i. Warning

The author makes no warranties that this document is free of errors.

See also important "Building hints" in section 7 below.

1. Introduction

My old NAD amplifier (bought 1988) was aging, so I was thinking about
buying a new amplifier. Interested in electronics I was looking at different
construction kit alternatives. Such kits often have attractive prices as well.
Finally I fell for the Velleman K8060 discrete power amplifier 200 W.
A Hi-Fi stereo system requires a dual setup. The main reasons for choosing
this amplifier were that it has fine data, a reasonable price, I like the
discrete construction and that it has built in power supply (excluding
the transformers). The amplifier was built during November 2005.
Here is a summary of my experiences of building and listen to it.

2. What is an ideal amplifier?

I have actually not seen a definition of an ideal amplifier, but something
like this could fit:

An ideal amplifier is completely linear over the whole observed frequency
range without adding noise or distortion to the signal.

This statement is also valid for a complete stereo or electronic music system
including speakers, CD player etc.

Of course such an "ideal music system" does not exist, but it is possible
to come close.

3. Some thoughts about home stereo systems

This text is now moved to a separate web-page found here.

4. Stereo system setup

The new stereo system consists of the following components:

• Home-made Velleman K8060 discrete power amplifier 200 W (Hi-Fi stereo setup)

• NAD C 542 CD player (with HDCD support)

• DALI 7 A speakers, three way, 8 Ohm, max 200 W (bought 1988 but still working very well)

5. Data for the Velleman K8060 amplifier

Each Velleman K8060 amplifier (mono) unit has the following specifications:

200 W music power (100 W rms) at 4 Ohm load.
140 W music power (70 W rms) at 8 Ohm load.
Class AB type.
Distortion: 0.02 % at 1 kHz / 10 W.
Damping factor: > 800.
Frequency response: 3 Hz - 200 kHz (-3 dB)
Sensitivity: 0.6 V rms.
Signal to noise ratio: 115 dB.
Power supply: 2 x 25 - 30 V AC / 120 VA.

6. Advantages and disadvantages with the Velleman K8060 amplifier

Advantages:

• Very good overall sound (my subjective thought with these speakers).
• Very linear frequency response with not so enhanced bass.
• Enough power to drive large home speakers.
• The construction kit is quite easy to build.
• Quite cheap to buy compared to commercial amplifiers.
• Low idle power consumption (about 13 W for a stereo setup).

Disadvantages:

• A smooth "click" in the speakers when the amplifier is turned off.
• Separate RCA switch required for many signal sources.
• No built in treble and bass adjustments (perhaps an advantage?).
• No built in balance adjustment.
• No fancy "bells and whistles".

7. Building hints

It is very much recommended to carefully follow the building instruction
that comes with the Velleman K8060 construction kit (see the references)!

Here are some further experiences and hints.

The Velleman K8060 amplifier construction kit is quite easy and straight
forward to build and solder. The trickiest moment is to mount the Darlington
transistors on the heatsinks. I think I spent about two hours per amplifier
unit (mounting in the box excluded). It is recommended to have one toroid
transformer per amplifier unit (although somewhat more expensive). The
transformers (120 VA, 2 x 30 V) must also be fused (1 A, 230 V, slow) on
the primary side. This is very important. Be also very careful to connect
the secondary side cables from the transformers correctly to the power input
of the amplifiers. It is also very much recommended to replace the 3300 μF
capacitors that comes with the amplifier kit with the "tweaked" capacitors
of 4700 μF to reduce ripple noise. A stereo volume potentiometer 10 k
log is better to have than the 47 k log potentiometer shown in the manual
for the kit. The lower resistance reduces signal noise to the speakers.
The bias current to the Darlington transistors must be adjusted before using
the amplifier. Adjust the bias voltage over the power resistors to 10 - 15 mV
with the trim potentiometers. A digital multimeter is practical to have at
hand during the building process, as well as a good soldering pen. Check
that everything seems to work and the red LEDs on the amplifier board are
light before connecting to the speakers. Note correct polarity.

8. Components and prices

The total price for the Velleman K8060 amplifier stereo setup is about 1600
SEK or $ 220. The prices below are given in SEK (November 2005) including
VAT (25 %) but no delivery costs. These electronics shops are found in
Sweden. Fancy boxes are quite expensive, but I found a steel box in the
electronics recycle bin. Prices for some cables must also be added (not
so expensive).

Nr	Component	Company	Article nr	Price per item (SEK)	Price (SEK)
2	Velleman K8060 amplifier kit	Electrokit	12008060	199.00	398.00
2	Pre-drilled heatsink	Electrokit	41000413	149.00	298.00
2	Toroid transformer 120 VA, 2 x 30 V	Electrokit	41000236	232.50	465.00
4	Capacitor 4700 μF, 50 V	ELFA	67-014-60	43.75	175.00
1	Volume potentiometer stereo 10 k log	ELFA	64-145-02	121.25	121.25
2	Banana contact panel female red	ELFA	40-612-14	18.75	37.50
2	Banana contact panel female black	ELFA	40-612-06	18.75	37.50
2	RCA contact panel red and black	Autema	?	12.50	25.00
2	Fuse holder with cables 230 V	Kjell & Company	39802	9.00	18.00
2	Fuse 1 A, 230 V, slow	Kjell & Company	39868	2.50	5.00
1	Mains voltage switch 230 V, 5 A	Kjell & Company	36014	12.00	12.00
				Price total (SEK):	1592.25

9. Some images (photos) of the stereo setup

1. Overview of the setup. One of the DALI 7 A speakers, the NAD C 542 CD
player, the home-made Velleman K8060 stereo amplifier and some CDs.

2. A closer look at the NAD C 542 CD player, the home-made Velleman K8060
stereo amplifier and again some CDs. Note the separate RCA switch to the
right of the amplifier.

3. The quite minimalistic and black painted front panel of the amplifier
with mains voltage switch and volume control.

4. The not painted back panel of the amplifier with RCA and speaker contacts.

5. The amplifier seen from above. Note the dual setup with two Velleman
K8060 amplifier boards with heatsinks and two toroid transformers.

6. A closer look at one of the Velleman K8060 boards with heatsink and the
toroid transformers.

7. Another view of one of the Velleman K8060 boards with heatsink and the
toroid transformers.

10. References

Construction kit manual (to download):

• k8060.pdf (662 kbyte), "Illustrated assembly manual K8060",
  by Velleman Components, 2005

Some useful Internet links:

• Velleman Components
• Electrokit (in Swedish)
• ELFA (in Swedish)
• Autema (in Swedish)
• Kjell & Company (in Swedish)
• Hi-Fi klubben (in Swedish)