Do It Yourself!

Editor's Note: in the main, Stereophile has steered clear of DIY audio projects, leaving them to magazines like The Audio Amateur, which was published by the late Edward T. Dell. But one of the exceptions was this 1967 article on the "Brute," a tube amplifier design by none other than Ed Dell. Note that the DIY competition mentioned by Gordon Holt is long closed to entries.—John Atkinson

There's a platitude to the effect that the road to Hell is strewn with good intentions. Well, we don't see ourselves as headed for perdition, but we must admit that we are surveying a rather impressive-looking junk pile of good intentions at this point.

This issue was going to be a snap to get out. The main article had been written, the photos had been taken and all we had to do, we figured, was draw a few diagrams. Well, we'll spare you the gory details. Suffice it to say that things did not go quite as smoothly as anticipated, which is why you are receiving the last issue of 1966 early in 1967.

This issue is devoted almost entirely to the construction article we've been promising for longer than we like to think about. Those who want to tackle the project will find the article to be much more detailed and helpful than the typical construction piece, while those of you who aren't interested in a do-it-yourself project but happen to own a Dyna Stereo 70, or a Mark IV amplifier, will get a lot of useful technical information about these units that will be invaluable for trouble-shooting purposes at home.

Originally, we had planned to publish Mr. Dell's construction article on the deluxe Stereo 70 in two parts, but we decided at the last minute that it would make more sense to keep all of the material together in one issue, so that it could serve as sort of an instruction manual for those who build up the amplifier. As a result, most of our other regular features got squeezed out of this issue. We also dropped four pages from this issue, to allow us to get it out as soon as possible.

In the next issue, which is already well under way, we'll be making up for lost time with the largest equipment reports section we've ever had. To wit; In the next issue we'll have reports on the Futterman H3A amplifier, the Acoustic Research AR4x speaker, the Shure V15-II pickup, the KLH Model 20 modular system, Ampex 915 and 4010 speaker systems, the latest version of the Ortofon S-15 pickup, the Janszen Z-900 speaker system, the Utah HS-3 speaker system, the Revox tape recorder, the Audio and Design tonearm, and the long-awaited IMF/London Mark IVA pickup.

Speaking of construction articles, we have noted for some time that there is not a really versatile stereo microphone mixer available for under several thousand dollars. Neither is there likely to be, in the foreseeable future, simply because it is not the kind of thing that is considered to be a "consumer item." Mixers for home use tend to be very basic, offering mixing facilities and nothing more. And for the advanced recordist, mixing alone is only half of what's needed.

So, The Stereophile is going to hold a contest. Anyone who can come up with a really good mixer design that can be built for under $300 (at regular prices or surplus-parts prices) is invited to submit a schematic and a description, along with performance test results, to The Stereophile for consideration. If we like the looks of it, well ask to borrow a built-up sample of the unit for testing under actual-use conditions. The mixer that we feel offers the best all-around compromise between flexibility, performance, and price will be published as a construction article in a future issue, and we'll pay $100 in cash for the design that we use.

Here are some features you might consider: (1) At least four, and preferably six, inputs; (2) Provision for feeding at least one input into both channels, with a panning control; (3) Provision for ganging two or more inputs, so they may be controlled by a single knob without affecting other channels; (4) Sufficient input-voltage-handling ability to avoid overload when a high-output mike is used close to the sound source; and finally, (5) Provision for inserting unity-gain external devices (equalizers, reverb units, etc.) into individual channels. And we don't care if you pirate circuits from commercial designs, as long as you pirate suitable ones, and cite the sources.

To save you unnecessary time and expense, we suggest you contact us before you start buying parts, describing in detail the features and specifications of the unit you intend to produce. If it looks like a possible winner, we'll give you the go-ahead on the project.—J. Gordon Holt

The Brute: A Super-Amplifier for the Do-lt-Yourself Perfectionist
It is difficult for anyone who has never built anything from scratch to appreciate the very high degree of personal satisfaction to be gained from the successful completion of such a project. Apart from the sheer pleasure of accomplishment, there are such accessory rewards as the ownership of an absolutely unique item—the only one in the world that's exactly like it—and the awe with which less-adventurous friends will view the product of your endeavors. And when your masterpiece also happens to be one of the best of its kind, there is more than just pride of accomplishment to justify the work you put into it.

Such is the amplifier described in this article, the first construction piece we have published but, hopefully, not the last. The amplifier is a deluxe version of the Dynaco Stereo 70, beefed up by a massive power supply, equipped with metering facilities for the critical output stages, and constructed from the kind of components that all amplifier manufacturers might well be using if they didn't have to consider the price of their products.

But why, of all things, build a tube-type amplifier at a time when tubes seem to have been virtually "phased out" in commercial amplifier designs? For two main reasons: The kinds of transistors that are capable of giving dependable, low-distortion audio service are not yet available at reasonable cost, and cheaper ones aren't uniform enough in manufacture to enable them to be thrown into a circuit without pretesting on a transistor curve plotter. (This is one reason why most transistor amp manufacturers insist on doing all repairs themselves, at the factory.)

And anyone who has been led to believe that tubes are obsolete in high-quality audio equipment should peruse some of the catalogs of professional amplifying equipment. Transistors are available for those who insist on them, but most professional equipment is still exclusively tube-type. Professional users are more interested in quality than novelty, and they have to be shown a good reason for switching from time-tested components before they'll make the switch. Evidently, they're still not entirely convinced about transistors.—Edward T. Dell

Robin Landseadel's picture

Interesting to note—the Mackie mini-mixers, developed in the 1990's, happen to fulfill all the criteria for Gordon Holt's contest. I was gifted a recent mode [VLZ 1202] as a birthday present this year, six microphone inputs, all with phantom power, multiple effects loops, eq, the works.

low2midhifi's picture

If my living accommodations were different, I'd have gone DIY for speakers 100% a long time ago. I purchased a kit from the defunct Audio Concepts from LaCrosse, Wisconsin years ago. For over two decades the kit was a reliable mainstay in one of my systems.

The components kit cost about $180.00, if my memory serves, plus shipping and handling. The kit had a coated fabric dome Seas tweeter, an AC-proprietary polymer 8" woofer, and a basic, completed crossover.

The rest of the project consisted--with some help and my parents' garage, table saw, and that Black & Decker classic 1980s workbench--of about 1 week's worth of sawing, sanding, assembly, and painting. We even used quarter-round molding to reduce sound diffraction at the corners of the enclosure.

The results were impressive compared to what was available at my budget back then. Until I finally donated the speakers about 5 years ago--outfitted with a replacement 8" Peerless paper driver, from the surviving Wisconsin-based supplier--the results were still very good.

The speakers were first a transmission line design. I later changed the configuration to a sealed monitor. The speakers were built like a tank, with ripped 2x4 to buttress the corners.

I had a friend who was encouraged by my project, and did one of his own. He went a step further with his 6 1/2" woofer, monitor project. He made a double wall of MDF and left a 1" space between the two walls. He then filled the void with sand before sealing up the enclosure. The results with his project as it related to the sound quality: excellent again.

Even today, you'd be hard pressed to find any speaker below $5,000 per pair with enclosures having the sheer durability of the those that my friend's project and mine had. These speaker projects both weighed in at about 30 pounds per speaker: a bit heavier than a Sonus Faber Guarneri Evolution or B&W 805D3, but less than a Wilson Audio Duette.

There are great kits to be had today. I guess one could debate if the gun-for-hire designers of the crossovers have all of the technical capability of a team of professionals of a major manufacturer. But the drivers on these kits are pretty much the same of what a wide variety of manufactures use for their own products. In fact some kits have drivers that a keen eye will find on products costing many thousands of dollars. And as to the enclosures, MDF is MDF; most manufacturers still use this material.

I know that this publication is devoted to featuring finished goods. However, for the money-strapped enthusiast, kits have to figure into the equation when one is thinking about new speakers.

Building one's own amp is probably a pursuit that few would have the patience or technical and assembly acumen to pull off. DIY speakers are an Everyman's solution for those who have the space and tools to do it.

leking's picture

remember reviewing The Audio Amateur of that year for this project..indeed that was an interesting read..still didn't find the hard copy only e version so if anyone has it, let me know - would love to purchase!!