Maybe i'm stupid or something.Probaly missing something.In original Leach plans he uses only one bridge rectifier and NOT two.What i'm trying to say is:you need 2x42Vsecondary when you have two bridge rectifiers and 4 caps(1 per rail).
Something like this:
Supernet do you have such supply?
Something like this:
Supernet do you have such supply?
You dont NEED 2 diode bridges .... you can join the middle 2 wires to effectively form a 84V centre tapped transformer then use a single bridge to form the rails ... you will need 2 cap banks not 4.
See http://users.ece.gatech.edu/~mleach/lowtim/pwrsply.html
To form a +/- supply you need either 3 or 4 secondary wires on the transformer and 2 caps banks 1 between each rail and ground.
See http://users.ece.gatech.edu/~mleach/lowtim/pwrsply.html
To form a +/- supply you need either 3 or 4 secondary wires on the transformer and 2 caps banks 1 between each rail and ground.
Yes, I use one 35A 400V rectifier, 4 × 4700microF caps and one 300VA toroid per channel. Amp works now fine for one year.
supernet
supernet
just to clarify supernet's comment above for shadow, 4x4700uF caps per channel is 2x4700uF caps per rail per channel.
swede shadow is already buying a transformer with dual secondaries so that problem is fixed.... we are currently discussing the voltage rating that the new transformer should have.
ps. the post that i was responding to has been deleted.
ps. the post that i was responding to has been deleted.
AudioFreak: sorry for deleting my last post. It was just a repeat of what everyone else had said. It was due to my browser's /&%/&¤#% cache, that didn't allow me to update the thread.
Though, I'm very impressed that the output transistors (or anything else by the way) have not blown yet. I've blown about 8 output transistors in my attempts to get a Leach Amp up and running. In my case the problem was more of the "counterfeith Motorola" transistor type of error.
Regards,
//magnus
Though, I'm very impressed that the output transistors (or anything else by the way) have not blown yet. I've blown about 8 output transistors in my attempts to get a Leach Amp up and running. In my case the problem was more of the "counterfeith Motorola" transistor type of error.
Regards,
//magnus
Yes i was probaly very lucky.Amp even work for 2hours and then shut down with distort sound.Interesting.
With transformer i know there is many ways to connect one to power suply.I'm currently running 2x18V and puts combined voltage of 54V(little low),two wires on sentral ground point,two on bridge rectifier.So i think 2x21V shoud perform just fine.
With transformer i know there is many ways to connect one to power suply.I'm currently running 2x18V and puts combined voltage of 54V(little low),two wires on sentral ground point,two on bridge rectifier.So i think 2x21V shoud perform just fine.
This might be interesting:
Taken from Plitron Site:
Taken from Plitron Site:
An externally hosted image should be here but it was not working when we last tested it.
shadow: You are right on the spot. It is the last one, the center tap, you should use.
I think you still have not got the concept on converting 2x42 Volt AC to the proper DC.
What you need is DC just about + 56 volts and - 56 volts, which is what you get from the 2 x 42 volt transformer. If you measure across RED and GRY on your picture and it is 2x42 volts, you should get 82 volts AC. If you rectify that and connect it to the filter caps, you will measure 115 Volts DC across the caps. If you measure from one end of one cap and to the ground you'll get just about 59 volts DC.
So how come you get a higher voltage (42 volts AC is just about 59 volts DC after rectification)? Just multiply 42 with sqrt(2), and you'll get the right voltage. What you will get is an average of the voltage across a whole AC cycle.
Regards,
//magnus
I think you still have not got the concept on converting 2x42 Volt AC to the proper DC.
What you need is DC just about + 56 volts and - 56 volts, which is what you get from the 2 x 42 volt transformer. If you measure across RED and GRY on your picture and it is 2x42 volts, you should get 82 volts AC. If you rectify that and connect it to the filter caps, you will measure 115 Volts DC across the caps. If you measure from one end of one cap and to the ground you'll get just about 59 volts DC.
So how come you get a higher voltage (42 volts AC is just about 59 volts DC after rectification)? Just multiply 42 with sqrt(2), and you'll get the right voltage. What you will get is an average of the voltage across a whole AC cycle.
Regards,
//magnus
all nice here,i must get one - and one + (for left channel - , for right +) from ground(other - and + are taken from caps),that means central ground point.With so much ground connections is this possible?
hmmm....
it is not the average it is the peak value of the sine that is SQRT(2) and that is what you get after rectifying (and caps)...
/micke
it is not the average it is the peak value of the sine that is SQRT(2) and that is what you get after rectifying (and caps)...
/micke
shadow said:
You can run both channels of the amp from the same rails that is not a problem.
See http://users.ece.gatech.edu/~mleach/lowtim/pwrsply.html
If you follow the instructions on that page you will not have a problem.
Each channel of the amp will need both a +ve and -ve supply rail
all of the power grounds (including the grounds from the speaker outputs) should return to one point (usually the caps ground point)
Sorry,but i know all that.With double secondary (2x42) wiring as prof. Leach recommends is impossible.
I still needs swede opinion.He see this problem.
I still needs swede opinion.He see this problem.
it's totally possible shadow you just wire the transformer to make a centre tap then do it as per the power supply professor leach describes.
Hi,
I'll bring a digital camera from work today and show you how I've solved it. All you need is the 3'rd transformer on your pictures (e.g a transformer with two cables in and four cables out).
There are a couple of ways to build the power supply. Here is one.
Put the two middle cables on the output together and connect them to a metal plate. From now on, that is your central ground. Any reference to ground in Prof. Leach's writings are made to that metal plate. This is very important. Any cable that is supposed to be connected to ground is to be connected to this plate.
Then, you get two (2) rectifiers. Connect the outer two cables on the transformers output to the inputs on both rectifiers (the two outer cables from the rectifier should be splitted, so you have four cables. Two for each rectifier.)
From the rectifiers you connect to the capacitors. If you have two large caps for each channel, connect (per channel) from between your caps to ground. That is what makes your +V and -V stick to their correct potential, referenced to ground.
Well, I'll show you pics on my amp tonite or tomorrow.
In my former post, (where I refered to the last transformer in your pics), I should have refered to the third one, where the two middle cables are connected. Don't do it any other way.
//magnus
I'll bring a digital camera from work today and show you how I've solved it. All you need is the 3'rd transformer on your pictures (e.g a transformer with two cables in and four cables out).
There are a couple of ways to build the power supply. Here is one.
Put the two middle cables on the output together and connect them to a metal plate. From now on, that is your central ground. Any reference to ground in Prof. Leach's writings are made to that metal plate. This is very important. Any cable that is supposed to be connected to ground is to be connected to this plate.
Then, you get two (2) rectifiers. Connect the outer two cables on the transformers output to the inputs on both rectifiers (the two outer cables from the rectifier should be splitted, so you have four cables. Two for each rectifier.)
From the rectifiers you connect to the capacitors. If you have two large caps for each channel, connect (per channel) from between your caps to ground. That is what makes your +V and -V stick to their correct potential, referenced to ground.
Well, I'll show you pics on my amp tonite or tomorrow.
In my former post, (where I refered to the last transformer in your pics), I should have refered to the third one, where the two middle cables are connected. Don't do it any other way.
//magnus
there is really no need to complicate matters so much ....
you only need 1 bridge.
You make a +ve and -ve supply from a CT transformer by using the outer 2 wires for the bridge and the output from the bridge is the +ve and -ve rails with the CT of the transformer being the ground.
you only need 1 bridge.
You make a +ve and -ve supply from a CT transformer by using the outer 2 wires for the bridge and the output from the bridge is the +ve and -ve rails with the CT of the transformer being the ground.
Now it's too late i allready order 2x21V secondary,but if i connect that transformer like picture 2(series connected to double voltage) all shoud work cause 2x21=42x1.41=59.4V .
Inner wires connect together as you all told me to CGP(central grou...)
Voltage will be OK cause 2x42V you cant use full output(141V DC)you can use half that voltage.So i think these two shematics puts out same voltage,or i'm missing something?
Inner wires connect together as you all told me to CGP(central grou...)
Voltage will be OK cause 2x42V you cant use full output(141V DC)you can use half that voltage.So i think these two shematics puts out same voltage,or i'm missing something?
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