. DIY
      2. Pedal Construction
      3. Pedal Mods
      4. Pedal Reviews
    2. Synth Theory
      1. "top-down" (modules, waveforms, topology0
      2. "bottom-up" (transistors, etc)
    3. Circuits 101
    4. Synth Circuit demonstrations

I think I should be able to get on a schedule or something. For instance, I could assign a percentage to each big topic--I could make a decision along the lines of "I want 30% of my posts to be about synthesizers". I could look in my archives and notice that only 25% of my posts had been about synthesizers, and then, well, I'd know what my next post topic would be.

Then I could subdivide each big topic into percentages for each subtopic, etc.

I'll probably make a spreadsheet. By the gods, I sure do love spreadsheets.

I feel like this kind of system would help me stay diligent about posting, and also ease the difficulty of deciding not just what post to make next, but what kind of work I should be doing IRL! If my next post is supposed to be about a song I've written and I haven't written any ... well I guess it's time to write a song!

I think I'm not going to post the percentages publicly, mostly because I don't want people telling me "ZOMG you did it wrong" and also so I can reserve the right to tweak the numbers.

Do you think I'm missing anything? Which of these topics sounds the least boring? Which sounds the least interesting?

The audience I wish I had has just as many "non-techie" types as "techie" types. Don't feel like you shouldn't comment just because you find all of the listed topics boring.

Also of course ... how do I wrap up that list of topics into a sentence that describes me?