Tag Archives: nashville

Austin Ribbon Mic Completed

The completed Austin ribbon mic. This one will be given away at the Producer’s and Engineer’s Summit at Welcome To 1979 in Nashville, coming up in November.

Here’s a look at my Austin ribbon mic, I completed it yesterday. Building this mic certainly was actually really easy, except for one part… installing the ribbon in the frame. I had to do this several times… six, to be exact. I  had various problems. One, for example, didn’t show it’s ugly head until I’d completed an installation… tiny tears all along the edge of the ribbon. I learned they were caused by the ruler I was using, which had a cork backing that was set slightly behind the ruler’s edge. This small unsupported space allowed the foil room to stress and tear. I corrected this by using a length of rectangular aluminum as a straightedge, this pressed down on the foil right at the cutting edge.

Another problem I had was corrugating the ribbon. I was trying to protect the ribbon by corrugating it with the release paper on the top and bottom, but doing so a) causes the ribbon to curl up, and b) makes the corrugations shallower. If the ribbon isn’t sufficiently corrugated, it is extremely difficult to get it tensioned properly. The tension is important… the ribbon can neither sag in the frame, nor should it be too tight. I had the latter problem, and the ribbon developed a longitudinal curl, so scratch that ribbon.

But thanks in no small part to Rick’s patient support via several emails, I finally got one in. It wasn’t perfect… it could be centered just a hair better… but it looked ok, so I closed it up and finished the mic.

And considering everything, it sounds quite lovely. The last time I used a ribbon mic was 25 years ago, when I did my thesis recording using a pair of RCA TK77’s that the university owned, so I don’t have much of a frame of reference, but it seems to have a nicely balanced frequency response. From what I understand, construction errors show up as poor highs or lows. I don’t have a frequency analyzer set up yet so I can’t give any numbers, but my subjective analysis says “nice.” Now, like all ribbons, the output is rather low, and I did my testing using a rather crappy mic preamp. On voice, one has to crank the gain up quite a bit, and this gave me a lot of preamp noise. For someone who is a low talker, this wouldn’t work. But I got a rather useable level on my acoustic guitar.

Again, I can recommend Rick’s kit quite highly, especially if you’ve never built a mic before. He’s done everything that can be done to insure a good outcome, and the one I built certainly worked out well. That’s not to say it’s simple… you need patience, and good, steady hands will help as well. But I’ve already got parts here to build four more for myself!

Creation Audio Labs

If you’ve been reading this blog for awhile, you know that I’ve been setting up a small studio. The heart of the studio will be my analog mixer, my 1981 Soundcraft 800, which I found in Atlanta for $500. The heart of this mixer is the master module, and the master module didn’t work. There were a number of baffling problems with it… no tone osc, no headphone signal, left side meter read off the scale while the right side read nothing… so I was a little afraid to try to tackle these repairs myself. And a cursory inspection showed no obvious problems that I could see… no burn marks, bulging caps, or exploded bits. I needed professional help.

I had no idea that Creation Audio Labs existed until I read a recent article in Pro Audio Review, where someone had their Soundcraft Ghost extensively rebuilt and upgraded by these folks. That they are only 100 miles away in Nashville, Tennessee, was a bonus. I exchanged some emails with Alex Welti and found out that yes, they could help me. He gave me a rough estimate and I sent the module off to have the work done.

It took them awhile to get to it, but I just got the word yesterday that my module was repaired and on the way back. Reading over the work order reveals that this was the smartest move I’ve made in some time. Apparently, someone else had tried to fix the module and thoroughly f^$&ed it up. They had to repair many broken traces on the PC boards (there are two main boards stacked on top of one another, and another small board for the meter… another reason I didn’t want to tackle it) and found a number of bad transistors, replaced and socketed several ICs… three and a half hours of bench work. While this is a lot of time, it’s also amazing that they were able to get it all done in just three and a half hours. It would have taken me three and a half days, and I’m sure they found problems I’d have missed.

I’m really grateful that these guys are in business, I’d have been in big trouble otherwise. The work was fairly priced… I feel I got a REALLY good deal, since without them I’d have nowhere to turn. I recommend them highly.

At The NETA Quality Workshop

Chattanooga is a comparatively small town in terms of media production, but living here has a number of advantages. A big advantage is our location… roughly equidistant to several very large metro areas, specifically Nashville and Atlanta. I can be in either place ready to work in about two hours. And while I do work in both places, there are sometimes other reasons to travel… continuing education, for example.

At the NETA Quality Workshop in Nashville, TN, Jan 2011

The National Educational Telecommunications Association’s (NETA) annual conference was held in Nashville last week. As a part of that conference,  the Public Television Quality Group held a one-day workshop on production quality standards within PBS. This working group is an active education and training effort on the part of PBS to help stations transition to digital broadcasting and create “best practices” for digital production. And since I have worked on several PBS shows in the past, I thought it would be advantageous to attend. Fortunately, their workshops are open to non-members, and not too expensive to attend (only $60 for the day).

Jerry Field discussing aspect ratio issues

Most of the people attending work in a PBS station environment… I believe Wallace Braud, myself, and two others were the only freelancers there out of about sixty people attending. Some of the presentations were really only applicable to station engineering staff, such as “Managing Your Broadcast Multiplex” and Practical Implementation of AFD at Your Station.” But several of the presentations were either directly or indirectly related to audio, field video production/data capture, or audio aspects of post production. Much of this material is directly related to how I work, and will help me to be a better audio engineer.

(I’m sure you won’t sleep until you know what AFD means… Active Format Description is a 4-bit code that describes the aspect ratio of a video signal, i.e., full frame 4:3 (standard television), pillarbox (black bars on the sides), letterbox (black bars top & bottom), full-frame 16:9(widescreen), etc. Can be incredibly confusing for a station. Without AFD, the broadcast signal is easily screwed up.)

There was a great deal of discussion about audio levels. In the analog days, this was easier… there was a maximum audio level that you could not exceed. It was easy enough to measure with an analog power meter, and

The Optimod 8100 comp/limiter, circa 1987

controlled by the OptiMod, an audio compressor/limiter placed just ahead of the transmitter. If a program was a little too hot, the OptiMod would clamp the signal and avoid a fine. With DTV, though, it’s now a matter of the maximum number of audio bits that are allowable, and there is still some ambiguity in the standard in terms of sample time. ( the legal level is set by ATSC A/85, “Recommended Practice: Techniques for Establishing and Maintaining Audio Loudness for Digital Television.” a 70-page document.)

Audio levels are measured in DBFS. Anything over 0 dBFS is Very Bad, and occurs when the audio level exceeds the number of bits available. It sounds extremely nasty. In DTVs early days, folks new they had to set their internal reference tone below 0, but where? After some wrangling, the standard is set at PBS for -24dBFS average loudness, tone set at -20, dialog peaks at -10.

While there was much more at the PBS Quality Group Workshop, (like a good explanation of Dialnorm and how it works) my clearer understanding about how the folks at PBS approach digital audio levels was worth the price of admission.