Tuesday, March 1, 2011

Blogging my audio electronics creations

Here we go!

 I've decided to set up this blog as a convenient place so that anyone interested can follow along with my DIY audio projects and perhaps the occasional random thought.  Some of you may know me as a frequent contributor to the online forums at AX84 where I post under my own name, Paul Fawcett, or (less frequently) on the Music Electronics Forum (where I post as "Wombaticus").  My main interest has been in building and designing tube amps intended for guitar, and I have done a fairly extensive range -- everything from small single-ended 5W practice amps, to tweed-inspired combos, to full-on 50W and 100W heads.  More recently, I've developed an interest in stand-alone effects, and vintage pro-audio equipment.  I also have modest but still-developing commercial aspirations, and will eventually have some offerings available at my website, www.wombatamps.com

I'm a scientist by training and my general philosophy to amp design and building is informed by that attitude. There's a huge amount of bullshit surrounding music gear and audio in general, and my basic position is skeptical. While there are undoubtedly some "golden eared" individuals among us, I find that claims of audiophiles are often suspect, and snake-oil salesmen abound.

You won't find any snake oil here.

The trick is separating the BS from the truth.  Indeed, there are certain solid and scientifically justified principles, which if followed, will lead to excellent results.  One of my heroes and mentors in this field is Merlin Blencowe, aka the "Valve Wizard".   I've always loved the tag-line on his website: "Putting the science into Mojo", and that's what I aspire to.  Aside from the masters of yore in the old "wisdom literature", some other guys who really know their shit, and I admire greatly, are Randall Aiken over at Aiken amps and RG Keen, who runs the well-know Geofex website. I'm also a member of Gothik Amps, a consortium of like-minded individuals.

As a practical matter, what does this mean? Well, it means my focus is on the basics... start with getting the fundamental circuit design right - the frequency response doesn't lie! I'm a huge fan of circuit simulation...of course, it's important to know when simulation can mislead you, but I'll often run hundreds of simulations of a circuit in LTSpice before ever picking up a soldering iron.   Second, I'm really big on getting the layouts right. "Don't bozo the layout!" is still rule #1.   It's amazing to me how many designs, even commercial ones, manage to screw-up their ground schemes, or put sensitive components in wrong place, and end up with buzzy amps as a result  Finally, you need to select the best components for the job...while I love tube audio and the sound that tubes contribute, I'm by no means a "tubeist".  Frankly, there are certain jobs that a transistors are just better at doing, and I am absolutely not afraid to use a transistor here and there - when it's the right part for the job, and I'm confident that they will be sonically transparent.

While circuit design and layout are paramount, and probably account for 80% of your tone, I do acknowledge that intelligent component choice is what can put you over the top and take the sound from "good" to "outstanding".  In particular, I favour using really good quality (often custom wound) output transformers, low ESR power supply caps, nice film coupling capacitors,  and over-specced metal film resistors for the lowest possible noise floor.  Most of that isn't really controversial, except for perhaps the last.  It's a subject that sparks holy wars, but I find that old-fashioned carbon composition resistors contribute nothing but horrible hiss... just one example of where the mojo isn't.  Give me a 2W metal film resistor and 2W mil-spec potentiometers any day. Tubes make a difference too, of course, but I find that its hard to prejudge what will work best.  For a given circuit, sometime a vintage NOS tube is better, sometimes a current production tube works better - it's often a matter of "tube rolling" to find the right one for a particular circuit.   Finally, as a result of my "no sacred cows" attitude, even when I've built amps clearly inspired by the vintage greats, I don't think I've ever done an exact clone. There's always room for improvement.. to paraphrase the AX84 tagline, "Respect the past, but don't be enslaved by it"!




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