Velleman K8084 User manual

VOLUME AND TONE CONTROL - PREAMPLIFIER

K8084

ILLUSTRATED ASSEMBLY MANUAL H8084IP-1

Total solder points: 162

Difficulty level: beginner 1 2 3 4 5 advanced

Whenusingoneofouramplifiers(bigorsmall),youalways

needavolumecontrolandpreferablyalsoatonecontrol

Features & specifications

When using one of our amplifiers (big or small), you always need a volume control and preferably also a tone

control. This kit comes complete with all input / output connections and potentiometers.

Furthermore it is possible to amplify or attenuate the input signal.

FEATURES:

 stereo volume control

 stereo Baxandall bass and treble control

 bass and treble potentiometers with centre click

 customizable attenuation or amplification

 complete with knobs

SPECIFICATIONS:

 supply voltage: 2 x 12VAC / 100mA

 frequency response: 3Hz - 500kHz (-3dB)

 standard amplification: x1

 signal to noise ratio: 98dB

 harmonic distortion: < 0.005% (@1KHz)

 maximum output: 5V RMS

 tone control:

+ and -15dB @ 20Hz

+ and -15dB @ 15kHz

 Input impedance: 50k ohms

 PCB dimensions: 105 x 70mm / 4,1 x 2,75"

modifications reserved

Assembly hints

1. Assembly (Skipping this can lead to troubles ! )

Ok, so we have your attention. These hints will help you to make this project successful. Read them carefully.

1.1 Make sure you have the right tools:

• A good quality soldering iron (25-40W) with a small tip.

• Wipe it often on a wet sponge or cloth, to keep it clean; then apply solder to the tip, to give it a wet look. This is called ‘thinning’and will

protect the tip, and enables you to make good connections. When solder rolls off the tip, it needs cleaning.

• Thin raisin-core solder. Do not use any flux or grease.

• A diagonal cutter to trim excess wires. To avoid injury when cutting excess leads, hold the lead so they

cannot fly towards the eyes.

• Needle nose pliers, for bending leads, or to hold components in place.

• Small blade and Phillips screwdrivers. A basic range is fine.

For some projects, a basic multi-meter is required, or might be handy

1.2 Assembly Hints :

⇒ Make sure the skill level matches your experience, to avoid disappointments.

⇒ Follow the instructions carefully. Read and understand the entire step before you perform each operation.

⇒ Perform the assembly in the correct order as stated in this manual

⇒ Position all parts on the PCB (Printed Circuit Board) as shown on the drawings.

⇒ Values on the circuit diagram are subject to changes.

⇒ Values in this assembly guide are correct*

⇒ Use the check-boxes to mark your progress.

⇒ Please read the included information on safety and customer service

* Typographical inaccuracies excluded. Always look for possible last minute manual updates, indicated as ‘NOTE’on a separate leaflet.

Assembly hints

1.3 Soldering Hints :

1- Mount the component against the PCB surface and carefully solder the leads

2- Make sure the solder joints are cone-shaped and shiny

3- Trim excess leads as close as possible to the solder joint

REMOVE THEM FROM THE TAPE ONE AT A TIME !

AXIAL COMPONENTS ARE TAPED IN THE

CORRECT MOUNTING SEQUENCE !

 R1 : 1K (1 - 0 - 2 - B)

 R2 : 100K (1 - 0 - 4 - B)

 R16 : 10K (1 - 0 - 3 - B)

 R17 : 10K (1 - 0 - 3 - B)

 R18 : 10K (1 - 0 - 3 - B)

 R19 : 10K (1 - 0 - 3 - B)

 R20 : 10K (1 - 0 - 3 - B)

Hint for R21 to R24

Modify the resistances marked RF

and RA to increase the input sen-

sitivity (more amplification).

The formula is:

amplification = (RF/RA) + 1

E.g. to double the amplification because

the input of the connecting device is too

weak, mount 100K for RF (R22 and

R23).

 R21 : 100K (1 - 0 - 4 - B)

 R22 : 1K (1 - 0 - 2 - B)

 R23 : 1K (1 - 0 - 2 - B)

 R24 : 100K (1 - 0 - 4 - B)

3. Resistors

R...

Construction

 D1 : 1N4007

 D2 : 1N4007

 D3 : 1N4007

 D4 : 1N4007

2. Diodes. Watch the polarity !

D...

CATHODE

 ZD1 : 9V1

 ZD2 : 9V1

1. Zenerdiodes. Watch the

polarity !

CATHODE

ZD...

Hint for R2 and R4:

To weaken the input (divide)

E.g. to connect the input with an ampli-

fier output.

Choose an inferior value for R2 and

R4.

The dividing factor = (R1/R2) + 1

E.g. a value of 100Ωfor RD (R2 and R4)

will divide the input by 11.

 R3 : 1K (1 - 0 - 2 - B)

 R4 : 100K (1 - 0 - 4 - B)

 R5 : 10 (1 - 0 - 0 - B)

 R6 : 10 (1 - 0 - 0 - B)

 R7 : 1K (1 - 0 - 2 - B)

 R8 : 1K (1 - 0 - 2 - B)

 R9 : 3K3 (3 - 3 - 2 - B)

 R10 : 1K (1 - 0 - 2 - B)

 R11 : 1K (1 - 0 - 2 - B)

 R12 : 10 (1 - 0 - 0 - B)

 R13 : 3K3 (3 - 3 - 2 - B)

 R14 : 3K3 (3 - 3 - 2 - B)

 R15 : 10K (1 - 0 - 3 - B)

 C19 : 47µ F

 C20 : 47µ F

 C21 : 220µ F

 C22 : 220µ F

 IC1 : 8p

 IC2 : 8p

4. IC sockets, Watch the

position of the notch!

 LD1 : 5mm Red "Power"

6. LED. Watch the polarity !

COLOR= 2...5

LD...

CATHODE

Construction

 T1 : BC547

 T2 : BC557

7. Transistors

 C1 : 15pF (15)

 C2 : 15pF (15)

 C3 : 100pF (101)

 C4 : 100pF (101)



C5 : 4,7nF (472)



C6 : 4,7nF (472)



C7 : 4,7nF (472)



C8 : 4,7nF (472)



C9 : 47nF (473)



C10 : 47nF (473)

5. Capacitors.

c... C...

 SK1 : 3p AC input

8. Terminal block

 C11 : 47nF (473)

 C12 : 47nF (473)



C13 : 47nF (473)



C14 : 47nF (473)



C15 : 47nF (473)

 C16 : 47nF (473)

 C17 : 1µ F / 63V

 C18 : 1µ F / 63V

9. Electrolytic capacitors

C...

Connect a 2 x 12V / min. 100mA transformer with power connector

SK1 (e.g. our 212007C). This is a 2 x 12V 3-wire transformer, 1 wire is

the common 0 and generally of another colour.

A transformer without connecting wires will be marked 12 – 0 – 12.

 SK2 : input

 SK3 : output

10. Dual RCA Jacks

 RV1 : A 50K (Volume)

 RV2 : B 50K (Bass)

 RV3 : B 50K (Treble)

11. Potentiometers

RV1

12. Test

100mA

12V

Construction

Connect the mains voltage to the transformer; mount a 100mAT security fuse in series with the transformer.

Use a high-quality power cord and plug for the connection to the mains.

When the transformer is live, the LED will light.

 Disconnect from mains.

 Mount the ICs into the socket (mind the position of the notch)

 Reconnect the mains.

 Check if the LED lights.

 Connect a device with the input e.g. MP3 player, CD player.

 Connect the output with a power amplifier.

 Turn down the volume to its minimum.

 Switch on the power amplifier.

 Hint: you can also connect headphones instead of a power amplifier. You can use connections GND-TPR-

TPL; GND is the ground.

Test

13. Building into a enclosure

Enclosure

To avoid hum, it is recommended to mount the K8084 and the transformer into a Metal housing.

Drill the holes for the connections and the potentiometers.

 Hint:You can drill the holes for the knobs or the potentiometers and mount the knob afterwards.

1 hole in the print (next to RV3) is provided to connect the earthing to the housing through the metal spacers

or bolts.

Hint:

 Mount the transformer as far away as possible from the circuit to avoid humming.

 It is recommended to leave this circuit under voltage; disconnect the voltage only when not in use for a

long time. Always switch off the power amplifier first before switching off the preamplifier.

14. PCB

PCB

Table of contents

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