A channel strip that features the best of Fearn preamplification, compression, and EQ.
The VT-15 Vacuum Tube Recording Channel combines the mic preamp from the D.W. Fearn VT-1, and the DI
input functionality of the VT-3, plus the acclaimed dynamics control of the VT-7 Compressor, and the most-often used features
of the VT-4 Equalizer.
The mic preamp section has all the features of the VT-1 (#180271) (the single-channel version of the VT-2 (#180272)), plus
a built in Line Pad (the same as the LP-1 (#180295), and a front-panel 1/4" jack for an instrument input from an electric
or electronic guitar or keyboard.
The compression section is identical to a single channel of the VT-7 Stereo Compressor (#180292), including a switchable high-pass
filter in the sidechain to reduce low frequency compression when necessary.
The equalization section is a scaled-down version of the versatile VT-4 LC Equalizer (#180274). It has a single frequency
for each of the LF Boost, LF Cut, HF Boost, and HF Cut. These frequencies were determined by analyzing which were the most
often used settings on the VT-4. Approximate equalization frequencies: LF Boost 100Hz, shelving; LF Cut 90Hz,
shelving; HF Boost 9.8kHz, with adjustable Q; HF Cut 11kHz, shelving. The controls are continuously variable, from -12dB of
cut to +12dB of boost. The HF Q is also continuously variable.
Which comes first, compression or equalization?
Sometimes you need the compression before the EQ, and sometimes the EQ should come first. The VT-15 does not lock you into
only one configuration; a front panel switch allows you to instantly switch from Comp/EQ to EQ/Comp.
A full-size true
VU meter monitors either gain reduction or output level. The mic/line input connector is a XLR female, and the output is a
XLR male, both on the back panel. The Instrument input is a 1/4" jack on the front panel. The D.W. Fearn VT-15 is in a standard
rackmount package, 5.25" high (3RU). A rear panel switch allows the VT-15 to instantly be converted from 120 to 240 VAC operation,
Important Note: Having many tubes, the VT-15 can generate a considerable amount of heat. We highly
recommend using D.W. Fearn Vented Rack Panels (#180296) above and below the unit for proper cooling.
of the VT-15 Vacuum Tube Recording Channel
With the success of the VT-1/VT-2 Vacuum Tube Microphone Preamplifiers, the VT-4 LC Equalizer, the VT-7 Stereo Compressor,
and the VT-I/F and VT-3 Vacuum Tube DIs, there was a great temptation to combine the features of all of these products into
one recording channel.
But I had a problem with the concept. I did not want to be tied into having the compression
come before the equalization, or vice-versa, so a prime design goal was to make the order of the processing switchable. That
way the user has a choice of compression before equalization or equalization before compression. Different circumstances require
different approaches to processing.
Achieving this switching with a minimum of noise and level change was solved
quickly, but all the switching in the audio path could result in a degradation of the noise performance of the VT-15.
By definition, an "all-in-one" box has many compromises over using separate units. I was not satisfied with the VT-15 until
the overall performance was as close as possible to using a VT-1/VT-7/VT-4. The final result is a box that has about 4dB more
noise than the separate units under most circumstances - a negligible difference for most applications.
the VT-15 is capable of a tremendous amount of gain (about 90dB in the first prototype), it became a bit tricky to use properly.
As long as you were familiar with optimizing gain structure in a studio environment, it worked great. But not everyone has
that background, and in the heat of a session, it may get neglected. The result could be distortion - and not the kind you
would normally find pleasing. Optimizing the gain structure and headroom was an ongoing project, complicated by a period of
18 months when we could not keep
up with the orders for our VT-7 Stereo Compressor. In fact, I put the VT-15 project on hold entirely for six months. When
I returned to it over the summer of 2007, the pieces fell into place and the VT-15 was ready to meet the world.
The mic preamp is identical to the VT-1/VT-2 circuit with one exception: an instrument input has been added. The compressor
is identical to one channel of the VT-7 Stereo Compressor. The equalization is a highly simplified version of the VT-4 LC
Equalizer, with just one frequency for the low-frequency boost, low-frequency cut, high-frequency boost, and the high-frequency
cut. The chosen frequencies were based on my experience using the VT-4 and feedback from many users.
Can the VT-15
replace the VT-1/VT-2, VT-7, and VT-4? Not really. The separate units have features that are just not practical to duplicate
in the VT-15. But for many applications, the VT-15 provides the next best thing.
Douglas W. Fearn
D.W. Fearn VT-15 Vacuum Tube Recording Channel Features:
- Mic Preamp/Compressor/Equalizer in one unit
- Instantly switch from Comp/EQ to EQ/Comp.
- Switchable high-pass filter in the sidechain
- All class-A triode vacuum tube audio path
- All controls are independent and can be used in any combination
- Constructed of heavy-gauge aluminum
- full-size true VU meter monitors
Pros who can use anything choose D.W. Fearn for the best possible sound.
D.W. Fearn VT-15 Vacuum Tube Recording Channel Specifications:
- Mic Input: 150 ohms
- Input Load Impedance: 1.5k ohms
- Minimum Input Level: -65 dBm nominal
- Maximum Input Level @ 20 cps: -30 dBm without pad, -5 dBm with 20 dB pad
- Instrument Input impedance: 1 Megohm
- Line Input Load Impedance: 40k ohms
- Maximum Line Input Level @ 20 cps: +25dBm (+35dBm with pad)
- Gain: <60 dB optimum (capable of 75dB)
- Frequency Response:± 0.25 dB 20 cps to 20 kc, ± 0.5 dB 11 cps to 28 kc, -3 dB @ 0.5 cps & 50 kc
- THD + Noise: <0.25% 20 cps to 20 kc
- Intermodulation Distortion SMPTE: <0.80%
- Signal to Noise Ratio: 72 dB typical operation
- Equivalent Input Noise: -124 dbm typical operation
- Output: low-Z, transformer balanced
- Maximum Output Level: +22 dBm unterminated
- Compression Range: up to 30dB
- Compression method: Pulse-width modulator
- Low-frequency Boost 100 cps, shelving
- Low-frequency Cut 80 cps, shelving
- High-frequency Boost 9.8 kc, peaking
- High-frequency Q 0.6 to 1.7
- High-frequency Cut
- 12 kc, shelving
- Power Requirements: 100, 120, or 220 VAC 50/60Hz, 50 W
- Dimensions: 19" (48.26cm) W x 5.25" (13.34cm) H x 9" (22.86cm) D
- Weight 18 lbs (8.16kg)
(specifications are preliminary and subject to change)