Avtech AV-110J-PS-D User manual

INSTRUCTIONS
MODEL AV-110J-PS-D
0 to ±400V, 50 kHz
VARIABLE-GAIN DUAL-CHANNEL
LINEAR AMPLI IER
SERIAL NUMBER: ____________
1
A V T E C H E L E C T R O S Y S T E M S L T D .
N A N O S E C O N D W A V E O R M E L E C T R O N I C S
S I N C E 1 9 7 5
P.O. BOX 265
OGDENSBURG, NY
U.S.A. 13669-0265
TEL: 888-670-8729 (USA & Canada) or +1-613-686-6675 (Intl)
AX: 800-561-1970 (USA & Canada) or +1-613-686-6679 (Intl)
info@avtechpulse.com - http://www.avtechpulse.com/
X
BOX 5120, LCD MERIVALE
OTTAWA, ONTARIO
CANADA K2C 3H4

WARRANTY
Avtech Electrosystems Ltd. warrants products of its manufacture to be free from
defects in material and workmanship under conditions of normal use. If, within
one year after delivery to the original owner, and after prepaid return by the
original owner, this Avtech product is found to be defective, Avtech shall at its
option repair or replace said defective item. This warranty does not apply to
units which have been dissembled, modified or subjected to conditions
exceeding the applicable specifications or ratings. This warranty is the extent of
the obligation assumed by Avtech with respect to this product and no other
warranty or guarantee is either expressed or implied.
TECHNICAL SUPPORT
Phone: 888-670-8729 (USA & Canada) or +1-613-686-6675 (International)
ax: 800-561-1970 (USA & Canada) or +1-613-686-6679 (International)
E-mail: info@avtechpulse.com
World Wide Web: http://www.avtechpulse.com
2

TABLE O CONTENTS
WARRANTY......................................................................................................................2
TECHNICAL SUPPORT...................................................................................................2
TABLE OF CONTENTS....................................................................................................3
INTRODUCTION...............................................................................................................5
HIGH-VOLTAGE PRECAUTIONS....................................................................................5
SPECIFICATIONS.............................................................................................................6
REGULATORY NOTES....................................................................................................7
FCC PART 18..............................................................................................................................7
EC DECLARATION OF CONFORMITY.....................................................................................7
DIRECTIVE 2002/95/EC (RoHS)................................................................................................8
DIRECTIVE 2002/96/EC ( EEE)...............................................................................................8
INSTALLATION................................................................................................................9
VISUAL CHECK..........................................................................................................................9
PO ER RATINGS......................................................................................................................9
CONNECTION TO THE PO ER SUPPLY................................................................................9
PROTECTION FROM ELECTRIC SHOCK..............................................................................10
ENVIRONMENTAL CONDITIONS...........................................................................................11
FUSES.............................................................................................................................12
AC FUSE REPLACEMENT......................................................................................................12
DC FUSE REPLACEMENT......................................................................................................13
FUSE RATINGS........................................................................................................................13
FRONT PANEL CONTROLS..........................................................................................14
REAR PANEL CONTROLS............................................................................................16
GENERAL INFOR ATION............................................................................................17
BASIC CONTROL.....................................................................................................................17
CABLE LENGTHS....................................................................................................................17
OPERATIONAL CHECK.................................................................................................18
ECHANICAL INFOR ATION......................................................................................20
TOP COVER REMOVAL..........................................................................................................20
RACK MOUNTING....................................................................................................................20
ELECTROMAGNETIC INTERFERENCE.................................................................................20
AINTENANCE..............................................................................................................21
REGULAR MAINTENANCE.....................................................................................................21
CLEANING................................................................................................................................21
3

WIRING DIAGRA S.......................................................................................................22
IRING OF AC PO ER, STYLE 1.........................................................................................22
IRING OF AC PO ER, STYLE 2.........................................................................................23
PCB 158N - LO VOLTAGE PO ER SUPPLY, 1/3.............................................................24
PCB 158N - LO VOLTAGE PO ER SUPPLY, 2/3..............................................................25
PCB 158N - LO VOLTAGE PO ER SUPPLY, 3/3.............................................................26
PCB 170B - HIGH VOLTAGE DC PO ER SUPPLY..............................................................27
MAIN IRING...........................................................................................................................28
PERFOR ANCE CHECK SHEET..................................................................................29
Manual Reference: /fileserver/officefiles/instructword/av-110/AV-110J-PS-D,ed1.odt.
Last modified January 27, 2010.
Copyright © 2010 Avtech Electrosystems Ltd, All Rights Reserved.
4

INTRODUCTION
The AV-110J-PS-D is a variable-gain dual-channel linear amplifier. The input range is 0
to ±2V, and the output range is 0 to ±400V. The outputs can drive load impedances of
10 kΩ and higher. The amplifier bandwidth is 50 kHz.
The gain for each of the two independent channels may be adjusted from +1 to +200.
Units with the -INV or -SCHA options also have an inverting mode, allowing the gain to
be adjusted between -1 and -200.
HIGH-VOLTAGE PRECAUTIONS
CAUTION: This instrument provides output voltages as high as ±400 Volts, so
extreme caution must be employed when using this instrument. The instrument should
only be used by individuals who are thoroughly skilled in high voltage laboratory
techniques. The following precaution should always be observed:
1. Keep exposed high-voltage wiring to an absolute minimum.
2. Wherever possible, use shielded connectors and cabling.
3. Connect and disconnect loads and cables only when the amplifier is turned off.
4. Keep in mind that all cables, connectors, oscilloscope probes, and loads must
have an appropriate voltage rating.
5. Do not attempt any repairs on the instrument, beyond the fuse replacement
procedures described in this manual. Contact Avtech technical support (see page
2 for contact information) if the instrument requires servicing.
5

SPECI ICATIONS
Model: AV-110J-PS-D
Output amplitude: 0 to ±400 V
Maximum current: 40 mA
Load impedance: ≥ 10 kΩ
Output resistance1: ≈ 0Ω
Bandwidth (f-3dB): 50 kHz
Rise time (20%-80%, for
maximum output): 3.5 us
Output power
(maximum) 16 W
Voltage gain2: ×1 to ×200
Gain polarity: Standard: Non-inverting (+)
Optional5: Switchable between Non-inverting (+) and Inverting (-) modes
Input range2: 0 to ± 2 Volts (1 kΩ input impedance)
Dual channel: Yes (-D Option3)
Regular DC offset option2,4,7: ± 100 V
Extended DC offset
option2,6,7:± 400 V
Connectors: In, Out: BNC
Dimensions: 100 mm x 430 mm x 375 mm (3.9” x 17” x 14.8”)
Power requirement: 100-240 Volts, 50-60 Hz
1) “Output resistance” is the internal resistance in series with output. Non-zero output impedances (ROUT) will
reduce the maximum output amplitude slightly when operating into low load impedances. That is, VOUT = VSET ×
RLOAD / (RLOAD + ROUT), where VSET is the set amplitude and RLOAD is the load resistance.
2) These parameters can easily be adapted to meet special requirements. Contact Avtech
(info@avtechpulse.com) with your special application!
3) To specify the two channel option add the suffix -D to the model number.
4) To specify the regular DC offset option, add the suffix -OS to the model number.
5) Add the suffix -INV to specify the switchable gain polarity feature.
6) To specify the extended DC offset option, add the suffix -OS to the model number.
7) The sum of the amplitude and the offset must remain within the rated output amplitude range – i.e., this option
does not change the minimum or maximum obtainable output voltage.
6

REGULATORY NOTES
CC PART 18
This device complies with part 18 of the CC rules for non-consumer industrial, scientific
and medical (ISM) equipment.
This instrument is enclosed in a rugged metal chassis and uses a filtered power entry
module (where applicable). The main output signal is provided on a shielded connector
that is intended to be used with shielded coaxial cabling and a shielded load. Under
these conditions, the interference potential of this instrument is low.
If interference is observed, check that appropriate well-shielded cabling is used on the
output connectors. Contact Avtech ([email protected]) for advice if you are unsure
of the most appropriate cabling. Also, check that your load is adequately shielded. It
may be necessary to enclose the load in a metal enclosure.
If any of the connectors on the instrument are unused, they should be covered with
shielded metal “dust caps” to reduce the interference potential.
This instrument does not normally require regular maintenance to minimize interference
potential. However, if loose hardware or connectors are noted, they should be tightened.
Contact Avtech (inf[email protected]) if you require assistance.
EC DECLARATION O CON ORMITY
We Avtech Electrosystems Ltd.
P.O. Box 5120, LCD Merivale
Ottawa, Ontario
Canada K2C 3H4
declare that this pulse generator meets the intent of Directive 89/336/EEC for
Electromagnetic Compatibility. Compliance pertains to the following specifications as
listed in the official Journal of the European Communities:
EN 50081-1 Emission
EN 50082-1 Immunity
7

and that this pulse generator meets the intent of the Low Voltage Directive 72/23/EEC
as amended by 93/68/EEC. Compliance pertains to the following specifications as listed
in the official Journal of the European Communities:
EN 61010-1:2001 Safety requirements for electrical equipment for
measurement, control, and laboratory use
DIRECTIVE 2002/95/EC (RoHS)
This instrument is exempt from Directive 2002/95/EC of the European Parliament and of
the Council of 27 January 2003 on the Restriction of the use of certain Hazardous
Substances (RoHS) in electrical and electronic equipment. Specifically, Avtech
instruments are considered "Monitoring and control instruments" (Category 9) as defined
in Annex 1A of Directive 2002/96/EC. The Directive 2002/95/EC only applies to Directive
2002/96/EC categories 1-7 and 10, as stated in the "Article 2 - Scope" section of
Directive 2002/95/EC.
DIRECTIVE 2002/96/EC (WEEE)
European customers who have purchased this equipment directly from Avtech will have
completed a “WEEE Responsibility Agreement” form, accepting responsibility for WEEE
compliance (as mandated in Directive 2002/96/EC of the European Union and local
laws) on behalf of the customer, as provided for under Article 9 of Directive 2002/96/EC.
Customers who have purchased Avtech equipment through local representatives should
consult with the representative to determine who has responsibility for WEEE
compliance. Normally, such responsibilities with lie with the representative, unless other
arrangements (under Article 9) have been made.
Requirements for WEEE compliance may include registration of products with local
governments, reporting of recycling activities to local governments, and financing of
recycling activities.
8

INSTALLATION
VISUAL CHECK
After unpacking the instrument, examine to ensure that it has not been damaged in
shipment. Visually inspect all connectors, knobs, and handles. Confirm that a power
cord is with the instrument. If the instrument has been damaged, file a claim immediately
with the company that transported the instrument.
POWER RATINGS
This instrument is intended to operate from 100 - 240 V, 50 - 60 Hz.
The maximum power consumption is 125 Watts. Please see the “ USES” section for
information about the appropriate AC and DC fuses.
This instrument is an “Installation Category II” instrument, intended for operation from a
normal single-phase supply.
CONNECTION TO THE POWER SUPPLY
An IEC-320 three-pronged recessed male socket is provided on the back panel for AC
power connection to the instrument. One end of the detachable power cord that is
supplied with the instrument plugs into this socket. The other end of the detachable
power cord plugs into the local mains supply. Use only the cable supplied with the
instrument. The mains supply must be earthed, and the cord used to connect the
instrument to the mains supply must provide an earth connection. (The supplied cord
does this.)
Warning: ailure to use a grounded outlet may result in injury or death due to
electric shock. This product uses a power cord with a ground connection. It must be
connected to a properly grounded outlet. The instrument chassis is connected to the
ground wire in the power cord.
The table below describes the power cord that is normally supplied with this instrument,
depending on the destination region:
9

Destination Region Description Option Manufacturer Part Number
United Kingdom, Hong Kong,
Singapore, Malaysia
BS 1363,
230V, 50 Hz -AC00 Qualtek1370001-E01
Australia, New Zealand AS 3112:2000,
230-240V, 50 Hz -AC01 Qualtek1374003-A01
Continental Europe, Korea,
Indonesia, Russia
European CEE 7/7
“Schuko” 230V, 50 Hz -AC02 Qualtek1364002-D01
North America, Taiwan NEMA 5-15,
120V, 60 Hz -AC03 Qualtek1312007-01
Switzerland SEV 1011,
230V, 50 Hz -AC06 Qualtek1378001-E01
South Africa, India SABS 164-1,
220-250V, 50 Hz -AC17 Volex22131H 10 C3
Japan JIS 8303,
100V, 50-60 Hz -AC18 Qualtek1397002-01
Israel SI 32,
220V, 50 Hz -AC19 Qualtek1398001-01
China GB 1002-1,
220V, 50 Hz -AC22 Volex22137H 10 C3
PROTECTION ROM ELECTRIC SHOCK
Operators of this instrument must be protected from electric shock at all times. The
owner must ensure that operators are prevented access and/or are insulated from every
connection point. In some cases, connections must be exposed to potential human
contact. Operators must be trained to protect themselves from the risk of electric shock.
This instrument is intended for use by qualified personnel who recognize shock hazards
and are familiar with safety precautions required to avoid possibly injury. In particular,
operators should:
1. Keep exposed high-voltage wiring to an absolute minimum.
2. Wherever possible, use shielded connectors and cabling.
3. Connect and disconnect loads and cables only when the instrument is turned off.
4. Keep in mind that all cables, connectors, oscilloscope probes, and loads must
have an appropriate voltage rating.
5. Do not attempt any repairs on the instrument, beyond the fuse replacement
procedures described in this manual. Contact Avtech technical support (see page
2 for contact information) if the instrument requires servicing. Service is to be
performed solely by qualified service personnel.
10

ENVIRONMENTAL CONDITIONS
This instrument is intended for use under the following conditions:
1. indoor use;
2. altitude up to 2 000 m;
3. temperature 5 °C to 40 °C;
4. maximum relative humidity 80 % for temperatures up to 31 °C decreasing linearly
to 50 % relative humidity at 40 °C;
5. Mains supply voltage fluctuations up to ±10 % of the nominal voltage;
6. no pollution or only dry, non-conductive pollution.
11

USES
This instrument contains four fuses. All are accessible from the rear-panel. Two protect
the AC prime power input, and two protect the internal DC power supplies. The locations
of the fuses on the rear panel are shown in the figure below:
AC USE REPLACEMENT
To physically access the AC fuses, the power cord must be detached from the rear
panel of the instrument. The fuse drawer may then be extracted using a small flat-head
screwdriver, as shown below:
12
Fuses #1 and #2
(AC fuses)
Fuse #4
(DC fuse)
Fuse #3
(DC fuse)
Fuse
Drawer
Pry out the fuse
drawer using a
screwdriver.

DC USE REPLACEMENT
The DC fuses may be replaced by inserting the tip of a flat-head screwdriver into the
fuse holder slot, and rotating the slot counter-clockwise. The fuse and its carrier will
then pop out.
USE RATINGS
The following table lists the required fuses:
uses
Nominal
Mains
Voltage
Rating Case Size
Recommended Replacement Part
Littelfuse Part
Number
Digi-Key Stock
Number
#1, #2 (AC)
115 V 1.0A, 250V,
Time-Delay 5×20 mm 0218001.HXP 2419-ND
230 V 0.5A, 250V,
Time-Delay 5×20 mm 0218.500HXP 2416-ND
#3 (DC) N/A 4.0A, 250V,
Time-Delay 5×20 mm 0218004.HXP 2421-ND
#4 (DC) N/A 4.0A, 250V,
Time-Delay 5×20 mm 0218004.HXP 2421-ND
The recommended fuse manufacturer is Littelfuse (http://www.littelfuse.com).
Replacement fuses may be easily obtained from Digi-Key (http://www.digikey.com) and
other distributors.
13

RONT PANEL CONTROLS
1. POWER Switch . This is the main power switch. When turning the instrument on,
there may be a delay of several seconds before the instrument appears to respond.
2. OVERLOAD Indicator . When the instrument is powered, this indicator is normally
green, indicating normal operation. If this indicator is yellow, an internal automatic
overload protection circuit has been tripped. If the unit is overloaded (by operating at
an exceedingly high duty cycle or by operating into a very low impedance), the
protective circuit will disable the output of the instrument and turn the indicator light
yellow. The light will stay yellow (i.e. output disabled) for about 5 seconds after
which the instrument will attempt to re-enable the output (i.e. light green) for about 1
second. If the overload condition persists, the output will be disabled again (i.e. light
yellow) for another 5 seconds. If the overload condition has been removed, the
instrument will resume normal operation.
This overload indicator is only likely to come on in two situations:
•Briefly at startup. This is not a cause for concern.
•When the load impedance is too low (< 10 kΩ). In this case, turn off the
instrument and connect the proper load.
3. IN A Connector . The input signal for the Channel A amplifier is applied to this BNC
connector. The input must not exceed ±2V. The input impedance is approximately 1
kΩ. Depending on the length of cable attached to this input, and the source driving it,
it may be desirable to add a coaxial 50 Ohm terminator to this input to provide a
proper transmission line termination. The Pasternack (www.pasternack.com)
PE6008-50 BNC feed-thru 50 Ohm terminator is suggested for this purpose.
4. GAIN A Dial . This ten-turn dial is used to vary the gain of the Channel A amplifier
between < 1 and > 200.
5. GAIN POLARITY A Switch . (Optional. Requires -INV or -SCHA option.) Standard
units operate with non-inverting gain (+). Units with this switch also the gain to be
14
1
210
4
3
6
7
598

switched between non-inverting (+) or inverting (-) modes.
6. OUT A Connector . This BNC connector provides the main output of the Channel A
amplifier. The output is an amplified version of the input on (3). The gain (VOUT/VIN) is
controlled by (4) and (5).
Caution: Voltages as high as ±400V may be present on the center conductor of
this output connector. Avoid touching this conductor. Connect to this connector using
standard coaxial cable, to ensure that the center conductor is not exposed.
7. IN B Connector . The input signal for the Channel B amplifier is applied to this BNC
connector. The input must not exceed ±2V. The input impedance is approximately 1
kΩ. Depending on the length of cable attached to this input, and the source driving it,
it may be desirable to add a coaxial 50 Ohm terminator to this input to provide a
proper transmission line termination. The Pasternack (www.pasternack.com)
PE6008-50 BNC feed-thru 50 Ohm terminator is suggested for this purpose.
8. GAIN B Dial . This ten-turn dial is used to vary the gain of the Channel B amplifier
between < 1 and > 200.
9. GAIN POLARITY B Switch . (Optional. Requires -INV or -SCHA option.) Standard
units operate with non-inverting gain (+). Units with this switch also the gain to be
switched between non-inverting (+) or inverting (-) modes.
10.OUT B Connector . This BNC connector provides the main output of the Channel B
amplifier. The output is an amplified version of the input on (7). The gain (VOUT/VIN) is
controlled by (8) and (9).
Caution: Voltages as high as ±400V may be present on the center conductor of
this output connector. Avoid touching this conductor. Connect to this connector using
standard coaxial cable, to ensure that the center conductor is not exposed.
Units with the -OS or -XOS options will have additional controls (not shown) to
control the DC offset feature:
11.O SET A Dial . (Optional. Requires -OS or -XOS option.) This ten-turn dial is used
to vary the DC offset of the OUT A output, in the range of -100V to +100V (for -OS
units) or -400V to +400V (for -XOS units). The switch below this dial can be used to
enable/disable this feature.
12.O SET B Dial . (Optional. Requires -OS or -XOS option.) This ten-turn dial is used
to vary the DC offset of the OUT B output, in the range of -100V to +100V (for -OS
units) or -400V to +400V (for -XOS units). The switch below this dial can be used to
enable/disable this feature.
15
VOUT = VIN × GAIN,
GAIN = +1 TO +200,
ADJUSTABLE.
± 400V MAXIMUM.

REAR PANEL CONTROLS
1. AC POWER INPUT . An IEC-320 C14 three-pronged recessed male socket is
provided on the back panel for AC power connection to the instrument. One end of
the detachable power cord that is supplied with the instrument plugs into this socket.
2. AC USE DRAWER . The two fuses that protect the AC input are located in this
drawer. Please see the “ USES” section of this manual for more information.
3. DC USES . These two fuses protect the internal DC power supplies. Please see the
“ USES” sections of this manual for more information.
16
2
31
VOUT = VIN × GAIN,
GAIN = +1 TO +200,
ADJUSTABLE.
± 400V MAXIMUM.

GENERAL IN ORMATION
BASIC CONTROL
The AV-110J-PS-D is a DC-50 kHz variable-gain linear amplifier. The gain of each of
the two channels (designated “A” and “B”) is variable from +1 to +200, and is adjusted
by rotating the “Gain” associated control.
Units with the -INV or -SCHA options will also have a switch that can be used to enable
an inverting mode, in which case the gain is variable from -1 to -200.
The required voltage input signals are applied at the “IN” connectors.
This operation is illustrated below:
If the instrument has the -OS option, a DC offset in the range of of -100V to +100V (for
-OS units) or -400V to +400V (for -XOS units) may be added to each output. The total
output voltage (amplified signal + DC offset) must remain within the range of -400V to
+400V.
CABLE LENGTHS
The length of cable used to connect the load to the output of the function generator
should be less than 3 feet (1 meter), and ideally less than 18 inches (0.5 meters). At
longer lengths, the transmission line reflections caused by the cabling and the cable's
capacitance will distort the output signal and degrade the rise and fall times, particularly
if the signals with fast rise times are used.
The capacitance associated with any length of coaxial cabling will degrade the rise and
fall times of fast signals.
17
ARBITRARY
WAVE ORM,
VIN, ± 2V MAXIMUM
INPUT VOLTAGE, ON
"IN" CONNECTOR
OUTPUT VOLTAGE, ON
"OUT" CONNECTOR
VOUT = VIN × GAIN,
GAIN = +1 TO +200,
ADJUSTABLE.
± 400V MAXIMUM.

OPERATIONAL CHECK
This section describes a sequence to confirm the basic operation of the instrument. It
should be performed after receiving the instrument. It is a useful learning exercise as
well.
asic Test Arrangement
1) Connect a 10 kΩ, 16W non-inductive test load between the OUT A connector and
ground. A higher resistance may also be used, in which case the power rating may
be reduced. If cabling is used, keep it less than 3 feet / 1 meter in length. Confirm
that the oscilloscope probe and the test load are rated for 400 Volt operation.
2) Set the signal generator to produce a ±2V, 10 kHz waveform. (The input impedance
of the AV-110J-PS-D is 1 kΩ). Connect a cable from the SYNC connector of the
signal generator to the TRIG input of an oscilloscope. Set the oscilloscope to trigger
externally. Connect the main output of the signal generator to the input of the
amplifier.
3) Connect one oscilloscope probe (channel 1) to the output of the signal generator.
Set the Channel 1 vertical scale to 1 V/div.
4) Connect one oscilloscope probe (channel 2) to the 10 kΩ load. On the oscilloscope,
set the channel 1 vertical scale to 100 V/div, and the horizontal scale to 100 us/div.
18
AV-110J-PS-D
AMPLIFIER
OUT A
CONNECTOR
REAL-TIME
OSCILLOSCOPE
CHANNEL 1
CHANNEL 2
IN A
CONNECTOR
SIGNAL
SOURCE
(±2V maximum)
TRIG
MAIN OUTPUT
SYNC OUTPUT
AC
POWER
SCOPE
PROBE
TEST LOAD,
> 10 kΩ, 16W
SCOPE
PROBE
OUT B
CONNECTOR
IN B
CONNECTOR

5) Set the gain control to minimum (0.0). Turn on the amplifier and the signal
generator.
6) Rotate the gain control to its maximum setting. The Channel 2 waveform should
increase to ±400V, and have a shape similar to that of the Channel 1 waveform.
7) Repeat the previous steps using the IN B and OUT B connectors.
8) This completes the operational check.
19

MECHANICAL IN ORMATION
TOP COVER REMOVAL
If necessary, the interior of the instrument may be accessed by removing the four
Phillips screws on the top panel. With the four screws removed, the top cover may be
slid back (and off).
Always disconnect the power cord and allow the instrument to sit unpowered for 10
minutes before opening the instrument. This will allow any internal stored charge to
discharge.
There are no user-adjustable internal circuits. or repairs other than fuse replacement,
please contact Avtech (info@avtechpulse.com) to arrange for the instrument to be
returned to the factory for repair. Service is to be performed solely by qualified service
personnel.
Caution: High voltages are present inside the instrument during normal operation.
Do not operate the instrument with the cover removed.
RACK MOUNTING
A rack mounting kit is available. The -R5 rack mount kit may be installed after first
removing the one Phillips screw on the side panel adjacent to the front handle.
ELECTROMAGNETIC INTER ERENCE
To prevent electromagnetic interference with other equipment, all used outputs should
be connected to shielded loads using shielded coaxial cables. Unused outputs should
be terminated with shielded coaxial terminators or with shielded coaxial dust caps, to
prevent unintentional electromagnetic radiation. All cords and cables should be less
than 3m in length.
20
Table of contents
Other Avtech Amplifier manuals