Archive for the ‘Vanity and other sins’ Category

The younger version of me was very much into hard rock, alt-rock, and metal.  The types of amps and guitars I used all went to 11 and stayed there.  As I got older, I branched off into other directions.  In my mid-20s, I ditched electric altogether and played acoustic for 4 or 5 years, only to return to it with a Big Muff.  In my early-30s I explored more classic rock, but with modern tones.  Now, in my late-30s, I’ve gone from being an acrobatic, outside soloing, masturbator to being limited in my playing and learning about economy of notes and action. (more…)


Looking at the cover, I noticed that La-te-ra-lus has an alternate meaning (at least in-part).  La, Te, and Ra are notes in the Solfege sight reading method.   (more…)

I had just a few thoughts come to mind regarding modifying amps, modifying EQ, or creating your own.

It’s a fact that Mesa Engineering uses two modified forms of the Marshall tone stack for their Dual Rectifier series.  Compared to a classic Marshall tone stack, the Vintage/Raw tone stack moves the center of the “Mid” control down in frequency and has more attenuation.  This carves out some of the meatier part of the guitar frequency to make room for the massive lows and a high-mid emphasis.  The tone stack enabled for Channel 3 Modern has boosted upper-mids, but has a very similar, low-to-low-mid frequency response. (more…)

Wow.  After most of one year devoted to my favorite amplifier, I don’t have a regular topic to cover, now.  Toward the end of 2015, my health declined pretty dramatically.  I ended the Dual Rectifier analysis early, because it was taking too long to put the articles together.  Aside from helping people understand the amp or tweak it, my intention was to assist DIY circuit designers, by highlighting interactions between the preamp stages and the key changes Mesa made to the basic design as established by Marshall and Soldano.

Since this version is now obsolete, I felt there would be little harm in sharing an analysis.  I haven’t done this for people to copy the design in whole.  Since the schematic is available in dozens of places, that could already be done by anyone who would want to.  I want people who are making their own amplifiers to see what this example does and decide if anything from it should, or should not, be a part of their own design, or if a modified form could be used.

When my health became even worse than it already was, I was stopped dead in my tracks.  By the time I could sit at the computer again, the inspiration was waning; not by lack of my want to write it out, but by the effects of the disorders I have to contend with.  It’s a very difficult hobby and I don’t want to make mistakes if I’m trying to help others.

Left Undone

I had not originally planned to write about the power amp, but some of it was relevant to analyzing the preamp modes.  I put that into the “Overview” article, but there is more that could be said.  I’m not sure I’m going to be able to do it.  In particular, the negative feedback could use a more detailed analysis to determine exactly how much stability is being added.

The other thing is the power supply.  The effects from combinations of different settings of the power and rectifiers would help with understanding the compression and headroom designed into the stages.  In fact, with only a very quick look, I noticed that V1 and V2 are probably more compressed and act like a limiter compared to tubes upstream, but it would need an analysis to be sure of that and also the extent of it.


I’ve had a request to analyze the Mesa Boogie Mark V.  I might analyze select parts of it.  At this time, I don’t have the energy to go into massive detail and I don’t own a Mark to test the results.  I could post it as “just hypothesis”.

If I run into my own problems or cool, quirky tones, I’ll post about solutions or tweaks.  I also have one my old pedal designs to tinker with and some DIY ideas to look through, but I am not able to be in a hurry with any of it.

I wanted to give my deepest gratitude to all of the people who have visited this blog in 2015.  My statistics for visits and engagement aren’t massive (and I don’t expect that), but they exceeded my goal by more than 200% and my total page views were more than a 4000% increase over 2014.

In particular, the members of the Mesa community at The Boogie Board have provided inspiration, feedback, questions, critique, and support that helped shape the way information was presented in regard to the articles about the Dual Rectifier.  Thank you, very much.

As well, a handful of people from the Music Electronics Forum visited to check my work and I am incredibly grateful for the time and feedback from those who helped.

I hope everyone has an awesome 2016.  Cheers.

Mission Improbable

There are a few reasons I’ve been spending so much time exploring the Dual Rectifier.  Those reasons include: misinformation, biases and myths, and helping others.

The misinformation takes many forms.  Sometimes, it’s just reading about the DR having “active EQ” (false), that it isn’t a “solo” amp (false), or other equally dubious claims about the design that are ridiculous.  Biases and myths also fit in with the misinformation, but are just as much about the insecurities of the users as any misunderstanding of the amplifier.  Claims about early revisions being “superior” or the utility of the 2001 3 Channel version are as ridiculous as the circuit misinformation, because it’s all subjective.  If I was a little more cynical, I’d even think the second hand market is involved in promoting and spreading this kind of bias to increase, and retain the increases on, the obsolete designs.  Seeing as how Mesa designs them, builds them, markets them, receives feedback, and profits most from the sales, if the old amps were superior, they’d swap directly back to it due to customer demands and complaints. (more…)

This is the result of testing equipment during a time when I was trying for vintage guitar tones.  I used an MXL condenser pencil mic.  It was about 6 inches back, straight on, pointed 3 inches left and one inch down from the cone.  I wanted to capture a balanced, smooth sound.


DR and H400aSo…  got bored and threw in a Harmony H400a to my setup.  When I would split my signal from the guitar and send it to both, the Recto would hum from a ground loop.  I expected the same here, but there was not any hum at all.  It won’t work for Metal, but for some good ol’ Classic Rock, Blues, or whatever isn’t brootuhl, it’s fun.  The Mesa EQ actually sounds pretty good through the Harmony, but it’s very “middy” from the lack of lowest lows and highest highs due to an 8 inch speaker.  At the right balance, it sounds great and provides some nice stereo sounds.  If I were to ever get around to making the doodad to run the Harmony to a speaker cabinet, this would be awesome.  If you have similar gear, it doesn’t hurt to try something and see if it makes a decent sound.

I have some demos on there and a few personal things.  Just to let you know: if I miss a note, biff a riff, or otherwise do not perform perfectly, I don’t do a retake and I don’t really give a shit.  It is what it is and the demonstrations are about the sounds, not how awesome I am.

I have some videos to make for the EMG fuzzstortion mod, the split humbucker mod I did on one guitar, and the combo of a 5-way switch and spin-a-split mod on another.  My shoulder is jacked up.  Once it heals, I’ll be making more awesomely bad videos.

The pdf opens in this window.  Open it in another tab if you want to see it and follow along.

Table Dancing Double Multiplier Warmonger

This is an approximation for the preamp of an amp I love.  It has multiple channels, wazoos, doo-dads, and what-nots.  This is a bit different from the original.  It’s only one channel.  I moved a couple grid stop resistors to attenuate with the grid leak resistors.  Their values are different than the original, but are scaled to do the same functions.  I changed the value of parts of it to reduce noise, but have approximately the same frequency and performance responses in most cases.  I changed some of the cathode resistors to a more common value, but it’s close to tolerances and barely shifts it into a colder bias that makes little difference.  Some of these changes are also because it doesn’t need to have all the extra stuff in the overall circuit if it’s only one channel.

This is NOT an exact clone.  I think of it as a distillation of godliness into a smaller package with some wiggle room for my own preferences.  I didn’t include the tone stack, PI, or output.  I’ll leave that up to anyone who would like to further tweak it, in case they want to have a feature or omit a feature.  It’s about flexibility.

Some notes about the schematic:

  1. My software barely supports tubes and the pins are all labeled for 6,7, and 8.  This obviously is wrong on some of the tubes, but I couldn’t change it.  V2 and V4 would be 1,2 and 3.
  2. It doesn’t have a model for a regular mono jack or a cliff jack.  The stereo jack works fine enough for demonstration and I’m sure a person would be able to figure out what to do.
  3. You can change the input grid stop resistor to taste.  The original uses an alternate way of attenuating radio frequencies and I chose a small value to prevent attenuating the guitar if it’s volume knob is turned down a bit.
  4. You might consider lowering the value of V4’s cathode bypass cap if the bass response is too mushy.  Removing it altogether along with it’s series resistor might not be a bad idea, but will also attenuate the highs by a great amount and greatly reduce the gain of that stage.
  5. A somewhat smaller value on V3’s anode bypass cap will brighten the sound a little.  That’s there mainly to prevent oscillation, but it’s cutting a huge chunk of frequencies right out of the stage that aren’t going to oscillate.
  6. I made the grid stop resistor for V4 56k.  This is pretty low, but is partially to offer less attenuation and lends some brightness after some of the larger values upstream and to offset some of the attenuation in v3’s circuit.

I welcome any comments, questions, suggestions, or cease and desist letters anyone has.