Didnt notice where you had your scope leads hooked up...but,

it could be frequency dependent due to the operational characteristics of the amplifier. To check place a resistive load across the output and measure through frequency range, taking note of the peak to peak amplitude.

The scope was connected to the output of the Amplifier. The primary winding if you can call it that? is quite literaly a strip of copper formed as a spiral. It has a Bridge measured resistance of 0.004 Ohm.

Hope this helps?

Silly me, are you suggesting looking at the open circuit with say a 4ohm resistive load?

I would tend to think the inductance of the coil would be much too small to be at resonance, same goes for capacity of the coil. I suggest the resistor to see if it has a similar amplitude change through the frequency range.

Sorry as I stated earlier I am not the sharpest tool in the box!! your statement is way over my head. However the amplitude of the sinusoidal waveform does not change as the frequency is altered. Current starts to rise below 8Khz peaks at 10 khz and then drops off as the frequeny is increased towards 100Khz. but at that frequency I think because it is an audio amp it just isn't able to cope with such a high frequency.Can you really call it a coil???

As you must be aware I am new to using forum's, does the page react to a new post or do I have to refresh manually?

You have to re-fresh to see new messages.

You may not call it a "coil", but every structure has both inductive and capacitive properties, this is inherent in nature. Therefore every structure also has a resonant point. Because it has circular winding "patern" each loop will have roughly a inductive value equal which could be calculated

One-turn loop inductance calculation

The sum of the loops would equal the total inductance. You can buy an LCR meter to do this, however it would have to be a very sensitive one to know where you sit with a coil like that. Another way to find out what it is is to get a signal generator which delivers a constant voltage and amperage across its range (that is if you are using a resistive load). Now hook up your little transformer, and see where the signal strength, or amplitude drastically changes. Some resonant structures look like a dead short at certain frequencies, some look like very high resistances. This is called the impedance of a structure, and it is the ohmic equivalent for frequency sensitive systems (systems which are dominated by inductive and capacitive elements, rather than purely resistive).

I have seen that transformer plenty before, and there is a ton you can read on it, but a cool demonstration none the less. I was primarily interested in your little amplifier!

You will learn a lot playing around with fun stuff like this!!!

Thankyou for your input it is appreciated and I understand what you have stated.

What I really found interesting was the fact that you did not have to have the inner "coil" inside the outer one for it to work, so long as the wire runs through both it works??!! I also tried looping the wire to see if you got a turn ratio increase. No is the answer in fact the bulb dimmed.

BTW the amplifier module is an off the shelf unit by Kemo Germany and I have got to say it is very robust!!! I bought a 40 watt unit today and stangely it drew a great deal more current than was expected. I have no clue why. But sometimes I think that serendipity plays a part in these exotic experiments.