K4005B & K4006 kits - advice please

40 years ago, I built a Haffler amplifier and Haffler pre-amp which served me well until about a year ago, when one channel on the amplifier failed. I was not bright enough to realize there was not enough air circulating in the enclosure causing that end of the amplifier to fail.
Due to its age, I decided it best to build a new replacement. So I have chosen your two kits (below):
Re: K4005B amplifier, K4006 power supply, I note 2 things:

  1. Not all is included in the kits - there are no suggestions on mounting the finished kits (chassis, enclosure, etc.)
  2. No transformers came with either kit. It would have been nice to have note of this fact on the fact sheet of the advertisement for these kits.
    I have completed the K4006, a neat package. Where do I get the required transformers?
    Before starting on the amp, I’d like to know best mounting for the whole finished assemblies (on what?). Is there yet another kit for final assembly of the whole package, like a chassis? The Hafflers had everything needed to go from construction to plug-in (using) (namely, the chassis)!
    Thank you in advance for your advice,
    David Widmer, Maine, USA

Where did you find these? These are already old models. However, certainly not bad!

In the past there was a set with alu plates for these. Aren’t these mentioned in the manual? Can’t find them on the site anymore.

Transformers are mentioned in the manual of the K4006 and a list is also on the website. Depending on the power you need and the impedance of the speaker you connect, you’ll find the part number of Velleman.
It was indicated on the website that a transformer was not included.

Thank you for your prompt reply.
I bought the kits through what I understood was a reputable supplier. How old a kit have I bought? Looks like I’ve “come in through the back door”, so to speak! By “Al”, do you mean aluminum (Brit. - aluminium)? If so, there is indeed the aluminum heat sink in the kit that holds the assembled board. That is the item I have no idea how to mount, along with how to mount the assembled power supply board + transformers. I have 8 ohm bookshelf speakers - two in living room along with a whoffer, plus two shelf speakers in our kitchen which I and select living room only, or kitchen only, or both. Whoofer is hooked up at all times.
Where can I find a Velleman vendor near the state of Maine (USA)? It appears I will also need some sort of conductive paste for the transistors. Is there a part number for this, or is this something that should be readily available in any store? I’m not familiar with such an item.
Sorry to be such a bother, but I do want to be sure I can use this device when I finish it.

Please call our US support office, the can help you out with all your questions regarding distributors and availability.
(817) 284 77 85

Is there anyone else out there whom would like to comment on these exchanges to help me out?
Just curious - but would appreciate any further input on my questions before I call the mentioned phone number.

The most easiest and most sure thing you can do, is dial that number ;).

I don’t know if they are still available in the US but here in Belgium these kits are obsolete but again: don’t bother because they were very good, so be happy you have them. :wink:

Alu = aluminium plates. Your amplifier has a heatsink, which was the side panel of the whole case. So the case existed of aluminium plates for front, back, upper en lower cover. The two side panels were the two heatsinks for people who built two amplifiers in one case, or just one “dummy” heatsink (w.o. amplifier) and the heatsink from the (one) amplifier for people who just used one amplifier.

This should give you some insight before calling Velleman USA ;).

Good luck.

It has been some time since my last post, so I may not get a reply?
I have postponed beginning construction on my “new” K4005-B amplifier given that there were so many unanswered questions I had asked.
However, I have decided to “bite the bullet”, and have commenced construction. Already, I find new questions! The instruction manual mentions, Page 5, #1: Jumpers. there are three choices of sensitivities - 950mV, 500mV, and 150mV. Choice is made by which jumpers to install. There is a fourth option which I would like to pursue, and that is installing a bipolar 3-position switch which would give a choice of all three sensitivities. Doesn’t tell how to do this! Also mentioned is choice between installing jumpers OR installing a unipolar change over switch - again with no instruction on how!
Question 2: I have followed installing the resistors in the order they are on the “tape”, being instructed that they are taped in the correct sequence. In checking the codes on the resistors, I find several do not agree with the numbers given in the manual. I have stopped construction until I can find an answer to this dilemma!
Can anyone clarify this for me? Could the values of the resistors have been changed from those listed in the manual? There is a disclaimer in the manual that says: “Modifications and typographical errors reserved”. I still think “following the tape” plus the discrepancies are a big red flag!
I thank you in advance if you can help.


You could use a 3 position DPDT switch (center being off) for the input selection.
Make sure you have the switch in the correct position while using the unit.

The values may have change but it is difficult to tell since you did not list the values you have.
Like all manufactures mistakes can happen.
It’s always a good idea to audit all of the parts and check each part for the correct part number and value before installing them.

Please contact Velleman USA for support:
(817)284 7785
techsupport at vellemanusa dot com