Not quite a PASS amp yet but will hopefully be part of it.
Chances upon this (not that I was looking for an arc welder) 70 years old, beautifully designed and extremely well constructed 9KVA arc welder. The last picture us a steel insert in the aluminium cap, a well thought out design detail, hardly found in the Made-in-China products these days.
The top and the base are made of cast aluminium. Centre is 1.5mm thick sheet aluminium, finished in hammerite green.
It is a 3-phase only arc welder, on the label it says 130A@20V output, 9.2KVA, either I have to re-attend my secondary school physics class on ohm’s law or the man who did the calculation failed his maths.
I was looking at the Pass Amp 20 years ago, so this looks like a perfect low cost entry 🤣
When I hooked it up to the 3-phase supply it didn’t blow the apartment to pieces. The output measured 65Vac. Opening it up revealed that the transformer was wired to 2 phases, 450Vac across the primary, neutral not connected, 3rd phase omitted.
So I re-wired it to single phase, L1-N, 230Vac and the output fell to 41Vac. With that if I add a bridge rectifier and some electrolytic capacitors I should be able to get +-25Vdc.
So I ordered a Pass A5 clone today, with the +-25 Vdc I should be able to get 40W @8 ohm? to drive my Sonus Faber Concertino with 86dB sensitivity.
The reason why I chose not to build an A2 instead was that I may buy a “proper” toroidal transformer later if I cannot get rid of the transformer hum later.
Found an old thread by John Biles that someone suggested that the EMF emitted by the transformer would cause Leukaemia, this is in a grounded and fully enclosed aluminium case and perhaps that itself is a Faraday’s cage? Just to be on the safe side I am going to buy a EMF tester.
Wish me luck!
View attachment 1297311 View attachment 1297311
Chances upon this (not that I was looking for an arc welder) 70 years old, beautifully designed and extremely well constructed 9KVA arc welder. The last picture us a steel insert in the aluminium cap, a well thought out design detail, hardly found in the Made-in-China products these days.
The top and the base are made of cast aluminium. Centre is 1.5mm thick sheet aluminium, finished in hammerite green.
It is a 3-phase only arc welder, on the label it says 130A@20V output, 9.2KVA, either I have to re-attend my secondary school physics class on ohm’s law or the man who did the calculation failed his maths.
I was looking at the Pass Amp 20 years ago, so this looks like a perfect low cost entry 🤣
When I hooked it up to the 3-phase supply it didn’t blow the apartment to pieces. The output measured 65Vac. Opening it up revealed that the transformer was wired to 2 phases, 450Vac across the primary, neutral not connected, 3rd phase omitted.
So I re-wired it to single phase, L1-N, 230Vac and the output fell to 41Vac. With that if I add a bridge rectifier and some electrolytic capacitors I should be able to get +-25Vdc.
So I ordered a Pass A5 clone today, with the +-25 Vdc I should be able to get 40W @8 ohm? to drive my Sonus Faber Concertino with 86dB sensitivity.
The reason why I chose not to build an A2 instead was that I may buy a “proper” toroidal transformer later if I cannot get rid of the transformer hum later.
Found an old thread by John Biles that someone suggested that the EMF emitted by the transformer would cause Leukaemia, this is in a grounded and fully enclosed aluminium case and perhaps that itself is a Faraday’s cage? Just to be on the safe side I am going to buy a EMF tester.
Wish me luck!
View attachment 1297311 View attachment 1297311
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IME, stopping the effects of EMI that causes hum in a component can be a challenge. When I have tried steel as a shield it can be less than what I expected. To my surprises mu-metal was also less effective unless two sheets with a gap between them were used. Admittedly, the mu-metal was thin, but at the price paid, it was all that I could afford. I would bet that there is a reliable composition of materials that would be effective for this situation.
Here you have your answer :
"No mechanism by which ELF-EMFs or radiofrequency radiation could cause cancer has been identified. Unlike high-energy (ionizing) radiation, EMFs in the non-ionizing part of the electromagnetic spectrum cannot damage DNA or cells directly. Some scientists have speculated that ELF-EMFs could cause cancer through other mechanisms, such as by reducing levels of the hormone melatonin. There is some evidence that melatonin may suppress the development of certain tumors.
Studies of animals have not provided any indications that exposure to ELF-EMFs is associated with cancer (10–13). The few high-quality studies in animals have provided no evidence that Wi-Fi is harmful to health (8).
Although there is no known mechanism by which non-ionizing EMFs could damage DNA and cause cancer, even a small increase in risk would be of clinical importance given how widespread exposure to these fields is." (1)
1. Electromagnetic Fields and Cancer. National Cancer Institute. Consulted April 11th, 2024. Available here : https://www.cancer.gov/about-cancer...k/radiation/electromagnetic-fields-fact-sheet
