C Class Signal Processors
TUBE MICROPHONE/INSTRUMENT
PREAMPLIFIER WITH DIGITAL OUTPUT
Safety Instructions
Caution: To reduce the hazard of electrical
shock, do not remove cover or back.
No user serviceable parts inside. Please refer all
servicing to qualified personnel.
WARNING: To reduce the risk of fire or electric shock, do not expose this unit to rain or moisture.
The lightning flash with an arrowhead symbol within an equilateral triangle, is intended to alert the user to the
presence of uninsulated "dangerous voltage" within the products enclosure that may be of sufficient magnitude to
constitute a risk of electric shock to persons.
The exclamation point within an equilateral triangle is intended to alert the user to the presence of important operating and maintenance (servicing) instructions in the literature accompanying the product.
Important Safety Instructions
1. Please read all instructions before operating the unit.
2. Keep these instructions for future reference.
3. Please heed all safety warnings.
4. Follow manufacturers instructions.
5. Do not use this unit near water or moisture.
6. Clean only with a damp cloth.
7. Do not block any of the ventilation openings. Install in accordance with the manufacturers instructions.
8. Do not install near any heat sources such as radiators, heat registers, stoves, or other apparatus
(including amplifiers) that produce heat.
9. Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two
blades with one wider than the other. A grounding type plug has two blades and a third grounding
prong. The wide blade or third prong is provided for your safety. When the provided plug does not fit
your outlet, consult an electrician for replacement of the obsolete outlet.
10. Protect the power cord from being walked on and pinched particularly at plugs, convenience receptacles and at the point at which they exit from the unit.
11. Unplug this unit during lightning storms or when unused for long periods of time.
12. Refer all servicing to qualified personnel. Servicing is required when the unit has been damaged in any
way, such as power supply cord or plug damage, or if liquid has been spilled or objects have fallen into
the unit, the unit has been exposed to rain or moisture, does not operate normally, or has been
dropped.
Table of Contents
Introduction 2
C valve Features 3
Controls and Functions 4-5
Front Panel Layout 4
Rear Panel Layout 5
Operating the C valve 6-13
Setting Up the C valve 6-7
Setting a Good Level 8
Using The C valve For Getting A Sound 9
Using the Low Cut Filter 9-10
Using the Tube Process 10
Using the Enhancer 10
Using C valve With An External Signal Processor 11
Using the Digital Output 12
Using the Digital Link Jack 13
System Set-ups 14-15
Stacking and Tilting the C valve 16
C valve Connections 17
C•Class Dual Rack Adapter (optional) 18
Block Diagram 19
Specifications 20
Copyright 2003, Samson Technologies Corp.
Printed October, 2003
Samson Technologies Corp.
575 Underhill Blvd.
P.O. Box 9031
Syosset, NY 11791-9031
Phone: 1-800-3-SAMSON (1-800-372-6766)
Fax: 516-364-3888
www.samsontech.com
2
Congratulations! You just purchased one of the most useful audio tools for digital audio
recording, C valve from Samson Audio. The C valve is a high quality microphone/instrument
tube pre-amplifier offering a tremendous amount of transparent gain with a pristine audio
path that terminates in both balanced analog and S/PDIF digital outputs. By using discreet
transistor pre-amp topology, along with the warmth from the incorporation of the12AX7 tube,
the C valve takes advantage of the latest technology, together with time proven circuit technique. The result; a super clean pre-amp for microphones or instruments with the warmth
and personality of a classic unit, which makes C valve the perfect tracking device for any
recording situation. And, with the SATURATION control you can dial up specific amounts of
harmonics that are right for your recording or performance. An optical limiter with a musical
response is built into C valve, which will help you get a good level to your mixer or recorder.
The C valve also features a variable LOW-CUT filter and a musical ENHANCE circuit to add
a pleasant “high-frequency lift” to the overall sound. To monitor your input levels, the C valve
features a six segment LED bar VU meter, along with a classic analog circular VU meter,
which displays the output level. In order to bridge the classic sound of the warm mic-pre to
today’s digital audio world, the C valve features a high quality, 24Bit, A to D converter with a
selectable sample rate of 48 or 96K feeding the S/PDIF digital output . In addition, two C
valve’s can be linked together to make a stereo mic-pre with digital out. The C valve is a
perfect addition to any recording studio, especially those using computer based hard disk
recorders, as well as for live use to capture that studio sound live.
Although this unit is designed for easy operation, we suggest you take some time out first to
go through these pages so you can fully understand how we’ve implemented a number of
unique features. In this manual, you’ll find a more detailed description of the features of the
C valve, as well as a guided tour through the front and rear panels, step-by-step instructions
for using the C valve and full specifications. You’ll also find a warranty card enclosed—
please don’t forget to fill it out and mail it so that you can receive online technical support
and so we can send you updated information about other Samson products in the future.
With proper care and adequate air circulation, your C valve will operate trouble free for
many years. We recommend you record your serial number in the space provided below for
future reference.
Serial number:
Date of purchase:
Should your unit ever require servicing, a Return Authorization number (RA) must be
obtained before shipping your unit to Samson. Without this number, the unit will not be
accepted. Please call Samson at 1-800-3SAMSON (1-800-372-6766) for a Return
Authorization number prior to shipping your unit. Please retain the original packing materials
and if possible, return the unit in the original carton and packing materials.
Introduction
3
C valve Features
The Samson C valve microphone and instrument pre-amp utilizes the latest technology in circuit design. Here are
some of its main features:
•A high quality microphone or instrument pre-amplifier using discrete transistor and tube gain cells.
• On board Limiter for leveling the output is useful in recording and live sound applications.
• The total amount of harmonic overtones or “warmth” can be controlled using the Saturation control.
• An Input Gain control is included to maximize the overall input gain stage, handling levels from microphones or instruments.
•A pre-set “sweetening” equalization curve can be added using the Enhance switch.
• Positive or negative phase can be selected using the Phase switch.
• The addition of an Analog VU meter makes it easy to read the Output Level.
• 48-volt phantom power for powering condenser microphones is available by pressing the LED, backlit,
48-Volt push switch located on the front panel.
• S/PDIF output via an internal, high quality A-to-D (analog-to-digital) converter sends 24-bit digital audio to
hard disk recorders via the rear panel RCA connector.
• Sample rate selection via the front panel, backlit switch allows 48 or 96K sample rates.
• Six segment LED Input VU meter displays the level after the Gain control.
• Convenient 1/4-inch insert points are included for external signal processing.
• Balanced XLR microphone input and 1/4-inch balanced line input connectors allow easy hook up of mics
or instruments.
• Oversized, rubber bumpers with tilting feet allow several Samson C class units to be stacked and tilted in
an ergonomically correct operating position.
• The stylish, bead blasted, electric blue anodized front-panel is as easy to read as it is to look at.
• Three-year extended warranty.
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C valve Layout
1 INPUT GAIN – Rotary control used to adjust the
input level.
2 LOW FREQUENCY – This rotary control is used to
set the EQ cut off point for the Low Cut filter.
3 INPUT METER – Six segment LED VU meter dis-
plays the input level after being affected by the
Gain control.
4 SATURATION – Rotary control used to adjust the
total amount of harmonic overtones generated
by the tube circuit.
5 PILOT LIGHT - Illuminated indicator that rises in
intensity, and when fully lit, signifies the tube circuit is ready for operation.
6 VOLUME – Rotary knob used to control the over-
all Output level.
7 Digital Overload - LED indicator, which when
illuminated, displays the digital clipping point of
the Analog to Digital converter.
8 VU METER – Classic round analog VU meter dis-
plays the amount of output level.
9 POWER SWITCH – Heavy-duty rocker switch
which, when pressed to the “on” position, lights
the internal green LED, indicating the unit is powered up and ready for operation.
10 MIC/INST switch – This switch is used to select
the proper input operating level for either a
microphone or a line/instrument signal source.
11 48 VOLT – When pressed in, the switch will illu-
minate red indicating the 48-volt phantom
power is on.
12 PHASE – LED backlit switch which will invert the
phase of the mic or instrument input.
13 LOW CUT SWITCH – Used to engage the vari-
able low-cut filter, which attenuates or rolls-off
the low frequency at a rate of 12 dB per octave
starting at the point set by the Low Frequency
control knob.
14 VOCAL EQ - When pressed in, the push switch
activates the Vocal EQ circuit providing a pre-set
equalization curve for “sweetening” the signal
with a subtle, but useful, airy high-end lift .
15 LIMIT SWITCH – When engaged, the LED lights
indicating the Limiter circuit is activated.
16 ENHANCE - When pressed in, the switch acti-
vates the Enhance circuit which helps restore
the high frequencies that can be lost when the
signal is being protected by the on-board LIMITER.
17 48/96 SWITCH - LED backlit switch which is
used to select the sampling frequency of the
internal A-to-D converter for either 48 or 96
kiloHertz operation.
Front Panel Layout
A AC INLET – Connect the included AC1800 power
supply here.
B24BIT 48 / 96 (DIGITAL OUT)- 24-bit S/PDIF
Digital Output on an RCA connector.
C DIGITAL LINK IN- 1/4-inch input jack for con-
necting the balanced line output of a second C
valve so that the two units work as a stereo unit
transmitting the left and right signals from a single S/PDIF digital output.
DBALANCED OUTPUT – 1/4-inch TRS
(TIP/RING/SLEEVE) connector for balanced, line
level output.
E RETURN (INSERT) – 1/4-inch phone jack for car-
rying the return signal of the external processing
loop.
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F SEND (INSERT) - 1/4-inch phone jack for carrying
the send signal for the external processing loop.
G INSTRUMENT IN - 1/4-inch phone input jack for
connecting signals from instruments or line level
devices.
H MIC INPUT – 3-Pin XLR input connector for con-
necting microphone level signals.
Rear Panel Layout
C valve Layout
6
Operating The C valve
Setting up the C valve
Setting up your C Valve tube pre-amp is a simple procedure, which takes only a few minutes:
1. Remove all packing materials (save them in case of need for future service) and decide where the pre-amp is
to be physically placed. To avoid potential overheating problems, be sure that there is good ventilation around
the entire unit.
2. Plug the provided AC power adapter in the rear AC inlet, but don’t plug the power pack into a wall outlet just
yet.
3. Set the controls to the following positions:
4. Using a standard XLR microphone cable, connect your microphone to the MIC input located on the rear panel.
If you are using an instrument like a guitar or bass guitar, use a standard 1/4-inch phone cable and connect the
instrument to the INST input located on the rear panel. For a detailed wiring guide, see page 16 in this manual.
5. Now, connect the rear panel output to your mixer or recorder.
INPUT GAIN 6
LOW FREQUENCY 90
SATURATION 1
VOLUME -10
MIC/INSTRUMENT OUT
48-VOLT OUT
PHASE OUT
LOW CUT OUT
VOCAL EQ OUT
LIMIT OUT
ENHANCE OUT
48 / 96 48 (OUT)