A broadcast console makers perspective

I received a great email from Michael “Catfish” Dosch, console designer for Telos / Axia Audio Systems.  The email was sent in response to a comment I posted on the WEBE WICC Studio Build Out post.  I though the email was very interesting and informative, presenting a perspective that most broadcast engineers do not often see or appreciate.  I asked Mike if I could use it as the basis for a blog post and he agreed.  I am not going to blockquote the entire thing, but here is the unedited email and pictures.

Quote:

“Ken said you had a concern about the ruggedness of our consoles as compared to the old PR&E boards. You might not know this, but I was with PR&E before joining Telos. In fact, I designed many of those old PR&E boards. I guess that makes me an old console designer. Ahem.

The Element design is more modern in construction and styling, but it is no less rugged than those old PR&E boards. In fact, you could stand on it if you wish. The top is 1/4 inch machined aluminum plate supported by structural aluminum ribs on the backside. The chassis itself is made of custom extruded aluminum structural pieces, machined aluminum side panels. The flat sheet metal on the bottom is not structural, it’s only a cosmetic cover. You’ll see a lot of folded sheet metal in other consoles because it’s cheap and easy. But it’s not as rugged as the Element approach which is why we chose to go with a more complex and expensive mechanical design.

Telos Axia console cross section
Telos Axia console cross section, Courtesy of Axia Audio / TLS corp

One very visible difference between Element and a PR&E consoles is the use of lexan on the front panels (PR&E would use aluminum or steel on the top panel). This might seem less rugged, but it is actually chosen because it is a more durable surface than painted and silkscreened metal. It is more scratch resistant and it is rear-printed so that the markings never wear out. Silkscreens would wear off under heavy use — particularly next to faders and monitor controls — and look horrible over time. These lexan panels will look just as good after 15 years as they do now.

But lexan for all of its durability has its own limitations. The edges can crack under abuse. This is why you see many older Wheatstone consoles (they have used lexan overlays for many years) with cracks and tears at the very edges of the plastic. This is particularly troublesome in the fader slot. A frayed edge on a faders slot can cut your fingers. That is mighty unpleasant! So when we decided to use lexan, we wanted to have all the benefits and none of the drawbacks.

So we designed a machined recess on each channel allows the lexan insert to have its outside edges protected by the aluminum. More obvious is the bezels around each button and even the fader slot. Look carefully and you will notice that all of the control bezels edges are above the lexan. The edges of the lexan are not exposed and therefore not prone to cracking, chipping or splintering.

Axia Audio console control surface, courtesy of Axia Audio / TLS corp
Axia Audio console control surface, Courtesy of Axia Audio / TLS corp

In this drawing, you can see the panel without the lexan. The machined pocket to protect the outer edges of the lexan, plus the raised edges of the button and fader bezels to protect the edges around the holes. These button guards are also designed to prevent accidental actuation of the buttons. And while the guards are designed to protect accidental actuation, they never hinder deliberate activation. Notice the guards at the sides of the ON/OFF buttons and not on the top and bottom. Even operators with long fingernails will have no problems with these controls. The small round keys are engaged with a light touch of the fleshy pad of the fingertip.

Yes, I think we built great consoles at PR&E. But Axia was a fresh start, a chance to raise the bar even higher, by retaining many of PR&E’s better attributes and improving upon some of the weaker areas. DIPswitch configuration has been replaced with the convenience of the web browser. Spill-prone motherboards and electronics have been eliminated from the control surface. Unreliable monitor pots have been replaced with optical rotary encoders rated for 5,000,000 rotations.

And you asked about the faders. This is a particularly important component in a broadcast console. PR&E used Penny & Giles faders for many years. We used their Series-4000 faders in the X-Class consoles (BMXIII, AMX, ABX and STX). This was their top-of-the-line fader at the time and performed beautifully… for a year or two. Then our clients started experiencing field failures at a very high rate. We worked with P&G on a return/rework/replace program that took years to clean up. Our clients were disappointed and we spent a fortune making things right. It was that experience that caused us to begin searching for alternatives.

The market for high-end faders is quite small. There are tons of consoles out there for live sound, home recording, etc., but these products are sensitive to costs and generally use very cheap faders. There just aren’t enough high-end recording consoles or broadcast consoles being built to attract a lot of fader vendors. After a lengthy search, I disqualified all but two fader companies: P&G and a Japanese firm by the name of Tokyo Ko-on Denpa (TKD). I assigned one of our engineers to create a set of environmental and life-cycle tests to see if the TKD faders could keep up with the P&G faders. We were all shocked by the results.

Out of 100 of each type tested in various environmental conditions and physically cycled for the accelerated equivalent of 10 years of heavy use, we had only one TKD fader failure, compared to more than half of the P&G Series 4000 faders! We defined “failure” as any deterioration to specifications or any discontinuities. All the failed units had discontinuities (audio dropouts). We were able to clean the failed TKD fader and it passed the retest. About half of the failed P&G units were cleaned and passed the retest. So in the end, the practical results were TKD 100% good and P&G 75% good. Not what I expected at all.

We then designed a TKD fader into the Radiomixer. We watched the customer support logs carefully for problems. Out of the first 1,000 console channels shipped, we saw one TKD fader failure during the first year. Warranty replacement of course. The failure rate did not increase with use as you would normally expect. We were seeing consoles with 3 or 4 or 5 years of heavy use with no fader problems at all. I have heard of 20 year old Radiomixers with original faders still working great.

One particularly elegant feature of the TKD fader used in Element is a side loaded wiper arm. This prevents liquids or other foreign matter from spilling into the fader slot and directly into the fader element. This feature alone is probably responsible for extending the useful life of the faders by a considerable amount. Of course, these can be disassembled and cleaned just like a professional fader from P&G, they just don’t need it so often.

Axia Audio TKD faders, courtesy of Axia Audio / TLS Corp
Axia Audio TKD faders, courtesy of Axia Audio / TLS Corp

Some have the misconception that if a fader is not P&G, it must be cheap. Actually, these are very expensive faders, about the same cost as P&G. But they are so well made, I think they’re worth every dollar. I know there are still some folks out there who remember P&G’s glory days when they made bullet-proof faders. I remember fondly those days as well. But in my experience, the TKD fader is superior to the equivalent P&G fader. We feel so confident, that we warrant all Axia consoles for 5 years, including all components….”

End Quote

That is a great explanation of what goes into one of these consoles right from the designer.  The pictures are courtesy of Axia Audio / Telos Corporation and special thanks to Mike for taking time out to give us a glimpse into the mind of a console manufacture.

The Otari MTR10

I have come upon two of these units in very good shape:

Otari MTR10 1/4 inch 2 track reel to reel machine
Otari MTR10 1/4 inch 2 track reel to reel machine

Once upon a time, these were top of the line units.  I don’t know how much they cost new, but I’d imagine it is somewhere north of $3K in 1985.

Both machines work mechanically and electrically.  One machine has some slight grooves in the record and playback heads and looks a little more worn.    The other does not.  I will entertain all offers.   If a person would want the machine to be gone through and aligned, I’d charge three to four hundred dollars for my time.

Audacity digital editing software

Audacity logoAudacity is the name of a free digital audio editing software package made distributed by Sourceforge. It is distributed under Version 2 of GPL without exceptions.   It does require an .mp3 plug in to generate mp3 files.  According to the Sourceforge website:

Audacity was started by Dominic Mazzoni and Roger Dannenberg in the fall of 1999 at Carnegie Mellon University. It was released as open-source software at SourceForge.net in May of 2000…

Audacity is a free, easy-to-use and multilingual audio editor and recorder for Windows, Mac OS X, GNU/Linux and other operating systems. You can use Audacity to:

  • Record live audio.
  • Convert tapes and records into digital recordings or CDs.
  • Edit Ogg Vorbis, MP3, WAV or AIFF sound files.
  • Cut, copy, splice or mix sounds together.
  • Change the speed or pitch of a recording.

The full list of features is available here.

So, I have download a copy and installed it on my test machine in the basement (hardware requirements here).  My test machine is a stripped out P4 2.4 GHz Windows XP box that I can isolate from the network and experiment with.  On that machine with a digigram VX-880 soundcard, Audacity did very well.  I did not record multi track, but with 24 bit sound sampled at 48 KHz, the computer kept up nicely.  The basic editing features are intuitive and easy to manipulate with mouse and keypad.

For a quick to install downloadable program, it does very well.  Does it do everything like Adobe Audition or other professional editing software suite does? No.  But for the price, it can’t be beat.

RCA receiving tube manual, 1964 edition

RCA receiving tube manualI found this in the great clean out of 2010, Bridgeport, Connecticuit.  Once upon a time, I had a slightly newer version of this, I think from 1972 or so.  This version is from 1964 and gives a complete run down of most small tubes that were manufactured back then.

There is something about a well designed, well maintained piece of tube gear.  I remember an old Collins tube console that was in a production room at a small AM station.  The console went dead (paper clip shorted the B+) and I fixed it.

I recall listening to the test recording of my own voice from a reel to reel machine when I fixed the console.  It sounded better than I’d ever heard it, not that I have a great radio voice, by any means.

A tube is a voltage amplifier versus a transistor, which is a current amplifier.  A tube does not have the same fidelity as a transistor, as the voltage reaches it’s peak, it gets a little fuzzy, adding some distortion and harmonics.  Tube gear adds warmth, what a musician might call Timbre. The combination of fundamental frequency and varying amplitudes of harmonic frequencies that allow a listener to tell the difference between a piano and a guitar playing the same note.

This is what the current crop of tube mic preamps and other tube products tries to reproduce.  Several companies have come out with an amplifier design that has mostly transistors and one tube, usually a 12AX7.    Unfortunately, at least in my opinion, the fall a little short.  If you want to have the “tube sound,” it needs to be all hollow state.

What is intriguing to me are the schematic diagrams in the back of the book.  There is one for an audio amplifier:

RCA receiving tube manual audio amp schematic diagram C 1964
RCA receiving tube manual audio amp schematic diagram, C 1964

This is a single channel unit, for stereo, it would need to be duplicated.  Also, I would loose the tube rectifier in favor of a solid state full wave bridge, that would simplify T2 somewhat.  The OA2 could also be changed to a diode.  Looks like unbalanced audio in, which could be modified with an input transformer.

Another interesting diagram is this one, which can be used as a mic preamp:

Microphone Preamp schematic diagram RCA receiving tube manual C 1964
Microphone Preamp schematic diagram RCA receiving tube manual C 196

That looks like a pretty solid design, a few tweaks here or there to add some gain reduction and some type of output level adjustment and I would be a really cool piece of gear.  Again, the tube rectifier could be replaced with something solid state.  The output transformer would likely have to be changed to something like 600 ohms.

Couple that to something like this, the Collins 26U compressor/limiter, and one would have a great sounding microphone processor:

Collins 26U compressor limiter
Collins 26U compressor limiter

Looks pretty cool.  R10 is used to balance the two plate currents.  I would be interested in the transformer values, input/output impedances, voltages, etc.  The 6386 tube is very hard to find these days, a good substitute would be a 5670 which are still made by several manufactures.

Update:  This is a picture of a Collins 26-U sitting on my bosses floor.

Collins 26-U compressor limiter
Collins 26-U compressor limiter

A great online source for tube information is: Electron Tube Data Sheets.

If I have some time this winter, it may be a fun project to fool around with.