User manual DW FEARN VT7

[. . . ] FEARN VT-7 Vacuum Tube Compression Amplifier Operating Instructions How to Contact us: Telephone: 610-793-2526 Fax: 610-793-1479 Mail: P. O. 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 3 VT-7 Vacuum Tube Compression Amplifier Final Test Report Model _______________ Serial Number_______________Mains Voltage ______________ Date ___________________ Tested by ________ VU Calibrated to _______________ dBm Test Equipment _______________________________________________________________ Channel A Frequency Response: 20 cps to 20 kc/s +/- ___________ dB THD+Noise: 20 cps ______________ % 200 cps _____________ % 2 kc/s _______________ % 20 kc/s ______________ % Noise: ______________ dB below +4 dBm out Channel B Frequency Response: 20 cps to 20 kc/s +/- ___________ dB THD+Noise: 20 cps ______________ % 200 cps _____________ % 2 kc/s _______________ % 20 kc/s ______________ % Noise: ______________ dB below +4 dBm out Operational Tests: Compression Range ________ Attack ____________________ Release __________________ Shape ___________________ Link _____________________ GR Meter ________________ Listening Test ____________ Operational Tests: Compression Range ________ Attack ____________________ Release __________________ Shape ___________________ Link _____________________ GR Meter ________________ Listening Test ____________ VT-7 Compression Amplifier D. W. [. . . ] (This is true of all compressors. ) A fast release time adds density to the sound, often with the compression becoming more obvious. Long release times make the compression less obvious and more natural, but can "punch holes" in the lower level audio under certain conditions of high percussive levels. Harder/Softer This control adjusts the nature of the compression curve. Toward the "Harder" end of the control, the compression ratio is higher and the levels more tightly controlled. At the "Softer" end, the compression ratio is lower and the compression is more gentle. This is not merely a ratio control, however, as other parameters also change as the control is adjusted. More than any other control, this one needs to be adjusted by ear. This control interacts with the Threshold, Attack, and Release controls, so after changing the Softer/Harder control, you should experiment with others to obtain the effect you desire. Although the compression ratio changes with this control, there are other parameters that are changed as well. Its operation is complicated to explain, so it is much easier to understand it simply by experimenting. Link/Separate This is a two-position switch that links the two channels together for stereo operation. In the Separate position, the two channels operate completely independently, and can be used on totally different sources without any interaction. In the Link position, the two channels track each other precisely, so that the stereo image will remain constant even if one channel has much more level than the other. You can run a stereo signal with the switch in the Separate position for an effect. On a stereo pair such as a piano or other sub-mix stereo source, the image will tend to shift from left to D. W. FEARN VT-7 Compression Amplifier 19 right as the signal becomes louder in one channel compared to the other. This would be disconcerting on a stereo bus, but could be interesting on individual stereo tracks. When operating in the Link position, only the left side (Channel A) controls are operative. The right channel (B) controls will have no effect on the operation. The only exception is the Gain control, which will still adjust the level of the B channel in the Link position. Meter Switch The VU meter can be switched to read either output ("VU") or gain reduction ("GR"). In the VU position, the meter will indicate the actual output level of the VT-7. The "0" VU mark indicates +4dBm output In the "GR" position, the meter indicates the amount of gain reduction (compression), in dB. With no compression, the meter will rest at the "0" VU mark. As compression increases, the meter will move more to the left. [. . . ] If the output reference level needs to be changed, here is the procedure: 1. Terminate the output in the same impedance as the VT-7 will normally be feeding. This will almost always be a high-impedance bridging termination of 20k ohms or more. Allow at least a fifteen minute warm-up. [. . . ]