Tube Amp Designs, 2 Types…
Recently it occurred to me that there are 2 distinctly different approaches to tube gear design.
And while neither is strictly observed, there is a fundamental orientation to the design process itself that is significant.
And really this isn’t limited to just tube based audio gear, but because very few classic SS designs, using all vintage parts, (especially the silicon based parts) are high on the list of ‘projects I want to do’ these days, the tube based gear stands out as a more substantial example.
These 2 approaches begin at the very start of the design process itself.
To wit, does the design intent begin with using parts that are at the ready and already on hand, or are desired to be used, vs. a ‘clean sheet of paper’ approach, where the design is based upon achieving functional and operational goals to solve known circuit ‘deficiencies’.
So in a nut shell, approach…
#1) select the tube or tube(s) you want to use and design a circuit around them.
&
#2) design a circuit and then match tubes to properly run that circuit.
And the differences between these 2 approaches would seem to be relatively minor, except that the resultant SQ, will be different.
And to be sure, neither #1 nor #2 will be strictly followed, for instance some tube combinations just aren’t going to work well together, and in some cases won’t work at all…
And manufacturers have additional needs such as tube availability which in many cases precludes option #2 because they need to have a sufficient supply of tubes for their designs…
So approach #1 would be in the majority of the available tube gear, mostly because manufacturers can produce lots of examples of all kinds of tube circuits.
Also #1 is more ‘marketable’ in that the tubes chosen are already well known and are plentiful, so familiarity and acceptance is less of a stumbling block to purchasing ‘new’ tube gear.
Still the advantages of approach #2 is that the design comes first with the tubes being matched to perform as the design dictates.
Instead of the, dialing in the circuit to match up the tube(s) to work with each other approach, design approach #2 aims at optimizing the choice of tubes to function at (or near) their optimal operating points, so the entire circuit (not just the tubes) get dialed in, in order to function ‘properly’ in the 1st place.
Am I splitting hairs here?
Perhaps in some eyes, yes, but the differing results between these 2 design approaches can be quite significant in terms of SQ.
And for some, the very nature of the SQ is the primary and final determination of the desirability of an amp.
And in some cases so much so that some will go to extremes (read $$$$$$$$) in order to achieve SQ that meets their requirements.
And to be sure approach #1 is what most manufacturers employ, and realistically they are limited to those tubes that are either currently being manufactured, or are plentiful enough for production, with a few exceptions of course.
Which means it’s the DIY’rs and home builds where #2 can be found, although certainly not exclusively.
Many DIY’rs have specific tubes they want to use and so build around it (my BIG 45 amp is an example), and so the number of tube based circuits that fall into the #2 category is a rather small percentage of the overall number of available choices that are and have been made in the 1st place.
And it should be noted that approach #2 does require access to specific and customized designs by a ‘real’ designer and in an ongoing basis as the sought after final end results are pursued and do require.
So why bring all of this up in the first place?
Well, this distinction between these 2 approaches is generally unknown, except to designers and those who know not just how to design a tube circuit, but also those who would want to explore diverse kinds of design choices in the first place.
And to add yet another layer to all of this, most designers efforts are aimed at the production of these designs.
These designs are after all meant to be used and enjoyed and so ‘completing’ the design by having a working and fully functional ‘prototype’, ready to be replicated for sale to others, is often the point of spending the time to ‘perfect’ the transformation of a design idea into a fully functional working audio component.
In addition there are some designs and their implementations that have reached near cult status and lots of them are nearly 100 years old. They can sell for 100’sK$ or more. These designs use an ever diminishing supply of parts and not just tubes.
These designs were the result of research into all phases of sound reproduction and for all manner of commercial, industrial, and institutional uses. From recording studios, to sport stadiums, theaters to school PA systems and much much more.
Western Electric, to this day stands far above and far ahead of the vast majority of all current designs, and to the extent that there companies trying to replicate the original parts and to fully replicate this highly sought after gear.
I raise this because there are those who still, to this very day, continue to attempt to replicate the SQ that was achieved back ‘in the day’, only using todays available parts and components.
And because WE followed path #2 to such a marked degree, to the extent that they created, from scratch, component parts to match their designs, tubes, resistors, inductors, wire, and more.
And today those very same parts can bring eye-watering prices.
And as some know, pursuing SQ that beckons from just ever so slightly beyond our grasp, can be a life long obsession, hobby and avocation, and obviously one worthy of such life long ongoing pursuits.
Even if it gets excessive…
JJ