DW FEARN VT4 Gebruiksaanwijzing - Pagina 5

Blader online of download pdf Gebruiksaanwijzing voor {categorie_naam} DW FEARN VT4. DW FEARN VT4 16 pagina's. Vacuum tube lc equalizer

Throughout my career in recording, there have always been a few equalizers that stood

out as being exceptional. Among my favorites are the 1970s-era Neve input-strip eqs, and the

Trident CB9066 parametric. I began my equalizer development project by first building a

series of test circuits, using all the various tone-modification techniques. After listening to a

wide variety of equalization circuits, it was obvious to me that the passive inductor-capacitor

(LC) circuit was the one that sounded the most musical and natural to me.

In thinking about how I use equalization, I realized that having simultaneous boost and

cut at the low and end frequencies was often very useful. For mid-frequencies, I found that I

always cut, usually around 400 Hz, and never had any reason to boost in that range. If I were

using a parametric equalizer, I invariably tended to use the low-Q (broadest) settings, and if I

had a choice between shelving or peaking on the high and low end, I almost always prefered

the shelving curve.

So the VT-4 was designed around those preferences -- low-Q curves, shelving, with

simultaneous boost and cut, mid-range cut but not boost, and using passive LC circuitry.

The amplification stages would be vacuum tube, and since the VT-1/VT-2 mic preamps

have had such a gratifying acceptance in the world of recording, it was important to preserve

the same sonic characteristics that distinquished the preamps. I decided to try the Svetlana

6N1P dual triode, and was pleasantly surprised to find that it is a wonderful-sounding tube,

with many of the same sonic characteristics as the 6072A used in my preamps. The active tube

circuitry fell into place with relatively little effort. Now it was time to make the equalization

circuitry work the way I wanted.

To start, I used the filter design tables developed by Bell Labs in the 1930s. That got

the project off the ground and it was starting to sound pretty good. For several months, I lis-

tened to a variety of music through a prototype equalizer while I was working on other things,

and gradually narrowed-in on what sounded really good and what didn't. I would frequently

have a box of capacitors and clip leads next to the prototype and often clipped-in a different

value here or there and continued listening. Eventually, the final frequencies, curves, control

operation, etc. was determined. To this day, I have only a vague idea of what the actual curves

look like. Equalizers, like all audio equipment, should please your ears, not your test equip-

ment.

My experience with Jensen Transformers Inc. was so positive that I knew from the

beginning that I would utilize their products. The first couple of prototypes used inductors that

I wound myself, but for production units more-consistent inductors would be necessary. Jensen

agreed to manufacture the necessary inductors to my specifications, and the quality of the parts

is astounding.

History of the VT-4