Velleman High-Q K2572 User manual

UNIVERSAL STEREO
PREAMPLIFIER K2572
-Gain (presettable) : 40 dB
-Frequency response : 40Hz -30KHz (-3dB)
-Maximum input signal : 50mVrms (500mVrms)
-Output impedance : 1Kohm
-Power supply : 10 -30 VDC, regulated
-Supply current : typ. 5mA
-Dimensions : 44 x 65 mm (1.73" x 2.56")

2
VELLEMAN COMPONENTS NV
Legen Heirweg 33
9890 Gavere
Belgium
www.velleman.be

K2572 3
While the soldering iron is heating, read this first !
You want to enjoy your Velleman Kit as quick as possible, these
hints will assist you !
First, take your time. Hasty jobs often result in disappointments.
Make sure your workspace is wide, clean and well lit. Collect all
the necessary tools you might need for the assembly. Take
care, while unpacking that nothing is left in the wrapping or
boxes, such as small parts, manuals and leaflets. Please check
if all components are present. Use the supplied partlist as a
guide. In case there is something missing or damaged, return
the Kit to your dealer. Read all supplied manuals and notes
carefully before you start constructing...
The Velleman Kit Warranty
Please read this carefully. In most cases, you can easily solve
problems yourself. This text tells you all about.
The Kit, you have built or intend to build, was design by a team
of highly skilled design engineers. Before their design reaches
the customer, it has been tested and re-tested over and over
again. This procedure guarantees you that every design actually
works, when it is put together in the right way. But what if
something does go wrong ?
Avoid unnecessary expenses and loss of time ! Examine the
whole circuit closely. An even better procedure is to let
someone else do this for you. Every tiny detail is important. Are
all components put in the right place and correctly oriented.
Watch out for bad or forgotten solder joints and short-circuits !
What about the power supply ? Is it correct and present ? Does
the Kit require special calibration or adjustment ? Do the
possible external devices such as computers, audio sources or
power circuits match the Kit specifications ?

K2572 4
When all the above did not bring you any closer to a solution,
start thinking of a defective part or parts. Semiconductors like
transistors, FET’s, IC’s and processors, although very reliable
do not support abuse. You can send us suspect
semiconductors for inspection and eventual exchange but keep
in mind. Our experienced technicians can tell the difference
between a defective and a fried transistor, and in several cases
a stamp is much more expensive than a replacement
semiconductor bought at the local store.
Any Velleman-Kit if defective will be repaired or replaced at our
option within 30 days of purchase.
Simply return it to the place of purchase with proof of purchase.

K2572 5
INTRODUCTION
This universal pre-amplifier kit replaces the long-running K1803.
It has been upgraded with a low-noise integrated circuit and is
stereo instead of mono.
.
For audiophiles with a turntable who wish a complementary
phono amplifier, the K2573 stereo RIAA kit is fully compatible
with the K2572.
TECHNICAL DATA
Power supply : 10VDC minimum to 30VDC maximum, from a
stable source
Current consumption (no signal, no load) : typically 5mA
Amplification (adjustable) : 40 dB
Frequency range : 40Hz—30KHz -3dB
Output impedance : 1KΩ
Maximum input signal : 50mV (500mV)
UNIVERSAL STEREO PREAMPLIFIER ASSEMBLY
AND TOOLS
Check that you have all the parts.
RECOMMENDED TOOLS
Miniature 25W soldering iron
Multicore solder
Soldering iron stand and sponge

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ASSEMBLY
1. RESISTORS
Start assembly with the resistors .They are not polarized, so
they can be inserted in either direction. Only the three primary
color bands are mentioned. There may be a fourth band which
can be ignored.
Inventory
Sequence
of assembly
Reference Part number / description
mmR1 22KΩ(red-red-orange)
mmR2 22KΩ(red-red-orange)
mmR3 1MΩ(brown-black-green)
mmR4 1MΩ(brown-black-green)
mmR5 10KΩ(brown-black-orange)
mmR6 10KΩ(brown-black-orange)
mmRV1 Trim pot 1KΩ
mmRV2 Trim pot 1KΩ(These may be
flat as well as vertical)
2. CAPACITORS
These capacitors are not polarized, so they can be inserted
either way.
Inventory
Sequence
of assembly
Reference Part number / description
mmC4 100 nF Sibatit capacitor
(Sometimes marked as 104)

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3. THE ELECTROLYTIC CAPACITORS
Note carefully the positive leads before you fit the capacitor into
the PCB board. Watch the polarity !
Inventory
Sequence
of assembly
Reference Part number / description
mmC1 10 µF electrolytic capacitor
mmC2 1 µF electrolytic capacitor
mmC3 1 µF electrolytic capacitor
mmC5 1 µF electrolytic capacitor
mmC6 1 µF electrolytic capacitor
mmC7 1 µF electrolytic capacitor
mmC8 1 µF electrolytic capacitor
4. SOCKET
Inventory
Sequence
of assembly
Part number / description
mmIC socket
Mount IC socket where marked "IC1"
5. INTEGRATED CIRCUIT (IC)
Inventory
Sequence
of assembly
Reference Part number / description
mmIC1 8-pin integrated circuit
Mount the IC on its socket,
the notch being turned
toward C1.

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USAGE
10 connections are provided on the PCB to connect the circuit
with signal inputs, grounds and power supply. These
connections are identical to those of the RIAA K2573; you can
connect them by the numbers.
1. ground
2. out left
3. ground
4. in left
5. ground (power supply)
6. plus (power supply)
7. in right
8. ground
9. out right
10. ground
The ground connections near the IN and OUT connections are
used to connect the stranded wires (-) of the connecting leads.
The output amplitude of the right and the left channel are totally
independently controlled by RV1 for the right channel and RV2
for the left channel.
As current consumption is very low, voltage can be taken from
any stable power supply of between 10VDC and 30VDC. Lower
the gain from 100 to 10 if the input signal is higher than 50mV;
this is done by replacing R5 and R6 with 100kΩresistors.
REMARKS
An unstable power supply will give noise and hum. The leads to
and from the PCB must be as short as possible and use only
screened wires
Never place the preamp in the vicinity of transformers or mains
power lines

K2572 9
Universal Stereo Mono Preamplifier
PCB Layout and component placement

K2572 10
Modifications and typographical errors reserved
©Velleman Components nv.