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Summary of Contents for D.W. Fearn VT-7
- Page 1 D.W. FEARN VT-7 Vacuum Tube Compression Amplifier Operating Instructions...
- Page 2 How to Contact us: Telephone: 610-793-2526 Fax: 610-793-1479 Mail: P.O. Box 57, Pocopson, PA 19366 U.S.A. Shipping Address: 182 Bragg Hill Road West Chester, PA 19382 U.S.A. e-mail: dwfearn@dwfearn.com www.dwfearn.com D.W. FEARN VT-7 Compression Amplifier...
- Page 3 Pocopson, PA 19366 U.S.A. PROFESSIONAL Tel: 610-793-2526 RECORDING EQUIPMENT www.dwfearn.com Fax: 610-793-1479 Certificate of RoHS Compliance D.W. Fearn is committed to manufacturing products that are fully-compliant with the EU RoHS Directive. The following products are compliant: VT-1 VT-2 VT-3 VT-4...
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Page 4: Final Test Report
VT-7 Vacuum Tube Compression Amplifier Final Test Report Model _______________ Serial Number_______________Mains Voltage ______________ Date ___________________ Tested by ________ VU Calibrated to _______________ dBm Test Equipment _______________________________________________________________ Channel B Channel A Frequency Response: Frequency Response: 20 cps to 20 kc/s +/- ___________ dB... -
Page 5: Table Of Contents
T a b l e o f C o n t e n t s Final Test Report ................3 Warranty ..................7 History of the VT-7 .................9 1. Specifications ................11 2. Description................13 3. Installation ................15 4. Operation .................17 5. Theory of Operation ..............23 6. - Page 6 D.W. Fearn shall not be liable for technical or editorial errors or omissions in this manual, nor for incidental or consequential damages resulting from the use of this material. This instruction manual contains information protected by copyright. No part of this manual may be photocopied or reproduced in any form without prior written consent from D.W.
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Page 7: Warranty
During the warranty period, D.W. Fearn will, at no additional charge, repair or replace defective parts with new parts. This warranty does not extend to any VT-7 that has been damaged or rendered defective as a result of accident, misuse, or abuse; by the use of parts not manufac- tured or supplied by D.W. -
Page 8: History Of The Vt-7
Over many years of recording, I have had the opportunity to use and sometimes own some of the best compressors in the world. For the D.W. Fearn line of products, a compressor was obviously important. I began the search for the ultimate compressor design in 1995 and it wasn’t until 2004 that I developed the sound I was looking for. - Page 9 The VT-7 passes this test. There are not a lot of controls on the VT-7. Basically, there is just a knob to control the amount of compression (Threshold), the amount of gain, the attack and release times, and a knob that smoothly varies the compression characteristic from a “softer”...
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Page 10: Specifications
Dimensions 19” (48.26cm) W 5.25” (13.34cm) H 13” (22.9cm) D Weight 22 lbs (9.55 kg) Shipping Weight: 28 lbs (12.27 kg) (measurements are made with +4dBm input and output, no compression, into a bridging load) D.W. FEARN VT-7 Compression Amplifier... -
Page 11: Description
VT-7 to exceed the performance of vintage vacuum tube com- pressors. The VT-7 is capable of over 30dB of gain reduction, but all units above serial number 19 are limited to 15dB of compression to provide greater resolution in the Threshold control for set- ting moderate amounts of compression. - Page 12 D.W. FEARN VT-7 Compression Amplifier...
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Page 13: Installation
Be sure the top and bottom vent slots are not blocked. It is essential that air can flow into the bottom and out of the top of the VT-7. Equipment that runs cool can last for a very long time. - Page 14 Power The VT-7 is designed to operate from 100, 120, or 220-240 volt, 50/60 Hz power. The unit will be shipped for the voltage specified in the order, but may be changed in the field if nec- essary. (See the Maintenance section for detailed instructions on changing the primary volt- age).
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Page 15: Operation
In modern studio equip- ment, bridging line inputs are universal. If the device being fed by the VT-7 has an input ter- mination switch, that switch should be in the “off” position. - Page 16 The Threshold control adjusts the point where compression begins. With the con- Threshold trol all the way down, there is no compression and the VT-7 operates as a straight amplifier. As the control is turned clockwise, the amount of compression increases. This can be moni- tored on the VU meter (in the GR position), or by ear.
- Page 17 7 warms up, and change somewhat over time as various components age. This does not affect the sound of the VT-7 or the gain reduction range. There is a calibration control to set the 0VU indication but it is not something that a non-technical user should adjust.
- Page 18 Check for hum, buzz, or other noise. For the first few minutes after a cold start it is not unusual for the VT-7 to produce hiss, pops, and micro- phonic “clanks” as the internal elements of the tubes expand from the heat. Correct any ground loop problems before proceeding.
- Page 19 Semi-professional equipment frequently uses a reference level of -10 dBv (roughly 14 dB lower than pro equipment). Although the VT-7 can feed the unbalanced, -10 dBv inputs of semi-pro gear with no difficulty, the VT-7 VU meter will have to be recalibrated in order to be useful. (See Section 6 - Maintenance.) Use your ears to find the setting that sounds best to you for any given sound.
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Page 20: Theory Of Operation
The first stage is a 6072A configured as a Class A voltage amplifier with a gain of approxi- mately 30. Negative feedback from the plate of the second stage reduces distortion, flattens the frequency response, and makes the gain of the first two stages less dependent on individ- ual vacuum tube characteristics. D.W. FEARN VT-7 Compression Amplifier... - Page 21 VT-7 to be easily changed in the field. A fuse protects the VT-7. The Pilot lamp is a type 1819 bulb, operated far below its rated volt- age of 28. The life of the bulb is lengthened, and the light output is more compatible with other modern studio equipment.
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Page 22: Maintenance
Vacuum Tubes Eight tubes are used in the VT-7. Six are 6N1P and two are 6072A. There can be as much as a 15 dB difference in noise level among an assortment of tubes, and the 6072A tubes used should be carefully chosen to maintain low noise. - Page 23 Handle with care. Electrolytic Capacitors The VT-7 is designed and built to last for a long, long time, and it is possible that some com- ponents (e.g. electrolytic capacitors) may reach the end of their life long before the equip- ment becomes obsolete.
- Page 24 PWM board. Contact the factory for complete adjustment instructions. Note that the meter calibration can be off but the VT-7 will continue to operate normally otherwise. Some drift- ing of this adjustment is normal, and the reading will change as the VT-7 warms up over a period of an hour or so.
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