Samson Stereo Amplifier C Class User Guide

TUBE MICROPHONE/INSTRUMENT  
PREAMPLIFIER WITH DIGITAL OUTPUT  
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Table of Contents  
Introduction  
C valve Features  
2
3
Controls and Functions  
Front Panel Layout  
Rear Panel Layout  
4-5  
4
5
Operating the C valve  
Setting Up the C valve  
Setting a Good Level  
6-13  
6-7  
8
Using The C valve For Getting A Sound  
Using the Low Cut Filter  
Using the Tube Process  
Using the Enhancer  
Using C valve With An External Signal Processor  
Using the Digital Output  
9
9-10  
10  
10  
11  
12  
13  
Using the Digital Link Jack  
System Set-ups  
14-15  
16  
Stacking and Tilting the C valve  
C valve Connections  
C•Class Dual Rack Adapter (optional)  
Block Diagram  
17  
18  
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  
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Introduction  
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 tech-  
nique. 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.  
2
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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 micro-  
phones 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.  
3
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C valve Layout  
Front Panel Layout  
10  
11  
MIC/INST switch – This switch is used to select  
the proper input operating level for either a  
microphone or a line/instrument signal source.  
1
2
3
INPUT GAIN – Rotary control used to adjust the  
input level.  
LOW FREQUENCY – This rotary control is used to  
48 VOLT – When pressed in, the switch will illu-  
minate red indicating the 48-volt phantom  
power is on.  
set the EQ cut off point for the Low Cut filter.  
INPUT METER – Six segment LED VU meter dis-  
plays the input level after being affected by the  
Gain control.  
12  
13  
PHASE – LED backlit switch which will invert the  
phase of the mic or instrument input.  
4
5
SATURATION – Rotary control used to adjust the  
total amount of harmonic overtones generated  
by the tube circuit.  
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.  
PILOT LIGHT - Illuminated indicator that rises in  
intensity, and when fully lit, signifies the tube cir-  
cuit is ready for operation.  
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 .  
6
7
VOLUME – Rotary knob used to control the over-  
all Output level.  
Digital Overload - LED indicator, which when  
illuminated, displays the digital clipping point of  
the Analog to Digital converter.  
15  
16  
LIMIT SWITCH – When engaged, the LED lights  
indicating the Limiter circuit is activated.  
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 LIM-  
ITER.  
8
9
VU METER – Classic round analog VU meter dis-  
plays the amount of output level.  
POWER SWITCH – Heavy-duty rocker switch  
which, when pressed to the “on” position, lights  
the internal green LED, indicating the unit is pow-  
ered up and ready for operation.  
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.  
4
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C valve Layout  
Rear Panel Layout  
A
B
C
AC INLET – Connect the included AC1800 power  
F
SEND (INSERT) - 1/4-inch phone jack for carrying  
supply here.  
the send signal for the external processing loop.  
24 BIT 48 / 96 (DIGITAL OUT)- 24-bit S/PDIF  
G
INSTRUMENT IN - 1/4-inch phone input jack for  
connecting signals from instruments or line level  
devices.  
Digital Output on an RCA connector.  
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 sin-  
gle S/PDIF digital output.  
H
MIC INPUT – 3-Pin XLR input connector for con-  
necting microphone level signals.  
D
E
BALANCED OUTPUT – 1/4-inch TRS  
(TIP/RING/SLEEVE) connector for balanced, line  
level output.  
RETURN (INSERT) – 1/4-inch phone jack for car-  
rying the return signal of the external processing  
loop.  
5
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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:  
PHASE  
OUT  
OUT  
OUT  
OUT  
OUT  
48 (OUT)  
INPUT GAIN  
6
90  
1
-10  
OUT  
OUT  
LOW CUT  
VOCAL EQ  
LIMIT  
ENHANCE  
48 / 96  
LOW FREQUENCY  
SATURATION  
VOLUME  
MIC/INSTRUMENT  
48-VOLT  
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.  
6
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Operating The C valve  
Setting Up the C valve (continued)  
6. Plug the C valve power pack into a wall outlet and switch the unit on by pressing the power switch.  
7. If you are using an instrument with your C valve, press the MIC/INST switch in to set the C valve’s input to  
accept instrument levels. The LED will illuminate. If you are using a microphone skip this step and go on to the  
next step.  
8. The C valve features on board 48-volt phan-  
tom power supply for connecting condenser  
microphones.  
IMPORTANT NOTE: With all phantom power sup-  
plies, you can get an annoying POP when you engage  
the phantom power supply, or when you unplug a  
cable that has phantom power on it. Depending how  
loud you are monitoring, this POP can cause damage  
to your speakers, and even to your hearing. Be sure to  
turn your speakers, and/or headphone levels, all the  
way down when switching the phantom supply on and  
off or plugging and unplugging cables.  
If you are using a condenser microphone, turn  
down your monitor speakers and/or headphones,  
and then press the front panel 48 VOLT switch to  
engage the phantom power.  
9. Now, set a level by playing your instrument or  
singing into your mic, and slowly raise the INPUT  
GAIN control until you see the LED VU meter  
reach a level of about “0dB”.  
10. Be sure that your mixer or recorder’s input is  
enabled and turned up. Now, slowly raise the  
output VOLUME control until you reach a good  
level, about “-3dB”, on the analog output VU  
meter. Then, set a good level on your mixer or recorder.  
At this point you should be sending a clean signal to your mixer or recorder and you can experiment with the  
SATURATION, VOCAL EQ and ENHANCER features for fun. A detailed explanation of these functions will be  
covered in the following sections of this manual.  
7
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Operating The C valve  
Setting a Good Level  
One of the most important fundamentals of good audio engineering is setting proper levels. Even on a small typi-  
cal mixer, or basic multi-track recorder, there are several controls that affect the level of a signal as it makes it’s  
way from your sound source to your speakers and then, ultimately, the level of your headphone or monitor sys-  
tem. These include pre-amp gain, EQ, aux sends and returns, channel fader level, bus or group levels, and final-  
ly, the master fader. That’s not to mention the level of the 5:15 train on its way to Pennsylvania station who’s  
thunderous crossing horn can be picked up from 5 miles away while miking a nylon string guitar, despite the use  
of double moving blankets over the windows of your project studio. But that’s another story with another set of  
disciplines. Start off by being aware that anytime you change any control in the audio path, you are probably  
affecting gain somewhere. Then, be sure to carefully monitor the levels on your input and output meters to avoid  
a clipped signal with too many peaks. Also, remember your ear is the most sophisticated and calibrated piece of  
test gear you have. So, setting a good level should be approached from a technical point of view, and then con-  
firmed, by a creative point of view.  
INPUT GAIN – Control Knob  
1
As the name implies, the INPUT GAIN is used to set the level of the input signal. The  
rotary control knob provides a range of gain from +6 to +60 dB. The C valve can accept  
levels from most microphones when the MIC/INST switch is set to the MIC position.  
When the MIC/INST switch is set to instrument, the C valve can accept signals from  
instruments or line level sources. Once you set the MIC/INST switch to the proper posi-  
tion, you can use the INPUT GAIN control to adjust the level of your input signal. It is a  
1
good idea to start with the level low and raise it up as you need. Be sure to monitor the  
input LED VU METER and try to set the INPUT GAIN control so that the meter reads +0 to  
+6dB. If you see the OL LED light you are “Over–Loading” and the sound may become distorted. If this happens,  
simply back down on the INPUT GAIN control until the OL light stops flashing.  
2
LED VU METER – Input Level  
To monitor the signal being presented to the C valve’s input, there is a six-segment LED-bar VU  
meter indicating –20, -10, -6, 0, +6 and OL (OVER-LOAD). The level displayed on the meter will be  
affected by the MIC/INST switch so be sure that you have that set to the correct position for your  
sound source. The LED VU METER features “VU” ballistics, which means it reacts to the signal  
based on an average level. Use the VU METER when you are setting your initial input level with the  
INPUT GAIN control. Try to set the INPUT GAIN control so that the meter reads +0 to +6dB. If you  
see the OL LED light you are “Over–Loading” and the sound may become distorted. If this hap-  
pens,simply back down on the INPUT GAIN control until the OL light stops flashing.  
2
ANALOG VU METER - Output Level  
3
To monitor the signal being sent from the C valve’s OUTPUT, there is an ANALOG  
VU METER with a scale from infinity to +4dB. The level displayed on the meter will be  
affected by the MIC/INST switch so be sure that you have that set to the correct posi-  
tion for your sound source. The ANALOG VU METER features “VU” ballistics, which  
means it reacts to the signal based on an average level. Use the ANALOG VU  
METER when you are setting your output level using the VOLUME control. Try to set  
the level so that the meter reads about 0dB. If you see the needle stay all the way to  
the right, you are “Over–Loading” and the sound may become distorted. If this hap-  
pens, simply back down on the VOLUME control until the meter reads about 0dB.  
3
8
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Operating The C valve  
4
MIC/INST - Select switch  
The MIC/INST switch is used to set the operating level of the C valve’s input. When using a microphone, set the  
switch to the “MIC” position, which is selected when the switch is in the out position  
and the green LED is off. When you press the MIC/INST switch in, the green LED  
will illuminate indicating that the C valve is ready to accept a signal from an instru-  
ment like a guitar or bass guitar. You can also use the INST input to connect a line  
level device like a keyboard or drum machine.  
48 VOLT - Phantom Power Switch  
5
The C valve provides on-board phantom power supply for powering condenser  
microphones.  
4
5
6
IMPORTANT NOTE: With all phantom power supplies, you can get an annoying POP when you engage the phantom power  
supply, or when you unplug a cable that has phantom power on it. Depending how loud you are monitoring, this POP can  
cause damage to your speakers, and even to your hearing. Be sure to turn your speakers, and/or headphone levels, all the way  
down when switching the phantom supply on and off or plugging and unplugging cables.  
If you are using a condenser microphone, turn down your monitors speakers and/or headphones, and then press  
the front panel 48 VOLT switch to engage the phantom power. The red LED will illuminate indicating the phan-  
tom power is present on the mic connector.  
PHASE – Switch  
6
For a variety of miking and mixing techniques, it may be necessary to invert the signal phase from the source you  
have plugged into your C valve pre-amp. When the PHASE switch is pressed in, the yellow LED will light show-  
ing that the input signal is now out-of-phase.  
Using The C valve For Getting A Sound  
In addition to providing a pristine signal path, the C valve offers several features to  
help you get a sound. They include the LOW CUT, VOCAL EQ, LIMITER, ENHANCE  
and SATURATION control. Each one of these parameters has an effect on the signal.  
8
Using the Low Cut Filter  
Like any good mic pre, the C valve features a LOW CUT, or (High-Pass), filter for  
attenuating the bottom-end frequencies. The LOW CUT filter allows you to remove the  
lower frequencies that you sometime just don’t want to pick up. For example, when  
you are miking a high-hat you only want to capture the frequencies that the hi-hat is  
7
producing. Therefore, by using the LOW CUT filter, you can reduce the amount of  
pick-up from the low toms and bass drum that may leak into the hi-hat mic. You can use the same  
technique on other instruments like acoustic guitar, violin, piano and even on vocals. In live sound applications,  
the LOW CUT filter is especially useful for removing stage rumble. The C valve provides a variable LOW CUT fil-  
ter that allows you to adjust the exact frequency at which the low frequencies begins to roll-off, or attenuate.  
LOW CUT  
7
Use the LOW CUT switch to engage the LOW CUT filter. When the switch is pressed in, the green LED will illu-  
minate indicating the LOW CUT filter is active. The bottom-end will begin to roll-off starting at the frequency set  
on the LOW FREQUENCY control knob. The LOW CUT filter attenuates all the frequencies below the set fre-  
quency at a 12dB per octave slope.  
9
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Operating The C valve  
Using the Low Cut Filter ( continued)  
8
LOW FREQUENCY  
8
You can set the exact frequency to start attenuating the low-end using the LOW  
FREQUENCY control knob. Be sure that the LOW CUT filter switch is engaged  
as described in the previous section. The variable LOW FREQUENCY rotary  
knob allows you to set the low-cut filter to operate at any frequency from 18 to  
300Hz.  
Using the Tube Process  
The C valve features a 12AX7 vacuum tube for adding extra harmonic content to  
the signal. It produces a subtle amount of even order harmonic distortion (the dis-  
tortion we like), the amount of which can be controlled by the SATURATION con-  
trol knob.  
9
SATURATION  
9
Use the SATURATION rotary control knob to adjust the amount of “Tube  
Process”. Start with the SATURATION knob turned all the way down and slowly  
raise the control until you have the amount of “Tube Process” that you want.  
10  
VOCAL EQ  
The C valve features a pre-set equalization curve for “sweetening” your vocal, or  
for that matter, your instrument signal. The VOCAL EQ is a “shelving” equaliza-  
tion curve that lifts the high frequencies by 6db starting at 10 kilohertz. When  
you press the VOCAL EQ switch to the in position, the green LED will illuminate  
and you will be adding some airy top-end to the signal.  
LIMIT  
11  
In order to help set, and keep, a good signal level, the C valve features on on-  
board limiter circuit. A limiter is a type of dynamics processor that automatically  
controls the gain of the signal by setting the maximum level that the signal can  
10  
11  
12  
reach. Using a limiter will help you avoid unwanted peaks or overloads in the signal, which can sometime  
cause undesirable distortion. When the LIMIT switch is pressed in, the yellow LED will illuminate indicating  
the C Valve is limiting the signal.  
ENHANCER  
12  
The C valve’s ENHANCER will restore the high frequency content that can sometimes be lost when high gain  
reduction is applied from the limiter circuit. The enhancer circuit works by applying an equalized signal to the  
control voltage that is used in the LIMIT circuit. The equalized signal adds high frequencies back to the con-  
trol voltage so that the limiter works with a little less effect on the high frequency content. The result is a  
restoration of the high frequency even if the LIMIT circuit is heavily active, so you get a thick sound that’s not  
dull.  
Use the ENHANCER in conjunction with the LIMIT circuit, by pressing both the ENHANCER and LIMIT  
SWITCH in. The ENHANCER is active when the switch is in and the yellow LED is lit.  
10  
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Operating The C valve  
Using C valve With An External Signal Processor  
To further control your signal, the C valve features an insertion point, or “effects loop”, on two 1/4-inch phone  
jacks, INSERT SEND and RETURN. An insertion point is a patch-point that interrupts the signal, allowing you to  
bring that signal outside to be processed by another device. You can use these connections to interface an  
external signal processor like an equalizer, compressor, noise gate, reverb and other audio devices to process  
the signal directly inside the C valve. A common application for the C valve’s insert point is using a compressor.  
Insert Send and Return  
13  
13  
To send a signal to an external processor, use a standard 1/4-inch cable  
to connect the rear panel INSERT SEND jack to the input of the external  
processor. The signal is sent back to the C valve using a second 1/4-inch  
cable by connecting the output of the external processor to the RETURN  
jack located on the C valve’s rear panel.  
The diagram below shows a typical application for using a compressor (in  
this example a Samson C com opti) in the C valve’s insertion point.  
11  
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Operating The C valve  
Using the Digital Output  
17  
If you are using a digital recorder that has an S/PDIF digital input, you can take  
advantage of the C valve’s high quality 24-bit A-to-D converter to make a direct  
digital connection. Use a high quality co-ax digital cable to connect the C  
valves RCA S/PDIF output to the S/PDIF. When using one C valve, the mono  
signal is sent to both the left and right S/PDIF output. You can use two C valve’s for  
stereo recording by using the DIGITAL LINK jack as explained on page 13 of this manual.  
17  
The C valve’s A-to-D converter has a selectable sampling rate. Simply put, the sampling rate is how many times  
per second the A-to-D converter takes a digital picture of the sound. Use the 48 / 96 switch to select the sample  
rate that is compatible with your digital recording device.  
48 / 96 Switch  
18  
19  
The C valve has an internal 24-bit A-to-D converter that can be set to either 48 kilo-  
hertz or 96 kilohertz sampling rates. Be sure to set the digital input on your sound  
card or digital recorder to the same sample rate. To set the sampling rate on your  
sound card or digital recorder, see the manufacturers owners manual for your specific  
device. When the 48 / 96 switch is set to the out position (the LED is off), the sample  
rate is set to 48 kilohertz. When the 48 / 96 switch is set to the in position, the LED will  
illuminate indicating that the digital sampling rate is set to 96 kilohertz.  
Digital OL indicator  
19  
18  
In order to confirm that you are not clipping or overloading the input to the internal A-  
to-D converter, the C valve provides a Digital O.L. (Over Load) LED. Ideally, this LED  
should never come on while using the C valve’s digital output for recording or live use.  
If this LED illuminates, turn down the output VOLUME control, and if necessary the INPUT GAIN control.  
12  
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Operating The C valve  
20 Using the DIGITAL LINK Jack  
For stereo applications, you can connect two C valves together by using the  
DIGITAL LINK jack. The DIGITAL LINK jack is a 1/4-inch TRS (TIP, RING,  
SLEEVE) connector providing a balanced input that is connected directly to the  
C valve right channel input of the A-to-D converter. Since the C valve’s signal  
is internally connected to the left A-to-D converter input, the signal from the  
second C valve’s OUTPUT can be connected the DIGITAL LINK jack of the  
first unit to feed the right channel of the first C valve’s A-to-D converter. Now  
use the S/PDIF output on the first C valve as one stereo digital output. The  
signal from the first C valve (or the left channel) is being carried on the left side  
of S/PDIF output and the signal from the second C valve (or the right channel)  
20  
is being carried on the right side of the S/PDIF output. The following diagram shows a typical hook-up for con-  
necting two C valves with one stereo digital output.  
13  
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C valve System Set-Ups  
Using C Valve in a Live PA System  
In this example, a condenser microphone is connected to the C valve’s MIC input using a standard XLR cable. To  
make a balanced connection, the C valve’s output is connected to the input of a standard PA mixer using a stan-  
dard 1/4-inch TRS (TIP-RING-SLEEVE) cable. The mixers main left and right outputs are connected to powered  
PA speakers (for example, the Samson dB500a).  
Using C Valve to Warm-up a signal  
You can use the C valve to “warm-up” the signal from recorded tracks or instruments such as digital electric  
piano or bass, to name a couple. The example above shows the two C valves inserted into the insert point of a  
mixer on the keyboard and bass channels. Set the input and output level so that you get unity gain (the same  
level in and out), and then use the SATURATION control to adjust the amount of tube sound.  
14  
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C valve System Set-Ups  
C Valve Stereo Digital Recording Set-up with External Compression  
15  
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Stacking and Tilting the C valve  
Stacking the C valve  
You can stack one C valve, or  
any other Samson C Class  
units, on top of each other by  
simply lining up the bumpers.  
Important Note: When stacking  
the C valve, be sure that only  
the bottom unit has the tilting  
feet installed.  
Installing the Tilting Feet  
You can install the tilting rubber feet included with  
your C valve so that you can set the unit at a com-  
fortable operating angle on a workstation or desk-  
top. Follow the simple instructions below to install  
the tilting feet.  
Remove the bottom screw from right front  
bumper.  
Identify the right tilting foot by the locating  
“R” marking on the inside top.  
Position the angled foot under the right  
bumper as shown in the drawing.  
Use the included 4 x 10mm screw to attach  
the foot.  
Repeat the steps above for the front left  
bumper.  
16  
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C valve Connections  
CONNECTING THE C valve  
The are several ways to interface the C valve to support a variety of applications. The C valve features servo-  
balanced inputs and outputs, so connecting balanced and unbalanced signals is possible without any signal loss.  
The C valve can be used on a single instrument by connecting to a channel’s insert points, or on an entire mix  
"in-line" between a mixer’s outputs and a power amp or equalizer.  
INSERT POINTS  
Many mixers today provide channel and bus or group inserts. Insert points are input and output patch points that  
interrupt the channel or bus signal so that external processors can be connected. Channel insert points are ideal  
for connecting to when using the C valve to process a single channel like a vocal, bass or guitar. Bus insert  
points are ideal for compressing groups of instruments like vocals, strings or drums. If you are connecting to a  
channel’s insert points, you may have a single TRS jack for Send & Return. In this case, use an Insert "Y" Cable  
that is configured like the one in the wiring diagram below.  
Insert Cable 1/4” male TRS connector to two male 1/4”  
in send and return configuration.  
IN-LINE  
In live sound operation, the C valve can be installed in-line between a mixer and equalizer or power amplifier.  
For these applications the C valve provides both 1/4" TRS connectors and XLR connectors to easily interface  
with most any professional audio device. Follow the wiring examples below for your particular installation.  
XLR Balanced Wiring Guide  
Unbalanced 1/4” Connector  
Balanced TRS 1/4” Connector  
17  
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C•Class Dual Rack Adapter (optional)  
The C Class Dual Rack Adapter is available as an accessory from an authorized Samson dealer.  
1. Disconnect any cables, that may be connected, from the C•Class unit to be mounted, i.e., the power supply cable, audio  
cables, headphones.  
2. Align the holes in the C•Rack with the holes on the bottom of of the C•Class unit to be mounted. Use the supplied phillips  
head M4 machine screws to fix the unit to the rack as shown below.  
3. Repeat steps 1 and 2 to mount the second C•Class unit if desired.  
4. Once the units are mounted on the C• Rack, the assembly can be placed into a rack and secured via the rack ears. (Screws  
not supplied)  
5. To remove the C•Class unit from the C•Rack, reverse the instructions above.  
If you experience any difficulties, or require further assistance, contact Samson Customer Service at 1-800-3SAMSON (1-800-372-  
6766) M–F 9AM to 5PM (eastern standard time). For more product information please visit our website at  
18  
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C valve Block Diagram  
19  
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Specifications  
System Specifications  
Frequency Response  
Dynamic range  
THD  
Crosstalk  
Detector  
20Hz to 20kHz + - 0.5 dB  
95 dBu, un-weighted, 22 Hz to 22 kHz  
0.008 % typ. @ +4 dBu, 1 kHz  
90dB 22 Hz to 22 kHz  
RMS  
Inst/Line In  
Connectors  
Impedance  
Max. Input Level  
1/4"TRS jack  
1 meg Ohm balanced  
+21 dBu, balanced and unbalanced  
Mic Input  
Connectors  
Impedance  
Max. Input Level  
CMRR  
XLR  
2.5k Ohm balanced  
+21 dBu, balanced and unbalanced  
Typ. 40dB, >55dB @ 1kHz  
Analog Output  
Connectors  
1/4"TRS jack  
Impedance  
Max. Output Level  
60 Ohms balanced, 30 Ohms unbalanced  
+21 dBu, balanced and unbalanced  
Digital Output  
Connector  
Type  
RCA  
S/PDIF  
Converter  
Sampling Rate  
24-bit  
Selectable 48 / 96 kilohertz  
Insert Send  
Connector  
Impedance  
1/4" jack  
>100 Ohm  
+21 dBu  
Max. Input Level  
Insert Return  
Connector  
Impedance  
1/4" jack  
>10k  
Max. Output Level  
+21 dBu\  
Power Supply  
AC1800  
18 VAC, 1 Amp  
USA/Canada  
U.K.  
AC1800UK  
AC1800E  
Europe  
AC1800AU  
Australia  
Dimensions  
Net Weight  
1.61" (41 mm)H x 8.67'' (220.68 mm) x 7.5'' (192mm)  
2.5 lbs (1.14 kg)  
Shipping Weight  
7.5 lbs (3.4 kgs)  
20  
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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  
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