K1803 Universal Mono Pre-Amplifier Kit, Multi-Colour

I did a lot of kit and scratch-built stuff many years ago, so I'm not new to this. However, it has been a long long time, and my soldering did need a little brushing up. The design was brilliantly done; values of the resistors and capacitors were kept very simple, and the sequence of installation was a very good idea. We are using it as a line booster between a telephone headset output and a computer sound system for listening to Kingdom Hall meetings, since my wife is unable to attend most of our meetings in person. I settled on a single 9-volt battery (toggle switched) and have so much gain that I can hardly turn the pot. I would recommend this little board to anybody.

It's a good and cheap way to practice soldering and observe basic circuit signal flow. Mine did not work the way it was supposed to, but I still got the credit I needed for my physics lab. It's not a preamplifier you would put in a professional recording studio, but it's a good starting place if you plan to advance your circuitry knowledge!

To my surprise it draws less than ONE MILL when operating with my Icom 756. The gain is easily adjusted to the necessary value with the pot. on the board.

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It worked quite well with my Dynamic Mic and power amplifier. I removed the small potentiometer used for gain/ or volume and replaced it with wired hooked up to a full sized pot which was intalled on the control panel / box.

Easy to solder together, worked the first time, and sounds surprisingly good. You can't beat it for the money.

I wanted to like this preamp but unfortunately it's not what I expected. I assumed that this would output a line level signal, given that anything less would be useless, but it's more like instrument level (and a weak one at that). Maybe mine was defective, but I couldn't get anything more than that after lots and lots of testing.

It went together okay but the terminals were pretty close together for attaching the external wires. Hard to ensure there was no short. Instructions were good in terms of assembly.

pour des montages de ventilateurs supert bien

Oggetto ricevuto velocemente parliamo di un prodotto di qualità con elevate caratteristiche tecniche!!! Tutto perfetto venditore affidabilissimo!! Lo consiglio!!

Loved the kit and the way it was packaged, ( I can make use of the packaging to store other things in in my little workshop), had to go online to find / download the kit information, yet it arrived with a multi lingual paper warranty booklet in the kit which probably used more paper than an instruction booklet would have ! When built and tested this pre-amplifier kit worked well , I will be using more of these.

Über die Audioeigenschaften kann ich nicht viel sagen, da ich die Platine als NF-Messverstärker verwende. Im Prinzip ist auf dem Board auch nur eine OpAmp-Schaltung. Der LM358 ist ein gängiger Standard-OpAmp, für dessen Pinbelegung es viele alternative ICs gibt. Wer einen Bestückungsplan (nicht im Bausatz enthalten) benötigt, findet diesen nicht auf der beschriebenen Seite, sondern direkt auf www.velleman.eu oder einfach nach K1803 googeln. Die angegebenen maximal 40 mV Eingangsspannung kann ich nicht nachvollziehen und verweise auf das Datenblatt des LM358. Auch ist das Poti mit 250 kOhm vielleicht etwas groß. Bild 1 zeigt einen 5 kHz Sinus mit den angegebenen 40 mV an Eingang (gelb) und 1,4 V am Ausgang (blau), was einer Verstärkung von 30 dB entspricht. Bild 2 zeigt einen Sweep über den Angegebenen Frequenzbereich von 20 Hz bis 20 kHz. Ein Kästchen sind 1,43 kHz, restliche Parameter wie bei Bild 1. Bei 200 mV Input und nicht ganz so hoher Verstärkung sind selbst mit dem LM358 noch brauchbare Werte bis 40 oder 50 kHz möglich. In Bild 3 sieht man jedoch bei ca 30 dB (6 Volt Peak-to-Peak, blaue Kurve) und bei 12 Volt Versorgungsspannung bei der negativen Halbwelle erste Verzerrungen.

Un quitte intéressant obligeant l'utilisateur à s'équipé d'un fer à souder et de soudure électronique, mais qui permet de se remettre dans le bain après des années.