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Old 6th August 2005, 11:27 PM   #1
dome406 is offline dome406  United Kingdom
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Question A few questions

I am very new to electronics and just wanted a bit of advice on how to start, I have started to read Electronics Explained (by M.W. Brimicombe) and Success in Electronics (by Tom Duncan) and have started to gain a small understanding of how electronics work. I built a pair of Adire 281 speakers (I think 4ohm) last summer and I am interested in building a Gainclone amplifier from chipamp.com and a preamp from Decibel Dungeon for them. I have assembled battery kits from Maplins and have soldered inside Xboxes.

Do you think it is a good idea for me to start with a gainclone? I dont have too much experience with mains electricity so am I being a bit too ambitious.

Another thing which I dont clearly understand is the 'grounding' does everything which needs to be grounded run to the earth pin of the plug socket. As this has always confused me.

Sorry about all the questions but i dont really want to end up with £ss worth of smoking parts and dont really want to be injured doing something which I am inexperienced to do.

btw I am a student, Just in case you wondered And sorry if this has been posted 100's of times or it is in the wrong section.
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Old 6th August 2005, 11:37 PM   #2
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Hi,

A gainclone is a great place to start, just keep reading all you can. Places like Decibel dungeon are an excellent source of all the knowledge you will really need to get started.

BrianGT kits rock, and any circuit you see on DD won't let you down.

Just don't become a sheep, use your head, read the spec sheets and books, and keep an open mind.

Cheers!
Russ
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Old 6th August 2005, 11:50 PM   #3
dome406 is offline dome406  United Kingdom
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Thanks for the fast reply, but how do you test the oput voltage on transformers, do you have to put a load accross the outputs and then measure the voltages, thanks
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Old 6th August 2005, 11:54 PM   #4
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Quote:
Originally posted by dome406
Thanks for the fast reply, but how do you test the oput voltage on transformers, do you have to put a load accross the outputs and then measure the voltages, thanks

Only if you have a load that can handle it, first test it unloaded. That will give you a great idea what your max voltage could be at any given time.

Once you have a PS built, then check your rails to ground, and across your rails.

HTH
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Old 7th August 2005, 12:00 AM   #5
dome406 is offline dome406  United Kingdom
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thanks
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Old 7th August 2005, 12:08 AM   #6
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Default Re: A few questions

Quote:
Originally posted by dome406

Another thing which I dont clearly understand is the 'grounding' does everything which needs to be grounded run to the earth pin of the plug socket. As this has always confused me.
I forgot to answer this.

In most circuits ground is 1/2 the supply voltage, and everything is referenced from that. It does not necessarily have to be connected to Mains ground(earth) but it can be.

So, if you have a 48V center tapped transformer you will and up with a -24V rail 0V ground(which is really just your reference) and +24V. Lets explane this further, really GND is just your way of refernence a value to 0. Anything less than your GND voltage is negative relative to your GND, anything greater is positive.

So, if you looked at the trafo relative to the negative rail, it would be 0, 24V, 48V, but instead(for good reasons) we choose to look at it relative to the mid point(GND) or the center tap in a center tapped trafo. o get that mid point you either need a trafo with dual secondaries, or a center tap, or a virtual ground net(which is another topic).

I hope this helps.
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Old 7th August 2005, 08:47 AM   #7
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And if you buy a transformer, the final voltage after your rectifiers and caps will likely be about 1.4 x the advertised voltage. So if you buy a 30-0-30 traffo, it will give you around 42-0-42 rails.
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Old 7th August 2005, 08:44 PM   #8
dome406 is offline dome406  United Kingdom
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Thanks very much for the useful info I am going to start to oder the things I will need.
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Old 7th August 2005, 08:57 PM   #9
dome406 is offline dome406  United Kingdom
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Just one other quetion, I am wary of capcitors are the ones used quite safe (10uf and 1500uf 50v) or will I need to discharge them when I want to work on any part of the circuit after it has bee plugged in.

and is the best way to do this with a big resistor.

Thanks.
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