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About Aussieamps

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  • Birthday 28/10/1961

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  1. There seems to be a number of points of misunderstand regarding this saga. The first is I am committed to find out exactly what is going on, that is something I have always done for the last 20 years for my DIY amplifier customers. The reason I have not replaced the modules is I have not found anything wrong with them during both visits to my Lab. This particular design is a very mature design and as mentioned has been installed into many DIY installations. I have done tests on the said modules driving them with balanced as well as unbalanced signals to full power in
  2. Yes quite right, if I could I would have already flown over the strait, to sort this out, I have literally thousands of these DIY amp modules installed all over the world and very happy customers, the incorrect cap installation was me with my almost 60 year old very long sighted eyes. We will get to the bottom of what is actually going on. Thanks to Doug for being an absolute gentleman.
  3. I have tested Doug's NXL500 modules into 2 ohm loads with a 1uf X2 Type capacitor across the load and with a 1khz and 10khz and 20khz square waves , this type of load is about as tough a load you can expect any power amplifier to be able to handle, the phase margin on these amplifiers is approximately 50dB. They handle the load without any issues. I also did THD tests into 2 ohm loads at hundreds of watts, no oscillation. What I will be doing is to increase the input filter roll off at around 100khz, and add a small amount add differential filtering. The 100khz roll off is something even Nelso
  4. The clipping of the AC mains waveform is a symptom of hard loading on the local street power transformer, not DC on the mains, its really an offset and possibly inductive phasing issues that creates the DC component I believe. You will see examples of this issue if you try controlling a toroidal transformer with a triac, the result is a strange disturbence piggy backed on the AC waveform and the resulting acoustic growling from the transformer core. 🙂
  5. yes best to get back to the thread, 🙂
  6. Here is a diagram I got off the net for a 1:1 ratio isolation transformer when connecting a CRO input, use the same principle using a transformer isolation with lower AC voltages. There are other methods of connecting the CRO to meaure ac mains as well, one other method is to connect or power the CRO from the 1 to 1 ratio isolation transformer secondary and connect the CRO probe directly to AC mains, but again you need to know excatly what you are doing.
  7. Hi Andy if you already have a CRO then you can use almost any transformer you have on hand to do a basic observation of the ac mains. As i mentioned connect your CRO probe to the floating secondary winding and primary winding to ac Mains. the CRO probe ground lead gets connected to the other secondary winding wire. this ensures not only low voltage to the CRO but correct isolation for total safety. I hope this helps? I might do a quick diagram so anyone can visualise it.
  8. I think Mike you are missing the point, I will leave it at that!
  9. Guys you need to be very careful doing anything like this unless you know exactly what you are doing! There are a number of things you need to know, CRO amplifier input stages will only handle 300Volts typically on maximum attenuation, Australian AC mains is typically 240VAC its peak voltage is 340VAC. All AC mains measurement using a CRO; should be used with a suitable AC mains isolation transformer. If you do not have a 240vac to 240vac isolation transformer, use a 240vac to 12vac transformer or anything in the so called low voltage range. It is very important to electrically isolate yo
  10. A lot of the design process for the DIY boards involves trimming the cost of BOM for SMD components(Multiturn SMD Trimmers can cost as much as $8.00 each), personally I do not have any issues with the adjustment as I am very use to the very small trimmers. But having said that I understand the frustration with adjusting small SMD trimmers. They can be fiddly. 🙂 On some of my commercial designs, I do use opamp based DC servo's for DC offset control and they work very well indeed, keeping the DC offset to within 1mv or less all the time. 🙂 The DC offset trimmer on the NXL800 board will
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