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Old 8th May 2003
The Distressor's "daddy"
Dave Derr's Avatar

1) I seem to remember reading somewhere (was it TapeOp?) that you're not a degreed EE. Where did you get your electronics chops? Have you ever felt the need to get an EE degree?

No engineering degree. I was a music major in college. Self taught in electronics (Radio Shack AC Circuit Analysis really got me started!), but I do wish I had a lot better math chops. Ive taught myself quite a bit and have even worked thru a DFT or two with some help from my Eventide buddies, Ken Bodanowicz and Bob Belcher. They taught me all kinds of things and I should have watched them a lot closer even. It was a very lucky day for me when Richard Factor at Eventide gave me a chance as an engineer on his audio team.

2) What do you think about all the controversy surrounding certain electronic components? Do you have strong preferences for certain brands of resistor, capacitor, transistor, etc? Do you think there's a need for soft recovery rectifiers in audio power supplies?

Interesting Question. RESISTORS: I use 1% metal film resistors, Roederstien if i can get them. Ive never seen any noise or distortion difference between them or carbon - EVER. Im not sure they are more reliable but Im hoping lol. I use them because they do help in consistency and are less sensitive to temperature. We are a high ended manufacturer and people expect good components. Honestly tho, I have never measured or heard an improvement when using 1% metal film resistors over el cheapo carbon resistors.

Im not gonna even start in on Potentiometers... Ill just say I wish I didnt have to use them and that I have spent MONTHS OF MY #[email protected]&* LIFE TRYING TO OVERCOME THEIR CONSISTENT LACK OF CONSISTENCY!

CAPACITORS SUCK: There are lots of differences between capacitors, but in many applications, they dont matter. In many applications it makes all the difference in the world. I hate caps. When we have a failure... its usually a cap. As far as the sound of caps, theres lots of gotchas but generally if the biasing is correct, they will sound very similar except in high voltage applications with tubes where leakage and failure affect things. I have seen caps cause distortion, sometimes differently within one type or batch.

We do try to select our caps carefully. There used to be a rumor that the larger the cap the better. (The ol Bigger is better thing, right girls?). I have seen polarized caps cause problems in circuits. I have seen back to back caps used a lot to get away from that, only to double the problems of caps as they start to age. You hear people say avoid Tantalum coupling caps. I dont say that. Rupert Neve used Tantalum coupling caps, often. I bet about half the classic rock records made used NEVE stuff.

Are you thoroughly confused now? GOOD!

Transistor selection is extremely important. SOOooo many parameters have to be just right for you to get the best performance in an audio circuit. They are strange little beasts and interestingly, IC manufacturers have recently been able to beat all but the best , hand selected, discrete circuits in linearity. At least according to my test equipment and ears. Because they can use a lot of transistors in support circuitry to cancel out the affects of the transistors in the audio path, things are changing. Cancellation of miller effects, internal capacitance, stray parasitics and thermal gradients are much easier in a small area, like a die inside an IC. That being said, a good, discrete, transistor circuit offers huge sweet spots, and some soft clipping . Picking transistors is an art form and almost always requires lots of trial and error.

3) What kinds of objective measurements do you guys use when developing a piece of gear? Do you have much use for stuff like Audio Precision test equipment, or do you rely more on subjective listening tests?

Both. We have HP Audio Analyzers galore. We measure and test most everything. We have some custom computer software to test compression curves. We use mainly HP339A's and HP8903B's. WE have lots of scopes and toys. I also use this really neat PC software by Pioneer Hill called SpectraPlus. If you use this differential mode it cancels out your sound card problems and can give you great analysis right at your computer. They have a free demo. Tell em Dave sent you.

I have lots of speakers and sound sources to test things audibly. Thats a big part of course. Especially with compressors or anything non linear. Getting the thing to sound and feel right requires real world use. Im quite happy with my Mackie HR824s speakers. They do seem very flat so I can hear sub stuff. Their sound changes a lot off axis, mostly the tweeters. If you stand up, then sit when they are in the upright position, the high end sounds REALLY different. I use headphones too, of course. SONY MDR-7506.

4) What brand of CAD software do you use, if any? Do you do a lot of circuit simulation before building prototypes, or do you just have at it with perfboard and soldering iron? Care to share any PC layout tips particular to audio gear?

We have lots of cad systems. Autocad, Accel, Orcad, Tango, Multisim among others. Ive started doing simulations but its hit or miss, and you are dependant on the component models SPICE gives you, so we still breadboard and prototype most things. PC layout tips would be a big subject. Use wide traces, big pads, good boards and watch running inputs next to outputs.

5) Is all of your assembly done in house, or do you use board stuffers?
We have a lot of boards built by robots and by manual board stuffers. We put them in chassis here and test the hell out of them. The USA makes it hard to have a lot of employees. Our tax system penalizes you for growing and hiring. It penalizes you when you pay employees well. But we also have so much at our fingertips in this country. You can really get anything. But whenever we have something labor intensive, we often will farm it out.

6) Do you still have time to do much recording? If not, do you miss it?

Not much recording now since 1999. Just personal projects but we are putting a HD Protools system together currently. I miss parts of recording a lot. I dont miss dealing with all the egos , endless punching in at 4 AM in the morning, record execs, inept producers, bounced checks, the possies of rap artists, lol and lots of other little things.

I hope you can use some of this info! Thanks for the questions.